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1
Q

what is magnification? (cells)

A
  • how many times bigger an image is compared to the actual object
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2
Q

what is resolution? (cells)

A
  • the ability to distinguish between two points that are very close together
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3
Q

what is the resolution of light microscopes like & why? (cells)

A
  • poor resolving power
  • they have a long wavelength of light
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4
Q

what is the resolution of electron microscopes like? (cells)

A
  • high resolving power
  • they have a shorter wavelength of light
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5
Q

what are the two main advantages of using electron microscopes over light microscopes? (cells)

A
  • they have a high resolving power
  • as electrons are negatively charged the beam can be focused using electromagnets
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6
Q

what are the two types of electron microscopes? (cells)

A
  • transmission electron microscopes (TEM)
  • scanning electron microscope (SEM)
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7
Q

how does a transmission electron microscopes (TEM) work? (cells)

A
  • consists of an electron gun that produces a beam of electrons if focused onto a specimen by a condenser electromagnet
  • beam passes through thin section of specimen
  • if electrons absorbed then dark appearance
  • if electrons pass through then bright appearance
  • imaged produces is photographed & given to a photomicrograph
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8
Q

what is a photomicrograph? (cells)

A
  • a photograph of an image produced by a microscope
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9
Q

what is the resolving power of a TEM & why is it difficult to achieve in practice? (cells)

A
  • 0.1nm
  • difficulties preparing specimens limit the resolution that can be achieved
  • a higher energy electron beam is required & this may destroy the specimen
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10
Q

what are the main limitations of both TEMs & SEMs? (cells)

A
  • whole system must be in a vacuum so no live specimens
  • complex ‘staining’ process is required & image is not in colour
  • specimen must be extremely thin (TEM only)
  • image may contain artefacts (things that may result from the way the specimen is prepared) so we can’t be sure it actually exists in the form seen
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11
Q

can 3D images be obtained from a TEM? (cells)

A
  • yes
  • thin specimens result in a flat 2D image
  • 3D images can be built up by looking at a series of sections through a specimen & the photomicrographs produced
  • process is slow & complicated
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12
Q

how does a scanning electron microscope (SEM) work? (cells)

A
  • directs a beam of electrons onto the surface of the specimen from above
  • beam is then passed back & forth across specimen in a regular pattern
  • electrons are scattered by the specimen & pattern of scattering depends on the contours on the specimens surface
  • specimens do not need to be thin to penetrate
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13
Q

what is the resolving power of an SEM? (cells)

A
  • 20nm
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14
Q

can 3D images be produced by scanning electron microscopes? (cells)

A
  • yes
  • they can be built by computer analysis of the pattern of scattered electrons & secondary electrons produced
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15
Q

what is cell fractionation? (cells)

A
  • the process where cells are broken up & the different organelles are separated out
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16
Q

what happens before cell fractionation takes place? (cells)

A
  • tissue sample of cells must be put into a cold buffered solution that is of the same water potential as the tissue
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17
Q

why does the pre-cell fractionation solution need to be cold, buffered & of the same water potential is the tissue? (cells)

A
  • cold: to reduce enzyme activity that may break down organelles
  • buffered: so the pH doesn’t fluctuate (any change in oh could alter the structure of organelles or affect enzyme function)
  • same water potential: to prevent organelles from bursting/shrinking due to an osmotic loss or gain of water
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18
Q

what is stage one of cell fractionation? (cells)

A
  • homogenisation
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19
Q

what is the process of homogenisation? (cell fractionation) (cells)

A
  • cells are broken up by a homogeniser
  • this releases organelles from the cell
  • the resultant fluid (homogenate) is filtered to remove any complete cells or large pieces of debris
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20
Q

what is the second stage of cell fractionation? (cells)

A
  • ultracentrifugation
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21
Q

what is the process of ultracentrifugation? (cell fractionation) (cells)

