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A-level Biology > Chapter 3 - Cell Structure > Flashcards

Chapter 3 - Cell Structure Flashcards

(108 cards)

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1
Q

what is an object

A

the material placed under the microscope

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2
Q

what is an image

A

the appearance of the material viewed under the microscope

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3
Q

why is the resolution of an electron microscope greater than that of an optical microscope

A

electrons have a very small wavelength compared to light

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4
Q

equation for magnification

A

magnification = size of image/size of real object

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5
Q

what is magnification

A

how much bigger the image is than the specimen you’re looking at

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6
Q

what is resolution

A

how well a microscope can distinguish between two points that are close together

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7
Q

what do optical microscopes use to form an image

A

light

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8
Q

what do electron microscopes use to form an image

A

electrons

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9
Q

maximum resolution of a light microscope

A

0.2 micrometres

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10
Q

maximum resolution of light microscopes

A

1500 x

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11
Q

maximum resolution of electron microscopes

A

0.0002 micrometres

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12
Q

maximum magnification of electron microscopes

A

1,500,000 x

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13
Q

what are the two types of electron microscopes

A

transmission electron microscopes TEM

scanning electron microscopes SEM

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14
Q

hoe do transmission electron microscopes work

A

a beam of electrons is focussed onto a specimen using electromagnets
the electrons are transmitted through the specimen
denser parts of the specimen absorb more electrons so they appear darker

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15
Q

what are the main limitations of TEM 3

A

they can only be used on thin specimens
the whole system must be observed in vacuum- living specimens can’t be viewed
a complex preparation process mans artefacts are common

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16
Q

what are artefacts

A

things that you can see on the microscope but aren’t part of your specimen

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17
Q

how many micrometers are in a millimetre

A

1000

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18
Q

how many nanometers in a micrometre

A

1000

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19
Q

how do scanning electron microscopes work

A

a beam of electrons is scanned onto the surface of a specimen
this knocks electrons off of the specimen which are gathered in a cathode ray tube to form an image

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20
Q

advantages of TEM

A

high resolution images mean you can see internal structures like chloroplasts

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21
Q

advantages of SEM

A

they can be used on thick and living specimens

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22
Q

disadvantages of SEM

A

the resolution is lower than TEM

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23
Q

what is an eyepiece graticule

A

a transparent rule with number but no units

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24
Q

how to calibrate a microscope

A

1) divide total length of stage micrometer by how many intervals to find one micrometer unit
2) find a point where the two lines are equal
3) work out how many micrometers units equal how many eyepiece units
4) convert the stage micrometre units to micrometers
5) divide stage units by eyepiece units to find the value of one eyepiece unit
6) this can be used in calculations

