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Biology Y12 > Section 2:Cell Structure > Flashcards

Section 2:Cell Structure Flashcards

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1
Q

Define magnification

A

Measure of enlargment

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2
Q

Define resolution

A

A measure of how clear an object is OR the minimum distance apart two objects can be in order for them to apear as seperate items

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3
Q

How is total magnification calculated?

A

magnification of eyepiece lens x magnification of objective lens

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4
Q

How is the image size calculated?

A

total magnifcation x actual size

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5
Q

How do you convert mm into µm?

A

Multiply by 1000

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6
Q

How do light microscopes work?

A

A condenser lens on the microscope is used to focus a beam of light coming from the object

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7
Q

Three points

Give advantages of the light microscope

A
  • Cheaper than electron microscopes
  • Able to see the image in its true colour
  • Specimens can be dead or living
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8
Q

Two points

Give disadvantages of light microscope

A
  • Unable to see smaller organisms e.g. rhibosomes
  • Resolution is limited due to the wavelength of light wave
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9
Q

Three points

How does an electron microscope work?

A
  1. Beam of electrons are passed through the specimen
  2. This is focused by electromagnets onto a fluorescent screen to produce to produce an image which can be photographed
  3. Parts of the specimen which absorbed electrons appear dark
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10
Q

Four points

Give disadvantages of electron microscopes

A
  • The whole system must be in a vaccum~living specimens can’t be observed
  • Specimen must be extremely thin (TEM only)
  • Artefacts may appear
  • A complex staining process is required, and even then the image is not in colour
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11
Q

What are the different types of electron microscopes?

A

Transmission electron microscope(TEM) and scanning electron microscope(SEM)

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12
Q

What is different in the methods for SEM and TEM?

A

TEM~beam of electrons is passed through the specimen and certain parts absorb the electrons
SEM~beam of electrons is passed over the surface of the specimen and collects the electrons scattered over the surface

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13
Q

What is different about the images produced by a TEM and a SEM?

A

SEM produces a 3D image, whereas TEM can only produce a 2D image

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14
Q

What is different about the resolving power of the SEM and TEM?

A

SEM has a lower resolving power than the TEM

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15
Q

What are the two stages in cell fractionation?

A
  1. Homogenation~breaking up the cells
  2. Ultracentrifugation~seperating the organelles out
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16
Q

Three points

Before cell fractionation the tissue is placed in a solution. Describe the features of the solution with explanations

A
  • Cold~reduce enzyme activity that may break down organelles
  • Isotonic(same WP as the tissue)~to prevent organelles bursting or shrinking due to osmotic gain or loss of water
  • Buffered~keep pH constant to prevent structure of organelles altering or enzymes function changing
17
Q

Two points

How can cells be homogenised?

A
  • Using a pestle and mortar
  • Using an electric blender
18
Q

What is the fluid mixture left after homogenisation?

A

The homogenate

19
Q

Why is the homogenate filtered?

A

To remove parts of the cell which have not been broken up properly

20
Q

Four points

Describe how ultracentrifugation is carried out

A
  • The filtrate is placed in the centrifuge
  • At a low speed for a set period of time
  • A pellet is formed at the bottom of the test tube containing the largest organelle
  • Repeat this at higher speeds until the desired organelle forms a pellet
21
Q

Define supernatant

A

The fluid left at the top of the test tube after being placed in a centrifuge

22
Q

Why is it possible to sepearte cell organelles using centrifugation?

A

Organelles differ in density~denser organelles seperate off first

23
Q

What is the difference between eukaryotic and prokaryotic cells?

A

Eukaryotic cells have a true nucleus unlike prokaryotic cells

24
Q

What is the main function of the cell surface membrane and describe its structure?

A

Controls entry and exit of substances from the cell
* Phospholipid bilayer
* Carrier or channel proteins, may be appear on the inner or outer surfaces

25
Q

Three points

Describe the functions of the nucleus

A
  • Controls cell activity via the production of mRNA
  • Retains genetic material via DNA
  • Produces rRNA and ribosomes
26
Q

Describe the structure of the nucleus

A

Nuclear envelope~double membrane,nuclear pore~allow passage of large molecules,nucleoplasm,chromosomes and nucleolus

27
Q

What is the main function of the mitochondria and describe its structure?

A

The production of ATP via aerobic respiration
* Bound by a double membrane~controls entry/exit of substances
* Cristae(inner)~provides large SA for enzymes involved in respiration
* Matrix(outer)~contains proteins,lipids,ribosomes,enzymes and DNA=allows mitochondria to control the production of some of their own protiens

28
Q

What is the main difference between the rough and smooth endoplasmic reticulum?

A

The rough ER has ribosomes attached to the outer surface of the membranes,whereas the smooth ER does not and often appears mor tubular

29
Q

Two points

What are the main functions of the rough endoplasmic reticulum?

A
  • Large SA for synthesis of proteins and glycoproteins
  • Provides pathway for the transport of material through the cells (e.g. proteins)
30
Q

What is the main function of the smooth endoplasmic reticulum?

A

Synthesise,stores and transports lipids/carbohydrates

31
Q

Five points

Describe the structure of the golgi apparatus

A
  • Add carbohydrate to protein to form glycoproteins
  • Produce secondary enzymes e.g those secreated by the pancreas
  • Secreate carbohydrates e.g in plants cell wall
  • Transport, modify and store lipids
  • Form lysosomes
32
Q

Four points

Describe the function of lysosomes

A
  • Hydrolyse material ingested by phagocytic cells
  • Release enzymes to the outside of the cells in order to destroy material around the cell
  • Digest worn out organelles
  • Completely break down cells after they have died (autolysis)
33
Q

What’s the difference between ribosomes in eukaryotic cells and prokaryotic cells?

A

80s ribosomes are found in eukaryotic (slightly larger)
70s ribosomes are found in prokaryotic cells

34
Q

What happens in ribosomes?

A

Protein synthesis

35
Q

Three points

What is the function of the cell wall?

A
  • Provide mechanical strength to prevent cell bursting under pressure
  • Give mechanical strength to the plant as a whole
  • To allow water to pass along it
36
Q
A

Biology Y12 (10 decks)

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