Active Cellular Transport

Biology Index

Where are we going with this? The information on this page should increase understanding related to this standard:  Evaluate comparative models of various cell type…Evaluate eukaryotic and prokaryotic cells.

Article includes ideas, images, and content from Troy Smigielski (2021-09)

Active Cellular Transport

(Are we talking about phones yet?)

Whereas passive cellular transport occurs without the expenditure of energy (because concentrations of stuff are moving from high levels to low), active cellular transport occurs only when the cell uses energy to move something.

You will recall that in passive transport, substances moved through the concentration gradient from high to low.

But, sometimes your cells need a material that requires it move against the concentration gradient. This means that the cells need materials to go from an area of low concentration to an area of high concentration. 

A classic example of this (substances moving from low concentration to high) is seen in the sodium-potassium pump.

The Na+/K+ pump helps keep the sodium concentration high outside the cell and the potassium concentration high inside the cell. This is crucial in allowing your muscles to contract.

For this process to take place requires active cellular transport.

Active transport is transport of molecules from a low concentration to a high concentration.

Active transport requires two things: 

• energy 
• a transport protein (integral protein).

These things are needed because active transport moves against the concentration gradient, which does not happen naturally.

Think of it like this… Naturally, substances move from high concentration to low. This is like things flowing in water running downstream. Active transport is like swimming upstream; swimming against the current.

There are two (2) main types of active transport.

Both require the use of vesicles that are used to package the material being transported.

These vesicles do not require a transport protein to enter or exit the cell.

Hey! Now's a really good time to learn some more prefixes. Endo- and Exo- pop up in science all over the place! What do they mean?

Endo- kinda sounds like "enter" and that's what it (as a general concept) means. Endothermic means energy in the form of heat going in.

Exo- sounds a lot like exit. And… yeah, that's what it means. Exothermic means energy is given off; energy exits the… whatever.

 

Okay, back to our cellular transport discussion!

Endocytosis

Endocytosis occurs when materials enter the cell via vesicles

Phagocytosis: ingesting solid materials

Pinocytosis: ingesting liquid materials

Endocytosis is the first step in lysosomes breaking down a molecule.

Exocytosis

Exocytosis occurs when materials exit the cell via vesicles

PLOT TWIST!

We've previously established that…

Active transport requires two things: 

• energy 
• a transport protein (integral protein).

Also, we said that active transport can move things from low concentration to high.

Well… well… well…

Endocytosis and exocytosis don’t always move from low to high. AND, they don’t need a transport protein, but they do require energy.

Both types of active transport can work together:

_______________________________

How about a cool graphic to sum things up?

Passive Cellular Transport and Tonicity

Biology Index

Where are we going with this? The information on this page should increase understanding related to this standard:  Evaluate comparative models of various cell type…Evaluate eukaryotic and prokaryotic cells.

Article includes ideas, images, and content from Troy Smigielski (2021-09)

Passive Cellular Transport and Tonicity

(This sounds important!)

https://www.google.com/search?q=plasma%20membrane

All cells have a membrane. To be more specific, all cells have a phospholipid bilayer membrane that keeps stuff in and out of the cell. It is also called the plasma membrane.

The cell membrane is constantly moving like a wave. It is composed of phospholipids and other molecules such as cholesterol, proteins, and fatty acids. 

Scientists often describe the cell membrane with the fluid-mosaic model, which describes these 2 characteristics.

1. Fluid: constantly moving
2. Mosaic: multiple pieces in the membrane

In addition to the cell membrane, plant cells have cell walls that function to provide structure, support, and protection for the cell. They are made up mostly of cellulose, a polysaccharide carbohydrate.

Since cell membranes function to regulate what enters and exits the cell, there must be some method of getting material in and out. One of the methods is passive cellular transport.

Because cell membranes are made up of a phospholipids arranged in a bilayer, small, hydrophobic molecules can fit between gaps in the phospholipid heads. However, most large, charged, or hydrophilic molecules are unable to cross (pass through the membrane). Water is special in that it is polar and hydrophilic AND it can cross.

So, how do larger, charged, and/or hydrophilic molecules enter or exit the cell?

Larger, charged, and/or hydrophilic molecules enter or exit the cell through proteins that are embedded in the cell membrane. 

Integral proteins are transport proteins that are stuck in the cell membrane.

