B1 - Cell Biology Part 2

Question 1

Magnification equation and units

Answer 1

Magnification = image size/real size
Magnification = mm/mm

Question 2

How to prepare slide for microscopy (normal microscope)
(6 marks)

Answer 2

Add drop of water to the middle of a clean slide
Cut onion, separate into layers
Use tweezers to peel off epidermal tissue from the bottom of one of the layers
Using tweezers, place the epidermal tissue into water on the slide
Add a drop of iodine solution - to stain the epidermal tissue
Place a cover slip on top,

Question 2

How do you use a light microscope to look at your slide
(6 marks)

Answer 2

Clip the slide prepared on the stage
Select the lowest-powered objective lens
Use coarse adjustment knob to move stage up to just below the objective lens
Look down eyepiece, use coarse adjustment knob to move stage downwards until the image is in focus
Adjust focus with the fine adjustment knob until a clear image is shown on the slide
Swap to a higher-powered objective lens and refocus in case greater magnification is needed

Question 3

What is the equation for total magnification

Answer 3

Total magnification = eyepiece lens x objective lens

Question 4

What type of cell are cheek cells

Answer 4

Epithelial cells

Question 5

What is a specialised cell
What is differentiation
What are stem cells

Answer 5

A cell that is adapted to its function by having special shape and features.
When a cell changes to become specialised for its job
Undifferentiated cellsq

Question 6

What is the purpose of a sperm cell and how is it specialised to do this

Answer 6

To get male DNA to female DNA
Has a long tail and streamlined head to help it swim to the egg
Lots of mitochondria to transfer energy needed
Carries enzymes in its head to digest through the egg cell membrane

Question 7

Purpose of nerve cell
How is it specialised to do this

Answer 7

Carry electrical signals from one part of the body to another.
They are long to cover more distance
Have branched connections at their ends to connect to other nerve cells and form a network throughout the body

Question 8

Purpose of muscle cell
How is it specialised to do this

Answer 8

Contract quickly
They are long to have space to contract
Contains lots of mitochondria to transfer energy needed for contraction

Question 9

Purpose of root hair cell
How is it specialised to do this

Answer 9

Absorbing water and minerals
Long hairs to stick into soil
Large surface area for absorbing water and mineral ions from soil

Question 10

Purpose of Phloem and Xylem
How is it specialised to do this

Answer 10

Transporting substances
Xylem cells are hollow in the centre and phloem cells have very few subcellular structures, so that stuff can flow through them

Question 11

What does the nucleus of a cell contain
What do each chromosome carry

Answer 11

The nucleus of a cell contains chromosomes made of DNA
molecules. Each chromosome carries a large number of gene

Question 12

What is the purpose of mitosis?

Answer 12

To grow or replace cells that have been damaged
Repair damaged tissues

Question 13

Describe the process of growth and dna replication ( 6 marks)

Answer 13

Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria.
The DNA replicates to form two copies of each chromosome ( X shaped)
In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.
Finally the cytoplasm and cell membranes divide to form two
identical cells.

Question 14

Stem cells in the early human embryo (embryonic stem cells) can turn into..

Answer 14

any kind of cell at all

Question 15

Stem cells from embryos and bone marrow can be grown in a lab to produce..

Answer 15

clones and to differentiate into specialised cell for medicine

Question 16

Give examples of real life use of adult stem cells and embryonic stem cells

Answer 16

Adult: replace faulty blood cells
Embryonic: replace faulty cells

Question 17

Meristem tissue in plants can differentiate into..

Answer 17

any type of plant cell

Question 18

In therapeutic cloning an embryo could be made to have the same.. so the stem cells produced would not be

Answer 18

an embryo could be made to have the same genes as the patient, so the stem cells produced from it would not be rejected by patients body

Question 19

Why are people against stem cell research
(3 marks)

Answer 19

Because each human embryo is a potential human life
Others think that curing existing patients who are suffering is more important than the rights of embryos
Unwanted embryos from fertility clinics are usually destroyed

Question 20

What are the risks of using stem cells in medicine

Answer 20

Stem cells grown in the lab may become contaminated with a virus and could pass onto the patient

