Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A LEVEL BIO > topic 2A - cells & transport > Flashcards

topic 2A - cells & transport Flashcards

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

cell surface membrane

A

-controls the exchange of materials between the inside & outside of the cell
-partially permeable
-formed from a phospholipid bilayer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

cell wall

A

-permeable to most substances
-offers structural support to cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

nucleus

A

-contains chromatin (genetic material of the cell) from which chromosomes are made
-separated from the cytoplasm by a nuclear envelope (has many pores)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

chromosomes

A

made of sections of linear DNA wound around proteins called histones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

mitochondria

A

-site of aerobic respiration
-surrounded by double-membrane, inner membrane folds to form cristae
-the matrix formed by the cristae contains enzymes needed for respiration
-small circular pieces of DNA and ribosomes are found in the matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

chloroplast

A

-larger than mitochondria
-surrounded by a double-membrane
-thylakoids containing chlorophyll stack to form grana
-grana are joined together by lamellae
-site of photosynthesis
-contains small circular pieces of DNA and ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

ribosome

A

-formed in nucleolus
-made of almost equal amounts of RNA and protein
-free in the cytoplasm/part of the RER in eukaryotic cells
-site of translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

endoplasmic reticulum

A

RER:
-surface covered in ribosomes
-formed from continuous folds of membrane
-processes proteins made by the ribosomes

ER:
-no ribosomes
-involved in the production, processing and storage of lipids, carbohydrates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

golgi apparatus

A

-flattened sacs of membrane
-modifies proteins and lipids before packaging them into golgi vesicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

large permanent vacuole (+ in animals)

A

-sac in plant cells surrounded by the tonoplast
-selectively permeable membrane
-vacuoles in animal cells are small and not permanent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

vesicle

A

membrane-bound sac for transport and storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

lysosome

A

-specialist forms of vesicles
-contain hydrolytic enzymes
-break down waste materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

microvilli

A

increase the surface area for absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

cilia

A

-hair-like projections made from microtubules
-allows the movement of substances over the cell surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

flagella

A

-made of microtubules
-rotate in whip like motion to move cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

tissue

A

group of cells that work together to perform a particular function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

organs

A

different tissues work together to form organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

prokaryotic cells: key facts

A

-smaller than eukaryotic cells
-cytoplasm lacks membrane-bound organelles
-ribosomes are smaller than those in eukaryotic cells
-no nucleus
-a cell wall that contains murein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

plasmids

A

-small circular loops of DNA
-contain genes that can be passed between prokaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

slime capsule

A

-final outer layer
-helps to protect bacteria from drying out and from attack

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

structures that are always present in prokaryotic cells:

A

-cell wall
-cell membrane
-cytoplasm
-circular DNA
-ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

structures that are sometimes present in prokaryotic cells:

A

-flagellum
-capsule
-infolding of cell surface membrane (may allow photosynthesis)
-plasmid
-pili (for attachment to other cells/surfaces, involved in sexual reproduction)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are viruses?

A

-not alive
-much smaller than prokaryotic cells
-all viruses are parasitic, they can only reproduce by infecting living cells and using their protein-building machinery (ribosomes) to produce new viral particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

structure of viruses

A

-a nucleic acid core (their genomes are either DNA or RNA)
-a protein coat (capsid)
-some viruses have an an envelope formed from the phospholipids of a cell they were made in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

magnification

A

how many times bigger the image produced by the microscope is than the real-life object you are viewing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

resolution

A

the ability to distinguish between objects that are close together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what do optical microscopes use?

A

use light to form an image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

resolution of optical microscopes

A

-using light, can’t distinguish between two objects that are closer than half the wavelength of light
low resolution
-maximum resolution of around 0.2 micrometres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what can optical microscopes be used to observe?

A

-eukaryotic cells, their nuclei (possibly mitochondria and chloroplasts)
-living specimens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

maximum magnification of optical microscopes:

A

1500x

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what do electron microscopes use?

