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A Level Biology > Module 2 Section 1 - Cell Structure > Flashcards

Module 2 Section 1 - Cell Structure Flashcards

Pyper

1
Q

cell ultrastructure

A

the internal structure of cells

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2
Q

plasma membrane description - what’s it made from?

A

aka cell surface membrane
mostly made of lipids & proteins

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3
Q

plasma membrane function

A

controls the movement of substances in and out of the cell
has receptor molecules on it which respond to chemicals (e.g. hormones)

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4
Q

cell wall function

A

supports plant cells

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5
Q

nucleus description

A

contains chromatin (made from DNA and proteins) and often a nucleolus
has a nuclear envelope and nuclear pores

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6
Q

nucleus functions (3)

A
  • controls the cell’s activities
  • contains DNA, which contains instructions to make proteins
  • site of DNA replication and transcription (making mRNA)
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7
Q

nucleolus function(s)

A

makes ribosomes and site of rRNA production (which carries out protein synthesis)

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8
Q

nuclear envelope function

A

surrounds the nucleus
contains pores to allow substances to move between the nucleus and cytoplasm

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9
Q

RER description (2 parts - where is it found and what does it look like?)

A

rough endoplasmic reticulum
bound to the nuclear envelope
membrane-bound fluid-filled space

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10
Q

RER function

A

folds and processes the proteins that are made at the ribosomes

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11
Q

SER description

A

smooth endoplasmic reticulum
membrane-bound fluid-filled space, but not covered in ribosomes

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12
Q

SER function

A

synthesises and processes lipids and carbohydrates

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13
Q

lysosome description (2 parts - where’s it found?)

A

round organelle with membrane
only animal cells

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14
Q

lysosome function

A

contains digestive enzymes to digest invading cells or break down worn-out cell components

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15
Q

How do you spell the name of the organelle that contains digestive enzymes?

A

Lysosome

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16
Q

ribosome description (3 parts - where is it found and what’s it made of?)

A
  • may flow free in the cytoplasm or is attached to RER
  • not membrane-bound
  • made of proteins & RNA
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17
Q

vesicle description

A

small membrane-bound fluid-filled sac

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18
Q

vesicle function

A

transports substances in and out of the cells and between organelles

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19
Q

Golgi apparatus description

A

group of fluid-filled, membrane-bound flattened sacs
small circles (vesicles) often found at the edges of the sacs

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20
Q

Golgi apparatus 2 functions

A
  • processes & packages new lipids & proteins (processes proteins e.g. adding sugar chains/carbohydrate groups)
  • makes lysosomes
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21
Q

What does the Golgi apparatus look like?

A

Like the SER but surrounded by vesicles

Looks a bit like a WiFi symbol

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22
Q

mitochondrion description (3 parts - including shape)

A

oval-shaped (sort of like a peanut)
has a double-membrane; the inner membrane has loads of folds which form cristae
the matrix is inside, which contains enzymes involved in respiration

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23
Q

mitochondrion function

A

site of aerobic respiration, where ATP is produced

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24
Q

chloroplast description (3 parts)

A

double membrane-bound flattened organelle
thylakoid membranes inside which stack to form grana - these are linked together by lamellae (long, thin thylakoid membrane)

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25
Q

chloroplast function

A

some photosynthesis happens in the grana, other parts in thick fluid called the stroma

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26
Q

microtubule meaning

A

small protein cylinders

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27
Q

flagellum description

A

two microtubules in the centre with nine pairs around the edge

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28
Q

flagellum function

A

microtubules contract to make the flagellum move to propel the cell forwards

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29
Q

cilium description

A
  • have an outer membrane
  • ring of nine pairs of microtubules with two in the middle (9 + 2 formation)
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30
Q

cilia function (+ how do they do this?)

