Paper 1: Topic 4 Bioenergetics - Respiration (LV)

Question 1

Describe respiration

Answer 1

A series of exothermic reactions which are occurring continually inside all living cells (all plant and animal cells) to produce ATP

REMEMBER do not say it produces energy - this is impossible.

Question 2

What is the difference between breathing and respiration?

Answer 2

• Breathing is the process of ventilation i.e. inhalation and exhalation
• Breathing occurs in the lungs and involves the ribcage and the diaphragm
• Respiration is a series of chemical reactions that are taking place inside every living cell

Question 3

What is the purpose of respiration?

Answer 3

To break down glucose to enable energy to be released for other chemical reactions inside the cell

To produce ATP

REMEMBER: energy can’t be produced/made/created

Question 4

Define the term exothermic

Answer 4

A chemical reaction which transfers energy into the environment in the form of heat

Question 5

State 3 uses of the energy released by respiration

Answer 5

1. To build NEW larger molecules from smaller molecules e.g. build NEW proteins from amino acids, to build NEW complex carbohydrates from simple sugars, to build NEW lipids from fatty acids and glycerol
2. To enable muscles to contract and bring about movement
3. To maintain body temperature in birds and mammals

Question 6

Write the word equation for aerobic respiration

Answer 6

Glucose + oxygen → carbon dioxide + water + ATP

Hint: do not write energy as a product as energy can’t be made or created

Question 7

Give 5 examples of reactions involved in metabolism

Answer 7

1. Respiration
2. Conversion of glucose to starch, glycogen or cellulose
3. Production of amino acids from glucose and nitrate ions in plant cells Which are then used to synthesise NEW proteins
4. Breakdown of excess proteins to form urea for excretion in a process called deamination
5. Production of NEW lipids from 3 fatty acids and 1 glycerol

Question 8

What happens to the energy transferred in respiration?

Answer 8

It is used by the organism for metabolism that synthesise NEW molecules.

Note: Metabolism involves all enzyme controlled processes in a cell (or organism) which can either build up NEW molecules (anabolic reactions) or break down large molecules (catabolic reactions).

Question 9

State the two different types of respiration

Answer 9

Aerobic

Anaerobic

Question 10

Describe aerobic respiration

Answer 10

The complete breakdown of glucose in the presence of oxygen to produce ATP, carbon dioxide and water

Question 11

State the useful product of aerobic respiration

Answer 11

ATP

Question 12

State the waste products of aerobic respiration

Answer 12

Water and carbon dioxide

Question 13

Describe anaerobic respiration in human muscles

Answer 13

The INCOMPLETE breakdown of glucose in the ABSENCE of oxygen to produce ATP and lactic acid

Question 14

State the useful product of anaerobic respiration in skeletal muscles

Answer 14

ATP

Question 15

State the waste products of anaerobic respiration in skeletal muscles

Answer 15

Lactic acid

Question 16

Describe anaerobic respiration in plant and yeast cells

Answer 16

The INCOMPLETE breakdown of glucose in the ABSCENCE of oxygen to produce ATP, ethanol and carbon dioxide

Question 17

State the useful product of aerobic respiration

Answer 17

ATP

Question 18

State the waste products of aerobic respiration

Answer 18

Carbon dioxide and water

Question 19

Which form of respiration transfers the most energy?

Answer 19

Aerobic respiration

Aerobic respiration produces 36 ATP whereas anaerobic respiration only produces 2 ATP

Question 20

What is the term used to describe anaerobic respiration in yeast cells?

Answer 20

Alcoholic fermentation

Question 21

What is the economic importance of fermentation?

Hint: think of 2 useful products that can be made from fermentation

Answer 21

It is used in

• MAKING bread and
• MAKING alcoholic drinks (e.g. beer, wine)

Hint: do not just say ‘bread’ and ‘alcohol’

Question 22

Describe 5 changes that occur in the body during exercise

Answer 22

1. Increased heart rate
2. Increased breathing rate
3. Increased depth of breathing
4. Vasodilation of the arterioles at the skin’s surface
5. Vasconstriction of the arterioles to the digestive system

Question 23

Explain the reasons for the changes observed in the body during exercise

Answer 23

To deliver more oxygen to respiring muscle cells

To deliver more glucose to respiring muscle cells

To remove more heat from respiring muscle cells

To remove more lactic acids from contracting muscle cells

To remove more carbon dioxide from respiring muscle cells

Hint: you must remember to put the word MORE in to each sentence you write in this answer

Question 24

Describe and explain what happens to the rate of respiration in muscle cells during exercise

Answer 24

Description - remember to say what happens inside the cells

• Rate of respiration increases

Explanation:

• This produces more ATP - so more energy can be transferred to the environment
• If more aerobic respiration occurs then more carbon dioxide will be produced
• If more anaerobic respiration occurs then more lactic acid will be produced
• The muscle cells will also have a higher oxygen demand and a higher glucose demand so they can respire aerobically for longer

Question 25

Describe what happens in muscles as a consequence of long periods of vigorous exercise

Answer 25

Lactic acid accumulates

An oxygen debt occurs

Muscle fatigue occurs

Question 26

Explain the term oxygen debt

Answer 26

The quantity of EXTRA oxygen the body requires after exercise to

• react with the accumulated lactic acid
• and oxidise it (break it down) to glucose in the liver

HInt: do not say ‘amount of oxygen’

Question 27

Explain what happens to the lactic acid produced as a result of anaerobic respiration

Answer 27

• Blood flowing through the muscles transports lactic acid to the liver
• The liver converts some of the lactic acid back into glucose (for respiration)
• Some of the lactic acid is broken down to carbon dioxide and water

Question 28

Describe how you can test for the producion of carbon dioxide

Answer 28

• Test*: Bubble the gas through limewater
• Negative result*: the solution will remain colourless and transparent
• Positive result*: the solution will turn a milky white colour

Question 29

Write the chemical equation for aerobic respiration

Hint: remember to balance your equation

Answer 29

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 36 ATP

Question 30

Write the word equation for anaerobic respiration in skeletal muscles

Answer 30

Glucose → lactic acid + 2 ATP

Question 31

Write the word equation for anaerobic respiration in yeast or algal cells

Answer 31

Glucose → Ethanol + Carbon dioxide + 2 ATP

Question 32

Explain why blood flow to the skeletal muscles increases during exercise

Answer 32

To deliver more oxygen and more glucose to the skeletal muscles

• This means more aerobic respiration can take place
• This means more ATP is produced and more energy is released
• This means the muscles can contract more frequently and for longer

Remember: the delivery of MORE oxygen also prevents anaerobic respiration occurring and prevents the production of lactic acid

Question 33

Explain why blood flow to the heart muscles (cardiac muscle) increases during exercise

Answer 33

Please note: this question is about supplying the muscle that actually makes up the actual heart walls (not the skeletal muscles than cause movement)

• During exercise the heart rate has to increase
• This requires more* energy to be released from *more ATP
• So the heart muscle cells need to carry out more aerobic respiration
• Increasing the blood flow to the heart muscle supplies the heart muscle cells with more* oxygen and *more glucose
• This means the heart can contract more frequently AND it can contract more forcefully
• This then means the blood flows faster to the skeletal muscles

Question 34

What is meant by the term ‘muscle fatigue’

Answer 34

When muscles are unable to contract efficiently (due to the accumulation of lactic acid)

Question 35

Predict the colour change for each test tube when using hydrogen carbonate indicator.

Hydrogencarbonate indicator will turn purple as there is less carbon dioxide than atmospheric levels. The indicator will turn yellow as carbon dioxide levels increase above atmospheric levels.

Answer 35