A

-use electrons to form an image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

resolution of electron microscopes

A

-high resolution
-a beam of electrons has a much smaller wavelength than light
-maximum resolution of 0.0002 µm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what can electron microscopes be used to observe?

A

small organelles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what is the maximum magnification of electron microscopes?

A

×1,500,000

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what are the two types of electron microscopes?

A

transmission electron microscopes:
(TEMs)

scanning electron microscopes:
(SEMs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

how do TEMS work?

A

-use electromagnets to focus a beam of electrons
-beam of electrons is transmitted through the specimen
-denser parts of the specimen absorb more electrons & appear darker on the final image produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

advantages of TEMs

A

-give high-resolution images
-allows small organelles to be seen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

disadvantages of TEMs

A

-can only be used with very thin specimens

-cannot be used to observe live specimens (as there is a vacuum inside a TEM, all the water must be removed from the specimen and so living cells cannot be observed)

-the lengthy treatment required to prepare specimens means that artefacts can be introduced (artefacts look like real structures but are actually the results of preserving and staining)

-do not produce a colour image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

how do SEMS work?

A

-scan a beam of electrons across the specimen
-beam bounces off the surface of the specimen and the electrons are detected, forming an image
-this means SEMs can produce 3D images that show the surface of specimens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

advantages of SEMs:

A

-can be used on thick or 3-D specimens
-allow the 3-D structure of specimens to be observed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

disadvantages of SEMs:

A

-lower resolution images than TEMs
-cannot be used to observe live specimens
-no colour image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

electron microscope vs light microscope (basic differences)

A

-large and can’t be moved (e) v small and easy to carry (l)
-vacuum needed (e) v no vacuum needed (l)
-complicated sample preparation (e) v simple sample preparation (l)
-over 500,000x magnification (e) v up to 2,000x magnification
-specimens are dead (e) v specimens can be living (l)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

cell fractionation

A

the process of separating cell organelles from each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

homogenisation steps

A

-the sample of tissue must be placed in a cold, isotonic buffer solution

-the tissue-containing solution is then homogenised using a homogeniser
that grinds the cells up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

why is the solution ice-cold?

A

to reduce the activity of enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

why is the solution isotonic?

A

to prevent the shrinkage or expansion of the organelles via osmosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

why is the solution buffered?

A

to prevent organelle proteins from becoming denatured

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what is the objective of homogenisation?

A

to break the membrane of the cells and access the organelles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

steps of filtration:

A

-the homogenate (containing the homogenised cells) is then filtered through a gauze to separate out any large debris

-this leaves a filtrate that contains a mixture of organelles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

steps of ultracentrifugation

A

1) the filtrate is placed into a tube and the tube is placed in a centrifuge (machine that separates materials by spinning)

2) the filtrate is first spun at a low speed, the largest, most dense organelles settle at the bottom of the tube & form a thick sediment (pellet)

3) the rest of the organelles stay suspended in the solution above the pellet (supernatant)

4) the supernatant is drained off and placed into another tube, which is spun at a higher speed, heavier organelles settle at the bottom of the tube, forming a new pellet and leaving a new supernatant

5) the new supernatant is drained off and placed into another tube, which is spun at an even higher speed. this process is repeated at increasing speeds until all the different types of organelle present are separated out (or just until the desired organelle is separated out)

6) each new pellet formed contains a lighter organelle than the previous pellet

51
Q

order of organelle collection in ultracentrifugation

A

nuclei
chloroplasts
mitochondria
lysosomes
endoplasmic reticulum
ribosomes

52
Q

cell cycle

A

the regulated sequence of events that occurs between cell divisions

53
Q

3 phases of the cell cycle:

A

interphase
nuclear division (mitosis)
cell division (cytokinesis)

54
Q

what happens in interphase?

A

the cell increases in mass and size and carries out its normal cellular functions

55
Q

3 phases of interphase:

A

G1 phase
S phase
G2 phase

56
Q

what happens in the G1 phase

A

cells make the proteins required for growth (eg: enzymes)

57
Q

what happens in the S phase?

