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Biology - mr ellis > BIOLOGY MODULE 2 (papers 1,2, & 3) > Flashcards

BIOLOGY MODULE 2 (papers 1,2, & 3) Flashcards

cell structure, biological molecules, nucleotides and nucleic acids, enzymes, biological membranes, cell division and cellular organisation

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1
Q

what are prokaryotic cells?

A
  • single celled organisms
  • smaller, simpler e.g. bacteria
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2
Q

what are eukaryotic cells?

A
  • complex
  • include all animal and plant cells
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3
Q

what organelles are in an animal cell?

A
  • plasma membrane
  • RER
  • SER
  • nucleus
  • nucleolus
  • nuclear envelope
  • lysosome
  • ribosome
  • cytoplasm
  • Golgi apparatus
  • mitochondria
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4
Q

what organelles are in a plant cell?

A
  • plasma membrane
  • RER
  • SER
  • nucleus
  • nucleolus
  • nuclear envelope
  • ribosome
  • cytoplasm
  • Golgi apparatus
  • mitochondria
  • chloroplast
  • plasmodesmata
  • vacuole
  • cellulose cell wall
    (no lysosomes)
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5
Q

what is the plasma membrane?

A
  • membrane on surface of animal cells
  • inside cell wall of plant cells and prokaryotic cells
  • made of lipids and protein
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6
Q

what is the function of the plasma membrane?

A
  • regulates movement of substances in and out cell
  • has receptor molecules that allow it to respond to chemicals like hormones
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7
Q

what is the cell wall?

A
  • rigid structure surrounding plant cells
  • made mainly of cellulose
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8
Q

what is the function of the cell wall?

A

support plant cells

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9
Q

what is the nucleus?

A
  • surrounded by nuclear envelope (contains many pores)
  • contains chromatin
  • contains nucleolus
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10
Q

what is the function of the nucleus?

A
  • controls cell’s activities
  • DNA contains instructions to make proteins
  • pores allow substances to move between nucleus and cytoplasm
  • nucleolus makes ribosomes
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11
Q

what is the lysosome?

A
  • round organelle surrounded by a membrane
  • no clear internal structure
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12
Q

what is the function of the lysosome?

A
  • contains digestive enzymes
  • used to digest invading cells or break down worn out parts of a cell
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13
Q

what is the ribosome?

A
  • very small organelle
  • either floats or attaches to ER
  • made of proteins
  • not surrounded by a membrane
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14
Q

what is the function of the ribosome?

A

site where proteins are made

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15
Q

what is the RER?

A
  • system of membrane enclosing a fluid filled space
  • surface covered with ribosomes
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16
Q

what is the function of the RER?

A

folds and processes proteins made at ribosomes

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17
Q

what is the SER?

A

system of membrane enclosing a fluid filled space

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18
Q

what is the function of the SER?

A

synthesises and processes lipids

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19
Q

what is the vesicle?

A

small fluid filled sac in cytoplasm surrounded by a membrane

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20
Q

what is the function of the vesicle?

A
  • transports substances in and out cell and between organelles
  • formed at the Golgi, ER or cell surface
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21
Q

what is the Golgi apparatus?

A
  • group of fluid filled, membrane bound flattened sacs
  • vesicles seen at edges of sacs
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22
Q

what is the function of the Golgi apparatus?

A
  • processes and packages new lipids and proteins
  • makes lysosomes
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23
Q

what is the mitochondrion?

A
  • oval shaped
  • double membrane
  • inner membrane folded into cristae
  • matrix contains enzymes for respiration
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24
Q

what is the function of the mitochondrion?

A
  • site of aerobic respiration where ATP is produces
  • found in cells that require a lot of energy
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25
Q

what is the chloroplast?

A
  • small flattened structure
  • surrounded by double membrane
  • contains thylakoid membranes stacked to form grana
  • grana linked together by lanellae
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26
Q

what is the function of the chloroplast?

A
  • site of photosynthesis
  • parts of photosynthesis happen in grana and others in stroma
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27
Q

what is the centriole?

A
  • small hollow cylinders made of microtubules
  • found in animal cells and some plant cells
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28
Q

what is the function of the centriole?

A

involved in separation of chromosomes during cell division

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29
Q

what is the cilia?

A
  • small hair-like structures found on surface membrane of animal cells
  • cross section = 9 microtubules + 2 microtubules inside
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30
Q

what is the function of the cilia?

A
  • microtubules allow cilia to move
  • moves substances along cell surface
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31
Q

what is the flagellum?

A
  • longer than cilia
  • stick out from cell surface
  • cross section = 9 microtubules + 2 microtubules inside
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32
Q

what is the function of the flagellum?

A
  • microtubules contract to make flagellum move
  • motors to propel cells forward
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33
Q

what is involved in protein production?

A
  1. ribosomes on RER make proteins that are excreted or attached to cell membrane, free ribosomes make proteins stay in cytoplasm
  2. new proteins produced at RER are folded and processed in RER
  3. they’re transported from ER to Golgi in vesicles
  4. proteins enter more vesicles to be transported around the cell
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34
Q

what are the functions of the cytoskeleton?

A
  • microtubules & microfilaments support cells organelles
  • strengthen and maintain cell shape
  • responsible for movement of materials within cells
  • proteins in cytoskeleton allow cell to move
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35
Q

what are the differences between prokaryotes and eukaryotes?

A

eukaryotes vs prokaryotes
larger
smaller
linear DNA
circular DNA
nucleus - DNA inside
no nucleus - DNA in cytoplasm
no cell wall, cellulose in plants, chitin in fungi
polysaccharide cell wall - not cellulose/chitin
many organelles (mitochondria)
few organelles (no mitochondria)
flagella made of microtubules
flagella made of flagellin
larger ribosomes
smaller ribosomes

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36
Q

what are bacterial cells?

A
  • prokaryotic
  • to small to see internal structure with normal microscopes
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37
Q

magnification calculation

A

magnification = image size/actual size

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38
Q

conversion of mm to micrometers?

A

mm x1000 = micrometers
micrometers / 1000 = mm

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39
Q

what is a light microscope?

A
  • uses light
  • lower resolution than electron microscope
  • looks at whole cells/tissues
  • magnification = x1500
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40
Q

what is a laser scanning confocal microscope?

