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A level Biology > 2.1 cell structure and microscopes > Flashcards

2.1 cell structure and microscopes Flashcards

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1
Q

name the four types of microscopes

A

light microscope
transmission electron microscope
scanning electron microscope
laser scanning microscope

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2
Q

what is the difference between magnification and resolution?

A

magnification is the process of enlarging the apparent size

resolution is the ability to distinguish 2 objects as separate

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3
Q

what is the maximum magnification and resolution of a light microscope

A

magnification 1500x
resolution 200nm

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4
Q

what is the maximum magnification and resolution of an SEM

A

magnification 200.000x
resolution 0.1nm

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5
Q

what is the maximum magnification and resolution of a TEM

A

magnification 2millionx
resolution 0.1nm

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6
Q

what is the maximum magnification and resolution of a laser scanning microscope

A

magnification 1000x
resolution 180nm-500nm

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7
Q

how is the beam focused in a light microscope

A

light beam is focused through glass lenses

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8
Q

how is the beam focused in an SEM

A

an electron beam is focused with electromagnetic coils

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9
Q

how is the beam focused in a TEM

A

an electron beam is focused with electromagnetic lenses

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10
Q

how is the beam focused in a laser scanning microscope

A

a laser beam through a light source is focused with objective glass lenses

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11
Q

which microscopes have a sectional or external view of the specimen

A

light - both
TEM - sectional
SEM - external
Laser - both

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12
Q

what is an application of a light microscope

A

can be used to provide information about the activity of cells

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13
Q

what is an application of a TEM

A

internal view of organelles and cells

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14
Q

what is an application of an SEM

A

external 3D viewing of cells

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15
Q

what is an application of a laser scanning microscope

A

medical progression

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16
Q

why is the maximum magnification of a light microscope limited to 1500x

A

the wavelength of visible light ranges from 400-700nnm so structures closer than 200nm will appear as one object.

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17
Q

state advantages of light microscopes

A

cheap
easy to use
able to study live specimens

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18
Q

state disadvantages of light microscopes

A

limited resolution due to wavelength of light

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19
Q

state advantages of SEM

A

high resolution
high magnification
produces 3D images

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20
Q

state disadvantages of SEM

A

inability to analyze live specimens
costly
training is required
black and white images only

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21
Q

state advantages of TEM

A

high magnification
high resolution
provides information on the internal structures of cells

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22
Q

state disadvantages of TEM

A

inability to analyze live specimens
costly
training required
black and white images only

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23
Q

explain why a vacuum is needed for electron microscopes

A

they prevent the electrons from being scattered by air particles

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24
Q

explain in terms of staining how electron microscopes differ

A

in an SEM the metal salt stain sits on top of the specimen whereas on a TEM the metal salt stain passes through the specimen

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25
Q

use a named example to explain why staining is needed for light microscopes.

A

the main reason for staining is to highlight cells and parts of cells for a better visual, for example, acetic orcein stains DNA and chromosomes in cells dark red

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26
Q

briefly describe how to use a light microscope

A

put the slide on the STAGE and clip it in place
turn on the power supply and light source
look through the EYEPIECE and make sure the OBJECTIVE LENS is on the lowest magnification
adjust your FINE and COARSE focus as well as IRIS DIAPHRAGM

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27
Q

describe how to change between units

A

mm -> microm =1000 micromm-> mm=/1000
microm -> nm=1000 nm ->microm /1000

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28
Q

what is the formula for magnification

A

magnification = image size/actual size

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29
Q

what is the difference between prokaryotic and eukaryotic cells

A

prokaryotic cells contain a cell wall and plasmids in the cytoplasm. However, it doesn’t have a nucleus and membrane-bound organelles

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30
Q

describe the 10 structures of a prokaryotic cell

A

they contain:
a waxy protective capsule
peptidoglycan cell wall
plasma membrane
mesosome
plasmid
pili
ribosomes
cytoplasm
DNA loop
flagella

