Chapter 3 - Cells

Question 1

Describe the function of a chloroplast

Answer 1

Absorbs light for photosynthesis and produced carbohydrates

Question 2

Describe how the rough endoplasmic reticulum is involved in the production of enzymes

Answer 2

The rough endoplasmic reticulum has ribosomes which make protein

Question 3

Describe how a sample consisting only of chloroplasts could be obtained from homogenised plant tissue

Answer 3

Placed in a centrifuge and spun at low speed to remove cell wall material. The supernatant is re-spun at high speed until chloroplast is found

Question 4

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical (light) microscope

Answer 4

• add drop of water to slide
• obtain thin section of plant tissue and place on slide
• add potassium iodide
• lower cover slip using mounted needle

Question 5

Name two structures in a eukaryotic cell that cannot be identified using an optical microscope

Answer 5

Mitochondria 
Ribosome
ER
lysosomes 
Cell surface membrane

Question 6

Explain the advantages and disadvantages of using a TEM to investigate cell structure

Answer 6

ADVANTAGES:

• Small objects can be seen
• TEM has high resolution as wavelength of electrons is shorter

DISADVANTAGES:

• can’t look at living cells
• preperation may create artefact
• doesnt produce colour image

Question 7

Name two structures present in eukaryotic cells that are not present in the cells of prokaryotes

Answer 7

• nucleus
• nuclear envelope
• mitochondria
• chloroplasts
• Golgi apparatus

Question 8

Explain why the structure of a membrane is described as fluid-mosaic

Answer 8

Molecules moving are the fluid.

The proteins and phospholipids are the mosaic

Question 9

In which phase of the cell cycle does dna replication take place?

Answer 9

S phase/ interphase

Question 10

Give one process which occurs in the nucleus of a cell during interphase which is necessary before cell division can take place

Answer 10

Replication of dna

Question 11

Describe what happens during anaphase that results in the production of two genetically identical cells

Answer 11

Sister chromatids move to opposite poles

Question 12

Homologous chromosomes carry the same genes but they are not genetically identical. Explain why.

Answer 12

Homologous chromosomes carry different alleles

Question 13

Give two reasons why mitosis is important in the life of an organism

Answer 13

Increase in cell number
Replace cells
A-sexual reproduction

Question 14

Explain one advantage of cells lining the human gut dividing very frequently

Answer 14

To replace cells

Question 15

Describe the role of the spindle during mitosis

Answer 15

Attachment of centromeres then seperation of centromeres

Question 16

Explain how the absorption of glucose into the cell leads to the movement of water imto the cell

Answer 16

The glucose lowers the water potential of the cell therefore water moves in by osmosis

Question 17

Suggest how watering plants with sodium chloride solution affects the fresh mass of the potatoes

Answer 17

Water potential inside tomato plant becomes higher, water draw out of tomato by osmosis, most of the fresh mass is water

Question 18

What is the main function of the Cell surface membrane?

Answer 18

Controls the passage of substances into and out of the cell

Question 19

What is the main function of the nucleus?

Answer 19

Contains the dna, which holds the genetic information necessary for controlling the cell

Question 20

What is the main function of lysosomes?

Answer 20

Digests unwanted material in the cell

Question 21

What is the main function of the rough endoplasmic reticulum?

Answer 21

Synthesises and transports proteins around the cell

Question 22

What is the main function of the smooth endoplasmic reticulum?

Answer 22

Synthesises lipids

Question 23

What is the main function of the Golgi apparatus?

Answer 23

Packages and processes molecules such as proteins for use in other parts of the cell, or for export to outside the cell.
Also forms lysosomes

Question 24

What is the formula for magnification?

Answer 24

Magnification = size of image / size of real object