A

microtubules contract to make the cilia move, which can then move substances along the cell surface

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31
Q

centriole description (2 parts incl. what type of cell it is found in)

A

tiny bundle of small, hollow protein cylinders made of microtubules
animal cells and some plant cells

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32
Q

centriole function

A

involved with separating chromosomes during cell division

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33
Q

capsule 2 functions

A
  • prevents the bacteria from drying out
  • covers antigens to protect it from its host’s immune system
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34
Q

cisterna

A

a closed (and flattened) sac filled with liquid, forming part of some organelles

e.g. in the Golgi apparatus, RER

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35
Q

Where are cisternae found?

A

Endoplasmic reticulums and Golgi apparatus

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36
Q

Describe how cells’ ultrastructures help protein production.

A
  • Nucleolus produces ribosomes
  • Ribosomes synthesise proteins/polypeptide chains
  • These proteins go to the rough endoplasmic reticulum, which folds and processes them e.g. by adding sugar chains
  • The proteins are transported to the Golgi apparatus by vesicles via the cytoskeleton
  • They are then further processed e.g. trimming off sugar chains or adding more
  • The proteins are packaged into vesicles and transported around the cell, or out of the cell through the plasma membrane where the proteins are secreted by exocytosis
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37
Q

cytoskeleton meaning

A

‘cell’ skeleton
A large network of protein fibers and other molecules that gives shape and structure to cells

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38
Q

microfilament meaning

A

thin strands of proteins

39
Q

Explain the importance of the cell cytoskeleton (4).

A
  • keeps the cell in position
  • helps the transport of organelles and materials around the cell
  • helps maintain the cell’s shape and stability - strengthens the cell (e.g. some organelles are bound to the cytoskeleton)
  • microfilaments can allow the cell to move (e.g. a flagellum)
40
Q

Explain how the nature of the cytoskeleton allows it to perform its functions.

A

The cytoskeleton is dynamic (constantly changing) so it can respond to changes in the cell.

41
Q

Compare the way eukaryotes’ and prokaryotes’ DNA is found.

A

Eukaryotes: linear (has two distinct ends)
Prokaryotes: circular

42
Q

Compare the organisation of eukaryotes’ and prokaryotes’ DNA.

A

Eukaryotes: associated with histone proteins (which DNA coils around to help give chromosomes their shape and help control genes’ activity)
Prokaryotes: proteins fold and condense DNA (through supercoiling i.e. coiling coils into a ball)

43
Q

Compare the membranes of organelles of eukaryotes and prokaryotes.

A

Eukaryotes: membrane and non-membrane bound organlles
Prokaryotes: non-membrane bound organelles

44
Q

Compare the substances that make up the cell walls of different eukaryotes and prokaryotes.

A

Eukaryotes: cellulose cell wall in plants, chitin cell wall in fungi, no cell walls in animals
Prokaryotes: cell wall made of a polysaccharide peptidoglycan

45
Q

Do eukaryotic cells or prokaryotic cells have more organelles?

A

Eukaryotic cells

46
Q

Compare the flagella of eukaryotes and prokaryotes (what are they made of and how are they arranged?).

A

Eukaryotes: when present, microtubules are arranged in the 9 + 2 formation
Prokaryotes: made of the protein flagellin, arranged in a helix

47
Q

Compare the size of ribosomes in eukaryotes and prokaryotes.

A

Eukaryotes: bigger (>20nm, 80S)
Prokaryotes: smaller (<= 20nm, 70S)

48
Q

Where do you find 70S ribosomes (more than just one)

A

Prokaryotic cells
Mitochondria & chloroplasts in eukaryotic cells

49
Q

Compare the complexity of the cytoskeleton in eukaryotes and prokaryotes.

A

Eukaryotes: more complex
Prokaryotes: less complex

50
Q

occular lens

A

eyepiece lens

51
Q

diopter adjustment

A

next to eyepiece lens, raising or lowering the eyepiece to adjust the focus for each eye

52
Q

nose piece

A

the circular structure where the objective lenses are screwed in

53
Q

flat surface where slide is positioned

A

mechanical stage

54
Q

thing that keeps the slide in position

A

stage clip

55
Q

another name for the coarse/fine focus wheels

A

coarse/fine adjustment

56
Q

How can you reposition the stage (left & right movement)?