There are two types of integral proteins (see illustration below):

• Channel proteins have a hollow channel which allows large, polar molecules and/or ions into or out of the cell.
  
  
• Carrier proteins provide protection for larger, charged, and/or hydrophilic molecules as they enter or exit the cell.

These integral proteins are extremely important; they are necessary because the cell needs all kinds of large, charged, and hydrophilic compounds to carry out its normal function, 

There is a very important aspect to passive cellular transport. Look at the following image.

What do you notice about the direction the molecules are moving? They are all moving from where there are "more" to where there are "less."

Why?

The purpose of particle transport is to ensure the cell maintains homeostasis, or equilibrium. 

Woo… dropping some vocab in without telling us?

Equilibrium is the point when the number of solutes is the same on both sides of the membrane. When something is at equilibrium, it can be said to be in homeostasis. 

Not only are the numbers the same one both sides of the membrane, but also equilibrium is when the rate of materials going in equals the rate of materials going out.

Reprise; Equilibrium is…

• is the point when the number of solutes is the same on both sides of the membrane
• is when the rate of materials going in equals the rate of materials going out.

There are a couple of ways for cells to reach equilibrium, and they are all a form of passive transport. However, in order to discuss them properly, we need to make sure we understand a concept called concentration.

Concentration is simply the amount of a substance in a solution.

Passive transport is the movement of molecules or ions across the cell membrane from an area of high concentration to an area of low concentration.

It does not require energy.

Molecules naturally flow from high concentration to low concentration. The difference in concentrations between the inside and outside of the cell is called a concentration gradient.

Molecules naturally flow along the concentration gradient from [HIGH] to [LOW].

Almost everyone can easily visualize another type of equilibrium. Not cellular, but thermal. Heat energy, like molecules in passive transport, flows from matter with high levels of energy to matter with low levels. If the temperature of our soda is too high, we can transfer some of that heat to something that is colder. Ice? Sure! Putting ice into a drink introduces matter with low levels of energy. The energy from the warm soda flows into the ice. The result is lower energy in the soda—it cools off. Eventually, equilibrium is reached with all of the ice is melted (but then the high heat energy from the room starts to flow in low heat energy of the soda).

There are two major types of passive transport.

Diffusion is when a substance moves from an area of high concentration to an area of low. concentration.

Osmosis is when a water moves from an area of high concentration (of water) to an area of low concentration (of water). 

More formally, osmosis is the movement of a solvent (e.g. water) across a semipermeable membrane from a lower concentration of solute (not water) toward a higher concentration of solute (not water). 

So, if there is some water and a low concentration of a thing "over here" and some water and a higher concentration of a thing "over there" then the water will move from "here" to "there." 

The movement of the water by means of osmosis evens out the concentration of the "thing" on both sides of the semipermeable membrane.

Two Versions of Diffusion

Diffusion can be further broken down into two types.

Understanding diffusion benefits from understanding solutions, but we'll get more formally into that later on.  But, previewing, think of a solution as water with stuff dissolved in it. (Like sugar dissolved in water.)

Diffusion deals with the particles (the stuff) dissolved in the water moves from where there's a lot of them to where theres not many of them.

Simple diffusion is normal diffusion, which does not require any sort of transport protein. Simple diffusion occurs when particles move through the phospholipid bilayer directly.

Facilitated diffusion is diffusion that requires the use of transport proteins. Facilitated diffusion is required for larger particles and hydrophobic molecules. 

When will passive transport stop?

Passive transport will happen until the system reaches equilibrium. Remember that equilibrium is when the rate of materials going in equals the rate of materials going out.

Okay… let's think about this…

If solutes freely flow to an area of low concentration, what is preventing our cells from being flooded with random stuff?

 

Our cell membranes are selectively permeable (aka semipermeable), which means that they choose what comes in and what doesn’t. This is the key characteristic in being able to regulate entry and exit of materials. This protects our cells from swelling or shrinking.

Notice how the blue molecules are unable to move into the cell on their own. This is probably because they are too large. If the cell needed blue molecules, how would it let them in?

For the blue molecules to pass through the cell membrane, some sort of facilitated diffusion would need to occur.

So, diffusion and facilitated diffusion account for two types of passive cellular transport. There is one more.

Osmosis 

Osmosis is pretty much the opposite of diffusion. Whereas in diffusion, the particles move from place to place to even out concentration, in osmosis, water moves from place to place to even out the concentration.

