Paper 1: Topic 4 Bioenergetics - Respiration (LV)

Question 1

Describe respiration

Answer 1

An exothermic reaction which is occurring continually inside all living cells (all plant and animal cells)

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 larger molecules from smaller molecules e.g. build proteins from amino acids, to build complex carbohydrates from simple sugars, to build 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 to synthesise new proteins
4. Breakdown of excess proteins to form urea for excretion
5. Production of 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 the continual enzyme controlled processes of metabolism that synthesise new molecules

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 muscles

Answer 14

ATP

Question 15

State the waste products of anaerobic respiration in muscles

Answer 15

Lactic acid

Question 16

Describe anaerobic respiration in plant and yeast cells

Answer 16

The incomplete breakdown of glucose in the absence 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

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 the manufacturing of bread and alcoholic drinks (e.g. beer, wine)

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

• Rate of respiration increases

Explanation:

• This causes more energy to be transferred to the environment, more lactic acid to be produced and more carbon dioxide to be produced
• The muscle cells will also have a higher oxygen demand and a higher glucose demand

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

Question 26

Explain the term oxygen debt

Answer 26

The amount 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

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 + ATP

Question 30

Write the word equation for anaerobic respiration in skeletal muscles

Answer 30

Glucose → lactic acid + ATP

Question 31

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

Answer 31

Glucose → Ethanol + Carbon dioxide + 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 aerbic respiration can take place * This means more ATP is produced and more energy is released * This means the muscles can contract more ***Remember:*** the delivery of more oxygen also prevents anaerboc respiration occuring and prevents the production of lactic acid

Question 33

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

Answer 33

* During exercise the heart rate has to increase * This requires more energy to be released from ATP * So the heart muscle cells need to carry out more aerobic respiration * Increasing the bllod flow to the heart muscles supplies the 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)