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A Level Biology > Module - 2.1.1 Cell Structure > Flashcards

Module - 2.1.1 Cell Structure Flashcards

to understand cell structure & components

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is the cell theory?

A

A) Both animal & plant tissue are made out of cells
B) Cells are the basic units of all life
C) Cells can only develop from existing cells

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2
Q

What is magnification?

A

The number of times larger an image appears, compared with the size of the obeject

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3
Q

What is resolution?

A

The ability to distinguish 2 adjacent points as separate from each other

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4
Q

What is the purpose of a microscope?

A

Enables you to magnify an object & see things that are too small to see with the naked eye

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5
Q

What are the 4 different types of microscope?

A

Light microscope
Laser scanning microscope
Transmission electron microscope
Scanning electron microscope

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6
Q

What is an artefact?

A

A visible structural detail caused by processing the specimen & not a feature of the specimen (e.g. a bubble)

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7
Q

What are the features of a light microscope?

A

Relatively cheap
Easy to use
Portable
Can be used on living specimens
Can be magnified up to x2000
Limited resolution (400-700nm)

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8
Q

How do you use a light microscope?

A

Specimen on a slide is placed on a stage & held in place by clips
Select the lowest magnification objective lens
Use the course focus dial, raise the stage to the highest point & turn the dial away so the image focuses
While viewing the specimen, the diaphragm can be adjusted to ensure optimum light
Ensure object is in the centre & use the next objective lens & fine focus dial to focus on the specimen & detail

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9
Q

What are the features of a laser scanning microscope?

A

Uses a laser light to scan an object & create a digital image
Specimens are usually tagged with a fluorescent dye
Images produced have a high resolution & contrast
Depth selectivity - can focus on structures at different depths within a specimen
Can be used to observe thick/alive samples - often used in medical prep.

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10
Q

What are the features of electron microscopes?

A

A beam of electrons with a wavelength of 0.004nm is used
Electrons are fired from a cathode & focused using magnets onto a screen/photographic plate
Higher magnification of up to x5000000 & greater resolution
Internal cell structures can be viewed
Very expensive & can only be used in a controlled environment in a dedicated space
Fairly large & require a lot of training & skill to use
Complex specimen prep & living specimens can’t be used
Mistakes in sample prep can result in artefacts

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11
Q

How do you prepare a slide for an electron microscope?

A

Fix the sample in glutaraldehyde to make the tissue firm
Dehydrate it to replace the water with ethanol
Embed the dehydrated tissue in resin
Cut very thin slices using a diamond knife
Stain it using metal salts - scatter electrons differently (provides contrast)
Mount it on a copper grid
Place the specimen on the grid in a vacuum in the microscope

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12
Q

How do you prepare a slide for an electron microscope?

A

Fix the sample in glutaraldehyde to make the tissue firm
Dehydrate it to replace the water with ethanol
Embed the dehydrated tissue in solid resin
Cut very thin slices using a diamond knife
Stain it using metal salts - scatter electrons differently (provides contrast)
Mount it on a copper grid
Place the specimen on the grid in a vacuum in the microscope

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13
Q

How do you prepare a slide for an electron microscope?

A

Fix the sample in glutaraldehyde to make the tissue firm
Dehydrate it to replace the water with ethanol
Embed the dehydrated tissue in solid resin
Cut very thin slices using a diamond knife
Stain it using metal salts - scatter electrons differently (provides contrast)
Mount it on a copper grid
Place the specimen on the grid in a vacuum in the microscope

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14
Q

What are the features of a transmission electron microscope?

A

A beam of electrons is transmitted through a specimen to produce an image
Denser parts of the specimen absorb more electrons so they appear darker on the image
Resoluting power of 0.5nm & magnification of up to 2 million times
Specimens have to be very thin & chemically fixed through processes e.g. dehydration & staining
Forms a 2D black & white image

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15
Q

What are the features of a scanning electron microscope?

A

A beam of electrons is sent across the surface of a specimen & the reflected electrons are collected in a cathode ray tube
Resolving power of 3-10nm & magnification of x15 to x200000
Produces a 3D image of surfaces in black & white
Specimen has to placed in a vacuum & often coated in a fine metal film

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16
Q

What are the rules of scientific drawings?

A

Single clear lines drawn with a sharp pencil
No shading/colour on the diagram
Informative title to be included
Scale included to show approximate magnification
Actual size stated if a graticule is used
Low tissue plans may not include cells
High power diagrams show a few adjacent cells only - must have complete lines
Cells/tissues should be in correct proportions
Label lines drawn in pencil using a ruler - horizontal & don’t cross over

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17
Q

What are labels used for in scientific drawings?

A

To identify the tissue, cell, organelle etc.

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18
Q

What are annotations used for in scientific drawings?

A

To describe some detail about the features e.g. colour, shape, arrangement etc

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19
Q

What is a dry mount sample preparation & how is it done?

A

The simplest method of preparing a specimen - often used on hairs, parts of insects, pollen & parts of flowers

1) solid specimen are viewed hole/cut into very thin slices with a sharp blade
2) The specimen is placed onto the centre of the slide & the cover slip is placed over the sample

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20
Q

What is a wet mount sample technique & how is it done?