31
Q

describe the endosymbiotic theory

A

the idea that eukaryotes arose from prokaryotes- that organelles were once prokaryotes ingested by a larger bacteria

32
Q

what is the difference between the nucleus and the nucleolus

A

the nucleolus is inside the nucleus

33
Q

describe the structure of the nucleus

A

the nucleus is surrounded by a double membrane called the nuclear envelope that contains pores
the outer membrane joins up to the endoplasmic reticulum

it is the largest organelle 10-20micro metres in diameter

the nucleoplasm contains chromatin

34
Q

describe the function of the nucleus

A

contains nearly of all a cells genetic material; instructions for making proteins and makes mRNA for protein synthesis

35
Q

describe the structure of the nucleolus

A

not surrounded by a membrane

the dense spherical structure inside the nucleus

36
Q

describe the function of the nucleolus

A

makes RNA and ribosomes that pass into the cytoplasm through the nuclear pores

37
Q

describe the structure of the ribosomes

A

non-membrane bound

small spherical organelle that is about 20nm in diameter

made of ribosomal RNA

made in the nucleolus as two separate sub-units which pass through the nuclear envelope into the cytoplasm and then combine (40s and 60s sizes )

38
Q

describe the function of ribosomes

A

ribosomes that bind to the exterior of the endoplasmic reticulum are mainly used for synthesising proteins that will be exported outside the cell

ribosomes that are free in the cytoplasm, either singly or in clusters are primarily the site of assembly of proteins that will be used inside the cell

39
Q

describe the structure of rough ER

A

system of membranes containing fluid-filled cavities (cisternae) that are continuous with the nuclear membranes

coated in ribosomes

40
Q

describe the function of rough ER

A

it is the intracellular transport system: the cisternae form channels for transporting systems from one area of a cell to another

provides a large surface area for ribosomes which assemble amino acids into proteins - these proteins then actively pass through the membrane into the cisternae and are transported to the Golgi body for modification and packaging

41
Q

describe the structure of smooth ER

A

system of membranes with fluid-filled cavities (cisternae)that are continuous with the nuclear membrane

no ribosomes

42
Q

describe the function of smooth ER

A

contains enzymes that catalyse reactions involved with lipid metabolism such as:
-synthesis of cholesterol
- synthesis of steroid hormones

it is involved with absorption synthesis and transportation of lipids (from the gut)

43
Q

describe the structure of the Golgi apparatus

A

consists of stacks of membrane-bound flattened sacs

secretary vesicles bring materials to and from the Golgi body

44
Q

describe the function of the Golgi apparatus

A

proteins are modified for example:
-adding sugar molecules to make glycoproteins
-adding lipid proteins to make lipoproteins
-being folded into their 3D shape

then proteins are packaged into vesicles that are then pinched off and :
-stored in the cell or
-moved into the plasma membrane, either to be incorporated into the plasma membrane or exported outside the cell

45
Q

describe the structure of the mitochondria

A

they may be spherical or rod-shaped or branched and are 2-5 micrometers long

they are surrounded by two membranes with a fluid-filled space between them. The inner membrane is highly folded into cristae

the inner part of the mitochondrion is a fluid-filled matrix

46
Q

describe the function of the mitochondria

A

site of ATP during aerobic respiration

self-replicating so mare can be made if the cell needs more energy

they are abundant in cells where much metabolic activity occurs

47
Q

describe the structure of chloroplasts

A

these are large organelles that are 4-10 micrometers long

they are surrounded by a double membrane or envelope

the inner membrane is continuous with stacks of flattened membrane sacks called thylakoids which contain chloroplasts. Each stack of thylakoids is called a granum

the fluid-filled matrix is called stroma

48
Q

describe the function of chloroplasts

A

chloroplasts are the site of photosynthesis

during the first stage of photosynthesis, when light energy is trapped by chlorophyll and used to make ATP occurs in the grana, water is also split to supply hydrogen ions