A

the DNA in the nucleus replicates

58
Q

what happens in the G2 phase?

A

the cell continues to grow and the new DNA that has been synthesised is checked and any errors are usually repaired

59
Q

what is mitosis?

A

nuclear division where two genetically identical daughter nuclei are produced

60
Q

why is mitosis useful?

A

-lets unicellular zygotes grow into multicellular organisms
-damaged tissues can be repaired by mitosis

61
Q

asexual reproduction

A

offspring are genetically identical to the single parent used to produce them

62
Q

prophase

A

-chromosomes condense and are visible
-the two centrosomes move towards opposite poles
-spindle fibres begin to emerge from the centrosomes
-the nuclear envelope breaks down

63
Q

metaphase

A

-centrosomes reach opposite poles
-chromosomes line up at the equator
-spindle fibres (protein microtubules) reach the chromosomes and attach to the centromeres

64
Q

anaphase

A

-the sister chromatids separate at the centromere
-spindle fibres begin to shorten
-the chromosomes are pulled to opposite poles by the spindle fibres

65
Q

telophase

A

-chromosomes arrive at opposite poles and begin to decondense
-nuclear envelopes reforms around each set of chromosomes
-the spindle fibres break down

66
Q

cytokines

A

-the cytoplasm divides & two genetically identical cells

67
Q

how do cancers start?

A

when changes happen in the genes that control cell division (mutation)

68
Q

how is mitosis affected in cancer?

A

uncontrolled mitosis, which forms a tumour

69
Q

what is an oncogene

A

a mutated gene that causes cancer

70
Q

are mutations common?

A

yes

71
Q

do mutations usually lead to cancer?

A

no:
-most mutations either result in early cell death or result in the cell being destroyed by the body’s immune system

(most cells can be easily replaced, so these events usually have no harmful effect on the body)

72
Q

what are carcinogens?

A

any agents that may cause cancer

73
Q

examples of carcinogens:

A

-UV light
-tar in tobacco smoke
-x-rays

74
Q

which tumours don’t spread from their original site

A

benign (don’t cause cancer)

75
Q

which tumours invade neighbouring tissue?

A

malignant (cause cancer)

76
Q

what do malignant tumours do to organs/tissue?

A

interfere with the normal functioning of the organ, tissue in which they have started to grow

77
Q

metastasis

A

can break off the tumour and travel through the blood to form secondary growths in other parts of the body

78
Q

why is metastasis dangerous?

A

it can be very difficult to detect, locate and remove secondary cancers

79
Q

stages in the development of cancer

A

1) oncogenes arise due to carcinogens

2) cancerous cell does not respond to signals from other cells & continues to divide

3) cancerous cells aren’t removed by the immune system

4) the tumour gets bigger due to absorption of nutrients leading to rapid mitosis

5) tumour is supplied with blood, if the tumour is malignant, tumour cells spread in blood to other parts of the body

6) metastasis (tumour cells invade other tissues, secondary tumours form throughout the body)

80
Q

what mutated gene do most people with cancer posses?

A

a mutated p53 gene (a gene that helps to control cell growth)

81
Q

can viruses cause cancer?

A

yes, some oncoviruses cause cancers

82
Q

how do most current cancer treatments work?

A

by controlling the rate of mitosis

83
Q

methotrexate

A

inhibits the synthesis of DNA nucleotides in cells

84
Q

vincristine and taxol

A

prevent the formation of the mitotic spindle

85
Q

process of binary fission:

A

1) the single, circular DNA molecule undergoes DNA replication

2) any plasmids undergo DNA replication

3) the parent cell divides into two cells, with the cytoplasm halved between the two daughter cells

4) the two daughter cells each contain a single copy of the circular DNA molecule and a variable number of plasmids

86
Q

processes of viral replication

A

1) the virus attaches to the surface of the host cell

2) the viral DNA/RNA enters the host cell

3) viral DNA/RNA replicates, new viral proteins are made (new capsids)

4) new viral particles are assembled

5) host cell lyses (bursts) releases the newly made virus

6) host cell is destroyed as new virus leaves

87
Q

what does the cell surface membrane create?