A
  • tube of filtrate is placed in centrifuge & spun at slow speed
  • heaviest organelles (nuclei) are forced to bottom of the tube & form a thin sediment
  • fluid at top of tube (supernatant) is removed leaving only the sediment of nuclei
  • supernatant is transferred to another tube & spun in centrifuge at a faster speed than before
  • next heaviest organelles (mitochondria) forced to bottom of tube
  • process continued to at each increase of speed the next heaviest organelles are sedimented & separated out
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22
Q

what are the revolutions min-1 of nuclei, mitochondria & lysosomes? (cell fractionation) (cells)

A
  • nuclei = 1 000 revolutions min-1
  • mitochondria = 3 500 revolutions min-1
  • lysosomes = 16 500 revolutions min-1
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23
Q

what is the plasma cell membrane? (cells)

A
  • found in all cells
  • controls entrance & exit of molecules
  • protein & lipid (phospholipid bilayer)
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24
Q

what is the nucleus? (cells)

A
  • contains nuclear envelope & nuclear pores
  • DNA is either chromosomes or chromatin
  • chromatin stains darkly
  • lighter area of chromatin carry DNA for protein synthesis
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25
Q

what is the nucleolus? (cells)

A
  • ribosome production
  • built ribosome subunits from rRNA (ribosomal RNA) & proteins
  • exit through nuclear pores to cytoplasm & combine to form functional ribosomes
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26
Q

what is the centriole? (cells)

A
  • found only in animal cells
  • found in pairs
  • hollow cylinders made up of a ring of nine protein microtubules
  • organise microtubules
  • involved in cell division: spindle formation
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27
Q

what is the golgi apparatus? (cells)

A
  • stacks of membrane-bound sacs formed by fusion of vesicles from rER
  • continually changing
  • received vesicles from ER
  • packages & received proteins
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28
Q

what is the rough endoplasmic reticulum (rER)? (cells)

A
  • interconnected membrane-bound flattened sacs
  • has ribosomes attached to the outer surface
  • provides a large surface area for the synthesis of proteins & trafficking
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29
Q

what is the smooth endoplasmic reticulum (sER)? (cells)

A
  • lacks ribosomes on its surface & is more tubular
  • synthesise, store & transport lipids
  • synthesise, store & transport carbohydrates
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30
Q

what are the chloroplasts? (cells)

A
  • surrounded by a double membrane (envelope)
  • site of photosynthesis
  • found only in plant cells
  • thylakoid: site for the light dependent photosynthesis reaction
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31
Q

what is the thylakoid in chloroplasts? (cells)

A
  • the site for the light dependent photosynthesis reaction
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32
Q

what is the mitochondria? (cells)

A
  • double membranes
  • inner membrane called the cristae
  • site of aerobic respiration
  • ATP production
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33
Q

what are lysosomes? (cells)

A
  • bags of digestive enzymes
  • breakdown of unwanted structures within the cell or whole cell (e.g. acrosome)
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34
Q

what is the vacuole? (cells)

A
  • filled with water or ‘sap’
  • surrounding membrane = tonoplast
  • helps maintain pressure inside the cell to keep it rigid
  • involved in isolation if unwanted chemicals in the cell
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35
Q

what are the ribosomes? (cells)

A
  • found in all cells either free or bound to the rER
  • used for protein synthesis
  • work by reading triplet codons & stringing amino acids together
  • messenger RNA (mRNA)
  • ribosomal RNA (rRNA)
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36
Q

what is the cellulose cell wall? (cells)

A
  • found in all plant cells
  • contains microfibrils of cellulose to provide strength
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37
Q

what do we use to measure cells in a light microscope? (cells)

A
  • eyepiece graticule
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38
Q

what is used to calibrate an eyepiece graticule? (cells)

A
  • stage micrometer
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39
Q

what size ribosomes are in eukaryotic cells? (cells)

A
  • 80S
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40
Q

what size ribosomes are in prokaryotic cells? (cells)