To get to a formal definition, we need to learn a few concepts related to solutions.

A solution is a mixture of something dissolved into something else. The thing that dissolves is called the solute and the thing into which it is dissolved is called the solvent.

Sugar water is a mixture of the solute sugar in the solvent of water.

Solution: a homogeneous mixture of a solvent and a solute. 

so·lu·tion: a liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent).

"a solution of ammonia in water" 

(Source: 2021-09-27)

Solvent: a fluid into which other substances can be dissolved.

Solute: a substance that is dissolved into a solvent to form a solution.

Osmosis is the process whereby the solvent moves such that the concentration of the solute is evened out.

Osmosis will occur passively when the concentration of the solute is relatively different inside a cell as compared to outside the cell.

Osmosis is related to another concept called Tonicity.

Tonicity

Tonicity can be defined as the ability of a solution surrounding a cell to cause that cell to gain or lose water. Tonicity is a measure of osmotic pressure between two sides of a semi-permeable membrane.

To understand this, here are a few things to keep in mind.

Water will naturally move from a high concentration of water to a low concentration of water (osmosis). From a different perspective, water will move to where there is more solute.

 

Look at the image above. 

In the first case, there is a lot more water in the left compartment, meaning that the percent of water compared to solute is higher than on the right. Water will, by osmosis, move into the right chamber so that the concentrations even out.

When water moves to an area of more solute, it dilutes (dissolves) solute molecules.

We have names for different relative concentrations. And we get to use some fancy prefixes!

Hyper: more/above

Iso: the same

Hypo: less/below

There are 3 kinds of solutions:

Hypertonic solution - has more solute than the cell (cell will shrink)

Isotonic solution - has equal amounts of solute outside of the cell (cell will stay the same)

Hypotonic solution - has less solute than the cell (cell will swell)

So… if the solution is hypertonic, that means that there is a higher concentration of the solute outside the cell. Water will osmose out of the cell trying to even out the concentration, causing the cell to shrink.

If it is isotonic, then it has the same amount of solute inside and out… duh… nothing happens.

If the solution is hypotonic, that means there is a lower concentration of solute outside the cell. Water will osmose into the cell trying to even out the concentration and the cell will swell.

This seems important. You should say it again with different words.

Source, 2021-09

Hypertonic solutions have more solute outside of the cell. Water will move to where there is more solute. Water moves out of the cell.

Isotonic solutions have the same number of solute outside of the cell as it does inside of the cell. Water will move to where there is more solute. Since solute numbers are equal, water will move in and out at an equal rate.

Hypotonic solutions have less solute outside of the cell, which means it has more solute inside the cell. Water will move to where there is more solute. Water moves into the cell.

https://socratic.org/questions/in-a-hypnotic-solution-what-way-does-water-move

_____________________________

Let's take a shot at an overview…

The end goal of passive transport is to even out the concentration of <stuff> in the <liquid> so that inside and outside the a <membrane enclosed thing>, the concentration of <stuff> to <liquid> is the same.

The <stuff> is the solute… something like sugar or salt or another substance a cell needs. The solute is the particles, whatever they are.

The <liquid> is the solvent… water. Let's just leave it at that. So the solute is dissolved in the solvent to create a solution with some concentration.

The <membrane enclosed thing> is usually a cell, but the concepts apply to larger structures. Going forward, we'll limit the concept to cellular passive transport.

Concentration is a concept that describes how much solute is in a solvent: how much stuff is in a liquid. For instance, how much sugar is in the water. The less water (as compared to the other thing) the higher the concentration 

Sometimes to ship products (like orange juice) the liquid is removed leaving highly concentrated product. Putting water back in can return it to its original consistency.

For passive cellular transport to happen, the concentration of solute has to be different when inside and outside is compared. 

__________________

Diffusion:

In diffusion, the particles move

 •  Solutes will move from high concentration of "particles" to low.  

•  The solute moves in order to even out concentrations.

__________________

Osmosis:

In osmosis, the solvent move

 •  Solvents will move from low concentration of "particles" to high. 

•  It is conceptually okay to think of the solvent moving from there there's too much solvent to where there's not enough. However, the end result is equalization of concentration, which is a measure of solvent in solute.

•  The solvent moves in order to even out concentrations.