A
  • uses laser beams to scan specimen & tagged with fluorescent dye
  • laser causes dye to fluoresce (give off light)
  • light focused through a pinhole
  • image is 3D
  • used to look at objects at different depths
  • higher resolution than light microscope
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41
Q

what is a transmission electron microscope (TEM)?

A
  • uses electromagnets to focus beam of electrons transmitted through the specimen
  • denser parts of specimen absorb more electrons
  • high resolution images
  • only used on thin specimen
  • only shows inside of cell
  • 2D
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42
Q

what is a scanning electron microscope (SEM)?

A
  • scans beam of electrons across specimen
  • shows surface and inside of specimen
  • can be 3D
  • lower resolution than TEM
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43
Q

what is the maximum magnification and resolution for light, TEM and SEM miscoscopes?

A

light
- resolution: 0.2 µm
- magnification: x1500
TEM
- resolution: 0.0002 µm
- magnification: x >1,000,000
SEM
- resolution: 0.002 µm
- magnification: < x500,000

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44
Q

how do you stain a sample for a light microscope?

A
  • use dye (e.g. methylene blue/eosin)
  • increases contrast
  • different stains are used to make different things show up
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45
Q

how do you stain a sample for an electron microscope?

A
  • objects are dipped in solution of heavy metal
  • metal ions scatter electrons & increase contrast
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46
Q

what is a dry mount?

A
  • cut specimen
  • place on slide
  • cover with cover slip
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47
Q

what is a wet mount?

A
  • pipette small drop of water on slide
  • place with cover slip at an angle to remove air bubbles
  • then add stain to one edge of cover slip
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48
Q

what is the eyepiece graticule?

A
  • fitted onto eyepiece
  • numbers with no units
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49
Q

what is the stage micrometer?

A
  • is a microscope slide with an accurate scale (has units)
  • placed on the stage
  • used to work out divisions on eyepiece graticule at a particular magnification
  • helps to measure specimen
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50
Q

what are the functions of water?

A
  • reactant in chemical reactions
  • solvent (some substances dissolve in it)
  • transports substances
  • helps with temperature control
  • high specific heat capacity
  • high latent heat of vaporisation
  • is a habitat
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51
Q

What is the structure of water?

A
  • 1 oxygen atom (+) and 1 hydrogen atom ( +)
  • water is polar
  • slight negative oxygen attracts positive hydrogen (hydrogen bonding)
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52
Q

How is waters structure related to its properties and functions?

A
  • Hydrogen bands give water high specific heat capacity (they absorb lots of energy)
  • hydrogen bonds give water high latent heat of evaporation (takes lots of energy to break H bonds
  • polarity makes it very cohesive (water molecules stick together + helps water flow)
  • polarity makes it a good solvent (slight positive end of water molecule attracted to negative end of ion and vice verse, surrounding/ dissolving the ions)
  • less dense when is solid, ice floats & doesn’t affect organisms)
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53
Q

What are carbohydrates made from?

A

Monosaccharides

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54
Q

What is the structure of a carbohydrate?

A
  • made from polymers (molecule made from many monomers banded together)
  • Monomers that make carbs are monosaccharides
  • glucose is a monosaccharide with 6 carbon atoms
  • 2 forms a glucose (alpha and beta)
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55
Q

How is glucose’s ring structure related to its function?

A
  • Function: main energy source in plants and animals
  • structure makes it soluble so easily transported
  • its chemical bonds contain lots of energy
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56
Q

What is ribose?

A

Monosaccharide with 5 carbon atoms (pentose monosaccharide)

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57
Q

What are all carbohydrates made from?

A

Carbon, hydrogen, carbon
- for every carbon atom, 2 hydrogen atoms and 1 oxygen atom

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58
Q

How do monosaccharides join together to form disaccharides and polysaccharides?

A
  • Monosaccharides are joined by glycosidic bonds
  • during synthesis, a H atom on one monosaccharide baas to an OH group of another releasing water (conversation)
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59
Q

What is the relationship between the structure and function of starch (polysaccharide)?

A
  • Main energy storage material in plants
  • plants store excess glucose as starch
  • starch is a mixture of 2 polysaccharides of alpha glucose - amylose and amylopectin
  • is insoluble in water so doesnt enter cell by osmosis - makes it good for storage
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60
Q

what is amylose in starch?

A
  • long unbranched chain of alpha glucose
  • coiled structure due to angles of glycosidic bonds
  • makes it compact so good for storage and can fit more in
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61
Q

what is amylopectin in starch?

A
  • long branched chain of alpha glucose
  • side branches allow enzymes to get at glycosidic bonds easily
  • means glucose can be released quickly
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62
Q

What is the relationship between the structure and function of glycogen (polysaccharide)?

A
  • animal cells get energy from glucose but store excess glucose as glycogen
  • branched chain of alpha glucose so glucose can be released quickly
  • compact molecule so good for storage
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63
Q

What is the relationship between the structure and function of cellulose (polysaccharide)?

A
  • long unbranched chains of beta-glucose
  • forms straight cellulose chains
  • chains linked by hydrogen bonds to form microfibrils
  • provides structural support for cells
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64
Q

what are triglycerides?

A
  • kind of lipid
  • complex molecules - large molecular mass
  • contain carbon, hydrogen and oxygen
  • one molecule of glycerol and 3 fatty acids attached to it
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65
Q

what is the structure of a triglyceride?

A
  • tails made of hydrocarbons
  • hydrophobic tails
  • makes lipids insoluble in water
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66
Q

explain the bonds found in triglycerides

A
  • contain ester bonds between each fatty acid and glycerol
  • formed by condensation reaction
  • triglycerides are synthesised through esterification
  • triglycerides break down when the ester bond is broken
  • ester bonds broken in hydrolysis reaction
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67
Q

how can fatty acids be saturated or unsaturated?

A

HYDROCARBON TAILS:
saturated - dont have any double bonds between carbon atoms
unsaturated - have at least one double bond between carbon atoms, causing chain to kink

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68
Q

how are phospholipids similar to triglycerides?

