EXAM 2: Metabolism

Question 1

Metabolism

Answer 1

Chemical processes that occur within a living organism in order to maintain life

Question 1

Anabolism

Answer 1

The synthesis of complex molecules from simpler ones

Question 2

Catabolism

Answer 2

The breakdown of complex molecules into simpler ones

Question 3

Oxidoredeuctase

Answer 3

A class of enzyme that catalyzes oxidation reduction reactions

Question 4

Transferase

Answer 4

A class of enzyme that catalyzes the transfer of chemical groups between molecules

Question 5

Hydrolase

Answer 5

A class of enzyme that catalyzes hydrolysis of molecules

Question 6

Ligase

Answer 6

A class of enzyme that catalyzes the joining of two large molecules by forming a new chemical bond

Question 6

Lyase

Answer 6

A class of enzyme that catalyzes the breaking of various chemical bonds by means other than hydrolysis and oxidation

Question 7

Isomerase

Answer 7

A class of enzyme that catalyzes the conversion of a molecule from one isomer to another

Question 8

Enzyme

Answer 8

A substance produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction

Question 9

Apoenzyme

Answer 9

An enzyme that requires a cofactor but does not have one bound

Question 10

Holoenzyme

Answer 10

An apoenzyme together with its cofactor(s)

Question 11

Allosteric site

Answer 11

Relating to the alteration of a protein’s activity through the binding of an effector molecule at a specific site (that is not the active site)

Question 12

Define the terms metabolism, catabolism and anabolism and explain how they relate to each other

Answer 12

1. Define all three terms!
2. Relation
   Metabolism
   - Catabolism and anabolism are types of metabolism
   - Every cell acquires nutrients

Catabolism
- Simple units can be used in anabolic reactions
- releases ATP

Anabolism
- use units broken down from catabolism
- uses ATP

Question 13

Discuss oxidation-reduction reactions. Explain how electrons are involved. List examples

Answer 13

• OIL RIG lose/gain electrons
• Transfer of electrons from an electron donor to an electron acceptor
• Reactions always occur simultaneously
• Electron carriers that carry electrons from one molecule to the next
  Three important electron carriers:
  1. NAD+
  2. NADP+
  3. FADH2
  example: A + B—-> A+ and B-

Question 14

Describe the function and role of enzymes in the cell. Describe common features and how they relate to function.

Answer 14

• Enzymes are organic catalysts & increase the likelihood of a reaction
• They lower the activation energy of a rxn

6 categories of enzymes (common features)
Oxidoreductase
Transferase
Hydrolase
Lyase
Isomerase
Ligase

Question 15

What are inhibitors?
Discuss methods of enzyme inhibition.

Answer 15

• Inhibitors: Substances that block enzyme activity

Competitive inhibitors
- Shaped such that they fit into an enzyme’s active site and prevent the substrate from binding
- They can bind permanently or reversibly to an active site; reversible competition can be overcome by increase in substrate concentration

Noncompetitive inhibitors
- Do not attach to the active site but instead bind to an allosteric site on the enzyme
- This alters the shape of the active site so that enzymatic activity is reduced or eliminated

Feedback inhibition
- The end-product of a metabolic pathway allosterically inhibits the initial step, shutting down the pathway.

Question 16

Describe the process cellular respiration, including glycolysis, the Krebs cycle and the electron transport chain.

Answer 16

CR: a metabolic pathway where glucose is catabolized into ATP energy

1. Glycolysis
   - in cytoplasm
   - requires no Oxygen
   in: A 6-carbon glucose
   out: Net gain of 2 ATP, 2 NADH, and 2 pyruvic acid molecules
2. Pyruvate Oxidation (acteyl co-A)
   - mitochondrial matrix
   in: 2 pyruvic acid molecules
   out:2 acetyl-CoA, 2 CO2, 2 NADH
3. Krebs Cycle
   - Prok: cytosol, Euk: mit. matrix
   - requires Oxygen
   in: 2 acetyl-CoA, FAD+, NAD+, ADP + Pi
   out: 2 ATP, 2 FADH2, 6 NADH, 4 CO2
4. ETC
   - Prok: cell membrane, Euk: inner mit. membrane
   - requires Oxygen
   in: FADH2, NADH, O2, ADP + Pi
   out: ~34 ATP, NAD+, FADH

Question 17

Compare and contrast cellular respiration and fermentation. Discuss the steps involved in each

Answer 17

Glucose catabolized by two processes
Cellular respiration:
- List out all the steps
- Pyruvic acid is completely oxidized to make ATP by redox reactions

Fermentation:
- Yields far less ATP but still generates the necessary NAD+ electron carriers.
- Cells require constant source of NAD+
- Provide cells with alternate source of NAD+
- Uses an endogenous electron acceptor
- Does not fully oxidize glucose
- Doesn’t include ETC or Krebs
- Conversion of pyruvic acid into other organic compounds

Question 18

Discuss commercial products produced by fermentation process

Answer 18

CO2, ethanol - wine, beer
Acetone- nail polish remover

Question 19

Identify when oxidative phosphorylation and substrate level phosphorylation occur during glucose metabolism

Answer 19

Substrate level phosphorylation: occurs during glycolysis, the Krebs cycle, and fermentation.

Oxidative phosphorylation: the ETC (chemiosmosis)