Cell Biology

Question 1

How is the phloem adapted?

Answer 1

The end walls of (living) phloem cells contain small holes

Question 2

List 3 examples of specialisation in animal cells

Answer 2

Sperm - flagellum to move around, an acrosome containing digestive enzymes

Red blood cell - concave (high s.a), no nucleus, haemoglobin to transport oxygen around body

Nerve - long and thin, able to connect, myelin to contain impulses

Question 3

List 3 examples of specialisation in plant cells

Answer 3

Root hair cells - long projections (high s.a) and no chloroplasts as they’re underground

Phloem - the end walls of (living) cells contain small holes, no nucleus

Xylem - open-ended cells to allow the flow of water, (dead) cells contain lignin to make cell walls strong

Question 4

Describe a eukaryotic cell (organelles, size, etc)

Answer 4

• Plant and animal cells
• Bigger than prokaryotes
• Have a cell membrane, cytoplasm, etc
• Genetic material in nucleus

Question 5

Describe a prokaryotic cell (organelles, size, etc)

Answer 5

• Bacteria (unicellular)
• Smaller than eukaryotes
• Have a cell wall, cytoplasm, and a cell membrane
• Genetic material in a DNA loop, and plasmids

Question 6

What is the function of the phloem?

Answer 6

Transports glucose from the leaves around the plant (translocation)

Question 7

What is the function of the xylem?

Answer 7

Transports water from the roots to the leaves for photosynthesis (transpiration)

Question 8

What is the function of the nucleus?

Answer 8

Contains genetic material, controls what happens in the cell

Question 9

What is the function of the cytoplasm?

Answer 9

Where chemical reactions take place

Question 10

What is the function of ribosomes?

Answer 10

Protein synthesis

Question 11

What is the function of mitochondria?

Answer 11

Where respiration takes place

Question 12

What is the function of the cell membrane?

Answer 12

Controls what goes in and out of the cell

Question 13

What is the function of the cell wall?

Answer 13

Made of cellulose, holds the cell together

Question 14

What are the function of chloroplasts?

Answer 14

Contain chlorophyll, where photosynthesis takes place

Question 15

What is the function of the permanent vacuole?

Answer 15

Stores cell sap to keep the cell turgid

Question 16

How do you use a microscope? (req. practical)

Answer 16

1. Clip slide onto stage
2. Select lowest objective lens
3. Position the lens using the course focus until it almost touches the slide without looking through the eyepiece yet
4. Slowly turn the coarse focus until cells come into focus whilst looking through the eyepiece
5. Use the fine focus to focus the image more
6. Repeat with a higher objective lens

Question 17

Where are pacemaker cells located?

Answer 17

Right atrium

Question 18

Describe an electron microscope

Answer 18

• Expensive
• See in black and white
• Higher magnification
• Higher resolution

Question 19

Describe a light microscope

Answer 19

• Cheaper
• See in colour
• Lower magnification
• Lower resolution

Question 20

How do bacteria multiply?

Answer 20

Binary fission

Question 21

How do you prepare microorganism cultures? (req. practical)

Answer 21

1. Sterilise an inoculating loop over a Bunsen burner
2. Dip it into the bacteria and spread it over an agar plate
3. Close the lid quickly after to prevent contamination
4. Using tweezers, dip 3 paper circles into 2 types of antiseptic and one control, and place them in the agar plate
5. Seal it shut with tape and label it with the date and bacteria
6. Store it upside-down at 25 Celsius

Question 22

Describe the stages of mitosis

Answer 22

• The chromosomes double and each group is pulled to opposite ends of the cell
• The nucleus divides
• The cytoplasm and cell membranes divide to form 2 identical daughter cells

Question 23

What is a stem cell?

Answer 23

A cell that isn’t differentiated yet

Question 24

Where are adult stem cells found?

Answer 24

Bone marrow

Question 25

Name some difference between the two types of stem cell

Answer 25

Embryonic stem cells can differentiate into any type of cell

Question 26

What illnesses can be treated with stem cells?

Answer 26

Diabetes and paralysis

Question 27

What is therapeutic cloning?

Answer 27

Cloning

Question 28

What are the advantages and disadvantages of using stem cells?

Answer 28

Advantages: Cures conditions, uses wasted cells, can replace body parts, prevents organ rejection Disadvantages: Potential human life, transmission of infections

Question 29

What is active transport?

Answer 29

The movement of substances against a concentration gradient

Question 30

Write a method for an osmosis practical

Answer 30

1. Fill 5 boiling tubes with distilled water, 0.25mol sugar solution, 0.5mol, 0.75mol, and 1mol 2. Cut 5 potato cylinders using a cork borer, cut them all to 5cm, and record their starting masses 3. Put each cylinder into a test tube and wait 30 minutes 4. Remove cylinders and pat dry 5. Measure final lengths and masses 6. Calculate % change

Question 31

Explain how sexual reproduction can produce new varieties of plants

Answer 31

- Fertilisation occurs (fusion of gametes) - DNA is mixed - Meiosis causes variation

Question 32

Compare mitosis with meiosis

Answer 32

- Mitosis has one parent cell - Meiosis has 2 parent cells - Mitosis produces 2 identical daughter cells - Meiosis causes variation - Fertilisation occurs in meiosis, not in mitosis

Question 33

Why are bacteria incubated at 25 degrees?

Answer 33

To minimise growth of harmful pathogens

Question 34

Describe 3 benefits of using stem cells to clone plants

Answer 34

- Plants can be reproduced quickly - Save endangered species - Large numbers of plants with desirable features can be grown

Question 35

Define osmosis

Answer 35

The net movement of water particles across a partially permeable membrane down a concentration gradient (of water)

Question 36

Why should all potato cylinders come from the same potato?

Answer 36

The water concentrations are different in different potatoes

Question 37

What features increase the effectiveness of gas exchange?

Answer 37

- Thin membrane (short diffusion distance) - High surface area - Good blood supply - Good ventilation