Metabolism + Cellular Respiration

Question 1

Define the metabolism of a cell

Answer 1

Metabolism is the process by which cells break down energy source and release energy to be used for cellular processes

Question 2

Why are carbohydrates the major energy source of all living things?

Answer 2

Carbohydrates are molecules which are known to store a lot of energy within their bonds therefore, the metabolism of carbohydrates produces a lot of energy for cells.

Question 3

What is the formula for carbohydrate metabolism?

Answer 3

C6H12O6 –> 6CO2 + 6H2O + energy
sugar –> 6 carbon dioxide + 6 water + energy

Question 4

What is the primary energy currency in all cells?

Answer 4

ATP –> Adenosine Triphosphate

Question 5

What types of reactions are present in the metabolic pathway of photosynthesis?

Answer 5

Photosynthesis consists of reactions which require energy to build reactions. These types of reactions are known as anabolic reactions.

Question 6

What kinds of reactions are present in the metabolic pathway of cellular respiration?

Answer 6

Cellular respiration consists of a series of breaking-down reactions which release energy. These types of reactions are known as catabolic.

Question 7

What are the two types of catabolic metabolic pathways?

Answer 7

Catabolic pathways are those that consist of breaking down reactions and releasing energy. The two types of catabolic pathways include those that require oxygen and those that do not. These are called anaerobic and aerobic cellular respiration.

Question 8

Define the term entropy

Answer 8

Entropy is the displacement of energy during energy transfer which results in unusable energy in the form of heats.

Question 9

What does Gibbs’s free energy refer to?

Answer 9

Gibbs free energy refers to the total amount of usable energy resulting from chemical reactions after accounting for entropy and temperature

Question 10

Define Enthalpy

Answer 10

Enthalpy is the total energy change

Question 11

What are endergonic reactions?

Answer 11

Endergonic reactions are those reactions which:
- require an energy input
- They’re non-spontaneous meaning these reactions will not take place naturally without the addition of free energy

Question 12

What are exergonic reactions?

Answer 12

Exergonic reactions are those which:
- release energy
- spontaneous meaning they may take place naturally without any energy input

Question 13

What does it mean if a reaction is spontaneous or non-spontaneous?

Answer 13

Spontaneous: A reaction which may take place without any energy input

non-spontaneous: A reaction which may only take place with an energy input

Question 14

What is the relation between entropy and enthalpy?

Answer 14

entropy ( the loss of energy to unusable forms which results in disorder) is relative to enthalpy ( the total change in energy) as for when disorder increases, the total energy change decreases and vice versa

Question 15

What is activation energy?

Answer 15

Activation energy is the initial input of energy required for all chemical reactions to take place

Question 16

Why do spontaneous reactions require an input of activation energy to take place?

Answer 16

Although spontaneous reactions are those which release energy, for the reaction to take place, they must first reach a state of high energy in which the reactants are unstable for bonds to be broken.

Question 17

What catalyzes activation energy?

Answer 17

Heat energy, which speeds the movement of molecules increases the rate at which bonds may be broken and energy may be released. Heat allows for exergonic reactions to reach their transition state (the state at which the reactants of reaction are at a state of high energy and unstable) with a lower activation energy input.

Question 18

What is the difference between a catalyzed activation energy rate and an uncatalyzed rate?

Answer 18

The difference between an uncatalyzed and a catalyzed activation energy is the amount of free energy input required for the reaction to meet its transition state in which the reaction may begin to release energy in an exergonic reaction.

Question 19

What are the 3 laws of thermodynamics?

Answer 19

1) energy may not be created or destroyed
2) Not all energy transfer is 100% efficient, energy may be lost to unusable forms such as heat
3) The universe is constantly increasing in entropy (displacement) as all reactions result in the loss of some unusable energy

Question 20

What is ATP? Describe the different components of ATP

Answer 20

• ATP is the major energy currency of all cells
• ATP is made up of an adenosine molecule attached to a chain of 3 phosphate groups.

Question 21

What is phosphorylation?

Answer 21

Phosphorylation is the process in which ATP hydrolysis results in the gamma phosphates bond being broken from the ATP molecule and then coupling with different molecules to be used in different processes.

