2.1 cell structure

Question 1

what are the functions of the nucleus

Answer 1

1.acts as the control centre through the production of mRNA and protein synthesis
2. retains the genetic material of the cell
3. manufactures ribosomal RNA and ribosomes.

Question 2

what part controls energy and exit within the nucleus and how

Answer 2

the nuclear envelope is a double membrane surrounding the nucleus, controlling the entry and exit of materials in and out the nucleus and control the reactions taking place within it.

Question 3

what is the nucleolus

Answer 3

it is a small spherical body found within the nucleoplasm. it manufactures ribosomal RNA and assemblies the ribosomes.

Question 4

what are the inner folded membranes called in mitochondria and what does it do

Answer 4

cristae are shelf like extensions of the inner membrane providing a large surface area for the attachment of enzymes involved in respiration.

Question 5

what does the matrix do inside mitochondrias

Answer 5

the matrix makes up the remainder of the mitochondrion, it is the semi-rigid material containing protein, lipids and traces of DNA.

Question 6

what does the endoplasmic reticulum do

Answer 6

It follows the cells that need to manufacture and store large quantities of carbohydrates, proteins and lipids.

Question 7

what is RER

Answer 7

the rough endoplasmic reticulum has ribosomes present on the surface, it has a large surface area for the synthesis of proteins. also providing a pathway for the transport for the transport of materials throughout the cell.

Question 8

what is SER

Answer 8

smooth endoplasmic reticulum lacks ribosomes on its surface and is more tubular in appearance. the SER synthesises, stores and transports lipids and carbohydrates.

Question 9

what is the functions of the Golgi apparatus

Answer 9

1. add carbohydrates to proteins to form glycoproteins.
2. produce secretory enzymes such as those secreted by the pancreas.
3. secrete carbohydrates
4. transport, modify and store lipids
5. form lysosomes

Question 10

what are the functions of lysosomes

Answer 10

1. break down material ingested by phagocytic cells
2. release enzymes to the outside to destroy the material outside the cell
3. digest worn out organelles so that the useful chemicals they are made of can be reused.
4. completely break down cells after they have died.

Question 11

what do ribosomes do

Answer 11

they are important in protein synthesis.

Question 12

what are microvilli

Answer 12

finger-like projections of the epithelial cell that increase its surface area to allow more efficient absorption.

Question 13

how are chloroplasts adapted to their function

Answer 13

1.the granal membrane provides a large surface area for the attachment of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis.
2. the fluid of the stomata processes all the enzyme needed to make sugars in the second stage of photosynthesis.
3. chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis.

Question 14

define cell

Answer 14

single (smallest) unit making up a living thing

Question 15

define tissue

Answer 15

a group of cells with a similar function working together for a particular role

Question 16

define organ

Answer 16

a group of different tissues working for a particular role

Question 17

name 5 differences between prokaryotic cells and eukaryotic cells

Answer 17

1. prokaryotic cells have no nucleus
2. DNA is not associated with prokaryotic cells
3. DNA in form of plasmids in prokaryotic cells
4. Prokaryotic cells have no membrane bound organelles (mitochondria)
5. ribosomes in prokaryotes are smaller
6. Cell walls are made of murein in prokaryotes rather than cellulose.
7. Prokaryotes could have a capsule

Question 18

what is the role of the cell wall

Answer 18

physical barrier that excluded certain substances and protects against mechanical damage and osmotic lysis.

Question 19

what is the role of the capsule

Answer 19

polysaccharide layer on the outside of bacteria. protects bacterium from other cells and helps groups of bacteria stick together for further protection.

Question 20

what is the role of the cell-surface membrane

Answer 20

acts as a differentially permeable layer which controls the entry and exit of chemicals

Question 21

what Is the role of circular DNA

Answer 21

possesses the genetic information for the replication of bacterial cells

Question 22

what is the role of plasmids

Answer 22

small, circular, double stranded DNA molecules. possesses genes that may aid the survival of bacteria in adverse conditions

Question 23

what is the role of flagella

Answer 23

provides movement aid also functioning as a sensory organelle detecting conditions outside the cell.

Question 24

why are viruses not considered living

Answer 24

as they require a host to reproduce

Question 25

3 examples of viruses

Answer 25

HIV
Influenza
Coronavirus

Question 26

why to viruses have attachment proteins

Answer 26

they let the virus cling onto a suitable host cell

Question 27

what is the process called in which prokaryotic cells reproduce

Answer 27

binary fission

Question 28

what are the 4 steps of binary fission

Answer 28

1. the circular DNA strand and plasmids replicate
2. the cell gets bigger and the DNA loops move to opposite ends of the cell
3. the cytoplasm begins to divide
4. the cytoplasm divides and two daughter cells are produced.

Question 29

what are the 5 steps of viral replication

Answer 29

1. virus attaches to the host cells receptor proteins
2. genetic material is released into the host
3. genetic material and proteins are replicated by the host cell
4. viral components assemble together
5. replicated viruses are released from the host cell

Question 30

define magnification

Answer 30

increasing the size of the object being used

Question 31

define resolution

Answer 31

increasing the level of detail that can be seen. specifically its the ability to distinguish between 2 separate objectives.

Question 32

what are the 3 types of microscopes

Answer 32

1. light
   then 2 types of electron microscopes:
2. TEM (transmission electron microscope)
3. SEM (scanning electron microscope)

Question 33

Describe a light microscope

Answer 33

specimens are illuminated with light
this light is focused, specimens can be both living or dead however they need to be stained with a coloured dye to make them visible.

Question 34

describe transmission electron microscopes

Answer 34

they use electromagnets to focus an electron beam which is transmitted through the specimen where the deer parts of the specimen absorb more electrons so appear denser in the image.
specimens are locked in a vacuum so cannot be living

Question 35

describe scanning electron microscopes

Answer 35

an electron beam is scanned across the specimen
this displays electrons from the specimens surface
these electrons are collected in a cathode ray tube and form an image
3D images
dead specimens only

Question 36

what are the two types of cell fractionation

Answer 36

differential centrifugation
density gradient centrifugation

Question 37

what are the 5 (with reasons for) preparation steps for centrifugation

Answer 37

1. low temp - reduces enzyme activity
2. isotonic - stopping osmosis so the cells do not shrink or burst
3. buffered to minimise changes in pH - prevents enzymes/proteins becoming denatured
4. grinding with sand in mortar and pestle - break up cells and open contents
5. filtering - to remove large debris such as cell walls

Question 38

what are the two steps of fractionation

Answer 38

1. homogenisation
2. ultracentrifugation

Question 39

describe homogenisation

Answer 39

cells are broken up by a homogeniser (blender) releasing the organelles from their cell.
the fluid is then filtered to remove large peices of debris

Question 40

describe the 6 steps of ultracentrifugation

Answer 40

1. the tube of filtrate is placed in the centrifuge and spun at low speed
2. the heaviest organelles (nuclei) are forced to the bottom of the tube where they form a pellet
3. the fluid at the top of the tube (the supernatant) is removed leaving just the sediment of nuclei
4. the supernatant is transferred to another tube and spun in a centrifuge at a faster speed than before
5. the next heaviest organelles (mitochondria) are forced to the bottom of the tube
6. the process continues where the next heaviest organelles are separated from the supernatants.

Question 41

what is the difference between differential centrifugation and density gradient centrifugation

Answer 41

differential centrifugation fully removes and separates the organelles where density gradient centrifugation only settles the organelles to their level of densities.