2(d, e)

Question 1

Define ‘limiting factor’.

Answer 1

A limiting factor is something that is in short supply compared to all the other required factors therefore the single thing that is preventing the rate of the reaction increasing.

Question 2

What is the use of Magnesium(Mg2+) in the plant cell?(2)

Answer 2

Magnesium is part of the chlorophyll molecule and therefore a deficiency sign is the leaves turning yellow because chlorophyll is a green pigment and a lack of it will turn leaves a different colour.

Question 3

What is the use of Nitrate(NO3-) in the plant cell?

Answer 3

Nitrate is used for making amino acids and therefore proteins, deficiency signs would be stunted growth of plant.

Question 4

How and why is temperature controlled in greenhouses?(2)

Answer 4

Burning fuels in the greenhouse increases the temperature which increases the kinetic energy for enzymes which therefore increases rate of protein production which is key to plant growth.

Question 5

How and why is light intensity controlled in greenhouses?

Answer 5

Walls of greenhouses are glass so that sun can get in, furthermore polythene lights are sometimes added at night for light which is key in photosynthesis.

Question 6

How and why is Carbon Dioxide controlled in greenhouses?

Answer 6

Burning fuels releases Carbon Dioxide which is part of Photosynthesis.

Question 7

How and why is the soil controlled in greenhouses?(2)

Answer 7

Lime is added to the soil to make it a suitable pH also manure is added for good drainage.
An unsuitable pH will make mineral ion uptake difficult, while good drainage allows mineral uptake.

Question 8

State the balanced equation of Photosynthesis.

Answer 8

6CO2 + 6H2O → C6H12O6 + 6O2

Question 9

Function and source of Carbohydrates for humans?(2)

Answer 9

Broken down in glucose, hence provide long term energy.
Found in pasta, rice, sugar.

Question 10

Function and source of Lipids for humans(or fats and oils)?(2)

Answer 10

An energy store and provide insulation.
Found in butter, oily fish.

Question 11

Function and source of Proteins for humans?(2)

Answer 11

Needed for growth and repair of tissue, as well as to provide energy in emergencies.
Found in meat, fish.

Question 12

Function and source of Vitamin A for humans?(2)

Answer 12

Prevents night blindness, required for making a chemical in the retina.
Found in Liver, carrots.

Question 13

Function and source of Vitamin C for humans?(2)

Answer 13

Prevents scurvy, required for sticking together cells lining surfaces.
Found in fruit; oranges.

Question 14

Function and source of Vitamin D for humans?(2)

Answer 14

Prevents rickets, required for bones to absorb calcium and phosphate.
Found in eggs. Also made by the body when skin is exposed to sunlight.

Question 15

Function and source of Calcium for humans?(2)

Answer 15

Needed to make and repair bones and teeth.
Found in milk, cheese.

Question 16

Function and source of Iron for humans?(2)

Answer 16

Needed to make haemoglobin for healthy blood.
Found in red meat.

Question 17

Function and source of Water for humans?(2)

Answer 17

Almost every bodily function relies on water - constant supply required to replace water lost from sweat, urination and breathing.
Found in almost all food and drink.

Question 18

Function and source of Dietary fibre for humans?(2)

Answer 18

Aids the movement of food through the gut.
Found in Wholemeal bread, fruit.

Question 19

What are the seven essential nutrients?

Answer 19

Carbohydrates, proteins, lipids, vitamins, minerals and water. Fibre is an extra.

Question 20

How do energy requirements differ in different people?

Answer 20

Children and teenagers need more energy than older people. Pregnant woman also need more energy than other woman.

Question 21

Function of Mouth in the human alimentary canal?(2)

Answer 21

Salivary Glands in the mouth produce amylase enzyme in the saliva.
Teeth also break down food.

Question 22

Function of Oesophagus in the human alimentary canal?

Answer 22

The muscular tube that connects the mouth to the stomach.

Question 23

Function of Stomach in the human alimentary canal?(3)

Answer 23

Pummels food with is muscular walls.
Produces protease enzyme, pepsin.
Produces HCl to kill bacteria and to give optimum pH for the protease enzyme; pH 2.

Question 24

Function of Liver and Gall Bladder in the human alimentary canal?

Answer 24

Liver produces bile, while gall bladder stores it.

Question 25

Function of Pancreas in the human alimentary canal?

Answer 25

Produces protease, amylase and lipase enzymes which are released in small intestine.

Question 26

Function of Small intestine in the human alimentary canal?(2)

Answer 26

Releases protease, amylase and lipase enzymes to complete digestion.
Also where nutrients are absorbed out of the alimentary canal.
First part is the duodenum, last part is the ileum.

Question 27

Function of Large intestine in the human alimentary canal?

Answer 27

Where excess water is absorbed from the food.

Question 28

Function of Rectum in the human alimentary canal?(2)

Answer 28

Last part of the Large intestine.
Where the faeces are stored before excretion.

