B1 - Cell Biology

Question 1

Describe the differences between eukaryotes and prokaryotes

Answer 1

eukaryotes: contain their genetic material enclosed in a nucleus
prokaryotes: no nucleus to enclose genetic material, much smaller than eukaryotes.

Question 2

(Describe function of) nucleus

Answer 2

(What) contains genetic material that controls the activities of the cell

Question 3

cytoplasm

Answer 3

jelly like substance where most of chemical reactions take place

Question 4

cell membrane

Answer 4

holds the cell together and controls what enters and leaves the cell

Question 5

mitochondria

Answer 5

site of aerobic respiration

Question 6

ribosomes

Answer 6

Site of protein synthesis

Question 7

cell wall

Answer 7

structure made of cellulose which supports and strengthens the cell

Question 8

Permanent vacuole

Answer 8

contains cell Sap which gives the cell its shape

Question 9

Chloroplasts

Answer 9

contain green pigment called chlorophyll which absorbs light energy for photosynthesis

Question 10

what do plant cells contain that animal cells don’t

Answer 10

chloroplast
cell wall
permanent vacuole

Question 11

do bacteria cells have a nucleus, if not what do they have instead

Answer 11

No, Dna loops float freely in cytoplasm

Question 12

Describe how to set up and use a microscope

Answer 12

1. Place your prepared slide onto the stage and use the clips to hold it in place
2. Select the lowest power objective lens
3. Use the coarse focussing knob to move the stage up, just below the objective lens
4. Look down the eyepiece and slowly use the coarse focussing knob to move the slide downwards until the image is roughly in focus
5. Use the fine focussing knob to adjust the focus until you get a clear image
6. If you need to see the slide with greater magnification, swap to higher powered objective lens and repeat the steps until focus.

Question 13

Differences between light and electron microscope

Answer 13

Electrons: higher magnification and resolution, allows to see more detail of internal structures
Light: let us see individual cells and large sub cellular structures, uses light.

Question 14

Formula for magnification

Answer 14

Magnification = image / real

Question 15

why do we use a single layer of epidermal tissue

Answer 15

to see through the cell clearly and so that there is contrast under the microscope

Question 16

Why do we stain the sample

Answer 16

to highlight structures in the cell so they are clearer to see and more detailed

Question 17

What makes a successful drawing (microscope)

Answer 17

• drawn with clear unbroken lines
• cells and sub cellular structures drawn in proportion
• include title, labels and magnification used

Question 18

why do we look from the side when first moving the coarse focussing knob

Answer 18

risk of damaging slide

Question 19

How is a sperm cell specialised

Answer 19

• specialised for reproduction
• long tail and streamlined head to help it swim to egg easier and faster
• packed with mitochondria to provide energy needed
• carries enzymes in the head to help digest through the egg cell membrane

Question 20

How are the nerve cells specialised

Answer 20

• specialised to send electrical impulses around the body
• long axon to carry impulses covering longer distances
• axon covered with myelin which insulates the axon and speeds up transmission of nerve impulses
• end of axon contains synapses which allow impulses to pass from one nerve cell to another
• cell body contains dentrites which increase surface area so nerve cellls can connect easily

Question 21

How are muscle cells specialised

Answer 21

• specialised to contract quickly
• contain protein fibres that help change the length of the cell
• contain lots of mitochondria to generate energy needed

Question 22

How are root hair cells specialised

Answer 22

• specialised to absorb nutrients
• hairs increase SA allowing more efficient absorption
• do not contain chloroplasts

Question 23

How are xylem cells specialised

Answer 23

• specialised to carry water and dissolved minerals from the roots to leaves
• very thick walls containing lignin which support the plant
• end walls between cells break down and now form a long tube so water and dissolved minerals can flow easily
• contain no internal structures

Question 24

How are phloem cells specialised

Answer 24

• specialised to carry dissolved sugars up and down the plant
• phloem vessel cells: have no nucleus and ltd cytoplasm
• sieve plates: located at end of vessel cells and allow dissolved sugars to move through the cell interior
• companion cell: one connected to each vessel cell by pores and mitochondria provide energy for phloem cells

Question 25

Explain the 3 stages of the cell cycle

Answer 25

1. • cell grows bigger
     - dna replicates
     - number of sub cellular structures increase
2. • Chromosomes like up in the centre of the cell and cell fibres pull them apart
     - a complete set of chromosomes are pulled to opposite ends of the cell
     - the nucleus divides to form two nuclei
3. • cytoplasm and cell membrane divide to form two identical daughter cells

Question 26

How is the small intestine adapted for absorbing digestion products

Answer 26

• long length
• covered with lots of villi and micro villi which increase surface area massively
• good blood supply, rapidly removes the products of digestion and increases concentration gradient
• thin membrane to ensure short diffusion path giving rapid rate of diffusion