Cellular Transport

Biology Index

Where are we going with this? The information on this page should increase understanding related to this standard:  Evaluate comparative models of various cell type…Evaluate eukaryotic and prokaryotic cells.

Article includes ideas, images, and content from Troy Smigielski (2021-09)

Cellular Transport

(Is this moving an iPhone from one place to another?)

https://www.google.com/search?q=cellular+transport

Cellular transport actually has nothing to do with moving iPhones.

Cells need to take in nutrients form the environment. They also need to get rid of wastes. 

Living cells are constantly in the process of moving things from place to place. Things?  Substances… ions and molecules need to move from place to place within living cells.

But, they have a membrane that is designed to keep some stuff in and some stuff out. 

• Cell membranes function to regulate what enters and exits the cell.
• They are made up of a phospholipids arranged in a bilayer.

In order to move things in and out, cells, have a couple of mechanisms. Sometimes things just move through the phospholipid bilayer. 

BUT… most large, charged, or hydrophilic molecules are unable to cross the cell membrane. Water is special in that it is polar and hydrophilic AND it can cross.

So, how do larger, charged, and/or hydrophilic molecules enter or exit the cell?

Cellular transport is the movement of substances across cell membranes, either into or out of a cell.

Within the cell, substances are transported by the vesicles. However, to exit the cell requires something more. 

There are two types of transport systems:

• Passive Transport (and Tonicity)
• Active Transport

Enzymes

Biology Index

Where are we going with this? The information on this page should increase understanding related to this standard:  Evaluate comparative models of various cell type…Evaluate eukaryotic and prokaryotic cells.

Article includes ideas, images, and content from Troy Smigielski (2021-09)

Enzymes

(Hey! This rings a bell!)

Nearly all enzymes are proteins that serve as biological catalysts. In chemistry (and biochemistry), a catalyst is a substance that, though not actually a part of the reaction, increases the rate of a chemical reaction without, itself, being permanently changed. Enzymes do this.

Another way to say it is that enzymes accelerate chemical reactions between different biological molecules. The molecules that the enzymes operate on are called substrates.

Source, 2021-09-21

Each enzyme is very selective with regard to which process it speeds up. The "lock and key" analogy is a good way to think about this. 

In this analogy, the lock is the enzyme and the key is the substrate. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).

Smaller keys, larger keys, or incorrectly positioned teeth on keys (incorrectly shaped or sized substrate molecules) do not fit into the lock (enzyme). Only the correctly shaped key opens a particular lock. This is illustrated in graphic on the left. Source, 2021-09-21

Enzymes can break compounds down or put molecules together.

Most enzymes end in -ase. (Not to be confused by mayonnaise! Same sound, different spelling…)

The molecular shapes of enzymes are specific to the substrates with which they work. As was mentioned, enzymes only work with specific substrates. 

Look at the image to the right. The shape of the enzyme determines which molecules it can work with.

The enzymes pictured would be those that put molecules together to create a compound. Would it be possible for the enzyme on the right to work on one of the circles? Why or why not? No. The shape of the enzyme specifically works only with certain other molecules with a matching shape.

Each enzyme has an active site on it that recognizes a specific substrate.

• The active site is a region on the enzyme.
• The substrate is the molecule being acted on.

Once the active site binds to the substrate, the molecule becomes the enzyme/substrate complex. Small changes occur that help the enzyme fit tightly to the substrate. This is called the induced fit model.

Using a workshop as an analogy for enzymes, you could think of an enzyme as a clamp or jig. Parts could be held in the jig or clamp until glue bonds them together (or until a solvent separates them).

This enzyme is breaking a compound apart.

Inhibitory Molecules

Occasionally, an inhibitory molecule can cause the enzyme to not function. There are 3 kinds but we will focus on 2:

• Competitive inhibition: when a fake substrate binds to the active site which prevents the real substrate from attaching
  
  
• Non-competitive inhibition: when a molecule attaches to the enzyme at a place other than the active site

Enzyme Use

Enzymes are reusable which means they are able to function over and over again. This happens until they are destroyed or denatured.

Enzymes are influenced by 4 main environmental factors:

1. pH (measure of acidity)
2. Temperature
3. Amount of substrate
4. Salt concentration

Each enzyme will have operational range and an optimal range for each of the environmental factors. Outside the operational range, they will not work. They work best when within their optimal range.

The graph to the right shows a sample of the effect of pH on enzyme activity.