A
  • 70S
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41
Q

what are the stages of protein synthesis? (9 steps) (cells)

A
    1. transcription of DNA to mRNA
    1. mRNA leaves nucleus
    1. protein made on ribosomes enter rER
    1. protein moves through the ER assuming a 3D shape en route
    1. vesicles pinched off rER contain the protein
    1. vesicles from rER fuse to form flattened sacs of golgi apparatus
    1. proteins are modified within the golgi apparatus
    1. vesicles pinched off rER off golgi apparatus contain the modified protein
    1. vesicle fuses with cell surface membrane releasing protein (e.g. as extra cellular enzymes)
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42
Q

what is folded & modified in the rER?(protein synthesis)

A
  • polypeptide chain
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43
Q

how are cells in organisms produced? (cells)

A
  • mitotic divisions from a fertilised egg
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44
Q

how are specialised cells different from each other? (cells)

A
  • they have different genes depending on the cell
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45
Q

give an example of how cells are adapted for their function (cells)

A
  • muscle & sperm cells have lots of mitochondria (for respiration) because they undergo more movement
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46
Q

what is a tissue? (cells)

A
  • a collection of similar cells that work together to perform a specific function
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47
Q

what is epithelial tissue? (cells)

A
  • found in animals
  • consists of sheets of cells (thin, flat cells) that line organs where diffusion takes place (e.g. alveoli in the lungs)
  • line the surfaces of organs
  • often have a protective secretory function
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48
Q

what is xylem tissue? (cells)

A
  • found in plants
  • made up of a number of similar cell types
  • used to transport water & mineral ions throughout the plant
  • also gives mechanical support
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49
Q

what are organs? (cells)

A
  • a combination of tissues that are coordinated to perform a variety of functions
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50
Q

what tissues does the stomach contain & what do they do? (cells)

A
  • muscle tissue to churn & mix stomach contents
  • epithelial tissue to protect the stomach wall & produce secretions
  • connective tissue to hold together other tissues
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51
Q

what tissues do leaves have & what do they do? (cells)

A
  • palisade mesophyll made of leaf palisade cells that carry out photosynthesis
  • spongy mesophyll adapted for gaseous diffusion
  • epidermis to protect the leaf & allow gaseous diffusion
  • phloem to transport organic materials away from the leaf
  • xylem to transport water & ions into the leaf
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52
Q

why are capillaries not organs but arteries & veins are? (cells)

A
  • capillaries are only made up of one type of tissue (epithelium)
  • arteries & veins are made up of many tissues (epithelial, muscle & more)
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53
Q

what is an organ system? (cells)

A
  • organs working together as a single unit to perform a specific function
54
Q

what is the digestive system? (cells)

A
  • digests & processed food
  • includes organs like the salivary glands, oesophagus & stomach
55
Q

what is the respiratory system? (cells)

A
  • used for breathing & gas exchange
  • included organs like the lungs, bronchi & trachea
56
Q

what is the circulatory system? (cells)

A
  • pumps & circulates blood
  • included organs like the heart, arteries & veins
57
Q

give some examples of differences between prokaryotic & eukaryotic cells (cells)

A
  • prokaryotes don’t have a nucleus but eukaryotes do
  • prokaryotes have smaller ribosomes (70S) than eukaryotes (80S)
  • prokaryotes have no membrane bound organelles (e.g. mitochondria) but eukaryotes do
58
Q

what is the structure of HIV? (virus) (cells)

A
  • genetic material (RNA)
  • reverse transcriptase
  • attachment protein
  • capsid
  • lipid envelope
  • matrix
59
Q

what is the structure of a bacterial cell? (8 features) (cells)

A
  • capsule (only certain species)
  • cell wall
  • cell surface membrane
  • plasmid (only certain species)
  • ribosomes
  • cytoplasm
  • genetic material
  • flagellum (only certain species)
60
Q

what is the bacterial cell wall? (cells)

