Cell respiration and photosynthesis - IB Biology

Question 1

Write the full name of ATP

Answer 1

Adenosine triphosphate

Question 2

What is ATP

Answer 2

ATP is a nucleotide

Question 3

What properties of ATP make it suitable for use as the energy currency within cells

Answer 3

ATP is a good source of energy because it can be easily broken down to release energy when needed. The phosphate bonds in ATP are high-energy bonds, meaning that when they are broken, a significant amount of energy is released.

Question 4

Examples of life processes within cells that require ATP

Answer 4

• active transport across membranes
• synthesis of macromolecules (anabolism)
• movement of the whole cell
• movement of cell components such as chromosomes

Question 5

How does active transport across membranes require energy?

Answer 5

The form of passive transport is called facilitated diffusion and requires ATP.

It occurs when molecules such as glucose or amino acids move from high concentration to low concentration with the help of the carrier proteins or pores in the membrane.

Active transport requires energy for the process of transporting molecules against a concentration or electrochemical gradient.

Question 6

How does the synthesis of macromolecules require energy?

Answer 6

Dehydration reactions typically require an investment of energy for new bond formation.

Most macromolecules are made from single subunits, or building blocks, called monomers. The monomers combine using covalent bonds to form larger molecules known as polymers.

Question 7

How does the movement of the whole cell require energy?

Answer 7

The movement of a whole cell also uses active transport.

To move substances against a concentration or electrochemical gradient, a cell must use energy. Active transport mechanisms do just this, expending energy (often in the form of ATP) to maintain the right concentrations of ions and molecules in living cells.

Question 8

How does the movement of cell components require energy?

Answer 8

The movement of cell components also uses active transport.

To move substances against a concentration or electrochemical gradient, a cell must use energy. Active transport mechanisms do just this, expending energy (often in the form of ATP) to maintain the right concentrations of ions and molecules in living cells.

Question 9

What is a product of hydrolysis?

Answer 9

Energy is released by hydrolysis of ATP to ADP and phosphate. However, energy is required to synthesize ATP from ADP and phosphate. The amount of energy is sufficient for many tasks in the cell.

Question 10

What does ADP stand for

Answer 10

adenosine diphosphate

Question 11

State the principal substrates for cell respiration

Answer 11

Glucose and fatty acids are the principal substrates for cell respiration, but a wide range of carbon/organic compounds can be used.

Question 12

Why is glucose one of the principal substrates for cell respiration

Answer 12

One molecule of glucose gives 38 molecules of ATP, hence it is an instant source of energy.

It is also abundantly available and is stored easily in the body in the form of glycogen. It is also stored in plants in the form of starch or complex sugars.

Question 13

Distinguish between the processes of cell respiration and gas exchange

Answer 13

Cellular respiration is the process that occurs in the mitochondria of organisms (animals and plants) to break down sugar in the presence of oxygen to release energy in the form of ATP. Gaseous exchange is the diffusion of gases from a region of higher concentration to a region of lower one.

Once in the lungs, oxygen is moved into the bloodstream and carried through your body. At each cell in your body, oxygen is exchanged for a waste gas called carbon dioxide. Your bloodstream then carries this waste gas back to the lungs where it is removed from the bloodstream and then exhaled. Your lungs and respiratory system automatically perform this vital process, called gas exchange.

Question 14

Why is fatty acids one of the principal substrates for cell respiration

Answer 14

Fat is a macronutrient group of compounds like carbohydrates and protein.

Fats are a substrate for cellular respiration. It gives the highest amount of energy among fats, carbohydrates, and proteins.

Fat is a triglyceride molecule. Triglyceride is degraded to fatty acid and glycerol. This fatty acid undergoes the process of beta-oxidation.

This is a series of reactions that ultimately produce acetyl-CoA molecules with a reaction with coenzyme A which enters into Krebs’ cycle.

It produces energy in the form of ATP.

Glycerol can enter in glycolysis is glyceraldehyde-3- phosphate, it is an intermediate of glycolysis.

Question 15

Word equation for aerobic respiration

Answer 15

Glucose + Oxygen → Carbon dioxide + water + energy

Question 16

Word equation for anaerobic respiration

Answer 16

Glucose → ethanol + carbon dioxide + energy (2 ATP)

Question 17

Which type of respiration involves oxygen

Answer 17

aerobic respiration

Question 18

When is the mitochondria needed?

Answer 18

The mitochondria are needed for aerobic.

The mitochondria are not needed for anaerobic.

Question 19

Yield of ATP for anaerobic respiration

Answer 19

Anaerobic respiration results in the production of 2 ATP molecules

Question 20

Yield of ATP for aerobic respiration

Answer 20

Aerobic cellular respiration results in the production of about 30-32 ATP molecules.

Question 21

Waste product(s) for anaerobic respiration

Answer 21

The products of anaerobic respiration are lactic acid, carbon dioxide, and water

Question 22

Waste product(s) for aerobic respiration

Answer 22

Carbon dioxide and water are created as byproducts

Question 23

Where does anaerobic respiration take place?

Answer 23

Anaerobic respiration (without oxygen) takes place within the cell’s cytoplasm.

Question 24

Where does aerobic respiration take place?

Answer 24

Most aerobic respiration (with oxygen) takes place in the cell’s mitochondria.

Question 25

How to calculate the rate of reaction for cell respiration

Answer 25

the amount of oxygen used/time

Question 26

What is oxidation

Answer 26

This is the process of electron loss.

Question 27

Explain an example of oxidation

Answer 27

Dehydrogenation is the process by which hydrogen is removed from an organic compound to form a new chemical (e.g., to convert saturated into unsaturated compounds). The organic compound has been oxidized.

