Nutrition

Question 1

What is photosynthesis?

Answer 1

Green plants make glucose, a carbohydrate, from the raw materials carbon dioxide and water
At the same time oxygen is made and released as a waste product
The reaction requires energy which is obtained by the pigment chlorophyll trapping light
The light energy is converted into chemical energy in the bonds holding together the atoms in the glucose molecules.

Question 2

Why is photosynthesis important in the conversion of light energy to chemical energy?

Answer 2

Plants use the glucose they make as a source of energy in respiration
They can also convert it into starch for storage, into lipids for an energy source in seeds, into cellulose to make cell walls or into amino acids (used to make proteins) when combined with nitrogen and other mineral ions absorbed by roots
Photosynthesis is important to all life on Earth because the conversion of light energy to chemical energy provides energy for all consumers as the chemical energy in bonds can be passed on to other organisms when they eat.

Question 3

What is the photosynthesis equation?

Answer 3

Carbon dixoide + Water - Glucose + Oxygen

6C02 + 6H20 - C6H12O6 + 602

Question 4

What are the effects of temperature on photosynthesis?

Answer 4

As temperature increases, the rate of photosynthesis increases as the reaction is controlled by enzymes
However, as the reaction is controlled by enzymes, this trend only continues up to a certain temperature beyond which the enzymes begin to denature and the rate of reaction decreases.

Question 5

What are the effects of Light intensity on photosynthesis?

Answer 5

The more light a plant receives, the faster the rate of photosynthesis
This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply. This is due to how much the stomata can open and how much carbon dioxide can get inside.

Question 6

What are the effects of carbon dioxide concentration on photosynthesis?

Answer 6

Carbon dioxide is one of the raw materials required for photosynthesis
This means the more carbon dioxide that is present, the faster the reaction can occur
This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply. The factors which could be limiting the rate when the line on the graph is horizontal include temperature not being high enough or not enough light.

Question 7

What is the purpose of the waxy cuticle?

Answer 7

Protective layer on top of the leaf, prevents water from evaporating.

Question 8

What is the purpose of the upper epidermis?

Answer 8

Thin and transparent to allow light to enter the palisade mesophyll later underneath it.

Question 9

What is the purpose of the palisade layer?

Answer 9

Column shaped cells tightly packed with chloroplasts to absorb more light, maximizing photosynthesis.

Question 10

What is the purpose of the spongy mesophyll?

Answer 10

Contains internal air spaces that increases the surface area to volume ratio for the diffusion of gases. Mainly C02

Question 11

What is the purpose of the lower epidermis?

Answer 11

Contains guard cells and stomata.

Question 12

What is the purpose of a guard cell?

Answer 12

Absorbs and loses water to open and close the stomata to allow C02 to diffuse in, oxygen to diffuse out.

Question 13

What is the purpose of stomata?

Answer 13

Where gas exchange takes place, opens during the day and closes during the night. Evaporation of water takes place from here, In most plants, found in much greater concentration on the underside of the leaf to reduce water loss.

Question 14

What is the purpose of a large surface area for photosynthesis?

Answer 14

Increases surface area for the diffusion of C02 and absorption of light for photosynthesis.

Question 15

What is the purpose of chlorophyll?

Answer 15

Absorbs light energy so that photosynthesis can take place.

Question 16

What is the purpose of the network of veins for photosynthesis?

Answer 16

Allows the transport of water to the cells of the leaf and carbohydrates from the leaf for photosynthesis. (Water for photosynthesis, carbohydrates as a product)

Question 17

What is the purpose of the stomata for photosynthesis?

Answer 17

Allows carbon dioxide to diffuse into the leaf and oxygen to diffuse out.

Question 18

What is the purpose of the epidermis for photosynthesis?

Answer 18

The epidermis is thin and transparent which allows more light to reach the palisade cells.

Question 19

What is the purpose of the waxy cuticle for photosynthesis?

Answer 19

The waxy cuticle is thin and made of wax which protects the leaf without blocking the sunlight.

Question 20

What is the purpose of the palisade layer at the top of the leaf for photosynthesis?

Answer 20

Maximizes the absorption of light as it will hit the chloroplasts in the cells directly.

Question 21

What is the purpose of the spongy layer for photosynthesis?

Answer 21

Air spaces allow carbon dioxide to diffuse through the leaf, increasing surface area.

Question 22

What are the mineral requirements?