A
  • complex
  • mesh work of murein (tough protein)
  • murein is also called peptidoglycan
61
Q

what is the mucilaginous slime capsule? (bacteria) (cells)

A
  • protects cell
  • type if protein that stops cell from drying out
  • on the outside of cells
  • helps cells to stick to other cells
62
Q

what is the plasma membrane? (bacteria) (cells)

A
  • same structure in eukaryotes & prokaryotes
  • main boundary between the outside of cells & the environment
63
Q

what is circular DNA? (bacteria cells) (cells)

A
  • possesses the genetic information for the replication of cells
64
Q

what are plasmids? (bacteria) (cells)

A
  • possesses genes that at aid the survival of bacteria in adverse conditions
  • tiny circles of DNA carrying only a few genes which occur throughout the cytoplasm
65
Q

what are flagellum? (bacteria) (cells)

A
  • rotates & allows bacterium to move
  • not all bacterium have one but some have more than one
66
Q

what are viruses? (cells)

A
  • acellular, non-living particles
  • 200nm - 300nm in size
  • contain nucleic acids as genetic material but can only multiply in host cells
  • capsid = protein coat that covers a nucleic acid
  • lipid envelope/capsid have attachment proteins (essential so virus can identify & attach to host cells)
67
Q

what is mitosis? (cells)

A
  • cell division that produces two identical daughter cells that have the same number of chromosomes as the parent cells & eachother
68
Q

what is the order of the cell cycle? (cells)

A
  • interphase (pre mitosis)
  • prophase (mitosis)
  • metaphase (mitosis)
  • anaphase (mitosis)
  • telophase (mitosis)
69
Q

what is interphase? (cells)

A
  • happens before mitosis
  • period of cell growth & replication
  • three separate growth stages (gap phase 1, synthesis, gap phase 2)
70
Q

what is gap stage 1 (G1) of the cell cycle? (cells)

A
  • part of interphase
  • cell grows
  • new organelles & proteins are made
71
Q

what is synthesis (S) in the cell cycle (cells)

A
  • part of interphase
  • cell replicates its DNA so it is ready to divide by mitosis
72
Q

what is gap phase 2 (G2) of the cell cycle? (cells)

A
  • part of interphase
  • cell keeps growing
  • proteins needed for cell division are made
73
Q
  • what is the early prophase stage of mitosis? (cells)
A
  • DNA has already replicated
  • chromosomes become visible as long thin threads
  • each replicated chromosome is held together at the centromere (spindle apparatus)
  • these are called sister chromatids)
74
Q

what is the mid prophase stage of mitosis? (cells)

A
  • chromosomes shorten & thicken
  • nucleolus disappears & nuclear envelope breaks down
  • centrioles move to opposite ends on the cell
  • chromosomes are left free in the cytoplasm
75
Q

what is the late prophase stage of mitosis? (cells)

A
  • centrioles produce spindle fibres
  • chromosomes are drawn to the equator of the cell by spindle fibres attached to the centromere
76
Q

what is the metaphase stage of mitosis? (cells)

A
  • chromatids love to the equator of the cell & line up
  • chromatids are joined by the centromere that some microtubules from the poles are attached to
77
Q

what is the metaphase stage of mitosis? (cells)

A
  • chromatids love to the equator of the cell & line up
  • chromatids are joined by the centromere that some microtubules from the poles are attached to
78
Q

what is the anaphase stage of mitosis? (cells)

A
  • centromeres divide into two
  • spindle fibres shorten & pull the sister chromatids apart
  • chromatids move to opposite poles & are now known as chromosomes
  • ATP is required & is provided by the mitochondria (which gather around the spindle fibres)
79
Q

what happens to cells that are treated with chemicals that destroy spindle fibres? (cells)

A
  • chromosomes remain at the equator & are unable to reach the poles
80
Q

what is the telophase stage of mitosis? (cells)

