3.5 Chapter 12- Respiration

Question 1

Why is energy important?

Answer 1

• Life depends on continuous transfers of energy.
• Needed in plants and animals for biological processes
• e.g. active transport, DNA replication, cell division, protien synthesis, maintainance of body temperature, muscle contraction.

Question 2

Why is respiration important?

Answer 2

• Cells can’t get energy straight from glucose.
• Energy from glucose is used to form ATP for cells to use as an immediate energy source.

Question 3

What does ATP stand for?

Answer 3

Adenosine Triphosphate

Question 4

Describe the structure of ATP?

Answer 4

• A nucleotide
• Ribose (pentose sugar)
• Adenine (an organic nitrogenous base)
• 3 phosphate groups

Question 5

Draw ATPs structure and label it.

Answer 5

Answer on revision card.

Question 6

What is the role of ATP?

Answer 6

Carries energy around the cell to where it’s needed.

Question 7

Describe how ATP is formed.

Answer 7

• ATP is formed in a condensation reaction between ADP (Adenosine Diphosphate) and inorganic phosphate (Pi).
• Requires energy from an energy releasing reaction (e.g. respiration or photosynthesis)
• Catalysed by by ATP synthase.
• This process is known as phosphorylation as a phosphate molecule is added to the ADP.

Question 8

When is ATP synthesised?

Answer 8

• During photosynthesis- photophosphorylation
• During respiration- oxidative phosphorylation
• When phosphate groups are transferred from donor molecules to ADP- substrate-level phosphorylation

Question 9

How does ATP store energy and what are the features of this store?

Answer 9

• Stores energy made in respiration in the chemical store of the phosphate bonds (bonds between phosphate groups).
• ATP diffuses to parts of the cell that need energy.
• Unstable and low activation energy, easily breakable.

Question 10

How is energy released from ATP?

Answer 10

• ATP hydrolase (ATPase) breaks the phosphate bonds in a hydrolysis reaction (requiring water).
• Hydrolysing bonds- releases energy, splits the ATP into a ADP (Adenosine Diphosphate) and inorganic phosphate (Pi).
• The chemical energy released can then be used by the cell.

Question 11

What type of reaction is the hydrolysis of ATP?

Answer 11

• A reversible reaction.
• ADP and Pi are recycled to form ATP again.

Question 12

What is the formula of ATP reactions?

Answer 12

ATP + H₂O ⇌ ADP + Pi

Question 13

What are the benefits of using ATP as an energy source?

Answer 13

• Energy released in smaller, more manageable amounts, as it stores less energy, meaning little energy lost as heat.
• Small, soluable molecule- easily transported around the cell.
• ATP can be rapidly reformed once used up.
• Can’t leave cells so cells always have an immediate supply of energy.
• Immediate energy release- easily broken down by single reaction hydrolysis vs glucose/ other stores release- long process, several steps.
• Can make other molecules more reactive by transferring one of it’s phosphate groups (phosphorylation).

Question 14

What are the problems of using ATP as an energy source?

Answer 14

• Not a long term energy source- can’t be stored as immediate energy source due to unstable phosphate bonds, whereas carbohydrates and fats can be used as storage.
• Stores less energy than glucose/ other stores.

Question 15

Why does ATP have to be constantly remade and what does this require?

Answer 15

• Immediate energy release due to unstable bonds and single reaction hydrolysis.
• Requires ATP to be constantly remade in the mitochondria.
• Explains the large number of mitochondria.

Question 16

What are the uses of ATP?

Answer 16

• Metabolic processes- provides energy for making macromolecules e.g. starch, DNA.
• Muscle contraction- used for movement- more ATP hydrolysis means more muscle contraction.
• Active transport- changes the shape of carrier proteins.
• Secretion- needed to form lysosomes.
• Phosphorylation- activation of molecules- inorganic phosphate (Pi) can be added to other compounds to make them more reactive- lowers the activation energy especially in enzyme catalysed reactions.

Question 17

Describe ATP coupling.

Answer 17

ATP hydrolysis can be coupled to energy requiring reactions in the cell. The energy released is used directly to make reactions happen rather than being lost as heat.

Question 18

What is respiration?

Answer 18

• The release of energy from glucose in plants and animals.
• Metabolic Pathway- series of small reactions controlled by enzymes.

Question 19

What are the two types of respiration?

Answer 19

• Aerobic respiration- respiration using oxygen.
• Anaerobic respiration- respiration without oxygen.

Question 20

How is energy produced in respiration?

Answer 20

Various substances are used as respiratory substrates and are hydrolysed to produce ATP.

Question 21

What are the similarities between respiration and photosynthesis?

Answer 21

ATP production occurs when protons diffuse down an electrochemical gradient through the enzyme ATP synthase, embedded in the membranes of cellular organisms.

Question 22

What is the overall equation for aerobic respiration?

Answer 22

C₆H₁₂O₆ +6O₂ —> 6CO₂+6H₂O (+energy)

Question 23

Where does respiration occur and what does this provide evidence for?

Answer 23

• Respiration is common in all organisms.
• This provides indirect evidence for evolution.

Question 24

What is the equation for anaerobic repiration in plants and yeast?

Answer 24

Glucose —> Ethanol + CO₂ (+energy)

Question 25

What is the equation for anaerobic repiration in humans and mammals?

Answer 25

Glucose —> Lactate (+energy)