A

-an enclosed space separating the internal cell environment from the external environment

88
Q

phospholipid monolayer (structure)

A

-if phospholipids are spread over the surface of water
-they form a single layer with the hydrophilic phosphate heads in the water and the hydrophobic fatty acid tails sticking up away from the water

89
Q

phospholipid bilayer (structure)

A

two layers of phospholipids; their hydrophobic tails facing inwards and hydrophilic heads outwards

90
Q

role of phospholipids

A

1) ensures needed water-soluble molecules cannot leak out of the cell and unwanted water-soluble molecules cannot get in

2) can be chemically modified to act as signalling molecules by:
↳ moving within the bilayer to activate other molecules (eg. enzymes)
↳ being hydrolysed which releases smaller water-soluble molecules that bind to specific receptors in the cytoplasm

91
Q

why does the fluid mosaic model describe cell membranes as fluid

A

-the phospholipids and proteins can move around via diffusion
-the phospholipids mainly move sideways, within their own layers

92
Q

why does the fluid mosaic model describe cell membranes as mosaic

A

-different molecules of different sizes look like a mosaic from above

93
Q

structure of cholesterol

A

-cholesterol molecules have hydrophobic tails & hydrophilic heads
-fit between phospholipid molecules & oriented in the same way
-absent in prokaryotes membrane

94
Q

role of cholesterol in the membrane

A

1) cholesterol molecules sit in between the phospholipids, stopping them from packing too closely together (when temperatures are low; this stops membranes from freezing and fracturing)

2) interaction between cholesterol and phospholipid tails stabilises the cell membrane at higher temperatures by stopping the membrane from becoming too fluid
↳ cholesterol molecules bind to the hydrophobic tails of phospholipids, stabilising them and causing phospholipids to pack more closely together

3) increases strength and stability of membranes; without it membranes would break down and cells burst

95
Q

structure of glycolipids

A

(lipids with carbohydrate chains attached)
-carbohydrate chains project out into whatever fluid is surrounding the cell -found on the outer phospholipid monolayer

96
Q

role of glycolipids in the membrane

A

-glycolipids contain carbohydrate chains that exist on the surface which enables them to act as receptor molecules
↳ allows glycolipids to bind with certain substances at the cell’s surface

-some act as cell markers or antigens, for cell-to-cell recognition

97
Q

structure of glycoproteins

A

-proteins with carbohydrate chains attached
-these carbohydrate chains also project out into whatever fluid is surrounding the cell (they are found on the outer phospholipid monolayer)

98
Q

role of glycoproteins

A

-glycolipids contain carbohydrate chains that exist on the surface which enables them to act as receptor molecules
↳ allows glycolipids to bind with certain substances at the cell’s surface

-some act as cell markers or antigens, for cell-to-cell recognition

99
Q

what are the three types of receptor cells?

A

1) signalling receptors for hormones and neurotransmitters

2) receptors involved in endocytosis

3) receptors involved in cell adhesion and stabilisation (as the carbohydrate part can form hydrogen bonds with water molecules surrounding the cell)

100
Q

structure of proteins in the membrane

A

can be intrinsic:
embedded in the membrane of phospholipids

OR

can be extrinsic:
found on the outer surface of the membrane

101
Q

when are membranes less fluid?

A

1) when there is an increased proportion of saturated fatty acid chains, the chains pack together tightly and therefore there is a high number of intermolecular forces between the chains

2) at lower temperature as the molecules have less energy and therefore are not moving as freely which causes the structure to be more closely packed

102
Q

when are membranes more fluid?

A

1) an increased proportion of unsaturated fatty acid chains as these chains are bent, which means the chains are less tightly packed together and there are less intermolecular forces

2) at higher temperatures, the molecules have more energy and therefore move more freely, which increases membrane fluidity

103
Q

what is diffusion?