A
  • chromosomes reach their poles & become longer & thinner (leaves chromatin)
  • spindle fibres disintegrate
  • nuclear membrane & nucleolus reform
  • cell divides by mitosis
81
Q

what is cytokinesis? (cells)

A
  • cytoplasm divides
  • two new daughter cells with identical DNA are formed
82
Q

why can’t some cells divide? (cells)

A
  • because they don’t have centrioles
  • e.g. nerve cells - evidence = paralysis & brain death
83
Q

what is mitosis important for? (cells)

A
  • growth
  • repair
  • reproduction
84
Q

how do prokaryotic cells divide? (cells)

A
  • binary fission
85
Q

what is the process of binary fission? (cells)

A
  • circular DNA molecule replicates & both copies attach to the cell membrane
  • plasmids also replicate
  • cell membrane begins to grow to two DNA molecules & begins to pinch inward (divides cytoplasm in two)
  • new cell wall form between the 2 DNA molecules & original cell divides into two identical daughter cells
  • DCs have one circular DNA molecule & lots of plasmids
86
Q

how do viruses replicate? (cells)

A
  • non living so can’t undergo cell division
  • replicate by attaching to their host cell with their attachment proteins
  • they then inject their nucleus acid into the host cell
  • genetic information in the infected viral nucleus acid provides the ‘instructions’ for host cells metabolic processes to start producing viral components/nucleic acids/enzymes/structural proteins which are assembled into new viruses
87
Q

how do viruses replicate? (cells)

A
  • non living so can’t undergo cell division
  • replicate by attaching to their host cell with their attachment proteins
  • they then inject their nucleus acid into the host cell
  • genetic information in the infected viral nucleus acid provides the ‘instructions’ for host cells metabolic processes to start producing viral components/nucleic acids/enzymes/structural proteins which are assembled into new viruses
88
Q

name & summarise the three stages of the cell cycle (cells)

A
  • interphase (occupies most of the cell cycle, no division occurs)
  • nuclear division (when nucleus divides into two (mitosis) or four (meiosis)
  • cytokinesis (cytoplasm divides to produce two (mitosis) or four (meiosis) cells
89
Q

what causes cancer? (cells)

A
  • uncontrolled cell division
  • growth disorder of cells
90
Q

what are tumours? (cells)

A
  • a group of abnormal cells that develops as a result of uncontrolled cell division
  • can develop in any organ of the body but are most commonly found in the lungs, prostate gland, breast & ovaries
91
Q

name the two types of tumour (cells)

A
  • malignant
  • benign
92
Q

what is a malignant tumour? (cells)

A
  • grow rapidly
  • less compact
  • more likely to be life threatening
93
Q

what is a benign tumor? (cells)

A
  • grow slowly
  • more compact
  • less likely to be life threatening
94
Q

what can the rate of mitosis be affected by? (cells)

A
  • environment of the cell
  • growth factors
  • (2) types of gene (mutation of one of the genes leads to uncontrolled mitosis, which can lead to tumours)
95
Q

what is involved in the treatment of cancer? (cells)

A
  • killing dividing cells by blocking part of the cell cycle
  • this means that the cell cycle is disrupted & cell division ceases (hence the cancer growth also ceases)
96
Q

how do cancer drugs (chemotherapy) disrupt the cell cycle? (cells)

A
  • prevent DNA from replicating
  • inhibits the metaphase stage of mitosis by interfering with spindle formation
97
Q

how can cancer drugs impact normal cells? (cells)

A
  • disrupts cell cycle of normal cells
  • the drugs are more effective against rapidly dividing cells
  • cancer cells have a fast rate of division so are damaged to a greater degree
  • normal cells (e.g. hair producing cells) that divide rapidly are also vulnerable to damage (explains hair loss in cancer patients)
98
Q

what is a plasma membrane? (cells)

