B1 - Cell Biology

Question 1

How is genetic information stored in a prokaryotic cell?

Answer 1

It’s found free within the cytoplasm as a plasmid or a single large loop of circular DNA

Question 2

What is a plasmid?

Answer 2

A small circular loop of DNA found free in the cytoplasm

Question 3

What 3 cell components are found in plant cells which aren’t found in animal cells?

Answer 3

Chloroplasts, vacuole and cell wall

Question 4

What is the function of the nucleus?

Answer 4

It controls the activities of the cell and stores genetic information

Question 5

What’s the function of the cytoplasm?

Answer 5

Where chemical reactions happen

Question 6

What is the function of the cell membrane?

Answer 6

It controls what goes in and out of the cell and supports it

Question 7

What is the function of the mitochondria?

Answer 7

It’s where aerobic respiration takes place

Question 8

What is the function of the ribosomes?

Answer 8

Where protein synthesis occurs

Question 9

What’s the plant cell wall made of?

Answer 9

Cellulose

Question 10

What is the function of the plant cell wall?

Answer 10

It provides strength to prevent the cell from bursting when water enters by osmosis

Question 11

What’s the function of the vacuole?

Answer 11

It contains cell sap and it supports the cell and maintains its turgidity(swollen).

Question 12

What is the function of the chloroplasts?

Answer 12

They absorb light energy from the Sun in order for photosynthesis to take place

Question 13

How are sperm cells and animals adapted to their function?

Answer 13

• they have a tail in order to move
• mitochondria which provides energy for the sperm cell to move fast
• It has enzymes in its head which helps digest the egg cell membrane

Question 14

How are nerve cells and animals adapted to their function?

Answer 14

• elongated structure allows electrical impulses to be transmitted all over the body
• short branched extension lets them connect to other nerve cells and receive impulses

Question 15

How are muscle cells in animals adapted to their function?

Answer 15

• Mitochondria to provide energy for muscle contraction

Question 16

How are root hair cells in plants adapted to their function?

Answer 16

• Large surface area to absorb nutrients and water from soil

- Thin walls that allow for water absorption

Question 17

How old xylem cells in plants adapted to their function?

Answer 17

• They are strengthened by lignin which helps support the cell
• It has a continuous hollow tube allowing for water to flow easily

Question 18

How are flowing cells in plants adapted to their function?

Answer 18

• Sieve plates let dissolved amino acids and sugars to transport up and down the stem

Question 19

Why cell differentiation important?

Answer 19

It allows production of different tissues and organs that perform various vital functions in the body

Question 20

What’s the purpose of cell division in mature animals?

Answer 20

Repair and replacement of cells

Question 21

What’s the definition of resolution?

Answer 21

The smallest distance between two objects that can be distinguished

Question 22

How does a light microscope work?

Answer 22

It passes a beam of light through a specimen which travels through the eyepiece lens so it can then be observed

Question 23

What are the advantages of light microscopes?

Answer 23

Inexpensive

Easy to use

Question 24

What are the disadvantages of light microscopes?

Answer 24

Limited resolution and magnification

Question 25

How does an electron microscope work?

Answer 25

A beam of electrons are focused. The electrons hit a screen which emits visible light to produce an image

Question 26

What are the two types of electron microscope?

Answer 26

Transmission electron microscope and scanning electron microscope

Question 27

What is the advantage of electron microscopes?

Answer 27

Greater magnification and resolution

Question 28

Why do electron microscopes have a greater magnification and resolution?

Answer 28

Because a beam of electrons has a shorter wavelength than a beam of light

Question 29

How does bacteria multiply?

Answer 29

Binary fission

Question 30

How often does bacteria multiply?

Answer 30

Every 20 minutes

Question 31

What are the two ways in which bacteria can be grown?

Answer 31

Nutrient broth solution | Colonies on an agar gel plate

Question 32

Describe the preparation of an on contaminated culture using aseptic technique:

Answer 32

1) Pour sterile agar gel into petri dish 2) Sterilise the inoculating loop(through flame) 3) Dip the inoculating loop into the solution of microorganisms, make streaks with it on the surface of the agar 4) Put the lid on the petri dish and secure it with tape and store upside down 5) Incubate it at 25°

Question 33

Why must petri dishes and culture media be sterilised before use?

Answer 33

To kill any bacteria already present

Question 34

Why must inoculating loops be sterilised by passing them thru Bunsen burner flame?

Answer 34

To kill any bacteria present on the loop

Question 35

Why must the Petri dish lid be secured with tape and the whole dish stored upside down?

Answer 35

Stops bacteria in the air contaminating the culture | upside down - Prevent condensation from forming onto the colonies

Question 36

Why are cultures incubated at 25°?

Answer 36

So harmful pathogens are less likely to grow

Question 37

How is the number of bacteria in a population after a certain time calculated from the mean division time?

Answer 37

- Calculate number of times the bacteria will divide in a given time period from the mean division time - No. of bacteria in population at end of time period = no. of bacteria at the beginning of the time period x 2 (to the power of no. of divisions in time period)

Question 38

How many chromosomes are found in the nucleus of human body cells?

Answer 38

46 (diploid)

Question 39

How many chromosomes are found in the nucleus of gametes?

Answer 39

23 (haploid)

Question 40

What are the three main stages of the cell cycle?

Answer 40

1. Replication of DNA 2. Mitosis 3. Division of cell

Question 41

Why is mitosis important?

Answer 41

Produces identical cells containing the same genetic information and it produces cells for growth and repair

Question 42

What happens in the first stage of the cell cycle?

Answer 42

The cell grows and increases in mass the DNA is replicated and there’s more sub-cellular structures

Question 43

What happens in the second stage of the cell cycle?

Answer 43

Each chromosome is pulled to opposite poles of the cell then the nucleus divides

Question 44

What happens in the third stage of the cell cycle?

Answer 44

The cytoplasm and cell membrane divide and two identical daughter cells are produced

Question 45

What is the function of stem cells in embryos?

Answer 45

Can replicate themselves and differentiate | They can treat conditions such as paralysis and diabetes by dividing to replace damaged cells

Question 46

What is the function of stem cells in adult bone marrow?

Answer 46

They can differentiate into several types of cells to replace dead or damaged tissues

Question 47

What is the function of stem cells in plant meristems?

Answer 47

They retain the ability to differentiate into any type of plant cell throughout their life span

Question 48

What is therapeutic cloning? (cloning method)

Answer 48

An embryo is produced with the same genetic info as a patient Embryonic stem cells aren’t rejected by the patient’s immune system, so they can be used to treat certain medical conditions

Question 49

What are the advantages of cloning plants using meristem stem cells?

Answer 49

It can prevent rare plants from becoming extinct and it can make a lot of plants with a favourable characteristic

Question 50

What are the issues associated with the use of embryonic stem cells?

Answer 50

- They are sourced from aborted embryos, some people have an ethical objection - The development of stem cell therapy is slow expensive and difficult

Question 51

What substances are transported by diffusion in the lungs?

Answer 51

Oxygen diffuses into the blood from the lungs and carbon dioxide diffuses into the lungs from the blood

Question 52

What factors increase the effectiveness of a gas exchange surface?

Answer 52

- Large surface area - A thin membrane which shortens the diffusion path - Efficient blood supply for animals

Question 53

How do plants leaves and stems remain rigid?

Answer 53

Water moves in by osmosis causing the vacuole to swell and the cytoplasm to press against the cell wall