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25
what is cell fractionation
the process where cells are broken up and different organelles they contain are separated out
26
during homogenisation why is the solution a) cold b) same water potential as the tissue c) buffered
a) to reduce enzyme activity that could break down organelles b) to prevent organelles bursting or shrivelling due to osmosis c) any change in pH could affect the organelles or enzymes
27
what happens during homogenisation
cells are broken up in a blender to release organelles
28
what happens during filtration
the homogenate is filtered to remove any large sections of cell and debris
29
what happens during ultracentrifugation
the filtrate is poured into a test tube place in the centrifuge and spun slowly the heaviest organelles sink to the bottom forming the pellet whilst the rest of the organelles stay suspended in a fluid called the supernatant the supernatant is drained off, poured into another test tube and spun at an even higher speed the next heaviest organelles form the pellet and are remove
30
description of the nucleus
nuclear envelope surrounding chromatin and nucleoplatism
31
function of the nucleus
stores genetic info DNA
32
decription of mitochondria
double membrane. inner highly folded-cristae
33
function of mitochondria
makes energy ATP rich molecules during aerobic respiration
34
description of cell surface membrane
free in cytoplasm attached to RER smaller in prokaryotic cells
35
function of cell surface membrane
makes proteins
36
rough size of mitochondria
between 2 and 10 um
37
what is the chloroplast envelope
a double membrane surrounding the organelle
38
what are grana
stacks of thylakoid membranes inside chloroplasts
39
what is stroma
a matrix where the sugar are synthesised during photosynthesis
40
function of chloroplasts
site of photosynthesis
41
how are chloroplasts adapted for photosynthesis
the grana provide a large surface area for the first stage of photosynthesis chloroplasts contain ribosomes and DNA so they can quickly make proteins required for photosynthesis
42
what are the two types of endoplasmic reticulum
smooth endoplasmic reticulum SER | rough endoplasmic reticulum RER
43
what is the RER
a system of membranes covered in ribosomes | network of interlined sheets with ribosomes
44
functions of RER
ribosomes make protein and channel transport these proteins
45
what are cistern
a stack of membranes that make flattened sacks
46
functions of Golgi apparatus
processes and packages new lipids and proteins
47
description of Golgi apparatus
contains vesicles for export
48
what are Golgi vesicles
fluid filled sacks produced by the Golgi apparatus
49
function of Golgi vesicles
stores lipids and proteins made by the Golgi apparatus and transports them out of the cell
50
when are lysosomes formed
when vesicles contain enzymes like lipase and proteases
51
description of lysosomes
vesicles contain hydralytic enzymes
52
functions of lysosomes
modify proteins or lipids. package them is vesicles for export
53
description of ribosomes
free in cytoplasm attached to RER smaller in prokaryotic cells
54
function of ribosomes
makes proteins | protein synthesis
55
function of microvilli
increase surface area for absorption and diffusion
56
what is a cell wall
a rigid structure surrounding cells in plants algae and fungi it consists of cellulose embedded in a matrix
57
functions of the cell wall
to prevent the cell bursting form the movement of water | gives mechanical support to the cell
58
what are cell walls made from in fungi
chitin
59
what is tonoplast
the membrane surrounding the vacuole
60
what is a vacuole
a fluid filled sack surrounded by the tonoplast
61
function of a vacuole
stores water to keep the cell rigid and the plant turgid | helps to isolate unwanted chemicals
62
why do cells become specialised
to carry out specific functions
63
how do cells become specialised
certain genes can be turned on and off
64
what is a tissue
a group of cells working together to perform a specific function
65
function of the epithelial tissue
covers the inside and outside of organs
66
function of xylem
transports water and mineral ions throughout the cell and also gives mechanical support
67
what is an organ
a variety of tissues coordinated to perform a variety of functions
68
what do muscular tissues do in the stomach
churns content
69
what does epithelial tissues do in the stomach
protects stomach lining
70
which of the blood vessels are organs and which are tissues
organs arteries and veins | tissue capillaries
71
function of phloem
moves food away from the leaves in a plant
72
function of the epidermis in a plant
to protect the leaf
73
function of the spongy mesophyll in a plant
gaseous diffusion
74
function of the palisade mesophyll in a plant
photosynthesis
75
what does the digestive system do
digests and processes food
76
what does the respiratory system do
breathing and gas exchange
77
what does the circulatory system do
pumps and circulates blood
78
what are cell walls made from in bacteria
the glycoprotein murine
79
function of slime capsule
protects bacterium from other cells and helps them group together
80
function of circular DNA
contains informations needed for bacteria cells to replicate
81
function of plasmid
contains genes that may help the bacteria survive in adverse conditions
82
is the DNA of bacteria cells associated with proteins
no
83
why are viruses described as acellular
they are nucleic acids surrounded by a protein called the cashed they aren't alive
84
what is the function of attachment proteins an where are they found
they are found sticking out from around the cased and help virus cling to a host cell
85
how do viruses replicate
they use proteins to attach to host cells | they inject their DNA into the host cell
86
why can viruses only infect one type of cell
their attachment proteins are complementary to just one receptor cell
87
process of binary fission
the DNA and plasmids in the cell replicate the cell gets bigger and the DNA moves to the opposite end of the cell where it attaches to the membrane the cytoplasm begins to divide and new cell walls begin to form a new cell wall forms between the the two molecules of DNA creating two identical daughter cells
88
what is mitosis
a parent cell divides to produce two genetically identical daughter cells
89
3 uses of mitosis
growth repair and reproduction
90
what are the three stages in the cell cycle
interphase nuclear division cytokinesis
91
which stage isn't part of mitosis
interphase
92
what happens during interphase 2
the cells DNA unravels and replicates | the organelles and ATP are replicated
93
what happens during prophase 3
the chromosomes condense and become visible centrioles move to opposite ends of the cell forming the spindle apparatus the nuclear envelope breaks down
94
what happens in metaphase 2
the chromosomes line up along the cells equate | the spindle fibres attach to the centimetre
95
what happens in anaphase 2
the centromeres divide separating the chromatids | the spindles contract and pull chromatids to the cells pores
96
what happens during telophase 2
the chromosomes reach the poles and unravel | the cytoplasm divides and two nuclear envelopes form leaving two identical daughter cells
97
what is cytokinesis
the process by which the cytoplasm divides
98
what is cancer
a group od diseases characterised by a growing disorder of cells
99
characteristics of benign tumours
grow slowly are more compact and less life threatening
100
characteristics of malignant tumours
grow quickly less compact and are more life threatening
101
how do cancer drugs work
they disrupt the cell cycle to stop the tumour diving and growing
102
how does chemotherapy work
chemicals prevent the synthesis of enzymes needed for DNA replication
103
how does radiotherapy work
radiation damages DNA so the cell kills itself
104
formula for mitotic index
number of cells with visible chromosomes / total number of cells observed
105
why are hair cells often affected by the cancer drugs
the drugs target cells that divide rapidly such as hair cells
106
why do specimens have to be kept in a vacuum before using an electron microscope
the air would otherwise absorb the elctorns and prevent them from reaching the specimen
107
what chromosomes do women have
XX
108
what chromosomes do men have
XY

A-level Biology (19 decks)

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