At pH below approximately 1.75 and above approximately 11.75, the enzyme won't work.

It works best between a pH of roughly 6 to 7.

Based on how the enzyme behaves under different pH readings, we can determine both the optimal range and operational range.

Like pH, temperature rages affect enzyme effectiveness. 

Low temperatures cause reactions, in general, to be slower. This is also true with reactions catalyzed by enzymes; enzymes are less effective at low temperatures.

However, if the temperature gets too high, the enzyme will deteriorate (they become denatured). When this happens, the active site no longer fits with the substrate and the effectiveness goes down until it simple no longer works.

Another factor is the presences of substrate. Substrate concentration is an indication of how much substrate is present. 

If there isn't any substrate, the enzyme doesn't have much to do.

Imagine an assembly line that can put together 100 toy cars in an hour. It doesn't matter how fast the assembly line is if there are no wheels to put on.  If there are only 8 wheels, only 2 cars can be built.

If there are 8,000,000 wheels, then the assembly line can make 100 cars in an hour, but no more.

So, there is an increase in enzyme activity up to some level of concentration. After that, the enzyme is running at full speed.

Enzymes and Cellular Transport

How do enzymes relate to cell transport? The cells in your body are in constant demand of various compounds for various reasons, and these compounds are often created by enzymes before they can enter and exit your cells.

Your body needs ATP (energy) to play a guitar. How does it get that?

1. You eat mashed potatoes which are full of starch (a polysaccharide).
2. Amylase is used to break down starch into glucose.
3. Glucose is taken up into your cells by the protein insulin.
4. Glucose mixes with oxygen and goes through a series of reactions. 
5. At the end of this series, ATP Synthase creates ATP which gives your muscles the energy to strum.

_______________

Summary

Enzymes are proteins that serve as biological catalysts. 

Enzymes accelerate chemical reactions between different biological molecules. 

The molecules that the enzymes operate on are called substrates.

Each enzyme is very selective with regard to which process it speeds up.

Understanding Vectors and Vector Math

Physics Index

Where are we going with this? The information on this page relates to the skills needed to investigate and evaluate the graphical and mathematical relationship (using either manual graphing or computers) of one-dimensional kinematic parameters (distance, displacement, speed, velocity, acceleration) with respect to an object's position, direction of motion, and time.

Understanding Vectors and Vector Math

(Oh brother! What now?)

In THIS, the concepts of vectors were looked at "from a distance" and by example. Here, we'll try to get a little closer and start thinking more about the math… Examples seem like a good idea, though, so… Yeah…

Let's begin with this little reprise:

The study of objects in motion and forces acting upon them relies heavily on using vectors. Thus, having an understanding of vectors is very important. So… we should talk about this…

A vector is a concept connected to quantities that specifies a magnitude and a direction.  Answering many physics questions about the world around us best done by using vectors.

Representing Vectors

It is very, very common to draw diagrams showing how vector quantities are acting on an object. Usually, there will be some sort of reference thing… the horizon… the plane of a ramp… often, the x-y axis thingy. (Thingy? Really? That's the best you can do?)

Vectors, in the diagrams, are represented by arrows. 

• The direction that the arrow points indicates the vector's… direction.
• The length of the arrow represents its magnitude.

Vector arrows have a tail and a head. The pointy end is the head.

Strictly depicted, the length of the arrows should be drawn exactly in proportion to their lengths. So, a vector with a magnitude of 4 would be twice as long as one with a magnitude of 2 and half as long as one with a magnitude of 8. NOTE: any illustrations on this page are NOT strictly depicted!

Likewise, the angles should correctly represent the angle at which the vector operates on the object being observed.

Working With Vectors: The Big Picture

When more than one vector of any give quantity (e.g. force, velocity, acceleration) operates on the same object within some frame of reference, their effect combines. The the vector that results in the combination of each of the component vectors.

Component vector: Any individual vector having magnitude and direction within a given frame of reference.

Component vectors can be combined into a resulting vector (or the resultant vector).

What if you start with the resultant? Yeah, that can happen! 

A resultant vector can be broken down into its component vectors.

Working With Vectors: Graphical Conceptualization

Working with strictly depicted vector diagrams, all of the component vectors working on a single object can be rearranged such that they create a depiction of the resultant vector. 

