Section 4 - Respiration and gas exchange

Question 1

word Equation of anaerobic respiration in humans

Answer 1

Glucose -> lactic acid + energy

Question 2

word equation for anaerobic respiration in plants and fungi

Answer 2

Glucose -> ethanol + carbon dioxide

Question 3

Symbol and word equation for aerobic respiration

Answer 3

Glucose + oxygen -> carbon dioxide +water
C6H12O6 + 6O2 -> 6CO2 + 6H2O

Question 4

Respiration definition

Answer 4

Respiration is turning the chemical energy in food into energy we can use in our body

Question 5

Name and explain 6 adaptation of a leaf for gas exchange

Answer 5

1. Broad - large SA for diffusion
2. Air space - this maintains a concentration gradient
3. Thin - short diffusion distance
4. Stomata - lets gases exchange as they can move in and out of the leaf
5. Chloroplasts - increases rate of photosynthesis
6. Stomata can close or open by guard cells - increase gas exchange and prevents water loss so it doesn’t dry out

Question 6

Explain how guard cells open and close

Answer 6

Open: Water enters guard cells by osmosis guard cells become turgid and open
Closes: water leaves guard cells by osmosis guard cells become flaccid closing stomata

Question 7

How does the stomata manage the water levels in the leaf

Answer 7

When the leaf is full of water, the water moves into the guard cell so it opens and the leaf can lose water

Question 8

Describe the structure of the thorax

Answer 8

The lungs are surrounded by the ribs and the intercostal muscles. There is a trachea which is connected to the left and right bronchus, then the bronchioles branch out from each bronchus. On the end of the bronchioles are the alveoli. On the outside of the lung there are pleural membranes.

Question 9

Describe the relationship between photosynthesis and respiration

Answer 9

Plants carry out photosynthesis to produce glucose. To enable this process to occur the leaf cells absorb carbon dioxide and release oxygen.
At the same time the leaf is respiring. This means that they are using oxygen and producing carbon dioxide. When the rate of photosynthesis and respiration are equal the plant is at compensation point.

Question 10

Describe how the time of day/ weather effects photosynthesis and respiration

Answer 10

If the leaves are in bright sunlight then the rate of photosynthesis will be higher than the rate of respiration.
If there is no light or it is dim the rate of respiration will be higher then the rate of photosynthesis and there will be a net production of CO2

Question 11

Name the layers of the leaf top down

Answer 11

• Waxy cuticle
• Upper epidermis
• Palisade cells (contain chloroplast) (part of the mesophyll)
• Spongy cells (part of the mesophyll)
• Lower epidermis
• Guard cells

Question 12

Explain the process of inhalation

Answer 12

1. Diaphragm contracts and flattens and external intercostal muscles contract
2. Rib cage moves up and out
3. Volume of thorax increase
4. Pressure decreases
5. Air is drawn in

Question 13

Explain exhalation

Answer 13

1. Diaphragm relaxes and external intercostal muscles relax
2. Rib cage moves down and in
3. Volume of thorax decreases
4. Pressure increases
5. CO2 is pushed out

Question 14

Ventilation definition

Answer 14

The movement of air in and out of the lungs

Question 15

Explain how gas exchange in the alveoli works

Answer 15

Blood which is low on oxygen enters the capillary of the alveoli, CO2 moves into the alveoli from the blood and oxygen moves into the blood from the alveoli

Question 16

How has the alveoli adapted for gas exchange

Answer 16

1. Walls are only one cell thick - provides a short diffusion distance
2. Large surface area - Allows more O2 to diffuse in and CO2 to diffuse out
3. Good blood supply - maintains the concentration gradient
4. Moist- Molecules can on,y cross membranes when dissolved in water

Question 17

Name for effects of smoking

Answer 17

1. Smokers cough
2. Lung cancer
3. Emphysema
4. Carbon monoxide poisoning

Question 18

Respiration definition

Answer 18

“An exothermic reaction which transfers energy from glucose and is continuously occurring in living cells”

Question 19

Photosynthesis equation

Answer 19

6H2O + 6CO2 -> C6H12O6 +6O2

Question 20

Where does aerobic respiration take place

Answer 20

Mitochondria

Question 21

Where does all respiration take place

Answer 21

cells

Question 22

What colour does hydrogen carbon indicator turn when a leaf has been in light and why

Answer 22

purple, because the leaf has been photosynthesising so it is using up all the CO2

Question 23

What colour does hydrogen carbon indicator turn when a leaf has been in darkness and why

Answer 23

Yellow because the leaf has been respiring so it releases a lot of carbon dioxide

Question 24

How can smoking cause lung cancer

Answer 24

• Chemicals in cigarettes smoke called carcinogens, they are found in the tar which collects in the lungs
• The carcinogens mutate and form a tumour

Question 25

How can smoking cause emphysema

Answer 25

Smoking damages the walls of alveoli which fuse together to create enlarged and irregular air spaces
This reduces the SA for gas exchange so less oxygen is carried to the blood

Question 26

How can smoking cause Carbon monoxide poisoning

Answer 26

• The carbon monoxide found in cigarette smoke combines tightly with haemoglobin to form carboxyhemoglobin
• Less oxygen is carried round the body

Question 27

How can smoking cause smokers cough/chest infections

Answer 27

Tar damages the cilia which usually catches the dust and bacteria and clear mucus
So when cilia is damaged chest infections and smokers cough is more likely

Question 28

How can smoking cause bronchitis

Answer 28

Tar irritates the brochi and the bronchioles which encourages mucus to be produced but it can’t be cleared as the cilia are damaged
This causes chronic bronchitis

Question 29

How does light effect the rate of photosynthesis

Answer 29

If the light intensity increases so does the rate of photosynthesis but only up to a certain point

Question 30

How does carbon dioxide effect the rate of photosynthesis

Answer 30

Increasing the carbo dioxide levels increases the rate of photosynthesis up to a certain point

Question 31

How does temperature effect the rate of photosynthesis

Answer 31

As temperature increases so does the rate of photosynthesis because the is more kinetic energy for the enzymes but if it gets to hot the enzymes will denature

Question 32

How are leaves adapted for photosynthesis

Answer 32

1) Leaves are broad, so there’s a large surface area exposed to light.
2) Most of the chloroplasts are found in the palisade layer so they’re near the top of the leaf where they can get the most light.
3) The upper epidermis is transparent so that light can pass through it to the palisade layer.
4) The phloem and xylem deliver water and other nutrients to every part of the leaf and take away the glucose produced by photosynthesis. They also help to support the leaf structure.
5) The waxy cuticle helps to reduce water loss by evaporation.