Chapter 3-Cell Metabolism

Question 1

What is an Anabolic reaction?

Answer 1

An anabolic reaction is the production of larger molecules from smaller reactants. Requires energy.

Question 2

What is the first and second law of thermodynamics?

Answer 2

The First Law of Thermodynamics states energy cannot be destroyed or created, only transformed.

The Second Law of Thermodynamics states with every transfer or transformation of energy, some useable energy is released as heat.

Question 3

What is an endergonic reaction?

Answer 3

An Endergonic reaction is a chemical reaction that require an input of energy. Products contain more free energy than the reactants. Energetically uphill.

Question 4

What is an exergonic reaction?

Answer 4

An Exergonic reactions is a chemical reaction that release energy. Products will have less free energy than the reactants. Energetically downhill.

Question 5

What the difference between an exergoni and an endergonic reaction?

Answer 5

Exergonic reactions tend to proceed spontaneously

Endergonic reactions do not proceed spontaneously, only when energy is put into them.

Question 6

How do endergonic reactions in physiology occur?

Answer 6

Energy from the environment (food) is broken down in exergonic reactions to drive the endergonic reactions in our bodies

Question 7

What is activation energy

Answer 7

Activation energy is the energy required for the reactants to engage in a reaction. Most molecules lack the activation energy needed for a reaction to occur. Activation energy can take the form of heat (molecules colliding together). Activation energy barrier can also be surmounted through catalysts

Question 8

What are enzymes?

Answer 8

Enzymes are a class of proteins that serve as biological catalysts. Catalysts are chemicals that:
Increase the rate of a reaction
Are not changed by the reaction (so can be used repeatedly)
Have no effect on free energy of reactants or products.
In enzymatic reactions, reactants are called substrates

Question 9

How are enzymes named

Answer 9

The first enzymes discovered were given arbitrary names. An international committee later decided to end all enzymes with the suffix –ase.
They also decided to make the first part of the name apply to the function of the enzyme.
Phosphatases remove phosphate groups.
Synthetases catalyze dehydration synthesis.

Question 10

What is enzyme activity?

Answer 10

enzyme activity is measured by the rate at which substrate is converted to product
Influenced by:
Concentration of enzyme and substrate
Enzyme-substrate affinity
Temperature
pH
Regulation by modulators (allosteric regulation)
Covalent regulation (regulation by chemical groups)
Feedback inhibition
Feedforward activation

Question 11

Who will temperature affect the enzymatic reaction rates?

Answer 11

An increase in temperature will increase the rate of reactions until the temperature reaches a few degrees above body temperature. At this point, the enzyme is denatured. (Can be caused by fever)

Question 12

How will pH effect the enzymatic reaction rates?

Answer 12

Enzymes exhibit peak activity within a narrow pH range = optimum pH.
Due to changes in enzyme conformation
Optimum pH typically reflects the pH of the fluid the enzyme is found in: Stomach vs. saliva

Question 13

What is a metabolic pathway?

Answer 13

Most reactions are linked together in a chain (or web) called a metabolic pathway.
These begin with an initial substrate and end with a final product, with many enzymatic steps along the way.

Question 14

What is cellular respiration?

Answer 14

Cellular respiration AKA Glucose Oxidation is how we get energy to do work. Provides ATP (energy) for cellular processes
Three main stages:
Glycolysis (cytosol)
Krebs Cycle (mitochondrial matrix)
Oxidative Phosphorylation (across inner mitochondrial membrane)

Question 15

What is glycolysis?

Answer 15

First step in catabolism of glucose
Happens in cytoplasm and does not require oxygen
Occurs in the cytoplasm of the cell. Does NOT require oxygen.

For every molecule of glucose:
2 pyruvate created
2 ATPs consumed, 4 ATPs created, net 2 ATPs
2 NAD+ converted to 2 NADH
(glucose + 2 NAD+ + 2 ADP + 2 Pi —- 2 pyruvate + 2 NADH + 2 H+ + 2 ATP)

Question 16

What is glycogenesis?

Answer 16

Most body cells can’t store much glucose because it will pull water into the cell via osmosis.
Glucose is stored as a larger molecule called glycogen in the liver and skeletal muscles.
Glycogenesis is the process of combining glucose molecules into glycogen molecules for storage.