To do this, any of the vectors can, IF THEIR ANGLE WITHIN THE FRAME OF REFERENCE DOES NOT CHANGE, be moved so that its tail connects to head of the second vector. All of the vectors in the system can be moved in this same manner. This only works if the moved vector remains parallel to its original direction. (That is the same as saying that the angle does not change.)

A line from the tail of the first vector to the head of the last vector represents the resultant vector.

Moving a vector so that its origin is in a different place, but without changing its direction or magnitude is called vector translation.

Finding a resultant vector by translating component vectors is a process that is sometimes called "The Triangle Method."

The blue vector is translated to the end of the green vector, and
the red vector is the resultant vector.

The order in which the vectors are rearranged does not matter. (This will be true when we look at the math process, too.) This is true combining vectors is essentially adding their effects, and since there's some fancy name (the commutative property) for math that says it doesn't matter what order we do addition.

Source

Also, since… all that about adding their effects… if vectors point in opposite directions, their effects reduce each other, even to the point of cancelling totally. This is easily observed when two vectors are operating on a single line.

Think tug-of-war; two force vectors are pulling in opposite directions. When evenly matched, both forces have the same magnitude, but in opposite directions. Hence, the effect of the force does not result in the flag moving.

So (jumping ahead to math approaches), when operating in opposite directions, one vector can be thought of as positive and the other negative. 

Working With Vectors: Math Processes

Mathematically, working with vectors begins with nearly trivial simplicity, then becomes more and more complex. The simplest situations involve vectors on a single line / axis. Next up are vectors at right angles. Finally, when the vector is some arbitrary angle to the axes, the math becomes most complicated.

Vectors On One Line

When vectors lay on a single axis, all that is necessary is to assign positivity and negativity to the directions. Left is negative, right is positive. Or right is negative, left is positive. Up is positive, down is negative. Something like that…

The resultant vector is the sum of the signed component vectors.

A box moves from a point of origin 10 meters left, then 4 meters right, then 2 meters left, then 3 meters right. Where is the box in relationship to the point of origin.

∆d = d1 + d2 + d3 + d4

Where left is positive and right is negative, 

d1 = 10 m

d2 = -4 m

d3 = 2 m

d4 = -3 m

∆d = (10 + (-4) + (2) + (-3)) m

∆d = 5 m left

Vectors At Right Angles To Each Other

In the case where more than one vector acts on an object and they are at right angles, the process is fairly easy. 

The first thing to do is create a diagram aligning the vectors with the vertical and horizontal axes (x and y). If the vectors are perpendicular, one of them will align with each axis.

Then, translate one of the vectors so that its origin moves to the head of the other one. 

The resultant vector will be the hypotenuse of the triangle formed. 

• Its magnitude can be found using the Pythagorean Theorem.
• Its angle can be found using arctan (inverse tangent).

If you have several vectors that act on the same line, you can combine them into a single resultant vector. Once you have two perpendicular vectors, you can find the resultant (as above).

vector is some arbitrary angle to the axes

MORE TO COME!

ATP Quick Look: Adenosine Triphosphate-Cellular Energy

Biology Index

Where are we going with this? The information on this page should increase understanding related to this standard:  Evaluate comparative models of various cell type…Evaluate eukaryotic and prokaryotic cells.

ATP Quick Look

Adenosine Triphosphate-Cellular Energy

(So… We're really doing this?)

https://www.britannica.com/science/adenosine-triphosphate

Okay… cells need energy… and… 

In animals, the mitochondrion creates it…

…in the form of adenosine triphosphate (ATP). It's actually a fairly easy concept, although the bio-chemistry behind it is fairly detailed. (Promises, promises!)

In plants, "ATP is synthesized in the thylakoid membrane of the chloroplast. The process is called photophosphorylation. The "machinery" is similar to that in mitochondria except that light energy is used to pump protons across a membrane to produce a proton-motive force" (Source 2021-10)

Cells need energy for a number of different functions (e.g. cell metabolism, transportation across membranes, moving muscles). 

Energy in cells is stored as lipids (fats) and is made ready for use as carbohydrates (sugars). The ready-to-use sugars, however, are further processed into ATP by the mitochondrion. "ATP then serves as a shuttle, delivering energy to places within the cell where energy-consuming activities are taking place" [1].

ATP has two main parts:

The first part is the adenosine part. Adenosine is made of the nitrogenous base, adenine plus a sugar called ribose. 

