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biology - module 2 > biological molecules > Flashcards

biological molecules Flashcards

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1
Q

what is covalent bonding

A
  • when atoms share electrons to have a full outermost shell
  • is drawn by a single line
  • CNOH - goes down by 1
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2
Q

what is a condensation reaction

A

occurs when two molecules are joined together with the removal of water

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3
Q

what is a hydrolysis reaction

A

occurs when a molecule is split into two smaller molecules with the addition of water

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4
Q

what is a hydrogen bond

A

a weak interaction which happens whenever molecules contain a slightly negative charged atom bonded to a slightly positive charged atom

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5
Q

whats a monomer

A

the units joined together in a condensation reaction

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6
Q

whats a dimer

A

two monomers joined together

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7
Q

whats a polymer

A

when lots of monomers join together

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8
Q

does water have a low or high viscosity

A

low which means it can flow easily

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9
Q

why is water being a liquid at room temperature beneficial

A
  • provides habitat
  • forms a major component of tissues in living conditions
  • provides a reaction medium for chemical reactions
  • acts as an effective transport medium
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10
Q

is water non-polar or polar

A

polar

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11
Q

what is unique about water density

A
  • it gets more dense as it gets colder until 4°C
  • as it goes from 4°C to freezing point, (as its polar) the water molecules align themselves in a structure that is less dense than water which makes it float
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12
Q

why is it beneficial that ice is less dense than water

A
  • aquatic organisms have a stable environment to live in through the winter
  • bodies of water (such as lakes/ponds) are insulated against extreme cold
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13
Q

why is water a good solvent

A

because water clusters around the charged parts of the solutes because of its polarity - which helps seperate them

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14
Q

why is it beneficial that water is a good solvent

A
  • molecules and ions can move around and react together in water
  • molecules and ions can be transported whilst dissolved in water
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15
Q

why does a drop of water on a flat surface not spread out

A

because the hydrogen bonding between the molecules pull them together

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16
Q

whats surface tension

A

when the surface of water contracts and has the ability to resist force applied to it

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17
Q

what is high specific heat capacity

A
  • the amount of heat energy required to increase the kinetic energy and temperature of water
  • 4.2kJ of energy to raise temp of 1kg of water by 1°C
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18
Q

what is the high latent heat of vaporisation

A

the energy used to change state

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19
Q

why is latent heat of vaporisation useful

A

because when water evaporates it helps the molecules to break away from eachother to become a gas

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20
Q

what do carbohydrates contain

A
  • carbon
  • hydrogen
  • oxygen
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21
Q

what is the function of carbohydrates

A
  • acts as a source of energy
  • acts as a source of energy
  • acts as a structural unit
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22
Q

what are the three main groups of carbohydrates

A
  • monosaccharides (one monomer)
  • disaccharides (two monomers)
  • polysaccharides
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23
Q

key points about monosaccharides

A
  • simplest carbohydrate
  • important as a source of energy
  • are sugars and soluble in water but insoluble in non-polar solvents
  • can exist as a straight chain or in ring or cyclic forms
  • are the backbone of single-bonded carbon atoms with one double-bond to an oxygen to form a carboxyl group
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24
Q

what are the different isomers of glucose

A

α-glucose: H above and OH below
β-glucose: OH above and H below

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25
Q

what are the most common dissacharides

A
  • maltose
  • lactose
  • sucrose

maltose and lactose are reducing sugars whereas sucrose is non-reducing

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26
Q

key points about disaccharides

A
  • are sweet and soluble
  • are made when two monosaccharides join together
  • when they join, a condensation reaction occurs to form a glycosidic bonds
    -where two hydroxyl groups line up next to each other where a water molecule is removed which leaves an oxygen atom acting as a link
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27
Q

whats a polysaccharide

A

a polymer of a monosaccharide

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28
Q

whats a homopolysaccharide and a heteropolysaccharide

A

homopolysaccharide - made solely of one kind of monosaccharide (e.g. starch)
heteropolysaccharide - made up of more than one monomer (e.g. hyaluronic acid)

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29
Q

why are polysaccharides good energy stores

A
  • the structure of some polysaccharides help
  • are less soluble in water than monosaccharides because of their size
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30
Q

why is glycogen in animals and starch in plants (made from amylose and amylopectin) good stores of monosaccharides

