Cell Biology

Question 1

Eukaryotic cell

Answer 1

Has a nucleus

Larger than prokaryotic cells = slower reproduction

They are more complex as they have organelles

E.g. plant cell and animal cell

Question 2

Prokaryotic cells

Answer 2

They have no nucleus (have free DNA)

Smaller than eukaryotic cells = faster reproduction

They are simpler as they have no organelles (only ribosomes)

E.g. bacteria

Question 3

Commonalties between eukaryotic and prokaryotic cells

Answer 3

Both have DNA

They both have ribosomes, cell membrane and cytoplasm

Question 4

Nucleus

Answer 4

This contains the genetic material (DNA) of the organism and controls the cell’s activities

Question 5

Cytoplasm

Answer 5

Chemical reactions take place here

Question 6

Cell membrane

Answer 6

Controls which substances can pass in and out the cell

Question 7

Mitochondria

Answer 7

Releases energy

Respiration occurs in the mitochondria

Question 8

Cell wall

Answer 8

Contains cellulose to provide strength and support to the cell

Question 9

Vacuole

Answer 9

A space inside the cytoplasm that contains cell sap; it keeps the cell firm

Question 10

Chloroplasts

Answer 10

Contain a green pigment called chlorophyll

Photosynthesis occurs in the cholorphyll

Question 11

Ribosomes

Answer 11

Responsible for protein synthesis (making proteins)

Question 12

Magnification

Answer 12

How much bigger a sample appears to be than in real life

Question 13

Magnification formula

Answer 13

Image / actual

Question 14

Resolution

Answer 14

Ability to distinguish between two points on an image

Question 15

Microscopy practical

Answer 15

Put a thin sample of tissue onto a microscope slide

Add a few drops of a suitable stain/dye

Place a coverslip on top of the tissue and place the slide onto the microscope stage

Use the objective lens with the lowest magnification, and focus on the sample

Increase the magnification and refocus to see different features of the cell

Question 16

Adaptations of a sperm cell

Answer 16

Many mitochondria to provide energy

Flagellum and streamlined head to swim

Acrosome contains digestive enzymes

Question 17

Adaptations of a red blood cell

Answer 17

Concave shape increases surface area for absorbing O2

Has haemoglobin (red pigment that absorbs the O2)

No nucleus so more room for haemoglobin

Question 18

Adaptations of a palisade cells

Answer 18

Packed with chloroplast for photosynthesis

Tall shape = higher surface area = more absorption of CO2

Question 19

Adaptations of a root hair cell

Answer 19

Large surface area to increase rate of absorption

Thin cell wall to allow minerals to enter or leave

Question 20

Adaptations of a nerve cell

Answer 20

They have an long axon so they can carry messages up and down the body

The axon is insulated by a fatty myelin sheath increasing the speed of the nerve impulses

Dendrites receive incoming nerve impulses from other neurons

Question 21

Effect of antiseptics practical

Answer 21

Pour the sterile agar plates into the petri dish and allow to set fully

Sterilise the inoculating loop by heating it in the Bunsen burner flame

Dip the inoculation loop into the microorganism solution and spread evenly

Add a sheet of antiseptic and tape the lid shut

Measure the clear area around the soaked filter paper disks

Question 22

Chromosomes

Answer 22

Chromosomes carry genetic information in a molecule called DNA

Question 23

Mitosis

Answer 23

A type of cell division which produces 2 identical daughter cells to the parent

Question 24

Process of mitosis

Answer 24

Chromosomes are duplicated

The chromosomes are pulled to opposite sides of the cell

The cell membrane and cytoplasm split into two identical daughter cells

Question 25

Meiosis

Answer 25

A type of cell division which produces four non-identical gametes

Question 26

Process of meiosis

Answer 26

Chromosomes pair up in the middle of the cell Some parts of the chromosomes swap places The chromosomes are pulled to opposite sides of the cell The two new cells divide again This creates four gametes, each with half the normal number of chromosomes

Question 27

Cell division in plants

Answer 27

Cell division occurs in the meristem of a plant

Question 28

Stem cells

Answer 28

Unspecialised cells capable of developing into many different types of cells

Question 29

Embryonic stem cells

Answer 29

Develop into all the different types of cells in the body

Question 30

Advantages of embryonic stem cells

Answer 30

The stem cells produced aren’t rejected by the patients body They divide and grow rapidly Can create a wider variety of cells

Question 31

Disadvantages of embryonic stem cells

Answer 31

Can kill the embryo, unethical Expensive to research and develop Higher risk of cancer or tumors

Question 32

Stem cells becoming specialised

Answer 32

A stem cell starts to divide into a stem cell and a tissue The tissue then divides further becoming more and more specialised

Question 33

Therapeutic cloning

Answer 33

Produces stem cells with the same genetic make-up as the patient

Question 34

Process of therapeutic cloning

Answer 34

The nucleus from a human egg cell is removed The cell from a patient has its nucleus removed and placed into the donor egg cell The cell is stimulated to divide by an electric shock, developing an embryo Embryo grows and produces stem cells

Question 35

Diffusion

Answer 35

The net movement of particles from a high concentration to a low concentration

Question 36

Factors affecting diffusion

Answer 36

The difference in concentrations The temperature The surface area of the membrane

Question 37

Adaptations in organisms increasing the rate of diffusion

Answer 37

Large surface area Membrane that is thin, to provide a short diffusion path Having an efficient blood supply (in animals)

Question 38

Osmosis

Answer 38

The movement of water across a semi-permeable membrane from a high concentration to a low concentration

Question 39

Osmosis practical

Answer 39

Set up 6 boiling tubes, each containing the same volume of the sucrose solution, but with different concentrations Cut 6 potato cylinders to the same length Gently dry each potato cylinder using a paper towel Record intial mass of the potato cylinders Leave the potato cylinders in the boiling tubes for 40 minutes Remove each potato cylinder from its boiling tube Gently remove excess liquid from the surface of the cylinder with a paper towel and record its mass

Question 40

Active transport

Answer 40

The movement of dissolved molecules from an area of low concentration to high concentration (against the gradient), requiring energy as a result