The triphosphate part is made of… three phosphates in a chain. 

It is this phosphate chain wherein the energy is stored.

Before we go any further, let's define some things.

ATP = adenosine triphosphate: an adenosine + 3 phosphates

ADP = adenosine diphosphate: an adenosine + 2 phosphates

AMP = adenosine monophosphate: an adenosine + 1 phosphate

and remember that adenosine is made of the nitrogenous base, adenine plus a sugar called ribose

So… what happens is this…

It's actually a cycle in which ATP gives off energy to become ADP or (sometimes AMP) and then later, becomes ATP again.

In the mitochondria, ATP is formed, and then shipped out to the cell to do some work. Where work needs to be done, one of the phosphates is broken off from the ATP.

Since energy is stored in chemical bonds and since the phosphate bond has a relatively impressive bonding energy, the breaking of the phosphate bond gives off a lot of energy—energy that the cell needs for the various functions mentioned earlier.

https://www.biologyonline.com/tutorials/biological-energy-adp-atp

Back in the mitochondria, energy from sugar (to keep it simple) is used to reform that phosphate bond. In this way ATP is prepared for the next occasion that it is needed.

The ATP --> ADP --> ATP --> ADP… cycle goes on and one. (Likewise, if it's a case of breaking two bonds to become AMP, it's a cycle.)

To say it another way…

…sugar gets "burned" to provide energy to jam a phosphate onto an ADP making it an ATP.

…ATP goes out into the cell from the mitochondria.

…one of the phosphate bonds breaks releasing energy to power cell functioning.

…repeat

That's it… As a quick look, this is how ATP serves as the source of energy for cells.

Granted, this leaves out a LOT of details. More can be learned from the linked resources and many, many others.

Sources and more information…

1. https://www.britannica.com/science/adenosine-triphosphate

https://www.biologyonline.com/tutorials/biological-energy-adp-atp

Overviewing Vectors

Physics Index

Where are we going with this? The information on this page relates to the skills needed to investigate and evaluate the graphical and mathematical relationship (using either manual graphing or computers) of one-dimensional kinematic parameters (distance, displacement, speed, velocity, acceleration) with respect to an object's position, direction of motion, and time.

Overviewing Vectors

(Oh brother! What now?)

The study of objects in motion and forces acting upon them relies heavily on using vectors. Thus, having an understanding of vectors is very important. So… we should talk about this…

A vector is a concept connected to quantities that specifies a magnitude and a direction.  Answering many physics questions about the world around us best done by using vectors.

Understanding by example…

Whereas distance traveled is just a number and a distance unit… The race car driver drove 500 miles to win the race… displacement is a number and a distance unit AND a direction.

The box moved 20 m to the left.

The boxed changed position ( ∆x ) by a magnitude of 20 m and in the direction of left.

Working in 2D motion, the concept of vectors was assumed when positive and negative values were assigned to thing happening in opposite directions. When motion was to the right and acceleration was to the left, their magnitudes were given different signs. Likewise for up and down.

EXAMPLE 1

Working with Directions on the SAME line.

A ball with an initial velocity of 9 m/s is thrown directly upward on a planet where acceleration due to gravity is 3 m/s². How long will it rise before stopping? 

Solving this is simple (making it a fitting example): 

Find t

Where 

vi = 9 m/s

a = 3 m/s²

vf = 0 m/s

and where

vf = vi + at

Before solving, we need to "vectorize" the quantities. What's positive and what's negative? So… 2nd round… 

Find t

Where 

vi = 9 m/s up

a = 3 m/s² down

vf = 0 m/s up

and where

vf = vi + at

Not done yet… We need get the directions worked out so that we can math them! It's a nit that we usually do mentally, but… 3rd round… 

Find t

Where up is positive 

 

vi = 9 m/s up

a = 3 m/s² down  = -3 m/s² up 

vf = 0 m/s up

and where

vf = vi + at

Now, we can solve… easy!

 

vf = vi + at

0 = 9 m/s + (-3 m/s² )(t)

-9 m/s = (-3 m/s² )(t)

3 s = t

While that solution is relatively intuitive (up and down are in opposite directions; naturally, the ball will slow down), others (that will emerge in more complex situations) require the rigor of the formality in the 3rd round.

Moving on into 2 dimensions, we'll stick with displacement as the quantity… 

EXAMPLE 2

Pizza Delivery Route as Vectors

Suppose a city laid out in perfect blocks (like graph paper where the lines are roads).