A
  • both macromolecules
  • fatty acid head replaced with phosphate group
  • phosphate groups is hydrophilic and tails are hydrophobic
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69
Q

how does the structure of triglycerides relate to their function?

A
  • long hydrocarbon tails contain lots of chemical energy
  • lots of energy is released when they’re broken down
  • insoluble so dont cause cells to swell (water in by osmosis)
    -triglycerides bundle together, tails face inwards to shield from water
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70
Q

how does the structure of phospholipids relate to their function?

A
  • hydrophilic heads, hydrophobic tails
  • form double layer with heads facing out
  • centre of bilayer is hydrophobic so water-soluble substances cant easily pass through it
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71
Q

how does the structure of cholesterol relate to their function?

A
  • hydrocarbon ring structure attached to hydrocarbon tail
  • small size and flattened shape - allows cholesterol to fit between phospholipid molecules
  • at high temp, they bind to tails and so pack more closely - reduced fluidity
  • low temp, prevents phospholipids packing too close to increases membrane fluidity
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72
Q

what does cholesterol do in eukaryotic cells?

A

helps regulate fluidity of cell membrane by interacting with phospholipid bilayer

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73
Q

what are proteins?

A
  • polymers
  • monomers of proteins
  • dipeptide bond formed between amino acids
  • made of 1 or more polypeptides
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74
Q

what is the structure of an amino acid?

A
  • all amino acids have a carboxyl group and amino group attached to carbon
  • contain variable R group
  • all contain H, C, O, N and sometimes S
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75
Q

what is the bonding in an amino acid?

A
  • peptide bonds to form dipeptides & polypeptides
  • condensation reaction when bonds are formed
  • hydrolysis reaction when bonds are broken
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76
Q

what is the primary structure of a protein?

A
  • sequence of amino acids in polypeptide chain
  • change in amino acids may change structure of whole protein
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77
Q

what is the secondary structure of a protein?

A
  • polypeptide chain doesnt remain flat & straight
  • H bonds form between nearby amino acids in the chain
  • makes it coil into alpha helix or beta pleated sheet
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78
Q

what is the tertiary structure of a protein?

A
  • coiled or folded chain coiled and folded further
  • more bonds form between polypeptide chain
  • proteins made of single polypeptide chain, tertiary structure forms final 3D structure
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79
Q

what is the quaternary structure of a protein?

A
  • how multiple polypeptide chains assemble together
  • proteins made of 1+ polypeptide chain, quaternary structure is final 3D structure e.g. Hb
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80
Q

which bonds hold the primary structure together?

A

peptide bonds

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81
Q

which bonds hold the secondary structure together?

A

hydrogen bonds

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82
Q

which bonds hold the tertiary structure together?

A

ionic bonds - attraction between +/- R groups
disulfide bonds - cysteine binds to sulfur
hydrophobic & hydrophilic interactions - hydrophobic R groups clump together so hydrophilic R groups pushed to outside (affects folding)
hydrogen bonds

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83
Q

which bonds hold the quaternary structure together?

A
  • peptide
  • hydrogen
  • ionic
  • disulfide
  • hydrophobic & hydrophilic interactions
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84
Q

what are globular proteins?

A
  • round and compact
  • hydrophilic R group pushed to outside of molecule caused by hydrophobic interactions in tertiary structure
  • soluble so easily transported
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85
Q

what is the function of haemoglobin (globular protein)?

A
  • carries oxygen around the body in RBCs
  • is a conjugated protein (protein with non-protein attached (prosthetic group))
  • prosthetic group is haem, containing iron, which O binds to
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86
Q

what is the function of insulin (globular protein)?

A
  • hormone secreted by pancreas
  • regulated blood glucose levels
  • transported in blood
  • has 2 polypeptide chains, held by disulfide bonds
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87
Q

what is the function of amylase (globular protein)?

A
  • enzyme
  • catalyses breakdown of starch in digestive system
  • single chain of amino acids
  • has alpha helix AND beta pleated sheet structure
  • most enzymes are globular proteins
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88
Q

what are fibrous proteins?

A
  • insoluble and strong
  • structural proteins
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89
Q

what is collagen (fibrous protein)?

A
  • found in animal connective tissue
  • strong molecule
    minerals can bind to it to increase rigidity
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90
Q

what is keratin (fibrous protein)?

A
  • found in external structures of animals
  • flexible or hard and tough
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91
Q

what is elastin (fibrous protein)?

A
  • found in elastic connective tissue
  • is elastic so allows tissues to return to original shape after being stretched
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92
Q

what are inorganic ions?

A
  • don’t contain carbon
  • have an electric charge
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93
Q

what are named cations?

A
  • calcium
  • sodium
  • potassium
  • hydrogen
  • ammonium
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94
Q

what are named anions?

A
  • nitrate
  • hydrogencarbonate
  • chloride
  • phosphate
  • hydroxide
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95
Q

which test do you use for sugars?

A

benedicts

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96
Q

what are reducing sugars/how do you test for them?

A
  • all monosaccharides and some disaccharides
  • add benedicts and heat in water bath
  • positive test = coloured precipitate
  • higher conc of reducing sugar, further colour change goes
    blue - green - yellow - orange - red
  • more accurate way: filter solution and weight precipitate
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97
Q

what are non-reducing sugars/how do you test for them?

A
  • to test for non-reducing sugars they must be broken down into monosaccharides
  • add dilute HCl and heat in water bath until boiling
  • neutralise with sodium hydrocarbonate
  • then carry out ordinary benedicts test
  • positive = coloured precipitate, negative = remains blue
98
Q

how do you test for glucose?

A
  • test strips coated in reagent * dipped in solution
  • change colour if glucose is present
  • chart indicated glucose concentration
99
Q

how do you test for starch?

A
  • add iodine dissolved in potassium iodide to sample
  • positive = brown/orange to blue-black
  • negative = stays brown/orange
100
Q

how do you test for proteins?

A
  • solution needs to be alkaline so add drops of sodium hydroxide solution
  • add copper sulfate solution
  • protein present = purple
  • no protein = biuret stays blue
101
Q

how do you test for lipids?

A
  • shake test substance with ethanol & pour solute into water
  • lipid present = milky solution
  • more lipid = more milky
  • no lipid = solution stays clear
102
Q

how do you determine concentration of a glucose solution?

