Cell biology with all content

Question 1

what are uncontaminated cultures of microorganisms needed for

Answer 1

investigating disinfectant and antibiotic action

Question 2

describe the preparation of an uncontaminated culture using aseptic technique 7

Answer 2

use pre-sterilized plastic petri dish or glass petri dish and agar gel before with an autoclave

pour sterile agar gel into petri dish and allow tie to set

sterilize the inoculating loop by passing it through the Bunsen burner flame

dip inoculating loop into the solution of microorganisms and make streaks with the loop on the surface of agar

put the lid on the perti dish and secure it with tape

label accordingly and turn and store upside down

incubate the culture at 25oc in laboratories

Question 3

Why must inoculating loops be sterilised by passing

them through Bunsen burner flame?

Answer 3

To kill any bacteria present on the

inoculating loop

Question 4

Why must the Petri dish lid be secured with adhesive

tape and the whole dish stored upside down? 3

Answer 4

Stops bacteria in the air contaminating the culture.

Lid is not fully sealed to stop growth of
anaerobic bacteria in a lack of oxygen.

Upside down to prevent condensation from forming
and dripping down onto the colonies

Question 5

How is the number of bacteria in a population after a

certain time calculated from the mean division time?

Answer 5

Number of bacteria in population at end of time period =

number of bacteria at
the beginning of the time period x 2^number of divisions in the time period

In hours

Question 6

Why are cultures incubated at 25oC in

school laboratories?

Answer 6

Harmful pathogens are less likely to to

grow at this temperature.

Question 7

What are chromosomes made up of?

Answer 7

Chromosomes consist of DNA molecules
combined with proteins
They contain
genes which provide the instructions for
protein synthesis

Question 8

What is a gene?

Answer 8

A section of DNA which codes for a

protein

Question 9

What are the three main stages of the cell

cycle?

Answer 9

1. Replication of DNA and synthesis of
   organelles
2. Mitosis
3. Division of cell

Question 10

Why is mitosis important?

Answer 10

● Produces identical cells with the same genetic information.
● Produces additional cells for growth and
repair

Question 11

first stage of the cell cycle 4

Answer 11

-Longest stage
cells grow and increase
in mass,
 replicate DNA and synthesise
more organelles (eg. mitochondria,
ribosomes)

Question 12

Describe the second stage of the cell cycle

2

Answer 12

Each chromosome in a pair is pulled to
opposite poles of the cell
then the nucleus
divides.

Question 13

Describe the third stage of the cell cycle

Answer 13

The cytoplasm and cell membrane divide -

two identical daughter cells are produced.

Question 14

What is a stem cell?

Answer 14

An unspecialised cell which is capable of
differentiating into other cell types and of
self-renewal.

Question 15

What is the function of stem cells in embryos? 2

Answer 15

Embryonic stem cells can replicate, differentiate themselves into other types of cells.

may be able to treat conditions
such as paralysis and diabetes by dividing to replace
damaged cells

Question 16

What is the function of stem cells in adult bone marrow

Answer 16

Adult stem cells can differentiate into several cell types to replace dead or damaged tissues.

bone marrow stem cells can form many
different types of blood cell.

Question 17

What is the function of stem cells in plant

meristems?

Answer 17

are able to differentiate into any type of plant cell throughout
their lifespan
can differentiate into any cell
which is required by the plant.

Question 18

What is therapeutic cloning? 3

Answer 18

Cloning method where an embryo is produced with the same genetic makeup as the patient.
The stem cells which originate from the embryo will not be rejected by the patient’s immune
system, so can be used to treat certain medical
conditions

Question 19

What are the advantages of cloning plants using

meristem stem cells?

Answer 19

prevent rare plants from becoming extinct.

produce large numbers of plants with a
favorable characteristic.

produce identical plants for research.

Question 20

What are issues are associated with the use

of embryonic stem cells?

Answer 20

embryonic stem cells are sourced from aborted embryos

some people have an ethical/religious objection.

Development of stem cell therapies is slow, expensive and difficult.

Adult stem cells infected with viruses could transfer infections to
patients.

If donor stem cells do not have a similar genetic makeup to the
patient, an immune response could be triggered