Enzymes and Cell Respiration

Question 1

Enzymes?

Answer 1

A globular protein that increases the rate of biochemical reactions by lowering the activation energy

Question 2

Metabolism?

Answer 2

Complex network of interdependent and interacting chemical reactions occurring in living organisms

Question 3

Active site?

Answer 3

Region on the surface of the enzyme to which substrates bind to and start a reaction

Question 4

Substrates?

Answer 4

Reactant in biochemical reactions

Question 5

What are the 2 metabolic processes?

Answer 5

Anabolism : synthesis of complex molecules from simpler ones (Input of energy)
Catabolism : breakdown of complex molecules into simpler ones (release energy)

Question 6

Explain the lock and key hypothesis

Answer 6

Enzymes exhibit specificity to the substrates, substrates fit into the enzyme like a key into a lock
Structural: The 3D structure of the site is specific to the enzyme. If the substrate doesn’t fit, it won’t react
Chemical: Substrates that are not chemically attached to the site won’t react

Question 7

Why do enzymes exhibit specificity with the substrate?

Answer 7

Due to the matching physical and chemical properties of the enzyme and the active site

Question 8

Mechanism of enzymes?

Answer 8

Takes place in a watery environment
Enzymes and substrates bump into each other to allow the substrate to bind to the active site
The active site and substrate should collide in the correct orientation and with enough energy to start the reaction
Reaction could be catabolic or anabolic

Question 9

What is the optimal temperature for enzymes to react?

Answer 9

37° - 38°

Question 10

When do enzymes denature?

Answer 10

When the temperature is too high, it destroys the quarternary structure of the enzyme
When the pH is too low enzymes won’t be able to react

Question 11

What is the optimal pH for enzymes?

Answer 11

Depends on the enzyme. Some work best on very acidic environments (the stomach) or on very basic environments (the liver)

Question 12

What is the relationship between mass and metabolic rate?

Answer 12

Direct relationship.
More mass = higher metabolic rate

Question 13

Generation of heat by metabolic reactions?

Answer 13

Warm-blooded animals use heat generated by metabolism to maintain a constant body temperature
Heat is the only energy that cannot be used for other reactions

Question 14

What is enzyme inhibition?

Answer 14

Decreasing or stopping enzyme activity, enzyme production, or any enzyme-related processes

Question 15

Competitive inhibition?

Answer 15

Competitive inhibitor mimics the shape of the substrate binds to the active site, and competes for the active site.
e.g. Drug methotrexate

Question 16

Non-competitive inhibition?

Answer 16

Binds to the allosteric site to alter the conformation of the active site shape so the substrate can’t bind to it anymore

Question 17

End-product inhibition?

Answer 17

When the end product of a pathway is no longer needed and the reaction is stopped at the first step

Question 18

Mechanism-based inhibition?

Answer 18

Caused by an irreversible bonding of the inhibitor to the active site of a specific enzyme through a covalent bond which causes the enzyme to permanently lose its function
e.g. Penicillin

Question 19

What is cell respiration?

Answer 19

The gradual and controlled release of energy from organic compounds in cells to form ATP (Adenosine Triphosphate)

Question 20

What does it mean by respiratory substrates? What are the respiratory substrates used by our body?

Answer 20

Molecules that can be broken down in respiration and release energy
Glucose, Lipids, Proteins (last resort)

Question 21

How is cell respiration used in our body?

Answer 21

Muscle contraction, Active transportation, Protein synthesis, DNA/RNA replication, Cell signaling, etc.

Question 22

State the cellular respiration formula

Answer 22

C6H12O6 + 6O2 → 6CO2 + 6H2O

Question 23

Anaerobic respiration?

Answer 23

Cell respiration that occurs in the absence of oxygen at the cytoplasm.
Only glucose and carbohydrates can be used.
The waste product is lactic acid (lactate)
ATP yield is low
E.g. fermentation, bioethanol

Question 24

Aerobic respiration?

Answer 24

Cell respiration that occurs in the presence of oxygen at the mitochondria and the cytoplasm
All respiratory substrates can be used
Waste products are carbon dioxide and water
ATP yield is high
E.g. Decomposition of organic matter

Question 25

Variables affecting cell respiration?

Answer 25

Temperature, pH, oxygen concentration, and substrate concentration
If the temperature is too high, the enzyme will denature, if the temperature is too low, it cannot begin respiration.

Question 26

What is NAD and what is the role of NAD?

Answer 26

NAD (Nicotinamide Adenine Dinucleotide) is a coenzyme that is the main hydrogen carrier in metabolic reactions. When a NAD loses a hydrogen atom, it becomes reduced NAD or NADH

Question 27

What is the difference between oxidation and reduction?

Answer 27

Oxidation is where electrons are lost, oxygen is added and hydrogen is lost
Reduction is where electrons are gained, oxygen is removed and hydrogen is added

Question 28

What are the 5 processes of cell respiration?

Answer 28

Glycolysis
Link reaction
Krebs cycle
Electron transport chain
Chemiosmosis

Question 29

Glycolysis?

Answer 29

Splitting glucose into pyruvates.
Occurs in the cytoplasm
A hexose sugar is phosphorylated using ATP and then split into two triose phosphates
Oxidation occurs to remove hydrogen and NAD becomes NADH
Two pyruvates are produced and the net yield of two ATP’s

Question 30

Link reaction?

Answer 30

Pyruvate enters the mitochondrion matrix
Decarboxylation happens when enzymes remove one carbon dioxide and hydrogen from the pyruvate
Hydrogen gets accepted by the NAD to produce NADH
The product is acetyl group that reacts with coenzyme A
Acetyl CoA enters the Krebs cycle

Question 31

Krebs Cycle?

Answer 31

Acetyl CoA (2C) enters the Krebs cycle and joins a 4C group to form 6C
Oxidative decarboxylation of the 6C sugar to 5C compound produces CO2
Oxidative decarboxylation of the 5C compound to a 4C compound and produce CO2
Two CO2 are produced per molecule of the pyruvate/cycle
Three NADH+ H+ and one FADH2 per molecule of the pyruvate/cycle
One ATP is produced per molecule of pyruvate/cycle
NADH and FADH2 provide electrons for the electron transport chain

Question 32

Electron Transport Chain?

Answer 32

Occurs in the inner membrane
The electron carriers deposit their electrons and H+ ions
The protons from NADH pass through the first channel and the electrons stay in the inner membrane
Electrons move along the ETC and activate the next channel
H+ from the FADH2 passes through the second channel while electrons stay in the inner membrane
Electrons move along and lose energy while moving
There is now a high concentration of H+ on the other side which helps with chemiosmosis

Question 33

Chemiosmosis?

Answer 33

The diffusion of ions across a semipermeable membrane through a carrier protein
In this case, the ions are hydrogen protons and the carrier is ATP synthase. The flow of the H+ through the ATP synthase generates ATP
Movement of the H+ drives the rotation of ATP synthase and ATP is made
Chemiosmosis potentially produces 32 ATP molecules, but in most conditions, the yield is slightly lower
Excess H+ and e- are mopped up by using O2 to form water.