A
  • benedicts reagent and a colorimeter
  • colorimeter measures strength of coloured solution
  • helps measure conc of blue benedicts solution left after test
  • paler = more glucose = lower absorbance
103
Q

what is chromatography?

A
  • used to separate & identify things in a mixture
  • can be used to separate & identify biological molecules
  • 2 types: paper chromatography and thin layer chromatography
104
Q

what is the mobile phase of chromatography?

A
  • where molecules can move
  • mobile phase is a liquid solvent (ethanol/water)
105
Q

what is the stationary phase of chromatography?

A
  • where molecules can’t move
  • stationary phase is the paper in paper chromatography
  • stationary pahse is thin layer of solid on glass in thin layer chromatography
106
Q

what are the basic principles of chromatography?

A
  • mobile phase moves through or over stationary phase
  • components of mixture spend different amounts of time in mobile & stationary phase
  • longer time in mobile phase travel further
  • time spent in each phase is what separates out components of mixture
107
Q

what is the Rf value and how do you calculate the Rf value?

A
  • ratio of distance travelled (d.t.)by solute to distance travelled by solvent
    Rf = d.t. by solute/d.t. by solvent
108
Q

what are nucleotides used to make?

A

nucleic acids

109
Q

what is a nucleotide?

A
  • biological molecule
  • made from pentose sugar, nitrogenous base, phosphate group
  • monomers that make up DNA and RNA
  • ADP and ATP are nucleotides used to store and transport energy in cells
110
Q

what is the structure of a neucleotide?

A
  • deoxyribose sugar
  • each DNA neucleotide has the same sugar and phosphate group
  • has 4 possible bases (A,C,T,G)
  • molecule of DNA has 2 polynucleotide chains
111
Q

what are purines?

A
  • adenine and guanine
  • base containing 2 carbon-nitrogen rings joined together
  • larger
112
Q

what are pyrimidines?

A
  • thymine and cytosine
  • base containing 1 carbon-nitrogen ring
  • smaller
113
Q

what is the structure of RNA?

A
  • ribose sugar
  • has a phosphate group
  • has 4 possible bases (A, U, C, G)
  • made of single polynucleotide chain
114
Q

what are ADP and ATP (nucleotides)?

A

phosphorylated nucleotides

115
Q

how do you phosphorylate a nucleotide?

A
  • add one or more phosphate groups to it
  • ADP has adenine, ribose and 2 phosphate groups
  • ATP has adenine, ribose and 3 phosphate groups
116
Q

what is ATP?

A
  • provides energy for chemical reactions in the cell
  • is synthesised from ADP and Pi using energy
117
Q

what forms when ADP is phosphorylated?

A

ATP and a phosphate bond

118
Q

how do nucleotides join together to form polynucleotides?

A
  • join between the phosphate group of one and the sugar of another via condensation reaction
  • this forms a phosphodiester bond
  • chain of sugars and phosphate = sugar-phosphate backbone
  • polynucleotides can be broken down into nucleotides by hydrolysing phosphodiester bonds
119
Q

how is the double helix formed?

A
  • 2 DNA polynucleotide strands join together by hydrogen bonding between bases
  • complementary base pairing
  • 2 hydrogen bonds form between A-T
  • 3 hydrogen bonds form between C-G
  • antiparallel chains twist
120
Q

how do you purify DNA with a precipitation reaction?

A
  1. break up cells in sample e.g. blender
  2. make solution of detergent, salt and distilled water
  3. add broken up cells to beaker containing detergent and incubate beaker
  4. place beaker in ice bath & filter mixture
  5. add protease enzymes to break down some protein bound to DNA
  6. dribble col ethanol down side of tube so layer is formed on top of DNA-detergent mixture
  7. leave mixture and DNA will form white precipitate
121
Q

how does DNA copy itself/do self-replication? (describe the process)

A
  1. DNA helicase breaks H bonds between 2 polynucleotide DNA strands - unzips strands
  2. each original strand acts as a template for a new strand and floating nucleotides join exposed complementary bases
  3. nucleotides of new strand joined together by DNA polymerase to form sugar-phosphate backbone
  4. hydrogen bonds form and strands twist to form double helix
  5. each new strand contains one original and one new strand
122
Q

what is DNA replication?

A
  • semi-conservative = half the strands of new DNA are from original
  • very accurate
  • sometimes random, spontaneous mutations occur and change DNA base sequence and can alter sequence of amino acids and produce an abnormal protein
123
Q

how does DNA use genes to make proteins?

A
  • different proteins have different numbers and order of amino acids
  • order of nucleotide bases determines order of amino acids in a protein
  • each amino acid is coded for by a triplet in a gene
  • different sequences of bases code for different amino acids
124
Q

what is a gene?

A

sequence of DNA nucleotides that codes for a polypeptide

125
Q

how is DNA copied into RNA for protein synthesis?

A
  • DNA is found in nucleus of cells but organelles that make proteins are in cytoplasm
  • DNA is too large to move out the nucleus so a section is copied into mRNA (TRANSCRIPTION)
  • mRNA leaves nucleus and joins with ribosome in cytoplasm (TRANSLOCATION)
126
Q

what is mRNA? (messenger RNA)

A
  • made in nucleus
  • 3 adjacent bases = codon
  • carried genetic code from DNA in nucleus to cytoplasm where its used to make protein for translation
127
Q

what is tRNA? (transfer RNA)

A
  • found in cytoplasm
  • has amino acid binding site at one end and sequence of 3 bases at other end (anticodon)
  • carried amino acids to ribosomes during translation
128
Q

what is rRNA? (ribosomal RNA)

A
  • forms 2 subunits in a ribosome (large & small)
  • ribosomes move along mRNA strand during protein synthesis
  • rRNA in ribosome helps catalyse formation of peptide bonds between amino acids
129
Q

what is the genetic code?

A
  • a sequence of codons in DNA or mRNA
  • base triplets are read in sequence
  • triplets dont share or overlap bases
  • is degenerate (more combinations of triplets than amino acids)
  • have start/stop codons = tells cell when to star/stop protein production
  • is universal = same specific base triplets code for same amino acids in all living things
130
Q

what is involved in the first stage of protein synthesis (transcription)?

