Biology B2 (i)

What does the nucleus of a human cell contain?

It contains genetic material that controls the activites of the cell.

What is cytoplasm?

It is a gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions.

What is the cell membrane?

It holds the cell together and controls what goes in and out.

What is mitochondria?

These are where most of the reactions for respiration take place. Respiration releases energy that cells need to work.

What is made in the Ribosomes?

Proteins are made in the cell.

What three extra things does a plant cell have, that an animal cell does not?

The thirst thing is a rigid cell wall. This is made of cellulose. It supports the cell and strengthens it.

Secondly, Permanent vacuole. This contains cell sap, a weak solution of sugar and salts.

And lastly, chloroplasts. This is where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll.

How are palisade leaf cells adapted for photosynthesis?

Firstly, they are packed with chloroplasts for photosynthesis. More of them are crammed at the top of the cell - so they are nearer the light.

Secondly, they have a tall shape which means they have a lot of surface area exposed down the side for absorbing CO2 from air in the leaf.

Lastly, they have a thin shape that means you can pack loads of them in at the top of a leaf.

A fact about Palisade leaves cells are that they are grouped together to give the palisade layer of a leaf. This is the leaf tissue where most of the photosynthesis happens.

How are guard cells adapted to open and close pores?

They are in a special kidney shape which opens and closes the pores in a leaf.

Secondly, thin outer walls and thickened inner walls make the opening and closing work.

Lastly, the are sensitive to light and close at night to save water without losing out on photosynthesis.

Therefore, they are adapted to their function of allowing gas exchange and controlling water loss within the leaf organ.

How are red blood cells adapted to carry oxygen?

Firstly, they have a big surface area for absorbing oxygen. It also helps them pass smoothly through capillaries to reach body cells.

Secondly, they are packed with haemoglobin, the pigment that absorbs the oxygen.

Lastly, they have no nucleus. This leaves room for more haemoglobin.

Therefore, red blood cells are an important part of the blood (blood's actually counted as a tissue).

How are sperm and egg cells adapted for reproduction?

The egg contains huge food reserves to feed the embryo. The membrane of the egg instantly changes when the sperm fuses with edd to stop any more sperm getting in. This makes sure the offspring ends up with the right amount of DNA.

The sperm has a long tail and a streamlined head to help it swim to the egg. There are a lot of mitochondria in the cell to provide the energy needed. They also carry enzymes in their head to digest through the egg cell membrane.

What is diffusion?

Diffusion is the passive movement of particles from an area of high concentration to an area of low concentration. It happens in liquids and gases.

How do particles flow throug the cell membrane?

They flow from a high concentration to a low concentration. The bigger the difference in concentration, the faster the diffusion rate.

What three things does the rate of diffusion depends on?

One - Distance. Substances diffuse more quickly when they haven't as far to move.

Two - Concentration Difference. Substances diffuse faster if there's a big difference in concentration.

Three - Surface area. The more surface there is for molecules to move across, the faster they can get from one side to the other.

What is osmosis?

Osmosis is the movement of water molecules across a partially permable membrane from a region of high water concentration to a region of low water concentration.

How does osmosis help cells with the amount of water that is put in them?

If a cell is short of water, the solution inside it will become quite concentrated. This usually means the solution outside is more dilute, and so water will move into the cell by osmosis.

What is the equation for photosynthesis?

The equation for photosynthesis is, carbon dioxide + water reacting with sunlight and chlorophyll makes glucose + oxygen.

What are some limiting factors?

One limiting factor could be the amount of lgiht.

Another could be temperature.

Name a few ways in which you can artificially create the ideal conditions for farming?

You could use a greenhouse. These help to trap the suns heat, and make sure the temperature doesn't become limiting. You could also use a heater to keep the heat up or shades and ventilation to keep the temperature down.

You could supply the plants with superficial light.

You could also use a paraffin heater to increase the level of carbon dioxide in the greenhouse.

Keeping plants in a greenhouse ensures that no pests or diseases keep the plants healthy.

What six things do plants use glucose for?

One, respiration.

Two, making fruits.

Three, making cell walls.

Four, making proteins.

Five, stored in seeds.

Six, stored in starch.

What are Nitrates?

Nitrates are needed for making amino acids, which are then used to make proteins.

What is magnesium needed to make?

Chlorophyll, which is needed for photosynthesis.

What are the other minerals needed by plants?

Potassium and Phosphates, which are used for things like making DNA and cell membranes.

How can you tell if a plant is suffering from a lack of nitrates?

The plant starts to show stunted growth and won't reach it's usual size.

How can you tell if a plant is suffering from a lack of magnesium?

The leaves of the plant start to turn yellow.

What is monoculture?

It is where just one type of crop is grown in the same field year after year. This means that they all need the same minerals. Therefore, the soil becomes deficiant in the minerals the crop needs. A fertiliser will replenish the depleted minerals.

Why is there less energy and biomass everytime you move up a level on a pyramid of biomass?

Plants use energy making food during photosynthesis.

Most of the energy is lost during to the surroundings as heat.

It can also be lost in animals through droppings - excretion.

What are the two ways in which the 'efficiany' of food production can be improved?

1. Reduce the number of stages in the food chain.

2. Restrict the energy lost by farming.

What are some of the arguements against intensive farming?

1. Some people think that it's cruel and choose to eat organic meat.

2. The crowded conditions means that it's a favourable environment for the spread of diseases.

3. To prevent diseases, animals are given antibiotics. However, if these enter humans when they eat the meat. Then they will build up a defence against the antibiotics.

4. The animals need to be kept warm, taking up a lot of fossil fuels.

5. Our fish stocks are getting low but these are usually used to feed intensively farmed animals.