Unit 2 Exam Cards

Question 1

Which structures are present in prokaryotic cells?

Answer 1

• Slime layer
• Plasmids
• Circular DNA
• Pili
• Cell wall

Question 2

When an egg cell becomes fertilised, what is it called?

Answer 2

Zygote.

Question 3

Which type of cell has the potential to give rise to any type of cell?

Answer 3

Totipotent cells.

Question 4

Which type of stem cell is found in the blastocyst, which can give rise to most types of cell apart from extra-embryonic cells?

Answer 4

Pluripotent cells.

Question 5

Suggest some problems of using stem cells taken from another adult to treat disease.

Answer 5

• Risk of pathogens from the donor
• Risk of rejection
• Risk of abnormal growth/cancer

Question 6

Which structure within cells modifies proteins?

Answer 6

The Golgi apparatus.

Question 7

Define the term tissue.

Answer 7

A group of specialised cells with the same origin that perform a common function.

Question 8

Outline the function of xylem.

Answer 8

• Transport of water
• Transport of minerals
• Structural support

Question 9

Describe the structure of a cellulose microfibril.

Answer 9

• Cellulose made of beta glucose
• Glucose molecules joined by 1-4 glycosidic bonds formed through condensation reactions
• Glucose molecules in a straight chain
• Microfibril composed of many cellulose molecules
• Cellulose molecules held together by hydrogen bonds

Question 10

Define the term species richness.

Answer 10

The number of species in a habitat.

Question 11

Explain what is meant by the term genetic variation.

Answer 11

The variety of alleles in a gene pool.

Question 12

Explain why it is better to store seeds rather than keeping fully-grown plants for long term conservation.

Answer 12

• Seeds are smaller, so more can be stored
• Seeds can remain dormant for a long time
• Seeds do not require the maintenance of fully grown plants
• Greater genetic diversity if a large number of seeds are stored

Question 13

Suggest why seeds in seedbanks are stored at low temperatures in a dry atmosphere.

Answer 13

• Seeds less likely to germinate
• Reduces enzyme activity of micro-organisms
• Decreases the rate of decomposition

Question 14

Explain the term antimicrobial properties.

Answer 14

The property of being able to kill micro-organisms.

Question 15

Why must Petri dishes be sterile when the agar is poured into them?

Answer 15

To prevent the contamination of other bacteria and competition between the bacteria.

Question 16

Explain why Petri dishes must not be completely sealed with tape before incubation.

Answer 16

To prevent anaerobic conditions which could encourage the growth of pathogenic bacteria. The bacteria in the culture also require oxygen for respiration.

Question 17

Define the term endemic species.

Answer 17

A species which is restricted to one geographical area.

Question 18

How do zoo breeding programmes help conserve rare species?

Answer 18

• Protects the species from predators or poachers
• Use of studbooks
• Processes like IVF used for breeding
• Wild behaviour reinforced for reintroduction into wild
• Reintroduced into reserves

Question 19

Which ion is used for the production of chlorophyll in plants?

Answer 19

Magnesium ions.

Question 20

Which ion is a component of the primary cell walls in plants?

Answer 20

Calcium ions.

Question 21

What are nitrate ions used for in plants?

Answer 21

Provides nitrogen for the construction of vital molecules.

Question 22

Explain what is meant by the term haploid number of chromosomes.

Answer 22

Half the number of chromosomes found in somatic cells.

Question 23

Explain what is meant by the term gene locus.

Answer 23

The position of a gene on a chromosome.

Question 24

What is the role of rough endoplasmic reticulum in a cell?

Answer 24

Proteins produced by the ribosomes on the outer surface are transported through the ER to other parts of the cell by vesicles.

Question 25

What is the role of the Golgi apparatus in a cell?

Answer 25

Vesicles containing proteins from the rER fuse with the Golgi apparatus, which modifies the proteins .

Question 26

How do stem cells become specialised?

Answer 26

• Stimulus (chemical) activates certain genes in the stem cell
• Only the active genes are transcribed
• mRNA is only made at the active genes
• Proteins are made from the mRNA which determine the structure and function of the cell

Question 27

How is acrosin released from the acrosome?

Answer 27

• Chemical stimulus causes the acrosome to swell
• Vesicles fuse with the sperm cell membrane
• Exocytosis releases acrosin from the acrosome

Question 28

Suggest why organs are considered more complex than tissues.

Answer 28

• Made up of tissues
• Made up of many different cell types
• Often have more than one function

Question 29

Give two roles of the cell cycle.

Answer 29

• Growth
• Asexual reproduction

Question 30

How could you distinguish between a cell in metaphase and a cell in anaphase?

Answer 30

Metaphase:

• Chromatids at equator of cell
• Chromatids attached
• Centromere complete

Anaphase:

• Chromatids seperated
• Centromere split
• Spindle fibres shortening