A

Use the stage controls - two wheels on the lower side of the microscope

57
Q

diaphragm (microscope)

A

Controls the amount of light that reaches the specimen

58
Q

condenser (microscope)

A

Lens(es) below the stage that focusses light onto the specimen

59
Q

Where is the diaphragm located?

A

Above the condenser but below the stage

from the bottom up, they go in alphabetical order

60
Q

Types of microscopes

A
  • Compound light microscope
  • Laser scanning confocal microscope
  • Scanning electron microscope
  • Transmission electron microscope
61
Q

Why do light microscopes have a poor resolution?

A

Light is used, which has a long wavelength.

62
Q

Why do electron microscopes have a good resolution?

A

Beams of electrons are used, which have a shorter wavelength.

63
Q

Where do you need to use an electron microscope and why?

A

In a vacuum - otherwise the electrons can be absorbed by the air

64
Q

What do you need to do when preparing a TEM specimen, that you don’t have to do for a SEM specimen?

A

Thinly slice the specimen - the electrons aren’t being transmitted in a SEM

65
Q

What do laser scanning confocal microscope images look like?

A

Colourful (red, green & blue) due to flourescent dyes against a black background.
e.g. shows the cytoskeleton

66
Q

What do SEM images look like?

A

3D coloured images of the specimen’s surface
They are ordinary black and white, but colour is added afterwards

67
Q

What do TEM images look like?

A

2D images (that depend on the angle at which the specimen is sliced)
They are ordinary black and white, but colour can be added afterwards

68
Q

How do light microscopes work? How do they form images?

A

A beam of light passed through the specimen. Some parts of the object absorb more light than others, producing an image.

69
Q

How do laser scanning confocal microscopes work?

A

The specimen is tagged with fluorescent dyes.
A laser beam is passed through a lens, splitting it so that some of the light is directed to a small area on the surface of the specimen.
The laser hits the dyes, causing them to emit fluorescent light, which is focussed through a confocal aperture/pinhole (any light that isn’t focussed is rejected) onto a detector.
This is connected to a computer which generates an image. Multiple images can be combined to form 3D images of the specimen.

confocal = common focus

70
Q

How do scanning electron microscopes work?

A

Samples are treated with a solution of heavy metals (these ions are scattered to provide contrast between structures).

A beam of electrons is sent across the specimen, knocking some of the specimen surface electrons off. These electrons that bounce off are then collected to form an image.

71
Q

How do transmission electron microscopes work?

A

Samples are treated with a solution of heavy metals (these ions are scattered to provide contrast between structures).

Electromagnets focus a beam of electrons so that they are transmitted through the specimen to form an image. Denser parts of the specimen absorb more electrons so look darker on the image

72
Q

Why might a scientist use a laser scanning electron miscroscope?

A

A SEM allows you to see sections of small structures that would be difficult to physically section off/cut (e.g. embryos) and creates a 3D image

73
Q

Advantage of a laser scanning confocal microscope.

A

Can look at different depths of a specimen (3D)

74
Q

Disadvantage of a laser scanning confocal microscope.

A

Fluorescent dyes can be toxic to the cells

75
Q

Advantages of a SEM.

A
  • Can be 3D.
  • Lower resolution to transmission electron microscopes.
76
Q

Disadvantage of a SEM.

A

Samples have to be treated with a solution of heavy metals.

77
Q

Advantages of a TEM.

A
  • High resolution so can look at small organelles e.g. ribosomes.
  • Can look at internal structures of organelles in detail.
78
Q

Disadvantages of a TEM.

A
  • Samples have to be treated with a solution of heavy metals.
  • Specimens need to be very thinly sliced (which can be difficult).
  • Angle of slice can affect the image produced.
79
Q

Compare and contrast a scanning electron microscope and a transmission electron microscope. [4 marks]

A

Similarities:
Both use electrons / electromagnets;
Both use vacuums / can’t image live tissue;
Both have higher magnification than optical microscopes;
Both have higher resolution than optical microscopes

Differences:
Electrons are transmitted through the specimen in TEM whereas electrons are
reflected off the surface in SEM OR TEM shows internal structure whereas SEM shows surface;
SEM can produce 3D images whereas TEM cannot;
TEM gives higher resolution than SEM;
TEM has higher maximum magnification than SEM;
SEM can be used on thicker specimens than TEM

At least one statement from similarities AND differences is required for full marks.

