B4 Recap

B4 Recap

Monday 8th March 2021

Energetics Topic (B4)

1. Photosynthesis

2. Limiting Factors

3. Greenhouses

4. Photosynthesis Required Practical

5. Aerobic Respiration

6. Anaerobic Respiration

7. Effect of Exercise

Open Ended

Which part of the topic do you feel the least confident with?

Photosynthesis

Plants can make their own food via photosynthesis using light from the sun.

This light is absorbed by a pigment called chlorophyll in the chloroplasts found in plant cells.

This is an endothermic process.

carbon dioxide + water > oxygen + glucose.

Open Ended

Describe the role of the stomata in the gas exchange of plants. (2)

Multiple Choice

Which of these factors is an adaptation that makes a plant able to grow in the shade? (1)

• producing more chlorophyll

• taller stems

• deep roots

• more spongy mesophyll tissue

Open Ended

Photosynthesis is an endothermic reaction. What does this mean in terms of energy transfer?

Limiting Factors

'Limiting factors' refers to the factors which can limit how fast photosynthesis occurs.

- light

- carbon dioxide

- temperature

You need to be able to describe these limiting factors from a graph and explain how they affect the rate of photosynthesis

Multiple Select

Which of the following would increase the rate of photosynthesis? Pick TWO answers.

• Increasing the temperature from 40°C to 60°C

• Increasing the light intensity from 100 lux to 400 lux

• Increasing the carbon dioxide concentration from 0.4 per cent to four per cent

• Decreasing the temperature from 20°C to 10°C

The graph demonstrates how the rate of photosynthesis is affected by temperature. Describe and explain the trend in the graph. (4)

Split the question up!

The graph has two main parts - when it is increasing and decreasing.

Then explain why they increase and decrease.

Open Ended

The graph demonstrates how the rate of photosynthesis is affected by temperature. Describe and explain the trend in the graph.

Greenhouses

Greenhouses artificially create the ideal environment for plants.

Greenhouses trap the Sun's heat to prevent the temperature from becoming a limiting factor. They can use shades to control the temperature further should it become too hot.

Some farmers use artificial light (particularly after the sun goes down) to ensure that light does not become a limiting factor.

Farmers use paraffin heaters to keep greenhouses warm (temperature), but burning paraffin also releases carbon dioxide. This prevents carbon dioxide from becoming a limiting factor.

Open Ended

Discuss how a commercial plant grower, with locations in the UK and across Europe, could increase yields in a greenhouse. (3)

Photosynthesis Required Practical

https://www.youtube.com/watch?v=id0aO_OdFwA

Multiple Choice

Why was sodium hydrogencarbonate added?

• it is a source of carbon dioxide

• it has nutrients to help the plant grow

• it keeps the plant alive

• it lets us see the oxygen bubble easily

Multiple Select

A student investigated the effect of different parts of the spectrum on photosynthesis. She covered three test tubes containing pond weed with plastic filters.

She counted the bubbles produced over one minute intervals.

How could the student check the repeatability of her results. (2)

• repeat her experiment

• using different equipment

• comparing how close together her repeated results are

• using a different plant

Aerobic Respiration

All living things respire. Energy is needed for all kinds of processes.

This is an exothermic process.

glucose + oxygen > carbon dioxide + water + energy

Aerobic respiration occurs in the mitochondria.

Multiple Choice

Which of the following statements is TRUE about aerobic respiration in plants and animals? (1)

• In plants, the reactants are carbon dioxide and water

• When a molecule of glucose is oxidised, much more energy is released in animals

• The process is identical in animals and plants

Anaerobic Respiration

Mammals: glucose > lactic acid + energy (this takes place in the cytoplasm).

Yeast/Plants: glucose > ethanol + carbon dioxide + energy

yeast is used in the making of bread as the carbon dioxide makes the bread rise.

Anaerobic respiration produces x19 LESS energy than aerobic.

During anaerobic exercise, the lactic acid will build up in the muscles and need to be broken down = OXYGEN DEBT.

This lactic acid is taken to the liver to be oxidised (reacted with oxygen) to break it down.

Open Ended

Describe how anaerobic respiration is important in bread making. (2)

Multiple Choice

How much less energy is produced by anaerobic respiration than aerobic?

• x10

• x19

• x20

• x29

Effect of Exercise

Exercise puts a greater demand on the body for oxygen and glucose (both of which we use to respire aerobically).

More muscular contractions occur = more energy and oxygen needed.

More oxygen needed = increased breathing rate/breathing volume and heart rate.

If anaerobically respiring - then the oxygen debt must be repaid (which is why you breathe heavily after exercising!)

Multiple Choice

An elite sprinter's body is better adapted to respire anaerobically than the average individual. Which of these statements is true for an athlete AFTER exercise? (1)

• Lactic acid is taken to the liver in the blood

• Their heart and breathing rate falls to normal straightaway

• Their body has increased its glycogen content

Open Ended

What is meant by the term 'oxygen debt'? (2)