Question 22

What is energy coupling and an example?

Answer 22

Energy coupling is the process in which phosphorylation results in ADP and an organic phosphate. The energy released from the phosphorylation of the ATP is used to drive another reaction. For example, the phosphorylation of ATP is used to drive multiple reactions which break down glucose molecules in the glycolysis process of cellular respiration.

Question 23

What is the role of enzymes in metabolic pathways?

Answer 23

Enzymes reduce the activation energy required for exergonic reactions to take place by binding to reactant molecules, holding them in place to facilitate bond breaking.

Question 24

What does the induced fitting of enzymes mean?

Answer 24

Enzymes undergo a small shift in their structure to better fit the binding of substrates or create more optimal environments within their active sites to promote the reactions of substrates. This allows enzymes to catalyze reactions between the reactants more sufficiently.

Question 25

What are the two most significant properties of enzymes?

Answer 25

1) Enzymes catalyze reactions by decreasing the activation energy rates required to meet its transition state
2) Enzymes always remain unchanged

Question 26

What controls the rates at which metabolic enzymatic activity takes place?

Answer 26

Enzymes increase and lower activation rates depending on different factors such as their environment. Enzymes found in different parts of the body consist of different environmental factors such as differing pH levels and temperatures. These factors may control the rate at which enzymatic activity may take place.

Question 27

How do molecules regulate enzyme activity?

Answer 27

Molecules may regulate enzyme activity through competitive inhibition, non-competitive inhibition and allosteric activation.

Question 28

What is competitive inhibition?

Answer 28

Competitive inhibition is when molecules stop the binding of substrates to the active sites of enzymes. This is done by the binding of molecules very similar to an enzyme’s specific substrate, binding to the substrate and inhibiting the desired substrates from being catalyzed by the enzyme.

Question 29

What is noncompetitive inhibition?

Answer 29

Non-competitive inhibition is when molecules molecules bind to the enzyme’s allosteric site (a spot on the enzyme which not the active site) yet still stops substrates from binding to the enzyme

Question 30

What is allosteric inhibition?

Answer 30

Allosteric inhibition is a type of non-competitive inhibition in which a molecule may bind to the enzyme in a location which creates a change in the enzyme’s structure losing its affinity for its specific substrate

Question 31

What is allosteric activation?

Answer 31

allosteric activation is when a molecule binds to an enzyme causing a change in its structure which opposite to allosteric inhibition, induces its substrate to bind to the enzyme’s active site

Question 32

What are the steps in which glucose is broken down and converted into ATP during aerobic respiration?

Answer 32

1) glycolysis
2) Pyruvate oxidation
3) Krebs Cycle
4) Electron Transport Chain

Question 33

Describe the locations in which each step of aerobic respiration takes place.

Answer 33

1) glycolysis takes place outside the mitochondria within the cell’s cytosol
2) pyruvate oxidation (transition reaction) takes place in the mitochondria’s matrix
3) Krebs cycle takes place within the mitochondria’s matrix
4) The electron transport chain is embedded in the inner mitochondrial membrane

Question 34

Describe what happens during glycolysis and its products

Answer 34

Starting with glucose molecules, glycolysis is the process in which a series of redox reactions and substrate-level phosphorylation takes place to break down the glucose molecule into 2 pyruvate molecules and result in a net gain of 2+ ATP molecules and 2+ NADH molecules.

Glycolysis is split into 2 sets of reactions:

1) Glycolysis I - consists of endothermic reactions meaning these reactions require an initial input of 2 ATP moleules. With the initial input of ATP, the glucose molecule uses energy coupling or more specifically substrate-level phosphorylation to drive a series of reactions which break the glucose molecule down into its reactants for the glycolysis II

2) Glycolysis II - Here the two reactant molecules produced by the energy coupling reactions in glycolysis I undergo an exothermic reaction which now releases energy from the reactant molecules. This step requires no energy input. Throughout glycolysis II, rather than a series of energy coupling reactions and substrate-level phosphorylation, a series of redox (reduction and oxidation reactions) break the sugar molecules down even further producing 2 ATP molecules and 2 NADH molecules.