A
  • the membrane around & within cells
  • includes the membranes around & in organelles
99
Q

what is the cell surface membrane? (cells)

A
  • the plasma membrane that surrounds cells
  • forms the boundary between the cell cytoplasm & the environment
  • allows different conditions to be established inside & outside of cells
  • controls movement of substances in & out of cells
100
Q

what do phospholipids do in the cell membrane? (cells)

A
  • hydrophilic heads point to the outside of the membrane & are attracted by water on both sides
  • hydrophobic tails point into the centre of the membrane & are repelled by water on both sides
  • lipid-soluble material moves through the membrane via the phospholipid portion
101
Q

what are the functions of phospholipids in the can membrane? (cells)

A
  • allow lipid-soluble substances to enter & leave the cell
  • prevent water-soluble substances entering & leaving the cell
  • make the membrane flexible & self-sealing
102
Q

where do proteins occur in the cell membrane? (cells)

A
  • in the surface of the membrane
  • completely span the phospholipid bilayer
103
Q

what do proteins that occur in the surface of the phospholipid bilayer do? (cells)

A
  • never extend completely across it
  • give mechanical support
  • (along with glycolipids) act as cell receptors for molecules like hormones
104
Q

what do proteins that span the length of the phospholipid bilayer do?

A
  • protein channels form water filled tubes to allow water-soluble ions to diffuse across the membrane
  • carrier proteins bind to ions/molecules (e.g. glucose or amino acids) then change shape in order to move those molecules across the membrane
105
Q

what are the functions of proteins in the membrane? (cells)

A
  • provide structural support
  • act as channels transporting water-soluble substances across the membrane
  • allow active transport across the membrane through carrier proteins
  • form cell-surface receptors for identifying cells
  • helps cells adhere together
  • acts as receptors (e.g. for hormones)
106
Q

what does cholesterol do in the cell membrane? (cells)

A
  • add strength to membranes
  • are very hydrophobic so prevent the loss of water & dissolved ions from the cell
  • pull together fatty acid tails of phospholipid molecules which limits their movements & that of other molecules without making the membrane too rigid
107
Q

what is the function of cholesterol in the cell membrane? (cells)

A
  • reduces lateral movement of other molecules (including phospholipids)
  • makes the membrane less fluid at high temperatures
  • prevent leakage of water & dissolved ions from the cell
108
Q

what are glycolipids? (cells)

A
  • a carbohydrate covalently bonded with a lipid
  • carbohydrate extends from the bilayer into the watery environment outside of the cell where it acts as a cell-surface receptor for specific chemicals
  • e.g. the human ABO blood system operates as a result of glycolipids
109
Q

what are the functions of glycolipids in the cell membrane? (cells)

A
  • act as recognition sites
  • help to maintain the stability of the membrane
  • helps cells to attach to one another so form tissues
110
Q

what are glycoproteins & what do they do? (cells)

A
  • carbohydrate chains are attached to many proteins on the outer surface of the cell membrane
  • act as cell-surface receptors (more specifically for hormones & neurotransmitters)
111
Q

what are the functions of glycoproteins in the cell membrane? (cells)

A
  • act as recognition sites
  • helps cells to attach to one another & so form tissues
  • allows cells to recognise one another (e.g. lymphocytes can recognise an organism’s cells
112
Q

why do most molecules not freely diffuse across the cell surface-membrane? (cells) (4 things)

A
  • many are not soluble in lipids & therefore can’t pass through the phospholipid layer
  • many are too large to pass through the channels in the membrane
  • may are of the same as the charge on the protein channels & so even if they are small enough you pass through, they are repelled
  • many are electrically charged (polar) & therefore have difficulty passing through the non-polar hydrophobic in the phospholipid bilayer
113
Q

why is the arrangement of the cell-surface membrane known as the fluid mosaic model? (cells)

