Aqa Biology Igcse (Section 1: Cell Activity)

Front 1

Name the 5 parts of an animal cell.

Back 1

Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.

Front 2

Back 2

Front 3

What is the function of the nucleus?

Back 3

The nucleus controls all the activities of the cell. It contains the genes of the chromosomes that carry the instructions for making proteins needed to build new cells or new organisms.

Front 4

What is the function of the cytoplasm?

Back 4

The cytoplasm is a liquid gel in which most of the chemical reactions needed for life take place, for example the first stages of cellular respiration.

Front 5

What is the function of the cell membrane?

Back 5

The cell membrane controls the passage of substances such as glucose and mineral ions into the cell. It also controls the movement of substances such as urea or hormones out of the cell.

Front 6

What is the function of mitochondria?

Back 6

Mitochondria are structures in the cytoplasm where oxygen is used and most of the energy is released during respiration.

Front 7

What is the function of ribosomes?

Back 7

Ribosomes are where protein synthesis takes place, making all the proteins needed in the cell.

Front 8

Name the three additional parts that may be in a plant cell or algal cell.

Back 8

Cell wall, chloroplasts, permanent vacuole.

Front 9

Back 9

Front 10

What is the function of the cell wall?

Back 10

The cell wall is made from cellulose that strengthens the cell and gives it support.

Front 11

What is the function of chloroplasts?

Back 11

Chloroplasts are found in all the green parts of the plant. They contain chlorophyll, which absorbs light energy to make food by photosynthesis.

Front 12

What is the function of a permanent vacuole?

Back 12

A permanent vacuole is the space in the cytoplasm filled with cell sap. This is important for keeping the cells rigid to support the plant.

Front 13

Back 13

Front 14

What is the function of plasmids?

Back 14

Plasmids carry extra genetic information. Plasmids are used by scientists in the process of genetic engineering.

Front 15

Why are bacteria useful?

Back 15

We use them to make food like yoghurt and cheese. Others are used in sewage treatment and to make medicines. They are vital is decomposers in food chains and webs, and in natural cycles such as the carbon and nitrogen cycles. They are also an important part of a healthy gut.

Front 16

How do yeasts reproduce?

Back 16

Asexual budding.

Front 17

What is asexual budding?

Back 17

The process in which a new yeast cell grows out from the original cell to form a separate yeast organism.

Front 18

What is fermentation?

Back 18

The anaerobic respiration of yeast.

Front 19

When yeast cells use anaerobic respiration, breaking down sugar in the absence of oxygen, what do they produce?

Back 19

Ethanol and carbon dioxide.

Front 20

What is yeast useful?

Back 20

Yeast is important in the production of antibiotics such as penicillin, as decomposersin food chains and webs, and in the carbon cycle. It can be used to make alcohol and bread.

Front 21

What problems does yeast cause?

Back 21

Yeast breaks down and decomposes food people are storing.

Front 22

How are fat cells adapted?

Back 22

They have a small amount of cytoplasm and large amounts of fat.

They have few mitochondria as the cells need very little energy.

They can expand as they fill up with fat.

Front 23

How are cone cells adapted?

Back 23

The outer segment contains a visual pigment that changes chemically in coloured light. It needs energy to change back.

The middle segment is full of mitochondria to reform the visual pigment, letting you see continually in colour.

The final part is a synapse that connects to the optic nerve. When the visual pigment changes, a nerve impulse is triggered.

Front 24

How are root hair cells adapted?

Back 24

They increase the surface area for water to move into the cell.

They have a permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cells.

Front 25

How are sperm cells adapted?

Back 25

A long tail helps the sperm move towards the egg.

The middle section is full of mitochondria for the tail to work.

The acrosome stores digestive enzymes for breaking down the outer layers of the egg.

A large nucleus contains the genetic information to be passed on.

Front 26

What is diffusion?

Back 26

The spreading out of particles in a gas, or any substance in a solution (a solute) which results in a net movementof particles. The movement is from an area of high concentration to low concentration. Also known as down a concentration gradient.

Front 27

What affects the rate of diffusion?

Back 27

The greater the difference in concentration, the faster the rate of diffusion.

An increase in temperature increases the rate of diffusion.

Front 28

How is osmosis different from diffusion?

Back 28

Water moves from a dilute solution to a concentrated solution.

Front 29

If the concentration of solutes in the solution outside the cell is the same as the concentration inside the cell, the solution is ... to the cell.

Back 29

isotonic, animal cells are normal and plant cells are flaccid

Front 30

If the concentration of solutes in the solution outside the cell is higher than the concentration inside the cell, the solution is ... to the cell.

Back 30

hypertonic, animal cells will shrivel and plant cells become plasmolysed

Front 31

If the concentration of solutes in the solution outside the cell is lower than the concentration inside the cell, the solution is ... to the cell.

Back 31

hypotonic, animal cells will burst and plant cells will be turgid/normal

Front 32

What is useful about active transport? What is a downside?

Back 32

It can move particles against the concentration gradient. It requires energy.

Front 33

What cells carry out lots of active transport?

Back 33

Root hair cells and cells in your gut. They both have many mitochondria.

Front 34

As organisms get bigger, their surface area to volume ratio gets ... ?

Back 34

Smaller.

Front 35

What are the disadvantages of being a big organism?

Back 35

Gases and food molecules can no longer reach every cell inside the organism by simple diffusion.

Metabolic waste cannot be removed fast enough to avoid poisoning the cells.

Front 36

What adaptations make the process of exchange more efficient?

Back 36

Having large surface area provides a bigger area for exchange to take place.

Being thin provides a short diffusion path.

Having an efficient blood supply (in animals) moves the diffusing substances away and maintains a concentration gradient.

Being ventilated (in animals) to make gaseous exchange more efficient by maintaining a steep concentration gradient.

Front 37

What happens in the small intestine?

Back 37

Digested food molecules move into the bloodstream to reach your cells.

Front 38

What gets diffused in the small intestine and how is it adapted for diffusion?

Back 38

Digested food molecules get diffused into the bloodstream. This is because there is a much higher concentration of food molecules in the gut than in the bloodstream.

The lining of the small intestine is folded into villi to increase the rate of diffusion. Each villus is covered by microvilli for the same reason.

The lining of the small intestine has a good blood supply to carry away the digested food molecules as soon as they are diffused to maintain a steep concentration gradient.

The villi have thin walls so there is a short distance across which diffusion takes place.

Front 39

What gets transported via active transport in the small intestine?

Back 39

You will eventually have more dissolved food molecules in your blood than your digestive system so active transport moves glucose and other dissolved food molecules into the bloodstream.