A
  • they are compact
  • hold glucose molecules in chains which means it can easily be ‘snipped off’ the chain by hydrolysis
  • some chains are branched (glucose and amylopectin) and some are unbranched (amylose) - branched are more compacts and offer the chance for lots of glucose to be snipped off
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31
Q

where is cellulose found

A

in plants, forming cell walls

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32
Q

key points of cellulose

A
  • is tough, insoluble and a fibrous substance
  • is a homopolysaccharide - made from a long chain of up to 15000 β-glucose molecules
  • bonded through a condensation reaction forming glycosic bonds
  • chains are straight and lie side by side
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33
Q

what happens to the hydrogen and hydroxyl groups on carbon 1 in cellulose

A
  • are inverted
  • every other β-glucose molecule in the chain is rotated by 180° - helps prevent the chain from spiralling
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34
Q

what is the bond between the β-glucose molecules in cellulose

A
  • hydrogen bonds which gives extra strength
  • hydrogen bonds also form between rotated β-glucose molecules in different chains (hydroxyl group on carbon 2 sticks out enabling H bonds between chains)
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35
Q

whats a microfibril

A
  • when 60-70 cellulose chains are bound together
  • 10-30nm in diameter
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36
Q

whats a macrofibril

A
  • when microfibris bundle together (contains 400 microfibrils)
  • embedded in pectins to form plant cell walls
  • macrofibrils run in all directions criss-crossing the wall for extra strength
37
Q

what are bacteria cell walls made from

A
  • peptidoglycan
  • made from long polysaccharide chains that lie in parallel, criss-crossed by short peptide chains (made from amino acids)
38
Q

what are insect and crustaceans exoskeletons made from

A
  • chitin
  • has an acetylamino group on carbon 2
  • froms cross linkes between parallel chains of acetylglucosamine
39
Q

what are the key feature for the function of plant cell walls

A
  • plants have no rigid skeleton so each cell needs strength to support the plant
  • space between macrofibrils for water and mineral ons to pass through (membrane is fully-permeable)
  • wall has high tensile strength - prevents turgid cells from bursting and the turgid cells provide support
40
Q

what are lipids

A
  • contains larg amounts of carbon and hydrogen and small amounts of oxygen
  • insoluble in water (non-polar) but dissolve in alcohol
41
Q

what are 3 examples of macromolecules

A
  • triglycerides
  • phospholipids
  • steroids
42
Q

what are triglycerides made from

A

glycerol and fatty acids

43
Q

whats the structure of glycerol

A
  • has 3 carbon atoms
  • is an alcohol
  • has 3 -OH groups
44
Q

whats the structure of fatty acids

A
  • have a carboxyl group (-COOH) at one end attached to a hydrocarbon tail
  • carboxyl group ionises into H+ and -COO- groups
45
Q

what does it mean if a fatty acid is unsaturated or saturated

A
  • unsaturated - there is a C=C double bond (means fewer H atoms are bonded)
  • saturated - no C=C bond in the molecule
  • a single C=C bond makes a fatty acid monosaturated
  • more than one C=C bond makes it polysaturated
46
Q

what happens if there is more than one C=C bond in a fatty acid

A
  • it changes the shape of the hydrocarbon - gives a kink where the double bond is
  • kink pushes the molecules slightly apart, making it more fluid
47
Q

whats an ester bond

A
  • a condensation reaction happens between the -cooh group of the fatty acid and the -OH groupd of the glycerol
  • 3 fatty acids bond to 3 -OH groups
  • a water molecule is produces and an ester bond is formed
48
Q

whats the functions of triglyceride

A
  • energy source - triglyceride can be broken down in respiration to realease energy and generate ATP
  • energy store - as they are insoluble in water, they can be stored without affecting the water potential of the cell
  • insulation - adipose tissue stores lipids in whales, lipids in nerve cells act as an electrical insulator
  • buoyancy - as fat is less dense than water, used by aquatic mammals to stay afloat
  • protection - humans have fat around delicate organs to act as a shock absorber
49
Q

whats the structure of a phospholipid

A
  • glycerol, 2 fatty acids and a phosphate group
  • a condensation reaction between an OH group on a phosphate acid molecule (H3PO4) and one of the three -OH groups on the glycerol form an ester bond
50
Q

whats a phospholipids behaviour in water

A
  • the phosphate groups are polar whilst the fatty acids are non-polar
  • the heads are hydrophilic whilst the tails are hydrophobic whcih makes the phospholipid amphipathic
  • may form a layer on surface of water with heads in the water whilst tails stick out
  • can form micelles (tiny balls with the tails tucked away inside and the heads pointing outwards into the water)
51
Q

whats a phospholipid bilayer

A

where two rows of phospholipids form with the tails pointing inwards and the heads pointing outwards