When the cell needs glucose, it breaks glycogen down again into glucose. (Glycolysis)

Question 17

What is the linking step in cellular respiration.

Answer 17

The linking steps requires a pyruvate, CoA, and a NAD+ molecules and reacts to produce Acetyl CoA, CO2, NADH+H+

Question 18

SO, what happens from glycolysis to the kreb cycles?

Answer 18

Pyruvate leaves the cytoplasm from glycolysis and enters the matrix of the mitochondria.
Carbon dioxide is removed to form acetic acid.
Acetic acid is combined with coenzyme A to form acetyl CoA.
1 glucose makes 2 molecules acetyl CoA
Because, remember, 1 glucose was broken down into 2 pyruvates during glycolysis.

Question 19

What is the overall reaction of the krebs cycle?

Answer 19

Acetyl CoA + 3NAD+ + FAD + ADP + Pi+ 3H2O —– 2CO2 + 3NADH +3H+ + FADH2 + ATP + CoA

Question 20

What are the product at the end of the krebs cycle?

Answer 20

For each glucose (2 turns of the Kreb Cycle, glycolysis, and linking step):
10 NADH
2 FADH2
4 ATP
6 CO2

(Remember, 2 NADH and 2 ATP from glycolysis, and 2 NADH from the linking step)

Question 21

What is oxidative phosphorylation?

Answer 21

Also called the electron transport chain
Occurs across inner mitochondrial membrane. 90% of ATP produced from cellular respiration occurs in this step.
Electron transport molecules pass the electrons down a chain, with each being reduced and then oxidized.
This is an exergonic reaction, and the energy produced is used to make ATP from ADP.
ADP is phosphorylated.

Question 22

What is chemiosmotic coupling?

Answer 22

Energy released through electron transport chain pumps H+ ions into intermembrane space.
H+ ions flowing back into the matrix down their concentration gradient power ATP synthase to make ATP

Question 23

What is the overall reaction of oxidative phosphorylation?

Answer 23

10NADH + 10 H+ + 2FADH2 + 34ADP + 34 Pi + 6O2 — 10NAD+ + 2 FAD + 12H2O + 34 ATP

Question 24

What is the theoretical yield of ATP during cellular respiration?

Answer 24

Glycolysis and the Krebs Cycle yield 4 ATP.
These numbers are constant.
Oxidative phosphorylation in electron transport yields varying amounts of ATP, depending on the cell and conditions.
Theoretically, each NADH yields 3 ATP and each FADH2 yields 2 ATP.
Theoretical ATP yield is 36-38 per glucose.

Glycolysis and the Krebs Cycle yield 4 ATP.
These numbers are constant.
Oxidative phosphorylation in electron transport yields varying amounts of ATP, depending on the cell and conditions.
Theoretically, each NADH yields 3 ATP and each FADH2 yields 2 ATP.
Theoretical ATP yield is 36-38 per glucose.

Question 25

What happenes when our tissues are low on oxygen?

Answer 25

Saved by the Lactic Acid Fermentation Cycle
No ATP gets made directly by this process.
Does not require O2
Provides NAD+ so that glycolysis can continue to generate 2 ATP for every molecule of glucose that gets broken.

Question 26

What is a catabolic reaction?

Answer 26

A catabolic reaction breakdowns larger molecules into smaller molecules. Releases energy.

Question 31

What are the inputs and output and where does everything happen in cellular respiration?

Answer 31

Glycolysis
Cytosol
Input: 1 glucose
Out 2 pyruvates, 2 ATP, 2 NADH

Linking Step
In mitochondria; matrix 
Oxygen required 
Input: pyruvates 
Outputs: 2 acetylCoA, 2 NADPH,

Krebs Cycle 
Mitochondrial matrix 
Oxygen required
In: 2 AcetylcoA 
Out: 6 NADPH's, 2 FADH2, 2 ATP's 

Oxidative phosphorylation 
Happens along the inner mitochondrial membrane 
Oxygen required 
In: Electron carried by NADH and FADH2
Out: H2O, 34-36 ATP