B1.1 Cells

Question 1

What are eukaryotic cells?

Answer 1

They are complex cells containing genetic material in the nucleus. Plants and animals are eukaryotes.

Question 2

What is the size of a eukaryotic cell?

Answer 2

10 - 100 micrometers

Question 3

What is a prokaryotic cell?

Answer 3

A simple cell where genetic material floats in the cytoplasm. Bacteria and proticists are prokaryotes .

Question 4

What is the size of a prokaryotic cell?

Answer 4

1 - 10 micrometers

Question 5

What extra sub cellular structures do plant cells have?

Answer 5

Cell wall - made from cellulose to support the cell and keep it rigid

Vacuole - full of cell sap to help with stability

Chloroplast - contain chlorophyll(green pigment) which is needed for photosynthesis

Question 6

List the main organelles of an animal cell and their functions

Answer 6

Nucleus - contains genetic material(chromosomes) and controls cell activity. Also contains instructions for cell replication

Cytoplasm - a substance where chemical reactions occur

Mitochondria - the powerhouse of the cell where respiration occurs. They contain enzymes

Cell membrane - controls what enters and passes out of the cell. Also have receptor molecules

Question 7

Why do plant cells need extra structures?

Answer 7

They are producers which photosynthesis to make their food

Question 8

What are bacteria?

Answer 8

They are small unicellular organisms which can carry out the 7 life processes(mrs gern)

Question 9

Size of a bacterial cell?

Answer 9

1 micrometer

Question 10

Name some examples of prokaryotes

Answer 10

E.coli- food poisoning

Streptococcus- sore throats

Question 11

List the sub cellular structures that prokaryotic cells have and their function

Answer 11

Cell wall - holds cell together and protects it
cytoplasm - where the chemical reactions occur
Genetic material- floats in circular stands in the cytoplasm
Cell membrane - selects what enters and exits

Question 12

What extra subcellular structures does a bacterial cell have?

Answer 12

Flagella
Pili(hairs)
Slime capsule
Plasmids

Question 13

What are the functions of flagella and pili?

Answer 13

Flagella is a tail like structure which is used for movement

Pili are hairs which enable the cell to stick to cells and transfer genetic material

Question 14

What is the function of the slime capsule and plasmids?

Answer 14

Slime capsule protects the cell from dying out and helps it stick to surfaces

Plasmids are extra loops of dna which store extra genes for helping in times of stress

Question 15

What are microscopes and what do they do?

Answer 15

Microscopes are a piece of equipment which is used to magnify images and increase resolution of an image

Question 16

How does a light microscope work?

Answer 16

Light passes through a specimen on a slide and then through the objective lens and the eyepiece lens. The lenses magnify the image

Question 17

How do you prepare a sample?

Answer 17

1) take a clean slide and carefully place the sample onto it. Use a thin slice if you are using a thick sample
2) apply a drop of stain if needed or add a drop of water
3) place a coverslip on and gently tap into place to get rid of air bubbles

Question 18

Why do we use stains?

Answer 18

Many cells are colourless so we stain cells to differentiate different structures or highlight the whole cell. There are different stains used for different structures.

Question 19

List some common stains and their uses

Answer 19

Methylene Blue - animal cell nuclei
Iodine - plant cells nuclei
Crystal violet - bacteria cell walls
Eosin - cytoplasm

Question 20

Steps for using a microscope

Answer 20

1) move the stage to the lowest position
2) select the objective lens to the lowest magnification
3) place the slide on the stage and use clips
4) turn the coarse focus knob and then the fine focus until you see a clear image
5) change the objective lens for more detail

Question 21

What is resolution?

Answer 21

The smallest distance between 2 points which can be seen as separate entities

Question 22

What size of structures can the light microscope not see

Answer 22

Less than 0.2. Micrometers

Question 23

What is an electron microscope?

Answer 23

A microscope that uses electrons to view an image in the best detail possible yet. They allow use to study tiny things like viruses and mitochondrion

Question 24

How does a transmission electron microscope work?

Answer 24

They produce the most magnified image

A beam of electrons passes through the sample which is focused to form an image. Similar to light microscopy

Question 25

How does a scanning electron microscope work?

Answer 25

It produces a 3D image Electrons are sent across the surface and are collected to form an image

Question 26

Which electron microscope produces the highest magnification

Answer 26

SEM

Question 27

Which electron microscope produces a 3D image?

Answer 27

TEM

Question 28

What are the advantages and disadvantages of using a light microscope? (5v1)

Answer 28

It is cheap to buy, easy to maintain, easy to prepare a sample, portable, specimens can be living or dead Resolution is only up to 0.2 micrometers

Question 29

What are the advantages and disadvantages of using an electron microscope?

Answer 29

Resolution up to 0.1 nm Expensive to buy and operate, large and difficult to move, hard to prepare a sample, specimens must be dead, colouring must be added

Question 30

Explain how electron microscopy has increased our understanding of subcellular structures

Answer 30

Electron microscopes have allowed scientists to view inside subcellular structures and observe very small structures to improve our understanding

Question 31

Calculation to find total magnification

Answer 31

Total magnification = eyepiece lens magnification x objective lens magnification

Question 32

Calculation to find real size, image size

Answer 32

Real size x magnification = image size Magnification = image size/ real size