Chapter 5 - Cellular Function

Question 1

How is bioluminescence produced?

Answer 1

Light is emitted via a chemical reaction that converts chemical energy into visible light catalyzed by luciferase enzymes.

Question 2

What is bioluminescence used for and where is it found?

Answer 2

To warn, camouflage, communicate, navigate, mating, attracting prey.
Usually found in the deep sea, rarely seen on land (fireflies and some fungi).

Question 3

What is the fluid mosaic model?

Answer 3

Membranes (phospholipid bilayers) consist of a mosaic of diverse protein molecules embedded within a fluid phospholipid bilayer.

Question 4

________ and __________ alter the behaviour of membranes.

Answer 4

Double Bonds = a more fluid membrane due to kinks that stop it from packing tightly.
Cholesterol = stabilizes membrane at higher temps, keeps it fluid at lower temps.

Question 5

List the 6 basic functions of proteins?

Answer 5

Maintain cell shape; coordinate cell changes via attachments cytoskeleton/extracellular matrix; receptors for chemical messengers (intercellular communication); enzymes that catalyze reactions; glycoproteins for cellular recognition of self and intruders; and transport of substances across the membrane.
MCRERT

Question 6

What do we mean when we say a cell is selectively permeable?

Answer 6

They allow some substances to cross
more easily than others and block the passage of some substances altogether.

Question 7

Why do membranes form spontaneously?

Answer 7

Phospholipids, when mixed with water, will automatically form bilayers surrounding water, forming water-filled bubbles.

Question 8

What is diffusion and how does it differ from active transport?

Answer 8

The movement of a substance down its concentration gradient from an area of higher concentration to an area of lower concentration.
It requires no energy.

Question 9

What happens to diffusion when the concentration on both sides of the membrane are equal?

Answer 9

Diffusion is still occurring across the membrane, but there is no net change in the concentration. The movement in both directions is equal.

Question 10

What is facilitated diffusion? Does it require energy? Which molecules require facilitated diffusion?

Answer 10

The passive transport of a substance across a membrane through a specific transport protein, down its concentration gradient. Does NOT require energy.
Used for ionic or polar molecules that diffuse too slowly or not at all.

Question 11

Do substances move up or down their concentration gradient?

Answer 11

Down their concentration gradient from an area of higher concentration to an area of lower concentration.

Question 12

Do substances diffuse independently of each other?

Answer 12

YES
They move independently of each other down their own specific concentration gradients.

Question 13

What is aquaporin?

Answer 13

A transport protein used for facilitated diffusion of water. Creates a channel for water that can allow up to 3 billion water molecules to pass per second for a single aquaporin!

Question 14

What is the primary way water gets into and out of cells?

Answer 14

Osmosis! (a type of diffusion)

Question 15

Define osmosis.

Answer 15

Water diffusing across membranes from an area of higher water concentration to an area of lower water concentration.

Question 16

Define tonicity.

Answer 16

The ability of a solution surrounding a cell to cause that cell to lose or gain water, mainly depending on the concentration of solutes that cannot cross the plasma membrane.

Question 17

Define isotonic. How are water and a cell’s size affected by this type of solution?

Answer 17

(iso = same, tonos = tension) A solution has the same concentration inside and outside of the cell (aka isosmotic). There is no net movement of water across the membrane. The cell does not increase or decrease in size.

Question 18

Define hypertonic.

Answer 18

(hyper = above) In a hypertonic solution there is a higher concentration outside of the cell relative to the inside of the cell.

Question 19

Define hypotonic.

Answer 19

(hypo = below) In a hypotonic solution there is a lower concentration outside of the cell, relative to the inside of the cell.

Question 20

What will happen to a blood cell placed in distilled water (hypotonic)?

Answer 20

Water will move into the cell by osmosis, causing it to grow and possibly lyse or burst.

Question 21

What will happen to a red blood cell placed in a very salty (hypertonic) solution?

Answer 21

Water will move out of the cell by osmosis, causing cells to shrivel/shrink.

Question 22

How do plant (+ prokaryotes and fungi cells) and animal cells respond differently when placed in hypotonic solutions?

Answer 22

Both will swell while intaking water but the plant cell does not burst (because of the cell wall). Being swollen (turgid) is normal for plants.

Question 23

Define osmoregulation.

Answer 23

This term describes how cells
control excessive water uptake or loss to maintain homeostasis.
i.e. gills and kidneys of freshwater fish (think salmon!).

Question 24

Define turgid and plasmolysis.

Answer 24

T: A plant cell full of water that is very firm.
P: Water rushing out of plant cells in a hypertonic environment (shrivelling).