A
  1. starts when RNA polymerase attaches to DNA double helix at start of gene
  2. H bonds between 2 strands break, DNA uncoils
  3. one strand is used as a template to make an mRNA copy
  4. RNA polymerase lines up free RNA nucleotides & base pairing means mRNA strand is complementary to DNA (except T & U)
  5. once RNA nucleotides pair with bases on DNA, they form an mRNA molecule
  6. RNA polymerase moves along DNA separating strands and assembling mRNA
  7. H bonds between uncoiled strands of DNA re-form once RNA has passed so strands coil back
  8. when RNA polymerase reaches stop codon, it detaches from DNA
  9. mRNA moves out nucleus though nuclear pores and attaches to ribosome in cytoplasm
131
Q

what is involved in the second stage of protein synthesis (translation)?

A
  • occurs at ribosomes in cytoplasm
    1. mRNA attaches to ribosome and tRNA molecules carry amino acids to ribosome
    2. tRNA molecule attaches to mRNA by base pairing
    3. second tRNA molecule attaches itself to next codon in mRNA
    4. rRNA in ribosome catalyses formation of peptide bonds between amino acids attached to tRNA molecule so first tRNA molecule moves away
    5. third tRNA molecule binds to next codon on mRNA so second tRNA molecules moves away
    6. process continues until reaches stop codon
    7. polypeptide moves away from ribosome
132
Q

what are enzymes?

A
  • speed up chemical reactions by acting as biological catalysts
  • catalyse metabolic reactions at cellular levels and for whole organism (e.g. digestion)
  • action can be intracellular or extracellular
  • are globular proteins
  • active site is specific shape (where substrate binds) determined by tertiary structure
133
Q

what is an example of an intracellular enzyme?

A
  • catalase
  • hydrogen peroxide is the toxic by-product of many cellular reactions
  • catalase works inside cells to breakdown hydrogen peroxide into oxygen and water
134
Q

what is an example of an extracellular enzyme?

A
  • amylase (digestion)
  • found in saliva, secreted by the mouth in salivary glands
  • catalyses hydrolysis of starch and maltose in the mouth
135
Q

how do enzymes reduce activation energy?

A
  • make reactions happen at a lower temperature
  • this speeds up rate of reaction
  • formation of enzyme-substrate complexes lower activation energy
136
Q

what is the lock and key model?

A
  • the substrate fits into a specific enzyme
  • enzyme and substrate do need to fit together in the first place
137
Q

what is the induced fit theroy?

A
  • as substrate binds, active site changed shape slightly to fit substrate more closely
  • substrate deosnt need to be the right shape for the active site, but has to make the active sit change shape in the right way
138
Q

how does temperature influence enzyme activity?

A
  • rate increases with temperature
  • more heat = more kinetic energy = enzymes more likely to collide with substrate
  • when temp goes above optimum, enzymes bonds break and it denatures so cannot function as a catalyst
139
Q

what is the temperature coefficient (Q10)?

A
  • Q10 value for a reaction shows how much the rate of a reaction changes when the temperature is raised by 10°C
  • equation: Q10 = R2/R1
    *R2 = rate at higher temperature
    *R1 = rate at lower temperature
  • most enzyme controlled reactions have a Q10 of 2
140
Q

how does enzyme concentration affect rate of reaction?

A
  • more enzyme molecules = more likely a substrate molecule will collide and form an enzyme-substrate complex
  • increasing conc of enzyme increases rate of reaction
  • if substrate is limited, adding more enzyme has no further effect
141
Q

how does substrate concentration affects rate of reaction?

A
  • higher substrate concentration = faster reaction (more substrate molecules mean more collisions)
  • only true up to ‘saturation’ point - adding substrate after all active sites are full has no effect
  • substrate con decreases with time so if no other variables change then rate will decrease which makes initial rate the highest rate of reaction
142
Q

how do you measure the rate of enzyme controlled reactions?

A
  • measure how fast product appears (easy to collect oxygen and how fast its given off)
  • OR measure disappearance of a substrate rather than appearance of product and use this to compare rate under different conditions
143
Q

how would you investigate the effects of temperature in catalase activity?

A
  1. set up boiling tubes with same volume & conc of hydrogen peroxide, to keep pH constant add same amount of buffer solution to each tube
  2. set up apparatus to measure volume of oxygen produces from each boiling tube
  3. put each tube in water bath at different set temps along with another tube containing catalase
  4. use pipette to add same volume and conc of catalase to each tube
  5. record how much oxygen is produced in first min (stopwatch)
  6. repeat 3 times & find mean
  7. calculate mean rate of reaction at each temp (oxygen produced/time)
144
Q

what are cofactors?

A
  • non-protein substance bound to an enzyme
  • inorganic molecules or ions that help bind enzyme and substrate
  • arent directly involved in reaction so arent used up or changed
  • e.g. chloride ions are cofactors for amylase
145
Q

what are coenzymes?

A
  • type of organic cofactor
  • participate in reaction and are changed (like a second substrate)
  • act as carriers, moving chemical groups between enzymes
  • continually recycled
146
Q

what are prosthetic groups?

A
  • a cofactor that’s tightly bound to enzyme
  • e.g zinc ions area prosthetic group for carbonic anhydrase and are a permanent part of the enzyme
147
Q

what is competitive inhibition?

A
  • competitive inhibitors have similar shape to substrate
  • they compete with substrate to bind to active site but no reaction takes place
  • block active site
  • how much the enzyme is inhibited depends on conc of inhibitor and substrate
  • high conc of inhibitor = takes up nearly all active sites
  • high conc of substrates = chance of substrate getting active site before inhibitor increases
  • increasing conc of substrate increases rate
148
Q

what is non-competitive inhibition?

A
  • non-competitive inhibitors bind to enzyme away from active site (bind to allosteric site)
  • causes active site to change shape
  • dont compete with substrate molecules
  • increasing conc of substrate wont affect rate of reaction
149
Q

when is an inhibitor reversible?

A

if they’re weaker hydrogen bonds or weak ionic bonds, inhibitor can be removed

150
Q

what is an inhibitor irreversible?