49
Q

describe the structure of lysosomes

A

these are small bags formed from the Golgi apparatus and each is surrounded by a single membrane

they contain powerful hydrolitic (digestive) enzymes

50
Q

describe the function of lysosomes

A

they keep powerful hydrolitic enzymes separate from the rest of the cells

they engulf old organelles or foreign matter, digest them and return the digested components to the cell for reuse

they are abundant in phagocytic cells such as white blood cells and neutrophills

51
Q

describe the function of the plasma membrane

A

separate contents of the cell from the outside

permeable so it allows solutions to pass-through

52
Q

describe the structure of the plasma membrane

A

a thin flexible layer of phospholipids

53
Q

describe the structure of the cellulose cell wall

A

on the outside of the plasma membrane

made from bundles of cellulose fibers

54
Q

describe the function of the cellulose cell wall

A

strong and prevents plant cell from bursting when turgid

provides strength and support
maintains the cells shape
permeable and allows solutions to pass through

55
Q

describe the structure of the vacuole

A

surrounded by a membrane called the tonoplast and contains fluid

56
Q

describe the function of the vacuole

A

filled with water and solutes and maintains cell stability because when full it pushes against the cell wall and makes the cell turgid

57
Q

describe the structure of the vesicle

A

made from phospholipids

58
Q

describe the function of the vesicle

A

used for transportation

59
Q

how does the function of ribosomes that are free and those on the RER differ

A

Free ribosomes are mainly concerned with assembling proteins to be used within the cell. Ribosomes on RER
mainly assemble proteins that are exported out of the cell.

60
Q

how are chloroplasts moved nearer the surface on a dull day

A

Motor proteins drag chloroplasts along cytoskeleton threads or ‘tracks’.

61
Q

name one substance that passes into the nucleus

A

mRNA

62
Q

suggest why hydrolytic enzymes need to be inside a vesicle

A

To prevent them from digesting/breaking down the cell components.

63
Q

describe the structure of centrioles

A

consists of two bundles of microtubules at right angles to each other

the microtubules are made of tubulin protein subunits arranged to form a cylinder

64
Q

describe the function of centrioles

A

before the cell divides the spindle, made of threads of tubulin, forms from the centrioles. Then chromosomes attach to the middle part of the spindle and motor proteins walk along the tubulin threads and pull the chromosomes apart

involved in the formation of cilia and undulipodia

65
Q

describe the structure of microfilaments

A

they are 7nm in diameter and made of subunits of the protein actin

66
Q

describe the function of microfilaments

A

they are within the cytoplasm and give support and mechanical strength to keep the cell’s shape stable and allow cell movement

67
Q

describe the structure of intermediate filaments

A

10nm in diameter

made of a variety of proteins

68
Q

describe the function of intermediate filaments

A

they anchor the nucleus within the cytoplasm

extend between cells in some tissues between special junctions enabling cell-cell communication and allowing cells to adhere to a basement membrane stabilising the tissue

69
Q

describe the structure of microtubules

A

18-30nm in diameter

made of protein subunits called tubulin

70
Q

describe the function of microtubules

A

also, provide shape and support to cells and help organelles/substances move through the cytoplasm

they form the track along which motor proteins (kinesin) walk and drag organelles from one part of the cell to another

they form the spindle before a cell divides and these spindle threads enable a chromosome to be moved within the cell

71
Q

why are some human cells ciliated

A

to waft mucus

72
Q

name a type of human cell that can move and explain why that is important for its function

A

phagocytes

the can move so that they can engulf pathogens

73
Q

How do you use a graticule

A

lace a stage micrometer on the stage of the microscope.
Line up one of the divisions on the eyepiece graticule with a fixed point on the stage micrometer.
Count the number of divisions on the eyepiece graticule that correspond with a set measurement on the stage micrometer.
Calculate the distance in micrometres of one division on the eyepiece graticule.

A level Biology (25 decks)

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