Cell Structure

Question 1

What is Cell Fractionation?

Answer 1

the process where
- cells are broken up
- different organelles they contain are separated out based on size/mass using gravity

Question 2

The 3 Steps of Cell Fractionation.

Answer 2

1) homogenisation
2) filtration
3) ultracentrifugation

Question 3

Define what is meant by magnification.

Answer 3

Magnification - how many times bigger the image is compared to the actual size of a speciman

Question 4

Define what is meant by resolution.

Answer 4

Resolution - how clearly you are able to distinguish between two points close together on an object

Question 5

What is homogenisation?

Answer 5

When cells are broken up by homogeniser (blender), releasing organelles from the cell.
- makes a homogenate.

Question 6

What is filtration?

Answer 6

When the homogenate is filtered to get rid of any large pieces of debris.

Question 7

What is ultracentrifugation?

Answer 7

The process where fragments in filtered homogenate are separated in a centrifuge - which spins the tube at very high speeds.
- the heaviest organelles are forced to the bottom, forming pellets.
- leaving supernatant (fluid) at the top

Question 8

What type of microscope produces a 3D image?

Answer 8

SEM - scanning electron microscope

Question 9

List key features of TEM

Answer 9

• shoots beams of electrons at a thin sample and detects electrons that make it through to the other side
• very high resolution, so good for learning structure of inner components of a cell

Question 10

List key features of SEM

Answer 10

• uses focused beams of high-energy electrons which reflect off the surfaces of structures
• produces a 3D image
• samples do not have to be as thin

Question 11

Describe the key features of a cell surface membrane

Answer 11

1) it is a partially permeable membrane
- controls the exchange of materials between the internal and external cell environment
2) formed from a phospholipid bilayer

Question 12

Describe the key features of the cell wall

Answer 12

1) offer structural support - provided by cellulose
2) freely permeable

Question 13

Describe the key functions of chloroplasts

Answer 13

• surrounded by double membrane
• thylakoids - membrane bound flattened discs
• grana joined by flattened membranes - lamellae

Question 14

Explain the consequence of water loss from vacuoles

Answer 14

1) water moves out of the vacuole and cytoplasm
2) the vacuole shrinks
3) the cell wall is unsupported
4) the plant wilts

Question 15

What is the main component of fungal cell walls?

Answer 15

• Chitin

Question 16

List the structures in the nucleus

Answer 16

1) nuclear envelope
2) nuclear pores
3) nucleoplasm
4) chromosomes
5) nucleolus

Question 17

What is the nuclear envelope?

Answer 17

• double membrane surrounding the nucleus

Question 18

What is the nucleoplasm?

Answer 18

• granular, jelly-like material in the nucleus

Question 19

What is the nucleolus?

Answer 19

• small sphere inside the nucleus
• the site of rRNA production and makes ribosomes

Question 20

What is the function of the nucleus?

Answer 20

• site of DNA replication and transcription (making mRNA)
• contains genetic code for each cell

Question 21

What is the structure of the endoplasmic reticulum (ER)

Answer 21

• they have folded membranes called cisternae

Question 22

What is the difference between RER and SER?

Answer 22

RER - has ribosomes on the cisternae
SER - no ribosomes

Question 23

What is the function of RER?

Answer 23

• protein synthesis

Question 24

What is the function of SER?

Answer 24

• synthesises and stores lipids and carbohydrates

Question 25

List the structures in mitochondria

Answer 25

1) double membrane 2) inner membrane -cristae- 3) mitochondrial matrix 4) loop of mitochondria DNA

Question 26

What is the function of mitochondria?

Answer 26

- site of aerobic respiration - ATP production - DNA to code for enzymes needed in respiration

Question 27

What are the two types of ribosomes?

Answer 27

- 80s ribosomes - 70s ribosomes

Question 28

What are 80s ribosomes?

Answer 28

- large ribosomes - found in eukaryotic cells

Question 29

What are 70s ribosomes?

Answer 29

- smaller ribosomes - found in mitochondria, chloroplasts and prokaryotic cells

Question 30

What is the function of ribosomes?

Answer 30

- site of protein synthesis

Question 31

What are ribosomes made of?

Answer 31

- protein - mRNA

Question 32

State the structure of a vacuole

Answer 32

- fluid filled sac - surrounded by a single membrane called a tonoplast

Question 33

What is the function of a vacuole?

Answer 33

- temporary store of sugars and amino acids - provide support, make cells turgid

Question 34

What is the structure of chloroplasts?

Answer 34

- surrounded by double membrane - contains thylakoids - has fluid filled stroma containing enzymes for photosynthesis

Question 35

Which cells have cell walls?

Answer 35

1) plant cells 2) fungi cells

Question 36

Structure of cell wall in plants

Answer 36

- made of microfibrils of cellulose

Question 37

Structure of cell wall in fungi

Answer 37

- made of chitin

Question 38

Function of the cell wall

Answer 38

- provide structural strength to the cell

Question 39

Function of the plasma membrane

Answer 39

- controls what molecules enter and exit the cell

Question 40

What is the structure of the plasma membrane?

Answer 40

- phospholipid bilayer molecules embedded within and attached on the outside - proteins, carbohydrates, cholesterol

Question 41

Features of a eukaryotic cell

Answer 41

- DNA is contained in a membrane bound nucleus - DNA is coiled into linear chromosomes