80
Q

TEM shows ____ structure whereas SEM shows ____.

A

internal, surface

81
Q

Name four stains.

A
  • Iodine
  • Methylene blue
  • Eosin / H&E
  • Giemsa
82
Q

What does the H&E stain look like?

A

cytoplasm - pink due to the eosin
RNA/DNA e.g. in nuclei and ribosomes - purple/blue due to the haematoxylin

83
Q

What does the Giemsa stain look like?

A

Nuclei - purple
Red blood cells can look pink

Note: cytoplasms can look pink because Giemsa stains often contain eosin (which is also in the H & E stain)

84
Q

How do you prepare a microscope slide (2 types)?

A
  • Thinly slice specimen
  • Wet mount - pipette a drop of water onto middle of slide
  • Pick up specimen with tweasers and place in middle of slide
  • Add a drop of stain
  • Place a cover slip on top, gently tilting and lowering it to prevent air bubbles
  • Remove excess stain by gently dabbing with a paper towel
85
Q

Why are wet mounts used?

A
  • To prevent cells from drying out
  • For liquid specimens
86
Q

smear slide (+ example of use)

A

A wet mount where a thin layer of liquid is spread across part of the slide. Often used in blood samples

87
Q

stage micrometer meaning

A

microscope slide “ruler” placed on the stage with units (accurate scale) used to work out the value of each division on the eyepiece graticule at a particular magnification

88
Q

eyepiece graticule meaning (units?)

A

a “ruler” on the eyepiece with numbers but no units

89
Q

1 division on a stage micrometer is equal to 0.1mm. 2 divisions on a stage micrometer is equal in length to 16 eyepiece graticule divisions (eyepiece units). What is the real length of an object that is 15 eyepiece divisions long?

A

1 SM division = 8 EPG divisions
1 EPG division = 0.125 SM divisions

1 SM division = 0.1mm
0.125 SM divisions = 1 EPG division = 0.0125 mm

15 EPG divisions = 0.0125 * 15 = 0.1875 mm

90
Q

A plant cell was observed with an optical microscope. Describe how the length of the cell could be estimated. [2]

A

Measure the length of the plant cell with an eyepiece graticule (1) calibrated against a stage micrometer (1)

91
Q

Describe and explain how the structure of a chloroplast is related to its function. [4 marks]

A

Mark in pairs, e.g. 1 and 2 - up to 4 marks for:
* Thylakoids are flattened sacs (stacked into grana, connected by lamellae);
* (Which) increase surface area for photosynthesis

  • Chlorophyll / photosynthetic pigments;
  • (Which) absorb light for photosynthesis
  • Stroma contains enzymes;
  • For photosynthesis
  • (Stroma contains) DNA and ribosomes;
  • For protein synthesis
  • (Stroma contains) starch grains;
  • For energy storage.
92
Q

Describe and explain the structure and function of the cell vacuole in plant cells. [4 marks]

A
  • Has a single membrane / a tonoplast;
  • (to) maintain (internal) pressure / rigidity / prevents wilting / turgidity;
  • Contains cell sap / solution of dissolved sugars / salts / amino acids;
  • (Which) acts as a (temporary) food storage
    OR
  • (Which) isolates / separates unwanted chemicals (within the cell).
93
Q

How do you calculate the length of a scale bar when drawing a scientific drawing?

A

Scale bar image length = magnification * length you want the scale bar to represent

(and then you convert it back into mm/cm to draw it!)

94
Q

How do you calculate the magnification of a photograph from a labelled scale bar?

A

Scale bar image length = magnification * length scale bar actually represents

Magnification = scale bar image length / length scale bar actually represents

A Level Biology (9 decks)

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