A
  • fluid because the individual phospholipid molecules can move relative to one another. This gives the membrane a flexible structure that is constantly changing shape
  • mosaic because the proteins that are embedded in the phospholipid bilayer vary in shape, size & pattern
114
Q

define diffusion (cells)

A
  • the net movement of molecules or ions from a region where they are in high concentration to one where they are in low concentration until evenly distributed
115
Q

is diffusion a passive process & why/why not? (cells)

A
  • yes because it enquires no external energy
  • the energy used comes from the natural motion of the particles
116
Q

outline simple diffusion (3 points) (cells)

A
  • all particles are constantly in motion due to the kinetic energy they possess
  • this motion is random with no set pattern as to the way the particles move around
  • particles are constantly bouncing off one one another as well as off other objects
117
Q

what is facilitated diffusion? (cells)

A
  • diffusion that is made easier (facilitated) by transmembrane channels & carriers that span the plasma membrane
118
Q

outline facilitated diffusion (3 points) (cells)

A
  • it is a type of passive transport
  • occurs down a concentration gradient but occurs at specific points on the plasma membrane where there are special protein molecules
  • there are two types of proteins involved (protein channels & carrier proteins)
119
Q

outline the role of protein channels in the plasma membrane in terms of diffusion (6 points) (cells)

A
  • from water-filled hydrophilic channels across the membrane
  • allow specific water-soluble ions to pass through
  • channels are selective & each opens in the presence of a specific ion
  • if the particular ion is not present the channel remains closed
  • this means that there is control over the entry & exit of ions
  • the ions bind with the proteins causing it to change shape in a way that closes it to one side of the membrane & opens it to the other side
120
Q

what happens when specific ions bind to the protein channels in terms of diffusion? (cells)

A
  • it causes the protein to change shape in a way so that it closes to one side of the membrane & opens to the other side of it
121
Q

why is there control over the entry & exit of ions the protein channels? (cells)

A
  • the channels are selective & each opens in the presence of a specific ion
  • if the specific ion is not present the channel remains closed
  • this means that there is control over the entry & exit of ions
122
Q

outline the role of carrier proteins in the plasma membrane in terms of diffusion (4 points) (cells)

A
  • span the plasma membrane
  • when a molecule that is specific to the protein is present it binds with the protein
  • this causes it to change shape so that the molecule is released to the inside of the membrane (no external energy is needed for this)
  • the molecules move from a region where they are highly concentrated to one of lower concentration using only the kinetic energy of the molecules themselves
123
Q

how do carrier proteins change shape when they come into contact with their specific ions in terms of diffusion? (cells)

A
  • they change shape so that the molecules is released to the inside of the membrane
124
Q

what happens to molecules in carrier proteins in terms of diffusion? (cells)

A
  • the molecules move from a region where they are in high concentration to one of lower concentration
  • they only use the kinetic energy of the molecules themselves meaning the process is passive
125
Q

name the 4 factors that affect the rate of diffusion (cells)

A
  • distance
  • surface area
  • concentration difference
  • temperature
126
Q

how does distance affect the rate of diffusion? (cells)

A
  • the shorter the distance the faster the rate of diffusion
  • the further the particles have to travel the longer diffusion takes
127
Q

how does surface area affect the rate of diffusion? (cells)

A
  • the greater the surface area the faster the rate of diffusion
  • the greater the surface area the more space for molecules to diffuse across the membrane
128
Q

how does concentration difference affect the rate of reaction? (cells)

A
  • the greater the difference in concentration the faster the rate of diffusion
  • the greater the difference in concentration the greater the difference between a solute & solvent
129
Q

how does temperature affect the rate of diffusion? (cells)

A
  • the higher the temperature the faster the rate of diffusion
  • the higher the temperature the more kinetic energy the particles have
130
Q

what is the equation for Fick’s law? (cells)

A
  • the rate of diffusion is proportional to:
  • surface area X difference in conc./length of diffusion path
  • length of diffusion path is also known as membrane thickness

biology 🧬 (3 decks)

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