Question 28

What processes do redox reactions involve

Answer 28

Redox reactions involve both oxidation and reduction.

Question 29

When is NAD reduced?

Answer 29

NAD is reduced when it accepts hydrogen.

Question 30

What do the following pathways have in common:
- phosphorylation
- lysis
- ATP formation

Answer 30

Each pathway is catalyzed by a different enzyme.

Question 31

What does the regeneration of NAD allow for?

Answer 31

The regeneration of NAD allows for glycolysis to continue, with a net yield of two ATP molecules per molecule of glucose.

The conversion of pyruvate to lactate is a means of regenerating NAD in anaerobic cell respiration.

Question 32

Examples of how anaerobic cell respiration is used

Answer 32

• brewing
• baking
• yeast

Question 33

Similarities of anaerobic respiration in humans and yeasts

Answer 33

The pathways of anaerobic respiration are the same in humans and yeasts.

Question 34

Differences between the pathway of anaerobic respiration in humans and yeasts

Answer 34

NAD used in glycolysis can be regenerated by the conversion of pyruvate to ethanol and CO2 instead of lactate. This is the process that happens in humans.

However, in yeast, the aim is to produce ethanol rather than CO2. Wine is made from grape juice, which naturally has a high sugar concentration. Beer is made from barley grains, mixed with water. The grains contain large amounts of starch but yeasts cannot metabolize starch.

Brewing of wine or beer is carried out in large tanks, so diffusion of oxygen into the liquid tank is limited. The yeasts rapidly use up any oxygen present and then respire anaerobically. The ethanol produced remains dissolved but most of the CO2 bubbles to the surface and escapes. Depending on the amount of sugar present at the start, ethanol fermentation ends either when all the sugar has been used up or when the ethanol concentration becomes toxic to the yeast (1âbout 15% by volume)

Bread is made by adding water to flour, kneading the mixture to make dough, and then baking it. To give the bread a lighter texture, something must be added to the dough to create bubbles of gas. Yeast is often used for this purpose. If the dough is kept warm, the yeast will grow and respire. Initially, it respires aerobically but once all the oxygen in the dough has been used, the yeast starts to respire anaerobically. Because the dough is very viscous (sticky), the CO2 produced by anaerobic respiration cannot escape. Instead, it forms bubbles within the dough. These bubbles cause the dough to swell, or ‘rise’. Ethanol is also produced by anaerobic cell respiration but it evaporates during baking.

Question 35

Why are lipids and carbohydrates metabolized?

Answer 35

Lipids and carbohydrates are metabolized to form acetyl groups (2C), which are transferred by coenzyme (CoA) to the Krebs cycle.

The conversion from pyruvate to pyruvate to 2-carbon acetyl group in glycolysis forms a link between glycolysis and the Krebs cycle, so it’s referred to as the link reaction.

Question 36

Name the intermediates of the Kreb cycle

Answer 36

Citrate (6C) and oxaloacetrate (4C)

Question 37

When is citrate made?

Answer 37

Citrate is made by the transfer of an acetyl group to oxaloacetate and oxaloacetrates is regenerated by the reactions of the Krebs cycle, including four oxidations and 2 decarboxylations.

Question 38

How does the Krebs cycle work?

Answer 38

Acetyl groups produced by the link reaction are oxidized in the Kreb cycle, which is a cycle of reactions that happens in the matrix of the mitochondria.

Acetyl groups are fed into the cycle by transferring CoA to oxaloacetate, producing the organic acid citrate.

Oxaloacetrate has four carbon atoms and citrate has six carbon atoms. Citrate is converted back into oxaloacetate by a series of enzyme-catalyzed reactions. The number of carbon atoms is decreased by two decarboxylation reactions, in which carbon and oxygen are removed, producing CO2.

In aerobic respiration, all the carbon in substrates such as sugar or fat is removed by decarboxylation in the Krebs cycle to link reaction. CO2 is a waste product in most cells and is excreted.

Four reactions in the Krebs cycle are oxidations and release energy. Much of the energy released is held by the electrons that are removed in the oxidations. These electrons are transferred to NAD or FAD. Both these molecules act as carriers of electrons, they also accept protons, so they’re hydrogen carriers.

Question 39

What is FAD?

Answer 39

FAD is similar to NAD. When FAD or NAD accept a pair of electrons, they become reduced. Reduced NAD and reduced FAD transfer electrons and the energy they’re holding to the electron transport chain in the inner mitochondrial membrane.

Question 40

The net effects of one turn in the Kreb cycle?

Answer 40

• one acetyl group is consumed
• three NADs are converted to reduced NAD and one FAD to a reduced FAD
• two molecules of CO2 are released
• one ADP is converted to ATP

Question 41

When is energy transferred?

Answer 41

Energy is transferred when a pair of electrons is passed to the first carrier in the chain, converting reduced NAD back to NAD. Reduced NAD comes from glycolysis, the link reaction, and the Krebs cycle.

Question 42

What does ATP synthase do?

Answer 42

ATP synthase couples the release of energy from the proton gradient with the phosphorization of ADP.

Question 43

How does ATP synthase release energy from the proton gradient with phosphorylation of ADP?

Answer 43

Conceptually, ATP synthase is a lot like a turbine in a hydroelectric power plant. Instead of being turned by water, it’s turned by the flow of H ‍ ions moving down their electrochemical gradient. As ATP synthase turns, it catalyzes the addition of a phosphate to ADP, capturing energy from the proton gradient as ATP.

Question 44

Explain the role of oxygen as a terminal electron acceptor in aerobic cell respiration

Answer 44

Oxygen accepts electrons from the electron transport chain and protons form the matrix of the mitochondrion producing metabolic water and allowing continued flow of electrons along the chain.