A

Involves specimen being a liquid & is more difficult to prepare - can be used with living specimens e.g. pond water

1) Small drops of liquid is placed onto the slide & specimen is put on top
2) Slowly tilt & lower the cover slip so it covers the specimen ensuring no air bubbles can be trapped
3) Once the coverslip is placed the stain is added to one edge & is drawn under the slop by holding a paper towel next to the opposite edge

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21
Q

What is a squash slide sample technique & how is it done?

A

Good technique for soft samples e.g. root tip - cell division

1) A wet mount is prepared first
2) A lens tissue is used to gently press down on the coverslip - taking care to not break the coverslip

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22
Q

What is a smear slide sampling technique & how is it done?

A

Often used for blood samples

1) The edge of the slide is used to smear the sample, creating a thin, even coating on another slide
2) Cover slip is placed over the sample

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23
Q

Why are stains used for sample preparation?

A

Many samples of living tissue are transparent & so will let light pass through them so the tissues & structures are difficult to see so they’re used to see the cell structures

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24
Q

What stains are used for light microscopes?

A

Coloured dyes. Sections can be stained with multiple stains to show up different tissues within them (differential staining)

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25
Q

What stains are used for electron microscopes?

A

Stains that will absorb electrons - the parts end up looking black/shades of grey

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26
Q

What is differential staining?

A

Stains that bind to specific cell structures, staining each structure differently so the structures can be easily identified within a single preparation

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27
Q

What is the formula for magnification?

A

M = I/A

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28
Q

What is the formula for image size?

A

M x A

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29
Q

What is the formula for actual size?

A

A = I/M

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30
Q

What is an eyepiece graticule?

A

A measuring device which is placed in the eyepiece of a microscope & acts as a rule (without units) when you view an object under the microscope

31
Q

What is a stage micrometer?

A

A microscope slide with an accurate scale (with units) & is used to calibrate the value of eyepiece divisions & different magnifications

32
Q

What is the structure of a nucleus?

A

A large organelle surrounded by a nuclear envelope which contains many pores.
Contains chromatin & a nucleolus

33
Q

What is the function of the nucleus?

A

Controls the cells activities
Controls DNA transcription
Chromatin made from DNA & proteins & condenses to form visible chromosomes

34
Q

What is the structure of the nuclear envelope?

A

Double membrane with fluid between that surrounds the nucleus
Nuclear pores are protein complexes with a chamber through the centre

35
Q

What is the function of the nuclear envelope?

A

Separates the contents of the nucleus from the rest of the cell
Nuclear pores enable larger substances e.g. mRNA to enter/leave the nucleus

36
Q

What is the structure of the nucleolus?

A

Dense spherical structure without a membrane around it
Composed of proteins & RNA

37
Q

What is the function of the nucleolus?

A

RNA used to produce ribosomal RNA
Ribosomal RNA combines with proteins to synthesise ribosomes

38
Q

What is the structure of the rough endoplasmic reticulum (RER)?

A

A system of flattened membranes enclosing fluid-filled cavities (cisternae)
Surface coated with ribosomes

39
Q

What is the function of the rough endoplasmic reticulum (RER)?

A

Intracellular transport system - the cisternae form channels for transporting substances from one area of the cell to another
Provides a large surface area for ribosomes to assemble amino acids into proteins for transport to the Golgi apparatus

40
Q

What is the structure of the smooth endoplasmic reticulum (SER)?

A

A system of flattened membranes enclosing a fluid filled cavities (cisternae) that are continuous with the nuclear membrane & RER
No ribosomes on the surface

41
Q

What is the function of the smooth endoplasmic reticulum (SER)?

A

Synthesising lipids - phospholipids (cell membranes), cholesterol, steroid hormones (e.g. oestrogen)

42
Q

What is the structure of a vesicle?

A

A small fluid-filled sac in the cytoplasm surrounded by a single membrane

43
Q

What is the function of a vesicle?

A

Transports substances in & out of the cell (via the plasma membrane) & between organelles

44
Q

What is the structure of the Golgi apparatus?

A

A stack of membrane-bound flattened sacks (cisternae)
Secretory vesicles bring materials to & from the Golgi apparatus

45
Q

What is the function of the Golgi apparatus?

A

Receives proteins & lipids from the RER/SER, modifies them & packages them into vesicles ready for secretion
Responsible for the synthesis of ribosomes

46
Q

What is the structure of the mitochondria?

A

Spherical/rod-shaped/branched
Surrounded by a double membrane with a fluid-filled space (matrix) between
Inner membrane is highly folded into cristae
Has its own DNA

47
Q

What is the function of the mitochondria?

A

Site of aerobic respiration where ATP is produced
Self-replicating so more can be made as needed for cells requiring large amounts of energy

48
Q

What is the structure of chloroplasts?

A

Large organelles
Double outer membrane & a complex arrangement of internal membranes that form thylakoids (contain chlorophyll)
Thylakoids are grouped into stacks (grana) joined by intergranal lamellae.
Fluid filled matrix - stroma

49
Q

What is the function of chloroplasts?