Question 25

Where does active transport get its energy from? What is actually transferred to the transport protein to give it energy?

Answer 25

Adenosine triphosphate (ATP).
A phosphate group which causes it to change shape so the solute is released on the other side of the membrane.

Question 26

In active transport do substances move up or down their concentration gradient?

Answer 26

Cells expend energy to move a solute against/up its concentration gradient (i.e. from a lower to higher concentration).

Question 27

Does endocytosis moves substances into or out of cells? How?

Answer 27

ENdocytosis is a way to get large substances ENtered into the cell. (from outside to the inside).
Plasma membrane forms a vesicle surrounding substances which becomes a vesicle within the cell.

Question 28

Does exocytosis move substances into or out of cells? How?

Answer 28

EXocytosis is a way to get large substances EXported from the cell (from the inside to the outside).
Vesicle (from GA) becomes a part of the plasma membrane and dumps contents outside.

Question 29

Name the three kinds of endocytosis that we looked at. What’s the basis of how they all work?

Answer 29

Phagocytosis (Cellular Eating)
Pinocytosis (Cell Drinking)
Receptor-Mediated Endocytosis.
An in-folding and then pinching off of the plasma membrane into an internal vesicle

Question 30

How does phagocytosis differ from pinocytosis?

Answer 30

Ph.: Membrane arms (pseudopodia) hug food and enclose it in a large vesicle/vacuole which meets a lysosome and is digested.
Pi.: Same idea but much smaller vesicle and takes in any solute in the extracellular matrix. No digestion.

Question 31

How is receptor-mediated endocytosis similar/different from pinocytosis?

Answer 31

Similar vesicle size and lack of digestion.
RME is very selective due to a protein coating on the plasma membrane that binds to particular molecules. Includes coated pits and vesicles.

Question 32

Draw a diagram or series of diagrams showing your understanding of phagocytosis.

Answer 32

Draw and review lecture notes page 8.

Question 33

What is energy?

Answer 33

The capacity to cause change or perform work.

Question 34

What are the two basic forms of energy? Define each.

Answer 34

Kinetic Energy = the energy of motion.
Potential Energy = the energy that matter possesses as a result of its location or structure.

Question 35

Heat and light are forms of ____________ energy.

Answer 35

Kinetic

Question 36

The energy available to bicycle on top of a hill or that found within a molecule of glucose are forms of ____________ energy.

Answer 36

Potential.

Question 37

What is chemical energy?

Answer 37

The potential energy available for release in a chemical reaction and is the most important type of energy for living organisms.

Question 38

Thermodynamics is the study of:

Answer 38

(thermos = heat; dynamics = work)
The study of energy transformations. Energy can be converted into different forms (heat, electrical, mechanical, chemical energy).

Question 39

What is the First Law of Thermodynamics?

Answer 39

Law of energy conservation.
Energy can be transferred and transformed, but it cannot be created or destroyed.

Question 40

What is the Second Law of Thermodynamics?

Answer 40

The entropy law.
The entropy (chaos!) of the universe constantly increases.

Question 41

Cars convert 25% of the gasoline’s energy to do work; cells are about 34% efficient, using about 34% of the glucose’s energy to do work. Where does the majority the energy go?

Answer 41

🔥 HEAT🔥
With every conversion, some of the useful energy is lost and is often converted to heat.

Question 42

How are energy transformations different from transformations of physical matter?

Answer 42

Unlike physical matter which can be reshaped over and over again, energy, once dissipated, can never be re-concentrated. Increase in entropy is irreversible.

Question 43

Regarding energy, what is the primary difference between exergonic and endergonic reactions?

Answer 43

Exergonic reactions are chemical reactions that release energy (meaning the products have
less chemical energy than the reactants).
Endergonic reactions require an input of energy and store energy (products have more chem. energy).

Question 44

If the energy of the products is less than the energy of the reactants, the reaction must be ______. Examples?

Answer 44

Exergonic.
Burning wood and cellular respiration.

Question 45

If the energy of the products is more than the energy of the reactants, the reaction must be _______ . Examples?

Answer 45

Endergonic.
Photosynthesis (uses the sun’s energy)

Question 46

What is metabolism?

Answer 46

The total of all the thousands of exergonic and endergonic reactions carried out by every living cell.

Question 47

What is a metabolic pathway?

Answer 47

A series of chemical reactions that either builds a complex molecule (anabolism) or breaks down a complex molecule (catabolism) into simpler compounds.

Question 48

What do we mean by energy coupling? Is energy coupled directly?