Answer 22

Photosynthesis produces carbohydrates, but plants contain many other types of chemical
As plants do not eat, they need to make these substances themselves
Carbohydrates contain the elements carbon, hydrogen and oxygen but proteins, for example, contain nitrogen as well (and certain amino acids contain other elements too)
Other chemicals in plants contain different elements as well, for example chlorophyll contains magnesium and nitrogen
This means that without a source of these elements, plants cannot photosynthesise or grow properly
Plants obtain these elements in the form of mineral ions actively absorbed from the soil by root hair cells.

Question 23

What is the purpose of magnesium on plants?

Answer 23

Magnesium is needed to make chlorophyll and deficiency can cause yellowing between the veins of the leaves.

Question 24

What is the purpose of nitrate in plants?

Answer 24

Nitrates are a source of nitrogen needed to make amino acids to build proteins and DNA. Deficiency can cause stunted growth.

Question 25

Investigating photosynthesis practical: Water plant

Answer 25

The plant usually used is Elodea – a type of pondweed
As photosynthesis occurs, oxygen gas produced is released
As the plant is in water, the oxygen released can be seen as bubbles leaving the cut end of the pond weed
The number of bubbles produced over a minute can be counted to record the rate
The more bubbles produced per minute, the faster the rate of photosynthesis
A more accurate version of this experiment is to collect the oxygen released in a test tube inverted over the top of the pondweed over a longer period of time and then measure the volume of the oxygen collected
This practical can be used to investigate the effect of changing light intensity (by moving a lamp different distances away from the beaker containing the pondweed) or changing carbon dioxide concentration (by dissolving different amounts of sodium hydrogen carbonate in the water in the beaker)

Question 26

Investigating the production of starch and the need for chlorophyll:

Answer 26

Although plants make glucose in photosynthesis, leaves cannot be tested for its presence as the glucose is quickly used, converted into other substances and transported or stored as starch.
Starch is stored in chloroplasts where photosynthesis occurs so testing a leaf for starch is a reliable indicator of which parts of the leaf are photosynthesising.
Leaves can be tested for starch using the following procedure:

A leaf is dropped in boiling water to kill and break down the cell walls
The leaf is left for 10 minutes in hot ethanol in a boiling tube. This removes the chlorophyll so colour changes from iodine can be seen more clearly
The leaf is dipped in boiling water to soften it
The leaf is spread out in a Petri dish and covered with iodine solution
In a green leaf, the entire leaf will turn blue-black as photosynthesis is occuring in all areas of the leaf
This method can also be used to test whether chlorophyll is needed for photosynthesis by using a variegated leaf (one that is partially green and partially white)
The white areas of the leaf contain no chlorophyll and when the leaf is tested only the areas that contain chlorophyll stain blue-black
The areas that had no chlorophyll remain orange-brown as no photosynthesis is occurring here and so no starch is stored.

Question 27

What does a balanced diet consist of?

Answer 27

A balanced diet consists of all of the food groups in the correct proportions
The necessary food groups are:
Carbohydrates
Proteins
Lipids
Vitamins
Minerals
Dietary Fibre
Water

Question 28

What are the different food types and their functions/sources?

Answer 28

Carbohydrates: Source of energy. Break down of glucose. Bread, cereals, pasta
Proteins: Growth and repair. Meat fish, eggs
Lipids: Provides insulation and energy storage- butter, oil
Dietary fibre: Helps clean out our bowel- Vegetables, whole grains
Vitamin A: Needed for vision. Deficiency can lead to blindness. Carrots, cheese, eggs.
Vitamin C: Essential part of collagen protein, makes up hair, skin, gums and bones. Deficiency can lead to scurvy. Citrus.
Vitamin D: Helps body absorb calcium. DFCY: Rickets. Oily fish, eggs
Calcium: Strong teeth, bones, clotting blood. DFCY: Osteoporosis. Milk, cheese eggs
Iron: Needed to make Hemoglobin. DFCY: Anemia. Red meat, liver

Question 29

How do energy requirements change?

Answer 29

Age: In young adults it increases as they grow.
Activity levels: More active = Muscles are contracting more and respiring faster= More food
Pregnancy: Energy needed for growth of foetus.

Question 30

Investigating energy content in food: Practical

Answer 30

Measure a set volume of water and pour into a boiling tube
Record the starting temperature of the water
Record the mass of the food sample
Set food sample alight and put underneath the boiling tube to heat the water until it burns out
Record the final temperature of the water
Use the following equation to work out the energy content of the food sample per gram:
Energy Transferred = Mass of water (g) x 4.2 x temperature increase (C)/ mass of food (g)