A

Site of photosynthesis
Grana - light energy is trapped by chlorophyll & used to make ATP & split into water & ions
Stroma - where energy from ATP is used to make carbohydrates

50
Q

What is the structure of a vacuole?

A

Surrounded by membrane (tonoplast)
Contains fluid

51
Q

What is the function of the vacuole?

A

Plant cells - permanent vacuole
Filled with water & solutes & maintains cell stability when fully pushed against cell wall - makes cell turgid

52
Q

What is the structure of a lysosome?

A

Round organelle surrounded with a membrane - no clear internal structure
Small bags formed by the Golgi apparatus

53
Q

What is the function of lysosomes?

A

Contain powerful hydrolytic (digestive) enzymes - can engulf old organelles & foreign matter, digest them & recycle the material
Often abundant in phagocytic cells that ingest/invade pathogens

54
Q

What is the structure of cell membranes?

A

The membrane found on the surface of animal, just inside the cell wall of plant cells & prokaryotic cells
Mainly made up of lipids & proteins

55
Q

What is the function of cell membranes?

A

Acts like a barrier to the cell, controlling what enters & leaves due to the differential permeability of different biological molecules & protein carriers that pump substances in & out

56
Q

What is the structure of cilia?

A

Small hair like structures found on the surface membrane of some animal cells
Have an outer membrane & ring of 9 pairs of protein microtubules with a single pair in the middle

57
Q

What is the function of cilia?

A

Microtubules allow cilia to move
Movement of cilia push substances along the cell surface
Occur in large numbers along the cell surface
Nearly all cells in the body have 1 cilium that cats as an antenna & contains receptors to detect the environment

58
Q

What is the structure of the undulipodia (flagellum)?

A

Very similar to cilia (but longer)
Small hair-like structures that stick out from the cell surface & are surrounded by plasma membrane
They have an outer membrane & a ring of 9 pairs of protein microtubules with 2 in the middle

59
Q

What is the function of the undulipodia (flagellum)?

A

Microtubules contract to make the flagellum move & propel the cell forward
Flagellum used for a prokaryotic structure - different internally

60
Q

What is the structure of ribosomes?

A

Small spherical organelles (20nm in diameter)
Consists of 2 subunits
Made of proteins & ribosomal RNA
Not surrounded by a membrane

61
Q

What is the function of ribosomes?

A

Site where proteins are made
Ribosomes are attached to the RER exterior make proteins to be excreted outside the cell
Free floating ribosomes in the cytoplasm make proteins to be used inside the cell

62
Q

What is the structure of centrioles?

A

Consists of 2 bundles of microtubules at right angles to each other
Microtubules are made of tubulin protein subunits & are arranged to form a cylinder

63
Q

What is the function of centrioles?

A

Involved with the seperation of chromosomes during cell division
Chromosomes attach to the middle of the spindle & motor proteins walk along the tubulin threads, pulling chromosomes apart
Centrioles are involved in the formation of cilia & undulipodia

64
Q

What is the structure of the cell wall?

A

A rigid structure that surrounds plant cells
Made from bundles of cellulose fibres (carbohydrates)

65
Q

What is the function of the cell wall?

A

Strong & can prevent plant cells from bursting
Provides strength & support
Maintains the cell’s shape
Permeable due to plasmodesmata (pores within walls & allows solutions through)

66
Q

What is the cytoskeleton?

A

A network of protein structures within the cytoplasm

67
Q

What makes up the cytoskeleton?

A

Rod-like microfilaments made of sub-units of actin that forms a polymer (each being 7nm in diameter)
Straight cylindrical microtubules made of tubulin protein subunits (about 18-30nm in diameter)
Motor proteins, myosins, kinesins, & dyneins (molecular motors)
Contains enzymes & they have a site that binds to & allows hydrolysis of ATP for an energy source

68
Q

What are the 3 functions of the cytoskeleton?

A

Cellular movement - e.g. cilia & flagella contain microtubules that are responsible for movement
Intracellular movement of organelles & substances within the cell
Strength & support

69
Q

What is the function of microfilaments?

A

Within the cytoplasm -> give support & mechanical strength
Outside the cytoplasm -> keeps the cell’s shape stable & allow cell movement

70
Q

What is the function of intermediate filaments?

A

They anchor the nucleus within the cytoplasm
They extend between cells in some tissues, between special junctions enabling cell signalling
Allows cells to adhere to the basement membrane, stabilising tissues

71
Q

What is the function of microtubules?

A

Provide shape & support to cells
Help transport substances & organelles through the cytoplasm
Form the track along which motor proteins (dyein & kinesin) move, taking organelles along with them from one part of the cell to another
Form the spindle before a cell divides that move the chromosomes towards the opposite ends of the cell (anaphase)
Make up the cilia, undulipodia & centrioles

72
Q

Why do organelles need to work together?

A

Many cellular processes require the coordination of several different organelles

73
Q

What is an example of organelles working together?

A

Protein production & secretion from cells

A Level Biology (18 decks)

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