Question 29

How is food moved through the gut by Peristalsis?(3)

Answer 29

Muscular tissue all the way down the alimentary canal.
It squeezes balls of food through the gut otherwise the gut would get clogged up with old food.
The action of squeezing, which is waves of circular muscle contractions is called peristalsis.

Question 30

What do the digestive enzymes break down and why?(4)

Answer 30

Amylase(enzyme) converts starch into maltose, and maltase(enzyme) converts maltose in glucose.
Proteases(enzyme) convert proteins in amino acids.
Lipases(enzyme) convert lipids into glycerol and fatty acids.
This is because starch, proteins and fats are too big to pass through digestive system walls.

Question 31

What is the role of Bile in digestion?(3)

Answer 31

The HCl in the stomach makes the pH too acidic for enzymes in the small intestine to work properly.
Bile is alkaline - it neutralises the acid and makes condition alkaline for the enzymes to work best.
Bile also breaks down(emulsifies) the fat into tiny droplets to give best surface area for enzyme lipase to work on.

Question 32

How is the small intestine adapted for absorption?(3)

Answer 32

It’s very long, so there’s time to break down and absorb all the food.
Big surface area; covered in millions of villi which are also covered in villi themselves.
Villi have single permeable layer and very good blood supply to assist quick absorption.

Question 33

How can you measure the energy in food from calorimetry(burning it)?(4)

Answer 33

Get a dry food and after weighing it, skewer it on a mounted needle.
Add a set volume of water to boiling tube.
Measure the temperature of the water and set fire to the food using Bunsen burner.
Hold the food under boiling tube until it goes out; keep relighting until it does’t anymore.
Measure final temperature of water.

Question 34

How can you calculate the amount of energy in the food in Joules and Joules per gram?(2)

Answer 34

In Joules: Energy in Food =
(Mass of water) x (Temp change) x (4.2)
In Joules per gram: Energy per Gram =
(Energy in Food) / (Mass of Food)

Question 35

What is diffusion?(2)

Answer 35

The net movement of particles from a region of higher concentration to a region of lower concentration.
Small uncharged molecules(Crucially oxygen and carbon dioxide) can diffuse freely across a cell membrane.

Question 36

What is osmosis?(2)

Answer 36

The net movement of free water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane.
It will also take place across partially permeable Visking tubing.

Question 37

What is active transport?

Answer 37

The movement of particles from a region of lower concentration to a region of higher concentration using the energy from respiration.

Question 38

What is a crenated (animal)cell and a haemolysed (animal)cell?

Answer 38

If an animal cell is placed in a solution with higher water potential than its cytoplasm, water molecules move down the gradient by osmosis, the animal cell will burst open. It is haemolysed.
If an animal cell is placed in a solution with lower water potential than its cytoplasm, water moves out of the cell by osmosis, it shrinks. The cell is now crenated.

Question 39

When a plant cell is placed in a solution with higher water potential than its cytoplasm…

Answer 39

The cell membrane is pushed against the cell wall but it will not burst because the cell wall stops it getting any larger, the plant cell is turgid.

Question 40

When an animal cell is placed in a solution with lower water potential than its cytoplasm…

Answer 40

Water moves out of the cell by osmosis and the cell shrinks. It is crenated.

Question 41

Which factors affect the rate of movement of substances into and out of cells(osmosis and diffusion)?(4)

Answer 41

Concentration gradient - happen more quickly when there is a steep concentration gradient.
Surface area to volume ratio - Larger surface area in proportion to the volume increases the rate.
Distance - the rate is decreased if the distance over which diffusion has to take place is greater.
Temperature - rate is greater at a higher temperature, this is because high temperature provides particles with more kinetic energy.

Question 42

How is the structure of the leaf adapted for photosynthesis?(5)

Answer 42

The outer two layers of cells(upper and lower epidermis) are covered by the cuticle; it is waxy and so reduces water loss by evaporation. The upper epidermis is also relatively transparent to allow light to pass to the palisade layer.
The lower epidermis has lots of stomata which allow carbon dioxide to diffuse into the leaf, to reach the photosynthetic tissues. They also allow oxygen and water(vapour) to diffuse out of the leaf.
The palisade mesophyll layer(middle of the leaf) has lots of palisade cells that each contain hundreds of chloroplasts and have a good source of light.
The spongy mesophyll layer(beneath palisade layer) have cells that absorb carbon dioxide and release oxygen and water vapour; there is also air space between the cells to allow gases to diffuse in and out of mesophyll.
The xylem supplies the mesophyll cells with water from the constant transpiration stream, and the phloem carries away the products of photosynthesis, such as sugars to other parts of the plant.

Question 43

How can we test a leaf for photosynthesis through the production of starch in a leaf?(3)

Answer 43

Remove a leaf from a plant and place it in boiling water for 30 seconds(to stop all chemical reactions). Then place it in a boiling tube of ethanol and put that into a beaker of hot water, this is enough to remove most of the chlorophyll from the leaf.
When the leaf has turned pale yellow, after drying - spread it out on a tile and place a few drops of iodine solution on it. Any parts of the leaf containing starch will turn blue-black.
This only works if the plant has had plenty of light for some hours before the test.