Cell Biology random revision (pages 11 - 22)

Question 1

Describe the function of the cell membrane?

Answer 1

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

Question 2

Name the subcellular structure where proteins are made?

Answer 2

Ribosome

Question 3

What part of a plant cell is made of cellulose?

Answer 3

The cell wall

Question 4

Name the subcellular structure in a plant cell in which photosynthesis takes place?

Answer 4

Chloroplast

Question 5

Describe the difference between the way the genetic material is sotred in eukaryotic cells and prokaryotic cells?

Answer 5

The genetic material in eukaryotic cells is found in the nucleus. The genetic material in prokaryotic cells is found floating free in the cytoplasm, as a single loop of DNA and as plasmids

Question 6

True or False? An electron microscope has a lower magnification but a higher resolution than a light microscope. Explain your answer

Answer 6

False - an electron microscope has a higher magnification than a light microscope, as well as a higher resolution.

Question 7

Give the equation for calculating the magnification of an image?

Answer 7

Magnification = image size ÷ real size

Question 8

How many micrometres (um) are in a millimetre (mm)?

Answer 8

1000

Question 9

Describe how you would bring a cell sample into focus when using a light microscope?

Answer 9

Use the coarse adjustment knob to move the stage up to just below the objective lens. Look down the eyepiece and use the coarse adjustment knob to move the stage downwards until the image is roughly in focus. Then adjust the focus with the fine adjustment knob, until a clear image of the cells is visible.

Question 10

What does it mean if a cell is ‘specialised’?

Answer 10

The cell has differentiated into a certain type of cell that has a specific function

Question 11

What is the function of a nerve cell?

Answer 11

To carry electrical signals from one part of the body to another.

Question 12

Describe one way that a xylem cell is specialised for its function?

Answer 12

E.g. it’s hollow (so stuff can flow through it).

Question 13

Where in the cell are genes found?

Answer 13

In the nucleus (in chromosomes)

Question 14

This flowchart shows an outline of the cell cycle. What should go in the middle (b) box?

a) The cell grows and increases its number of subcellular structures.

b) ????

c) The cell divides by mitosis.

Answer 14

b) The cell duplicates its DNA

Question 15

How many daughter cells are produced when a cell divides by mitosis?

Answer 15

two

Question 16

What is a stem cell?

Answer 16

An undifferentiated cell that can divide to produce lots more undifferentiated cells. They can differentiate into different types of cell.

Question 17

What is the difference between an embryonic stem cell and an adult stem cell?

Answer 17

An embryonic stem cell can diffentiate into any type of cell, while an adult stem cell can only differentiate into certain types of cell.

Question 18

What is therapeutic cloning?

Answer 18

The process of making an embryo that has the same genetic information as a patient, in order to produce stem cells that can be used to treat the patient.

Question 19

Where are stem cells found in a plant?

Answer 19

The meristems

Question 20

Describe how diffusion occurs in a gas?

Answer 20

The particles spread out from an area of higher concentration to an area of lower concentration.

Question 21

What happens to the rate of diffusion if you decrease the concentration gradient?

Answer 21

It decreases

Question 22

What would you have to do to the temperature of a solution to increase the rate of diffusion through it?

Answer 22

increase it

Question 23

Explain why diffusion through a cell membrane is described as a ‘net’ movement?

Answer 23

Particles move in both directions across the membrane, but there’s an overall (net) movement from the side where they’re more concentrated to the side where they’re less concentrated.

Question 24

What is the name of the process by which water moves from a less concentrated solution to a more concentrated solution through a partially permeable membrane?

Answer 24

Osmosis

Question 25

When investigating the effect of the concentration of a salt solution on the mass of pieces of potato, what is the dependent variable?

Answer 25

The mass of the pieces of potato.

Question 26

Describe one way that the roots of a plant are adapted for taking in minerals and water?

Answer 26

E.g. Plant roots are covered in millions of root hair cells which stick out into the soil and give the roots a larger surface area.

Question 27

Why is respiration needed for active transport?

Answer 27

To release the energy needed for the process.

Question 28

Give two differences between osmosis and active transport?

Answer 28

Any two from, e.g.:

• Active transport requires energy, whereas osmosis doesn’t.
• Osmosis only involves water molecules, whereas active transport doesn’t.
• Active transport moves substances from an area of lower concentration to an area of higher concentration (against a concentration gradient), whereas osmosis moves water molecules from an area of higher water concentration to an area of lower water concentration (down a concentration gradient).

Question 29

Give one example of a waste substance that is removed from body cells by diffusion?

Answer 29

E.g.:

• carbon dioxide
• Urea

Question 30

Which would you expect to have a larger surface area to volume ratio - a large organism or a small organism?

Answer 30

A small organism

Question 31

Why do multicellular organisms need exchange surfaces but single-celled organisms don’t?

Answer 31

Multicellular organisms have a smaller surface area to volume ratio, so (unlike in a single-selled organism) not enough substances can diffuse from their outside surface to supply their entire volume.

Question 32

Give two ways that the efficiency of an exchange surface can be increased?

Answer 32

Any two from e.g.:

• By reducing the thickness of its membrane.
• By increasing its surface area.
• By ventilating it so that air moves around it more.
• By increasing the number of blood vessels it has.

Question 33

What gas diffuses out of the blood in the lungs?

Answer 33

Carbon dioxide

Question 34

Name the structures in the small intestine that increase its surface area?

Answer 34

Villi

Question 35

Explain why Villi are adapted to have only a single layer of surface cells?

Answer 35

Digested food is absorbed into the blood across the outer layer of the Villi. Having only a single layer of surface cells reduces the distance that substances need to travel and so increases the rate of absorption.

Question 36

Describe two features of a leaf that allow for efficient gas exchange?

Answer 36

An two from, e.g:

• A flattened shape.
• Stomata in the bottom of the leaf
• Air spaces inside the leaf.

Question 37

Explain why air spaces inside leaves are important for photosynthesis?

Answer 37

For photosynthesis to take place, carbon dioxide needs to be absorbed across the walls of cells inside leaves. The air spaces inside leaves mean that fewer of the plant cells are touching each other, so more of the plant cell walls are exposed and are available for gas exchange. This means more carbon dioxide is able to move into the cells.

Question 38

Name the gas exchange surface in fish?

Answer 38

Gills

Question 39

Fish gills are made up of gill filaments (thin plates). Explain how this adaptation affects the rate at which oxygen can diffuse into blood?

Answer 39

The gill filaments increase the surface area of the gills, meaning more water is able to flow across them. This means oxygen is able to diffuse from the water into the blood more quickly.