Answer 48

The use of energy released from exergonic reactions to drive essential endergonic reactions. ATP is key.
No, energy can be coupled from one reaction to a completely different reaction

Question 49

What is ADP and ATP? How are they related (thru which reaction)?

Answer 49

Adenosine Triphosphate (A-3-P) = adenine (nitrogenous base) + ribose (sugar) + 3 phosphates (- charge so they’re unstable/reactive).
ATP loses one phosphate thru hydrolysis to become adenosine diphosphate + energy.

Question 50

What is phosphorylation?

Answer 50

The transfer of a phosphate group (usually from ATP) to another molecule. This energizes the molecule so it can be used later in cellular work.

Question 51

What reactions and products does the cycle of ATP/ADP include?

Answer 51

Hydrolysis releases energy and turns ATP to ADP + P. The energy can power endergonic reactions.
ADP + P can later be used to create more ATP through phosphorylation (which uses energy from glucose).

Question 52

What are 3 types of cellular work? How is phosphorylation related to each?

Answer 52

Chemical - P provides energy for endergonic synthesis.
Mechanical - P causes muscle protein to change shape and contract.
Transport - P causes trans. proteins to change shape and release solutes through membranes.

Question 53

What is the energy barrier of a chemical reaction called? How does it work?

Answer 53

Activation Energy (EA) - the energy that must be absorbed by reactants to weaken the bonds so that they can break and new bonds can form

Question 54

What do enzymes do to the energy barrier of a chemical reaction? How does this affect reactions?

Answer 54

Enzymes lower the energy of activation required to initiate the reaction so the reaction can happen at a much faster rate.

Question 55

Do enzymes change the energy of reactants, products or the energy difference of the actual reaction?

Answer 55

No, they just lower the activation energy of the reaction, everything else stays the same.

Question 56

What is an enzyme?
What is a substrate?

Answer 56

E: Molecules (usually proteins, sometimes RNA) that function as biological catalysts.
S: A specific substance on which an enzyme acts.

Question 57

What is an active site on an enzyme? What happens to the active site if the protein becomes denatured?

Answer 57

Where a substrate binds via a weak chemical bond, typically in a pocket or groove on the enzyme’s surface.
Denatured proteins lose their shape and therefore their function.

Question 58

Can an enzyme act on any substrate? Why or why not?

Answer 58

An enzyme is very specific to its substrate and the reactions it catalyzes. As a protein, the 3-D shape of an enzyme determines, in part, its specificity. The properties of the amino acid R groups are also a factor.

Question 59

Are enzymes used up in reactions?

Answer 59

No. As catalysts, they increase the rate of chemical reactions without being consumed by the reactions. It can be reused!

Question 60

How is an enzyme’s activity/function affected by its environment?

Answer 60

Enzymes have optimal pH, salinity (saltiness), and temperature ranges where they’re most efficient.
Increased concentration of substrate can increase the rate of enzymatic reactions up to the saturation point.

Question 61

What is a cofactor and how does it differ from a coenzyme?

Answer 61

Cofactor (i.e. Zn, Fe, Cu) – a non-protein molecule or ion that is required for the proper functioning of an enzyme.
Coenzyme (i.e. folic acid, riboflavin, niacin, vitamins kinda) - cofactors that are also organic molecules.

Question 62

Chemicals that interfere with an enzymes ability to function are called __________. Is this interference permanent?

Answer 62

Inhibitors
It depends on the strength of the bond between inhibitor and enzyme. When it is weak, it is often reversible. Poisons often create strong bonds.

Question 63

What is the difference between competitive and non-competitive inhibitors?

Answer 63

CI: binds to the enzyme’s active site and competes with the substrate.
NCI: binds to the enzyme at another location (the allosteric site) and changes the shape of the active site.

Question 64

An inactive form of an enzyme that will eventually be converted into an active enzyme is referred to as a _______. Why are they made like this?

Answer 64

Proenzyme
To protect the cells (i.e. digestive enzymes become active once in the acidic stomach environment so they don’t digest the cells that make them)

Question 65

What is feedback inhibition? Why is it important?

Answer 65

Metabolic control where the product of a metabolic pathway acts as an inhibitor of an enzyme within the pathway. Shuts off the pathway once enough product is produced so energy isn’t wasted overproducing.

Question 66

What vegetable can help fight cancer? Why? How should it be prepared?

Answer 66

Raw veggies such as broccoli (especially broccoli sprouts).
Sulforaphane, an antioxydent.
Steamed for 3-4 minutes (not boiled).

Question 67

How does Advil (Ibuprofen) work?

Answer 67

It inhibits the enzyme that produces prostaglandins (molecules that increase pain and cause swelling or inflammation). Lots of other drugs are also enzyme inhibitors.