Okay, at point A is some dude or dudette who wants to get to point B. To do so, travel must result in TWO displacements (ish… Just hang in here as we develop the concept.)

The TOTAL displacement to the right has to be 3 blocks.

The TOTAL displacement up has to be 3 blocks, also.

Okay… suppose…

A pizza deliver robot is at point A. It sets out to delver a pizza by moving as follows:

1 block right…

2 blocks up…

1 block right…

1 block up…

1 block right.

Does it reach the customer at point B?

If you trace the path, you'll find out that, indeed, the pizza was delivered!

Okay… Let's ruin this…

Think x axis and y axis… meaning that (normally) right is positive and up is positive.

So, the total displacement is the total change in position… Let's go with 

∆P

Therefore conceptually

∆P = ∆x + ∆y (ish, not exactly, but we're getting there…

So, ∆x is how much did it move on the x axis. ∆y is how much did it move on the y axis.

Let's grab those movements from above… and sort them…

2 blocks up

1 block up

1 block right

1 block right

1 block right

So, up is y and right is x… 

∆x = 1 block + 1 block + 1 block

∆y = 2 blocks + 1 block

So, the total motion is (sticking with intuition, not formal math)

∆P = 3 blocks up + 3 blocks right

or 

∆P = 3 blocks(y) + 3 blocks(x)

What just happened?

We added vectors.

We took all of the x vectors and added them, then we took all of the y vectors and added them. Bam!

Okay, so… what if we wanted to get a little more formal?

We can do that…

Component vector: Any individual vector having magnitude and direction within a given frame of reference.

Component vectors can be combined into a resulting vector (or the resultant vector).

What if you start with the resultant? Yeah, that can happen! 

A resultant vector can be broken down into its component vectors.

Now, some caveats… common sense that needs to be outed… 

1. Within a frame of reference (for simplicity, let's say the x-y axis frame of reference), component vectors have magnitudes ONLY on one axis. 

2. The frame of reference will assign positive and negative to some direction on each axis; usually, up on the y axis is positive and right on the x axis is positive.

 

fig 3

3. The resultant vector can be described as the sum of the x components and the sum of the y components. 

 

4. However, it can also be described by its own (resultant) magnitude and an angle with respect to one of the axes (frequently, with respect to the x axis).

Returning to the pizza deliver (fig 3) robot, the blue line represents the resultant vector. 

While we can say that the total displacement is…

3 blocks right and 3 blocks up

we could also go with the x-y axis thing and say…

∆x = 3; ∆y = 3

Woh… that got mathy fast!

or we could say:

The resultant vector is some magnitude at some angle to the x axis. 

Using the Pythagorean theorem, the blue line has a length that is the square root of 18. Geometry tells us that the angle of a triangle with two equal sides is 45°.

So…the resulting vector is 

√18 = blocks long in a direction that is 45° above the x axis.

Enough, already… really! What happened to the pizza?

5. When "doing the math" you can't combine vectors of different quantities. For instance, you can't combine velocity vectors with acceleration vectors directly. They operate on an object differently. 

6. Many different paths to deliver the pizza can end up at the same place. The robot could go 10 to the right, 10 up, then 7 left and 7 down. The sum of these component vectors would yield the same displacement:

∆x = 3; ∆y = 3 

 

EXAMPLE 3

The 1100 mile per hour pitch.

In this example we are emphasizing the frame of reference. And… the math will be scant… so…

A really good baseball pitcher can hurl a ball at around 100 mph. 

The earth rotates, completing approximately 24,000 miles in approximately 24 hours; hence, a point on the surface of the earth has a velocity of 1000 mph.

So, some alien orbiting the sun at the same rate as planet earth is looking through a telescope tuned to ONLY see the baseball. 

From the frame of reference where the sun is not moving, then the velocity of the baseball (if thrown with the rotation of the earth is the sum of the pitch plus the velocity of a point on the surface of the earth.

Back up some… The sun is moving through the galaxy which is moving through the universe. Assuming that the universe is not moving, the velocity of the baseball is the sum of…

the pitch

the rotation of the earth

the motion of earth around the sun

the motion of the sun moving through the galaxy

and the motion of the galaxy through the universe…

Each of those component velocities could be added together to find the resultant velocity of the baseball.