A

if they’re strong, covalent bonds, inhibitor cant be removed easily

151
Q

what are examples of medicinal drugs that are enzyme inhibitors?

A
  1. antiviral drugs e.g. reverse transcriptase inhibitors, reverse transcriptase catalyses replication of viral DNA
  2. some antibiotics e.g. penicillin inhibits transpeptidase which catalyses formation of proteins in bacterial cell walls. this weakens cell wall and prevents bacterium regulating its osmotic pressure and is killed
152
Q

what are examples of metabolic poisons that are enzyme inhibitors?

A
  • cyanide, irreversible inhibitor of cytochrome c and inhibits cell respiration so cells die
  • malonate, inhibits succinate dehydrogenase
  • arsenic, inhibits action of pyruvate dehydrogenase which catalyses respiration reactions
153
Q

what are metabolic pathways regulated by?

A

end-product inhibition

154
Q

what is a metabolic pathway?

A
  • series of connected metabolic reactions
  • the product of first reaction takes part in second reaction and so on
  • each reaction is catalysed by a different enzyme
155
Q

what is end-product inhibition?

A
  • when the final product in a metabolic pathway inhibits enzyme that acts on earlier pathway
  • controls and regulates amount of end product
  • product and end-product inhibition is reversible so when product levels drop, level of inhibition falls so enzyme can function again
156
Q

how does enzyme inhibition help protect cells?

A
  • enzymes are sometimes synthesised as inactive precursors in metabolic pathways to prevent them causing damage to cells
  • part of precursor molecule inhibits its action as an enzyme
157
Q

what do membranes do?

A

control what passes through them

158
Q

what are plasma membranes (membranes at the surface of cells)?

A
  • are a barrier to cell and its environment, controlling which substances enter and leave cell
  • partially permeable
  • substances move across through diffusion, active transport and osmosis
  • allow recognition by other cells
  • allow cell communication/cell signalling
159
Q

what are membranes within cells?

A
  • membranes around organelles divide cell into components - act as a barrier between organelle and cytoplasm
  • can form vesicles to transport substances between different areas of the cell
  • control which substances enter and leave the organelle
  • membranes within organelles act as barriers between membrane and contents
  • sit of chemical reactions
160
Q

what is the fluid mosaic model?

A
  • describes arrangement of molecules in a membrane
  • phospholipid bilayer model
  • bilayer is fluid because phospholipids are constantly moving
  • cholesterol and protein molecules are present
  • some proteins have polysaccharide chain attached (glycoproteins)
  • some lipids have a polysaccharide chain attached (glycolipids)
161
Q

what is the role of phospholipids in cell membranes?

A
  • have a hydrophilic head and hydrophobic tail
  • heads face out, tails face in
  • centre of bilayer is hydrophobic so membrane doesnt allow water-soluble substances through it
162
Q

what is the role of cholesterol in cell membranes?

A
  • type of lipid
  • present in all but bacterial membranes
  • fit between phosohplipid molecules and bind to hydrophobic tails so they pack closer (membrane goes less fluid)
  • at low temp cholesterol prevents phospholipids packing too close so increases fluidity
163
Q

what is the role of proteins in cell membranes?

A
  • some form channels in the protein that allow small or charged particles through
  • other proteins transport molecules & ions across membrane by active transport and facilitated diffusion
  • also act as receptors for molecules in cell signalling
164
Q

what is the role of glycoproteins and glycolipids acting as receptors for messenger molecules (in a membrane?

A
  • they stabilise membrane by forming hydrogen bonds with water molecules
  • sites where drugs, hormones and antibodies bind
  • are antigens
165
Q

what is cell signalling?

A

how cells communicate

166
Q

how do cells communicate?

A

using messenger molecules:
- one cell releases messenger molecule
- molecule travels to another cell
- messenger molecule is detected by the cell as it binds to a receptor on its cell membrane

167
Q

what is the role of cell surface receptors in cell signalling?

A
  • proteins in cell membrane act as receptors for membrane molecules
  • receptor proteins have specific shaped (only messenger molecules with complementary shape can bind)
  • different cells have different types of receptors - they respond to different messenger molecules (cell that responds is a target cells)
168
Q

how do you investigate the permeability of cell membranes?

A
  1. cut 5 equal size pieces of beetroot and rinse to remove any pigment released
  2. place pieces in test tubes with 5cm3 of water
  3. place each tube in water baths of different temps
  4. remove pieces of beetroot leaving coloured liquid
  5. use colorimeter - higher permeability = more pigment released = higher absorbance of liquid
169
Q

what is the effect of temperature on membrane permeability?

A
  • increasing temperature increases membrane permeability
  • temps below 0°C: low energy so low movement, packed closely, membrane is rigid
  • temps between 0 and 45°C: phospholipids can move & arent packed as tight, membrane is partially permeable, as temp increases bilayer moves more - increases permeability
  • temps above 45°C: bilayer starts to melt, becomes more permeable, water inside cell expands, channel & carrier proteins deform so cant control what enters and leaves so increases permeability
170
Q

how does changing the solvent affect membrane permeability?

A
  • surrounding cells in solvent increases permeability of membranes
  • due to solvents dissolving lipids so membrane loses structure
  • different solvents increase permeability differently
  • increasing conc of solvent increases permeability
171
Q

what is diffusion within transport across membranes?

A
  • net movement of particles from high to low conc (down gradient)
  • molecules diffuse both ways but net movement is only to low conc
  • diffusion is passive - no energy needed
172
Q

how do small non-polar molecules diffuse through cell membranes?

A
  • able to diffuse easily though spaces between phospholipids (e.g. H2O & CO2)
  • water is small enough to fit between phospholipids so can diffuse across plasma membranes (diffusion of water molecules like this is osmosis)
173
Q

what factors does rate of diffusion depend on?

A
  1. concentration gradient - higher = faster
  2. thickness of exchange surface - thinner = faster
  3. SA - larger = faster
  4. temperature - warmer = faster (kinetic energy)
174
Q

how do you investigate SA affecting rate of diffusion?

A
  • cut agar jelly into different sized cubes & work out their SA:V
  • time how long it takes each cube to go colourless when placed in same conc of HCl
  • expect larger SA:V to go colourless fastest
175
Q

how do you investigate concentration gradient affecting rate of diffusion?

A
  • prepare test tubes containing different concentrations of HCl
  • put equal sized cubes of agar jelly in each test tube and measure time taken to go colourless
  • expect highest conc to be fastest
176
Q

how do you investigate temperature affecting rate of diffusion?

A
  • prepare many boiling tubes containing same conc of HCl and put tubes in varying temps
  • put equal sized agar jelly in each boiling tube and measure time taken to go colourless
  • expected higher temp to be fastest
177
Q

what is facilitated diffusion

A
  1. used by some larger molecules, polar molecules and ions
  2. moves particles down a conc gradient
  3. passive process
178
Q

how does facilitated diffusion use carrier proteins?

A
  • carrier proteins move large molecules into/out of the cell
  • different carrier proteins facilitate diffusion of different molecules
    1. larger molecule attached to carrier protein
    2. protein changes shape
    3. releases molecule on opposite side of membrane OO\/OO to OO/\OO
179
Q

how does facilitated diffusion use channel proteins?

A
  • channel proteins form pores in membrane for charged particles to diffuse through down conc gradient
  • different channel proteins facilitate diffusion of different charged particles OOOI IOOO
180
Q

how do substances move against a concentration gradient (high to low)?

A

active transport (same process as facilitated diffusion but ATP is used (active process) to move substance against gradient)

181
Q

how do cells take in substances?

A

endocytosis

182
Q

explain endocytosis

A
  • a cell surrounds a substance within a section of plasma membrane
  • membrane pinches off to form a vesicle containing ingested substance (endocytosis)
  • some cells take in much larger objects by endocytosis e.g. WBCs
  • active process
183
Q

how do cells secrete substances?

A

exocytosis

184
Q

explain exocytosis

A
  • some substances produced by the cell need to be released (exocytosis)
  • vesicles containing these substances pinch off from sacs of Golgi and move towards plasma membrane
  • vesicles fuse with plasma membrane and release contents outside cell
  • some substances are inserted striaght into plasma membrane
  • active process
185
Q

what is osmosis?

A
  • diffusion of water molecules across a partially permeable membrane down a WP gradient
  • molecules from high WP go to low WP
186
Q

what is water potential?

A

likelihood of water molecules to diffuse out of or into a solution

187
Q

what happens to animal cells with a higher water potential than the cell (hypotonic solution)?

A

net movement of molecules is into the cell - cell bursts

188
Q

what happens to animal cells with the same water potential than the cell (isotonic solution)?

A

water molecules pass into and out of cell equally - cell stays the same

189
Q

what happens to animal cells with a lower water potential than the cell (hypertonic solution)?

A

net movement of water molecules is out the cell - cell shrinks

190
Q

what happens to plant cells with a higher water potential than the cell (hypotonic solution)?

A
  • net movement of water is into cell - vacuole swells
  • and cytoplasm push against the cell wall so cell becomes turgid
191
Q

what happens to plant cells with the same water potential than the cell (isotonic solution)?

A

water moves into and out of cell equally - cell stays the same

192
Q

what happens to plant cells with a lower water potential than the cell (hypertonic solution)?

A
  • net movement of water is out the cell - cell becomes flaccid (limp)
  • cytoplasm and membrane pull away from cell wall - plasmolysis
193
Q

how can you investigate water potential?

A
  1. prepare sucrose solution of 0.0, 0.2, 0.4, 0.6, 0.8 1.0 M concentrations
  2. use cork borer to cut potatoes into same sized pieces
  3. divide into groups of 3 and measure mass ot each group
  4. place one group in each solution
  5. leave chips for as long as possible (same amount of time)
  6. remove chips & dry with towel
  7. weigh each group and record results
  8. calculate % change in mass
  9. plot results on graph
194
Q

what is the cell cycle?

A
  1. starts when a cell has been produced by cell division, ends with cell dividing to produce 2 identical cells
  2. consists of cell growth & DNA replication (interphase) & cell division (M phase - mitosis & cytokinesis)
  3. interphase is divided into G1, S and G2
    4, cell cycle is regulated by checkpoints to check process can continue
195
Q
  1. what happens during gap phase 1?
A

cell grows and new organelles and proteins are made

196
Q
  1. what happens at the G1 checkpoint?
A

cell checks that the chemicals needed for replication are present any damage to DNA before S-phase

197
Q
  1. what is the S phase (synthesis)?
A

cell replicates its DNA ready to divide by mitosis

198
Q
  1. what happens during gap phase 2?
A

cell keeps growing and proteins needed for cell division are made

199
Q
  1. what happens at the G2 checkpoint?
A

cell checks whether all DNA has been replicated without damage - cell then enters mitosis

200
Q

what is the order of the interphase section of the cell cycle?

A
  1. gap phase 1
  2. G1 checkpoint
  3. synthesis
  4. gap phase 2
  5. G2 checkpoint
    (then goes to mitosis and cytokinesis)
201
Q

what is mitosis needed for?

A
  • growth of multicellular organisms and repairing damaged tissues
  • also a method of asexual reproduction for some plants, animals and fungi
202
Q

what is interphase?

A
  • cell carries out normal functions
  • cells DNA is unravelled and replicated to double its genetic content
  • organelles are also replicated
  • ATP content is increased
203
Q

what is prophase?

A
  • chromosomes condense getting shorter and fatter
  • centrioles start moving to opposite ends of the cell forming spindle fibres
  • nuclear envelope breaks down and chromosomes lie free in cytoplasm
204
Q

what is metaphase?

A
  • chromosomes line up along middle of cell and become attached to spindle by their centromere
  • at metaphase checkpoint cell checks chromosomes are attached to spindle before mitosis continues
205
Q

what is anaphase?

A
  • centromeres divide, separating sister chromatids
  • spindles contract pulling chromatids to opposite ends of the cell
206
Q

what is telophase?

A
  • chromatids reach opposite poles on spindle
  • uncoil and become long and thin, now called chromosomes again
  • nuclear envelopeforms around each group of chromosomes (so now 2 nuclei)
207
Q

what is cytokinesis?

A
  • cytoplasm divides
  • animal cells: cleavage furrow forms to divide cell membrane
  • now there are 2 genetically identical daughter cells
  • separate process to mitosis
208
Q

how can you observe the cell cycle and mitosis?

A

by staining chromosomes to view under a microscope

209
Q

what is meiosis?

A
  • is a type of cell division that happens in reproductive organs to produce gametes
  • in sexual reproduction, 2 gametes join together at fertilisation to form a zygote
  • involves reduction division
  • cells formed by meiosis are genetically different - they end up with different combination of chromosomes
210
Q

what is reduction division?

A
  • cells that divide by meiosis have a full number of chromosomes
  • cells that form from meiosis have half the number of chromosomes (haploid)
211
Q

what does meiosis I involve?

A

reduction division

212
Q

what is prophase I?

A
  • chromoeomes condense
  • chromosomes arrange into homologous pairs and crossing over occurs
  • centrioles start moving to opposite ends of the cell forming spindle fibres
  • nuclear envelope breaks down
213
Q

what is metaphase I?

A

homologous pairs line up across centre of cells and attach to spindle fibres by their centromeres

214
Q

what is anaphase I?

A
  • spindles contract, separating homologous pairs
  • one chromosome goes to each end of the cell
215
Q

what is telophase I?

A

nuclear envelope forms around each group of chromosomes

216
Q

what is cytokinesis in meiosis I?

A

2 haploid daughter cells are produced

217
Q

what happens during meiosis II?

A
  • the 2 daughter cells undergo prophase II, metaphase II, telophase II and cytokinesis (stages very similar to stages in mitosis)
  • in anaphase II, pairs of sister chromatids are separated so each new daughter cell inherits one chromatid from each chromosomes
  • 4 haploid daughter cells are produced (gametes)
218
Q

what is crossing over of chromatids?

A
  • chromatids twist around each other and bits of the chromatids swap over
  • chromatids still contain the same genes but now have different combination of alleles
219
Q

what is independent assortment of chromosomes?

A
  • each homologous pair of chromosomes is made from one maternal and one paternal chromosome
  • when homologous pairs line up in metaphase I and are separated in anaphase I, its random which chromosome ends up with which daughter cell
  • so 4 daughter cells have different combinations of maternal and paternal chromosomes
  • leads to genetic variation
220
Q

what are stem cells?

A

unspecialised cells

221
Q

how do stem cells differentiate into specialised cells?

A
  • stem cells divide to become new cells which become specialised
  • in animals stem cells can replace damaged cells
  • plants are always growing so stem cells are used for new roots and shoots
  • stem cells (in meristems) can differentiate into xylem and phloem
  • can divide and produce more undifferentiated cells
222
Q

which stem cells differentiate to become xylem cells and phloem sieve tubes?

A

stem cells in the vascular cambium

223
Q

how are neutrophils adapted to their function?

A
  • defend body against diseases
  • flexible shape allows them to engulf foreign particles or pathogens
  • have many lysosomes in their cytoplasm that contain digestive enzymes to break down engulfed particles
224
Q

how are erythrocytes adapted to their function?

A
  • carry oxygen in the blood
  • biconcave disc shape = large SA for gas exchange
  • have no nucleus so theres more room for haemoglobin
225
Q

how are epithelial cells adapted to their function?

A
  • cover surfaces of organs
  • joined by interlinking cell membranes
  • ciliated epithelia have cilia that beat to move particles away
  • squamous epithelia are very thin to allow efficient gas exchange
226
Q

how are sperm cells adapted to their function?

A
  • have flagellum so can swim to egg
  • have many mitochondria to provide energy to swim
  • acrosome contains digestive enzymes to penetrate surface of egg
227
Q

how are palisade mesophyll cells adapted to their function?

A
  • do most of photosynthesis
  • have many chloroplasts so can absorb lots of sunlight
  • thin cell walls so CO2 can easily diffuse into the cell
228
Q

how are root hair cells adapted to their function?

A
  • absorb water and mineral ions from the soil
  • large SA for absorption
  • thin , permeable cell wall for entry of water and ions
  • have extra mitochondria to provide energy needed for active transport
229
Q

how are guard cells adapted to their function?

A
  • found in pairs with a gap between to form stroma
  • in light, they take up water and become turgid
  • thin outer walls and thickened inner walls forces them to bend outwards - opening stomata
  • allows leaf to exchange gases for photosynthesis
230
Q

what are tissues?

A

a group of cells (can be multiple types) specialised to work together to carry out a particular function

231
Q

what is the sqamous epithelium (tissue)?

A
  • single layer of flat cells lining a surface
  • found in many places incl. alveoli in lungs
232
Q

what is ciliated epithelium (tissue)?

A
  • layer of cells coveres in cilia
  • found on surfaces when things need to be moved
233
Q

what is muscle tissue (tissue)?

A
  • made of bundles of muscle fibres
  • 3 types of muscle tissue: cardiac, smooth, skeletal
234
Q

what is cartilage (tissue)?

A
  • type of connective tissue found in joints
  • shaped and supports ears, nose and windpipe
  • formed when cells secrete extracellular martix which they become trapped inside
235
Q

what is xylem tissue?

A
  • plant tissue that transports water and supports plant
  • contains hollow xylem vessel cells (dead) and parenchyma (living)
236
Q

what is phloem tissue?

A
  • transports sugars around the plant
  • arranged in tubes and made of sieve tube elements and companion cells
  • sieve cell end walls (sieve plates) have holes in so sap easily moves through
237
Q

what is an organ?

A

group of different tissues that work together to perform a particular function

238
Q

what are the levels of organisation in the body?

A

cells, tissues, organs, organ systems, organism

239
Q

what makes up the lungs (organ)?

A
  • squamous epithelial tissue
  • ciliated epithelial tissue
  • elastic connective tissue
  • vascular tissue
240
Q

what makes up leaves (organ)?

A
  • palisade tissue
  • epidermal tissue
  • xylem tissue
  • phloem tissue
241
Q

what is the respiratory system (organ system)?

A
  • made up of all organs, tissues and cells involved in breathing
  • trachea, larynx, nose, mouth, diaphragm
242
Q

what is the circulatory system (organ system)?

A
  • made up of all organs involved in blood supply
  • heart, arteries, veins and capillaries

Biology - mr ellis (76 decks)

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