Question 35

What is oxidation and reduction?

Answer 35

Oxidation is the process in which a reactant undergoes a chemical reaction in which it loses electrons

Reduction is the process in which a reactant undergoes a chemical reaction in which it gains electrons

Question 36

Describe what happens during pyruvate oxidation

Answer 36

The two pyruvate molecules which the glucose is broken down into during glycolysis then undergo pyruvate oxidation.

During pyruvate oxidation, the pyruvate molecules are transported into the mitochondria’s matrix through the outer and inner membrane.

facilitated by a transport protein, the carbohydrate passes through the membrane then with help of an enzyme known as the pyruvate dehydrogenase complex aids the oxidation of the pyruvate molecule.

NAD+ removes two electrons from the pyruvate and carbon dioxide is removed resulting in a two carbon acetyl group.

This acytly group combines with coenzyme A to produce a acetyl-CoA molecule.

Question 37

Describe what happens during the Krebs cycle

Answer 37

The Krebs cycle takes place in the mitochondrial matrix.

Taking the acetyl-CoA produced during pyruvate oxidation, the CoA is removed and the acetyl group is attached to a 4-carbon oxaloacetate molecule making a citrate molecule.

Next throughout a series of redox
and decarboxylation reactions, the citrate will be broken down producing a total of 6 NADH molecules, 2 FADH molecules, 2 ATP molecules and 2CO2 molecules.

After completing the cycle, the citrate molecule ends in its original state as an oxaloacetate molecule for other acetyl groups to attach to and undergo the Krebs cycle

The Krebs cycle completes the catabolization of the glucose molecule at the start of cellular respiration.

Question 38

What are electron carriers? What do they do?

Answer 38

The Krebs cycle produces a total of 8 electron carriers with a total of 12 electron carriers by the end of all the catabolizing reactions of cellular respiration.

Electron carriers are the NADH and FADH2 molecules produced throughout glycolysis, pyruvate oxidation and the Krebs cycle.

These molecules store and transport electrons to the electron transport chain to be used in the process of producing ATP.

Question 39

What happens after the Krebs cycle?

Answer 39

After the Krebs Cycle is completed, electron carriers including NADH and FADH2 carry electrons from the mitochondrial matrix to the electron transport chain of multi-enzyme complexes embedded within the folds of the inner membrane of the mitochondria, also known as the cristae.

At the electron transport chain, NADH dehydrogenase oxidizes electron carriers donating electrons to complex 1 of the electron chain.

As electrons move down the chain, electron carriers are first reduced and then oxidized at each complex.
Resultingly this drives hydrogen atoms through proton pumps across the inner membrane into the intermembrane space.

At the end of the electron transport through the complexes, the low-energy electrons are removed.

Oxygen present at the end of the chain combine with hydrogen allowing additional electrons to enter the chain and release more energy to pump more H+ ions into the intermembrane space creating a concentration gradient in which there are more H+ ions in the intermembrane space than the matrix.

Through a complex known as ATP synthase, H+ ions from the intermembrane space flow back down into the mitochondrial matrix through chemiosmosis. The movement of hydrogen atoms down the ATP synthase creates an electric charge which is used towards the phosphorylation of ADP with an organic phosphate.

Question 40

How many ATP molecules are produced by the end of the electron transport chain?

Answer 40

A total of 36 ATP molecules are produced by the end of the electron transport chain

Question 41

What is anaerobic cellular respiration?

Answer 41

The production of ATP within the cell without the use of oxygen

Question 42

Why is oxygen so crucial to aerobic respiration?

Answer 42

Aerobic respiration which is much more sufficient at producing ATP than anaerobic respiration can only take place in the presence of oxygen as it plays the role of allowing additional electrons to enter the electron transport chain and provide enough energy to pump enough hydrogen atoms into the intermembrane space creating a gradient and allowing chemiosmosis to take place. Humans are organisms which are mobile therefore we require more energy than other organisms and therefore oxygen is so crucial as for it allows aerobic cellular respiration to take place.

Question 43

What are the two types of anaerobic cellular respiration?

Answer 43

• Alcohol fermentation
• Lactic Acid fermentation