Metabolism

Question 0

Metabolic pathways

Answer 0

Metabolic reactions are organized into pathways, each step being catalyzed by an enzyme.
Starting molecule -> B -> C -> Product

Question 1

Metabolism

Answer 1

Sum of all of an organism’s chemical processes.

Question 2

What are the two types of metabolic pathways?

Answer 2

Catabolic and anabolic

Question 3

Catabolic pathways

Answer 3

-Release energy
-Break down complex molecules into simpler ones
Eg. cellular respiration: breaks down glucose into CO2 and water, provides energy for the production of ATP.

Question 4

Anabolic pathways

Answer 4

-Consume energy
-Build complex molecules from simpler ones
Eg. photosynthesis: synthesizes glucose from CO2 & water.
-Synthesis of macromolecules: released energy by catabolic pathways is used to drive anabolic pathways.

Question 5

Energy

Answer 5

• Ability to do work
• Kinetic or potential
• Can be transformed from one type to another

Question 6

Kinetic energy

Answer 6

Energy of motion

Question 7

Potential energy

Answer 7

Stored energy that matter possesses due to location or structure
eg. chemical reaction, diffusion, concentration (active transport)

Question 8

Thermodynamics

Answer 8

Study of energy transformation

Question 9

First law of thermodynamics

Answer 9

Energy can be transferred or transformed but it cannot be created or destroyed

Question 10

Second law of thermodynamics

Answer 10

Every energy transformation makes the world more disordered.
-Heat is the most random energy.

Question 11

Free energy

Answer 11

Portion of a system's energy that can do work.
G=H-TS
H, total energy of the system (enthalpy)
T, temperature
S, entropy (measure of disorder)

Question 12

Chemical reactions and energy

Answer 12

Change in free energy
delta G = delta H - T delta S
delta G = Gproducts - Greactants

Question 13

Two kinda of chemical reactions

Answer 13

Spontaneous & nonspontaneous

Question 14

Spontaneous chemical reactions

Answer 14

Exergonic (energy coming off system), delta G is negative.

Net release of energy (products have less energy)

Question 15

Nonspontaneous chemical reactions

Answer 15

Endergonic, delta G is positive
Requires input of energy
If a chemical reaction is endergonic, then the reverse must be exergonic

Question 16

Equilibrium

Answer 16

A+B↔️C+D

System cannot do work, cells at equilibrium are dead.

Question 17

Metabolic disequilibrium

Answer 17

Product is removed, prevents equilibrium from occurring.

The product becomes reactant for other metabolic pathways.

Question 18

Adenosine triphosphate (ATP)

Answer 18

Powers cellular work:

• Mechanical: breaking of cilia, muscle contraction, chromosome movements.
• Intracellular transport: Na, k-ATPase
• Chemical: polymerization
• Within the cell: hydrolysis of ATP is coupled to endergonic reactions, transfers phosphate group from ATP to another molecule.

Question 19

Structure of ATP

Answer 19

1. Adenine (nitrogen base)
2. Ribose (a five-carbon sugar)
3. Three phosphate groups
   (phosphate bonds are unstable, negative energy)
   ATP+H2O->ADP+Pi+energy

Question 20

Enzymology

Answer 20

• Enzymes are biological catalysts
• Most are proteins
• Not consumed by the reaction
• Speed up the metabolic rate of reactions by lowering energy barriers

Question 21

Chemical reactions

Answer 21

Involve bond breaking and bond making.

1) Transition state: molecules are unstable, reactants must absorb energy to reach this state (activation energy Ea)
2) Reaction occurs and energy is released as new bonds are formed

Question 22

Enzymes

Answer 22

Catalyze the conversion of substrate (reactants) to products.
E+substrate-> ESubstrate -> E + products

Question 23

Active site

Answer 23

• Pocket or groove in the protein’s surface, formed by a few amino acids.
• Binding of substrate causes a change in enzyme structure (induced fit)

Question 24

Allosteric enzymes

Answer 24

• Involved in regulation of metabolic pathways
• Comprised of two or more polypeptides, each with its own active site.
• Allosteric site (is not the active site) usually located where the polypeptides join.
• Two conformations: active and inactive.

Question 25

Allosteric enzyme Activation & inhibition

Answer 25

• Binding of the regulator stabilizes active form

- Binding of the regulator stabilizes inactive form

Question 26

Regulators

Answer 26

• Molecules that bind weakly to the allosteric site.
• Behave like reversible noncompetitive inhibitors.
• Often inhibitors & activators are similar in shape and compete for allosteric site.

Question 27

Phosphofructokinase

Answer 27

• Found in pathway of glycolysis.
• ATP is inhibitor (feedback: what is produced goes back to beginning of the chain and stops it).
• AMP activation
• Both bind at allosteric site

Question 28

Threonine deaminase

Answer 28

• Involved in production of isoleucine (amino acid)
• Feedback: end product acts as inhibitor (of activity and the pathway)
• Isoleucine binds allosterically

Question 29

Cooperativity

Answer 29

• Activation if enzyme activity
• Enzymes are comprised of more than one polypeptide
• Substrate binding to the active site of one subunit induces a conformational change in all subunits

Question 30

Mechanism to lower activation energy (4)

Answer 30

• Correct orientation of substrates
• Induced fit may distort the substrate’s chemical bonds
• Active site may provide a microenvironment for a specific reaction
• Side chains of the amino acid at the site may participate directly in the reaction.

Question 31

Rate of reaction

Answer 31

Dependent on concentration of the substate (if low, rate is low). If high, all active sites are engaged (saturation)

Question 32

Cofactors or coenzyme

Answer 32

Require additional, nonprotein molecules to function.

-Coenzymes: organic molecules, derived from vitamins.

Question 33

Enzyme inhibition

Answer 33

• Competitive: resemble substrate, bind at active site. overcome by increasing substrate concentration
• Non competitive: bind to another part, changes shape.