A

the net movement of a substance from a region of its higher concentration to a region of its lower concentration

104
Q

what happens after diffusion?

A

molecules reach an equilibrium, they are evenly spread within a given volume of space

105
Q

which factors affect the rate of diffusion?

A

-concentration gradient
-temperature
-surface area
-properties of molecules/ions

106
Q

how does concentration gradient affect the rate of diffusion?

A

-the difference in the concentration of the substance on the two sides of the surface
-a greater difference in concentration means a greater difference in the number of molecules passing in two directions

107
Q

how does temperature affect the rate of diffusion?

A

-molecules and ions have more energy at higher temperature
-the move faster leading to a higher rate of diffusion

108
Q

how does surface area affect the rate of diffusion?

A

-the greater the surface area, the more molecules/ions can cross the surface at any particular moment -> diffusion is faster
-surface. area can be increased by folding
-as a cell increases in size, the surface area to volume ratio decreases -> rate slows down

109
Q

how do the properties of ions or molecules affect the rate of diffusion?

A

-large molecules diffuse slower than smaller ones, they need more energy to move
-uncharged molecules diffuse directly across the phospholipid bilayer

110
Q

what is facilitated diffusion?

A

-for charged substances that cannot diffuse through the phospholipid bilayer of cell membranes
-these substances can only cross the phospholipid bilayer with the help of certain proteins (channel or carrier)

111
Q

what are channel proteins?

A

-water-filled pores that are gated
-part of the channel protein on the inside can move to close or open the pore
-substances move along conc gradient

112
Q

what are carrier proteins?

A

-can switch between two shapes
-the binding site of the carrier protein is open to one side of the membrane first, and then open to the other side of the membrane when the carrier protein switches shape
-the direction of movement depends on their conc on each side of the membrane

113
Q

what is osmosis?

A

the diffusion of water molecules from a dilute solution (high concentration of water/high water potential) to a more concentrated solution (low concentration of water/low water potential) across a partially permeable membrane

114
Q

what is water potential?

A

the tendency of water to move out of a solution

115
Q

what is the water potential of pure water

A

0kPa

116
Q

why can water pass through the phospholipid bilayer?

A

although water molecules are polar, they can still pass through the bilayer because of their small size

117
Q

the more negative the water potential, the _____ the water potential

A

lower

118
Q

what will happen if a plant cell is placed in pure water or a dilute solution?

A

-water will enter the plant cell through its cell surface membrane by osmosis
-the volume of the plant cell increases
-the expanding protoplast pushes against the cell wall and pressure builds up inside the cell (the inelastic cell wall prevents the cell from bursting & stops too much water entering)
-when a plant cell is fully inflated with water, it is fully turgid

119
Q

why is turgidity important for plants?

A

-the effect of all the cells in a plant being firm is to provide support and strength for the plant
-this makes the plant stand upright with its leaves held out to catch sunlight
-if plants do not receive enough water the cells cannot remain turgid and the plant wilts

120
Q

what will happen if a plant cell is placed in a concentrated solution?

A

-water will leave the plant cell through its partially permeable cell surface membrane by osmosis
-as water leaves the vacuole of the plant cell, the volume of the plant cell decreases
-the protoplast gradually shrinks and no longer exerts pressure on the cell wall
-as the protoplast continues to shrink, it begins to pull away from the cell wall

(plasmolysis)

121
Q

why are loses and gains of water more severe with animal cells?

A

animal cells do not have a supporting cell wall

122
Q

what happens if an animal cell is placed in a solution with a lower water potential than the cell?

A

-water will leave the cell through its partially permeable cell surface membrane by osmosis and the cell will shrink and shrivel up

123
Q

what happens if an animal cell is placed in a solution with a higher water potential than the cell?

A

-water will enter the cell membrane by osmosis
-the cell will continue to gain water by osmosis until the cell membrane is stretched too far and the cell bursts (cytolysis)

124
Q

isotonic

A

the solution outside of the cell has the same solute concentration as the inside of the cell

A LEVEL BIO (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions