B4: Bioenergetics

Question 1

What are the structures of the leaf and their purpose?

Answer 1

Waxy Cuticle - A waterproof layer on top of the leaf which prevents moisture being lost.
Epidermis - Acts as a barrier to the outside world
Palisade Mesophyll - Has a strong concentration of chlorophyll, and captures sunlights using chloroplasts for photosynthesis
Spongey Mesophyll - An area consisting of large empty gaps suitable for the diffusion of carbon dioxide & oxygen.
Phloem Vessels - Transport Glucose formed during photosynthesis away from the leaf.
Xylem Vessels - Transport water and Minerals up to the leaf from the root, so that it can be used in photosynthesis
Stomata - Gaps in the Lower Epidermis that allow the entry and exit of gas (and small loss of moisture)
Guard Cells - Cells on either side of the stomata that can open and close it.

Question 2

What is the word equation and balanced equation of Photosynthesis?

Answer 2

Word Equation:
Water + Carbon Dioxide → Oxygen + Glucose

Balanced Equation:
6H₂O + 6CO₂ → 6O₂ + C₆H₁₂O₆

Question 3

What are the primary organs of a plant and their functions?

Answer 3

The Stem: Supports the plant
The Leaves: The site of photosynthesis
The Roots: Absorbs moisture and Mineral ions

Question 4

What type of reaction is photosynthesis and why?

Answer 4

Endothermic, as energy is being taken in from the sun

Question 5

What is the experiment that proves the existence of photosynthesis, and its method?

Answer 5

Proof of Photosynthesis:
1. Place two plants under differing light conditions (One in intense light, the other in complete darkness)
2. Leave both plants for 10 minutes
3. Use an iodine to test for the presence of starch in each of them
↳ The one in the light should test positive (and turn black)
↳ The one in the dark should test negative (and show no change)

Question 6

What are the Limiting factors of photosynthesis?

Answer 6

1. The Intensity of Light
2. The Concentration of CO₂ in the surrounding environment
3. The Plant’s temperature
   Note: The concentration of chlorophyll can also affect this

Question 7

What do the Limiting factors of photosynthesis look like graphically?

Answer 7

CO₂: Gradual increase before plateauing
Light Intensity: Gradual increase before plateauing
Temperature: Has an optimum, at which it peaks. Beyond this optimum, enzymes denature and it falls to 0

Question 8

What is the ruling for calculating Light Intensity?

Answer 8

The Inverse Square Law:
In words: for every time the distance doubles, the intensity of light quarters.
Formulaic: 1 ÷ distance²

Question 9

How do plants use Glucose?

Answer 9

1. They store it in a PERMANENT FORM, such as starch, fats or oils
2. They combine it with NITRATE IONS to form AMINO ACIDS
3. They use it to RESPIRE
4. They use it to form CELLULOSE

Question 10

What are the advantages of artificially farming?

Answer 10

1. Maximise Crop Yield
2. Maximise Profits
3. Hard to control weather & conditions in an open field

Question 11

Which conditions are controlled when artificially farming, and how is it done?

Answer 11

The controlled conditions are: 
LIGHT INTENSITY
CO₂ CONCENTRATION
TEMPERATURE
MOISTURE LEVELS 
MINERAL ABUNDANCE

They are controlled using electricity and gas

Question 12

What are Hydroponics?

Answer 12

Hydroponics are a way of farming that involves cultivating crops in mineral-rich water.

Question 13

What are the advantages and disadvantages of Hydroponics?

Answer 13

Advantages:

1. Crops are clean & soil-free
2. No need to prepare land
3. Less staff required
4. Faster turnover

Disadvantages:

1. Expensive
2. Require constant monitoring
3. Vulnerable to power outages

Question 14

What is respiration?

Answer 14

A process that occurs within the cells of most organisms, which breaks down glucose to release energy. There are two types: aerobic and anaerobic

Question 15

What type of reactions are aerobic and anaerobic respiration, and why?

Answer 15

Exothermic, as Glucose is being broken down to release energy.

Question 16

What is aerobic respiration, and where does it occur?

Answer 16

Aerobic respiration is the breakdown of glucose WITH OXYGEN. It occurs in the mitochondria of the cell, as they contain the enzymes required to break down the Glucose.
↳ Each glucose broken releases 36 ATP during aerobic respiration

Question 17

What is the word equation and balanced equation of aerobic respiration?

Answer 17

Word equation:
Glucose + Oxygen → Water + Carbon Dioxide

Balanced equation:
C₆H₁₂O₆ + 6O₂ → 6H₂O + 6CO₂

Question 18

How do the reactants and products of aerobic respiration get transported by the body?

Answer 18

GLUCOSE is taken in via the DIGESTIVE SYSTEM.

OXYGEN is supplied by the RESPIRATORY SYSTEM.

OXYGEN and GLUCOSE are transported to the cells via THE CARDIOVASCULAR SYSTEM.

CARBON DIOXIDE and WATER are expelled from the body via THE RESPIRATORY SYSTEM and THE EXCRETORY SYSTEM.

Question 19

What is anaerobic respiration, where does it occur and under what conditions?

Answer 19

Anaerobic respiration is the breakdown of glucose WITHOUT OXYGEN. It occurs within the Cytoplasm of the cell.
↳ Each glucose broken releases 2 ATP during anaerobic respiration

It occurs when the body cannot supply enough oxygen to meet its energy requirement through aerobic respiration.

Question 20

What is the word equation and balanced equation of aerobic respiration IN PLANTS?

Answer 20

Word equation:
Glucose → Carbon Dioxide + Ethanol

Balanced equation:
C₆H₁₂O₆ → 2CO₂ + 2C₂H₅OH

Question 21

What is the word equation and balanced equation of anaerobic respiration IN ANIMALS?

Answer 21

Word equation:
Glucose → Lactic acid

Balanced equation:
C₆H₁₂O₆ → 2C₃H₆O₃

Question 22

What is oxygen debt?

Answer 22

When large amounts of lactic acid build up in the muscles, they cause muscle fatigue and cramps.

To clear this build up of lactic acid, the oxygen concentration gradient must be increased so that more oxygen is supplied to the muscles.

This oxygen required to clear all the lactic acid is known as Oxygen debt.

Question 23

What is the word equation and symbol equation for the breakdown of lactic acid?

Answer 23

Word equation:
Lactic acid + oxygen → Water + Carbon dioxide

Balanced equation:
C₃H₆O₃ + O₂ → H₂O + CO₂

Question 24

How does your body naturally respond to pay back oxygen debt?

Answer 24

1. Increases your heart rate
2. Increases your breathing rate
3. Increases your breath volume

Question 25

How do animals use the energy released during respiration?

Answer 25

1. To use active transport 2. To contract muscles 3. To send impulses along nerves 4. To facilitate the growth and repair of cells

Question 26

What effect does exercise have on your body, and how does your body adapt to it?

Answer 26

1. Increased activity increases the body’s energy requirement. 2. This leads to a higher rate of aerobic respiration 3. There is a higher demand for aerobic respiration’s reactants (Glucose & Oxygen) 4. The body responds accordingly by… ↳ Dilating your blood vessels (to increase blood reaching the muscles) ↳ Increase in Breathing rate (to increase O₂ levels & maintain its concentration gradient) ↳ Increase in heart rate (more reactants reaching the muscles via the blood) ↳ Increase in breath volume (same as increase in breathing rate)

Question 27

What is the REQUIRED PRACTICAL of Bioenergetics investigating?

Answer 27

The practical investigates how light intensity affects the rate of photosynthesis in an aquatic plant.

Question 28

What equipment is used in the REQUIRED PRACTICAL?

Answer 28

Equipment: 1. A Light source, such as a lamp 2. A metre long ruler 3. A beaker of water 4. A test tube of sodium hydrogen carbonate solution (1%) 5. An Aquatic plant, such as pondweed

Question 29

Which equipment helps maintain the CONTROL VARIABLES of the REQUIRED PRACTICAL?

Answer 29

The Water Beaker - The beaker of water is placed between the lamp and the plant, and absorbs any heat from the lamp, keeping the plant’s temperature constant. The sodium hydrogen carbonate solution - Ensures the CO₂ levels stay consistently high and don’t act as a limiting factor to the rate of photosynthesis.

Question 30

What is the method of B4s REQUIRED PRACTICAL?

Answer 30

Method: 1. Fill the test tube with solution (45cm³) 2. Cut the plant at its top so gas may be released and place it in the test tube, weighted down at its bottom 3. Place the lamp one metre away from the plant. 4. Leave it for 5 minutes to allow the plant to ACCLIMATISE. 5. Count the number of bubbles produced in the span of one minute & record the results 6. Move the lamp 20cm closer 7. Repeat steps 4-6 until you have results for 100cm, 80cm, 60cm, 40cm & 20cm

Question 31

How can you improve the REQUIRED PRACTICAL’S accuracy & repeatability?

Answer 31

Accuracy - Measure the volume of gas produced using properly calibrated equipment (we’re assuming all the gas here is oxygen) Repeatability - Repeat the experiment a multitude of times and calculate a mean

Question 32

What is metabolism?

Answer 32

Metabolism is the sum of all the reactions in your body.

Question 33

What are some examples of metabolic reactions?

Answer 33

1. Aerobic & Anaerobic respiration 2. Formation if amino acids via Glucose & Nitrate ions (Only done by plants) 3. Conversion of glucose to starch, glycogen and cellulose 4. Photosynthesis 5. Breakdown of excess protein in the liver to form urea 6. Formation of lipids from glucose & 3 fatty acids

Question 34

What are the Four Main blood vessels linked to the liver?

Answer 34

Maintenance blood supply vessels: Aorta - Supplies the oxygenated blood required for the liver to work Inferior Vena Cava - Removes the used de-oxygenated blood from the liver Blood processing supply vessels: Hepatic portal vein - supplies blood from the small intestine to be processed Hepatic Artery - Supplies blood from the heart to be processed

Question 35

What other significant features does the liver have (In relation to Bile)?

Answer 35

The Gall bladder - A small storage organ under the liver where bile is stored. Common Bile duct - The duct used to transfer bile from the gall bladder to the digestive system. Note: Bile is used to break down fats into fatty acids, kill pathogens and neutralise stomach acid.

Question 36

What functions does the liver have?

Answer 36

``` 1. Synthesises various products ↳ Vitamin D ↳ Blood Plasma Proteins ↳ Cholesterol ↳ Bile 2. Filtration & detoxification - Removes/destroys/excretes harmful pathogens, toxins, poisons, microbes etc. 3. Assists with digestion 4. Storage of Minerals & Vitamins 5. ```

Question 37

How does the liver connect to oxygen debt?

Answer 37

Lactic Acid is transported to the liver where it can be combined with oxygen and converted back inti glucose. ↳ This glucose is then stored in the liver or used in aerobic respiration.