Question 21

Describe the benefits of using meristem (stem cells)
( 3 marks)

Answer 21

Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
Rare species can be cloned to protect from extinction.
Grows crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers

Question 22

3 factors that affect diffusion

Answer 22

difference in concentrations
temperature
surface area of the membrane

Question 23

How does surface area of the membrane affect the rate of diffusion (2 mark)

Answer 23

The larger the S.A of the membrane, the faster the diffusion rate because more particles can pass through at once

Question 24

Explain the need for exchange surfaces
and a transport system in multicellular organisms
(4 marks)

Answer 24

Multicellular organisms have a smaller surface area compared to their volume
Not enough substances can diffuse from their outside surface to supply their entire volume
They need some sort of exchange surface for efficient diffusion
Exchange surface allows enough of necessary substances to pass through

Question 25

How are exchange surfaces adapted to maximise effectiveness (4 marks)

Answer 25

thin membrane, substances only have a short distance to diffuse
large surface area, lots of a substance can diffuse at once
Exchange surfaces in animals have lots of blood vessels to get stuff into and out of the blood quickly
Gas exchange surfaces in animals are often ventilated, air moves in and out

Question 26

How is a single celled organism adapted for sufficient transport of molecules ( 2 marks)

Answer 26

single-celled organism has a relatively large surface area to volume ratio.
Allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.

Question 27

How is active transport used in the guts

Answer 27

when there is a lower concentration of nutrients in the gut, but higher concentration of nutrients in the blood

Question 28

How are alveoli’s specialised to maximise diffusion
(4 marks)

Answer 28

An enormous surface area
Moist lining for dissolving gases
Very thin walls
Good blood supply

Question 29

Where is villi found and what is its purpose
How are villi adapted

Answer 29

S.I
Lots of microvilli to increase surface area so digested food is absorbed much quickly into the blood
Single layer of surface cells
Good blood supply to assist quick absorption
Cells have many mito - release energy needed for active transport

Question 30

Describe the potato osmosis investigation ( 6 marks)

Answer 30

Cut potato into identical cylinders
Get two beakers one should be pure water and other should be a very concentrated sugar solution with same volume of 25cm^3
Measure the mass of cylinders then leave one cylinder in each beaker for 24 hours
After 24 hours take them out and dry them with a paper towel and measure their masses
Cylinder has drawn in water by osmosis - increased in mass
Water has been drawn out - decreased in mass

Question 31

What problems may arise during/after the experiment
How can this be reduced
(Potato)

Answer 31

If potato’s were not fully dried - excess water would give higher mass
If water evaporate from the beakers - concentrations of sugar solutions would change
Repeating experiment and calculating a mean

Question 32

What is active transport - 3 marks

Answer 32

Minerals absorbed from a dilute solution, against a concentration gradient requires energy to do so

Question 33

How are exchange surfaces adapted to maximise effectiveness ( 4 marks)

Answer 33

They have a thin membrane, so substances only have a short distance to diffuse
Large surface area so lots of substances can diffuse at once
Exchange surfaces in animals have lots of blood vessel to get substances into and out of blood quickly
Gas exchange surfaces in animals are often ventilated too

Question 34

Two ways electron microscopes are better than light microscopes

Answer 34

Much higher magnification
Much higher resolution
Can see smaller things in more detail

Question 35

Convert 1mm to micrometers

Answer 35

1000 μm

Question 36

Convert 1μm to nanometer

Answer 36

1000 nanometers

Question 37

Convert 1μm to mm

Answer 37

1/1000

Question 38

Convert 1 nanometer to μm

Answer 38

1/1000

Question 39

How are gills adapted for gas exchange ( 6 marks)

Answer 39

Each gill is made of lots of thin plates called gill filaments
- increases surface area for exchanging gases
Gill filaments are covered in lots of lamellae - increases surface area even more
Lamellae have lots of blood capillaries to speed up diffusion
Thin surface layer of cells to minimise the distance that the gases have to diffuse
Blood flows through lamellae in one direction and water flows over in the opposite direction - maintains a large concentration gradient
Concentration of oxygen in the water always higher than that in the blood so as much oxygen as possible diffuses from the water into the blood