52
Q

key feature of a phospholipid bilayer

A
  • phospholipids are free to move around in their layer but will not expose their tails - gives some stability
  • the membrane is selectively permeable
53
Q

what is cholesterol

A
  • a steroid alcohol (sterol)
  • consists of 4 carbon-based rings or isoprene units
54
Q

key features of cholesterol

A
  • is small and hydrophobic
  • regulatyes the fluidity of the molecule
  • made in liver of animals (plants have a cholesterol derivative called stigmasterol)
  • the steroid hormones testosterone, oestrogen and vitamin D are all made from cholesterol
55
Q

what are proteins

A
  • large polymers of long chains of amino acids
56
Q

key features of proteins

A
  • form structural components of animals in particular (uscles are made of proteions - actin and myosin)
  • have a tendency to adopt specific shapes
  • membranes have protein constituents that act as carriers and pores for active transport
57
Q

what is the structure of an amino acid

A
  • contains carbon, hydrogen, oxygen and nitrogen (some contain sulfur)
  • there are over 500 different amino acids but only 20 are proteingenic
  • each protein chain of amino acids has an amino group (-NH2) at one end and a carboxyl group (-COOH) at the other
  • the R group is different in each amino acid (20 different types)
58
Q

whats the R group in glycine

A

H

59
Q

whats the only amino acid which contains sulfur

A

cysteine (CH3S)

60
Q

how are amino acids joined

A
  • through a covalent bone called peptide bonds
  • making a peptide bond involves a condensation reactin and breaking one involves a hydrolysis reaction
61
Q

what enzyme breaks down peptide bonds

A

protease enzyme in the intestines (also breaks down protein hormones)

62
Q

whats a dipeptide

A

two amino acids joined together

63
Q

whats the name for joining a long chain of amino acids together

A

polypeptide

64
Q

whats a buffer

A

a substance which helps resist large changed in pH

65
Q

how do amino acids act as buffers

A
  • when dissolved in water, the amino group and carboxyl group can ionise
  • the carboxyl group acts as an acid and the amino group acts as a base inn accepting H+ ions
  • at low pH (lots of H+ ions) the amino acid will accept H+ ions
  • at high pH (few H+ ions) the amino acid will release H+ ions
  • by accepting/releasing H+ ions, amino acids are able to regulate changes in pH (buffering)
66
Q

whats the primary structure of proteins

A
  • the sequence of amino acids in a protein chain
  • the number and order of the amino acids determine the shape of the protein
  • the function of the protein is determined by the structure
67
Q

whats the secondary structure of proteins

A
  • the coiling or folding of an amino acid chain
68
Q

what is an α-helix

A
  • a coil of amino acids - there are 36 amino acids per 10 turns of the helix
  • held together by hydrogen bonds between the -NH group of one amino acid and the -CO group of another 4 places ahead
69
Q

what is an β-pleated sheet

A
  • a zig zag structure where the chain of amino acids folds over onto itself
  • held by hydrogen bonds
70
Q

whats the tertiary structure of proteins

A
  • the overal three-dimensional shape of a protein molecule
  • very precise shape held together by multiple bonds (hydrogen, ionic, disulfide bonds) between amino acids which lie close to each other
  • can adopt a supercoiled shape (in fibrous proteins - e.g. colagen) or a more spherical shape (in globular proteins)
71
Q

whats the quaternary structure of proteins

A
  • how multiple peptide chains are arranged to make a complete protein molecule
  • may be held together by hydrogen, ionic or disulfide bonds
72
Q

what are the bonds that hold together all the different structures of proteins

A
  • primary structure - peptide bonds
  • secondary structure - hydrogen bonds
  • tertiary and quaternary structure - hydrogen, ionic and disulfide bonds
73
Q

what are hydrogen bonds

A
  • form between H+ ion with a slight positive charge and other atoms with a slight negative charge
  • in amino acids form hydroxyl, carboxyl and amino groups
  • can form between polar areas of the R groupds on different amino acids
  • the presence of multiple hydrogen bonds gives a lot of strength
74
Q

what are ionic bonds

A
  • form between a carboxyl and amino groups that are part of R groups (these ionise into NH3+ and COO-)
  • stronger than a hydrogen bond
75
Q

what are disulfid links/bridges

A
  • form between the R groups of 2 cysteines (as cysteine’s R group contains sulfur)
  • are strong covalent bonds
76
Q

what is a fibrous protein

A

regular, repetitive sequences of amino acids and usually insoluble in water

77
Q

key feature of collagen

A
  • is a fibrous protein
  • function is to provide mechanical strength
78
Q

give some examples of what collagen does

A
  • prevents arteries bursting when withstanding high pressure
  • tendons are made from collagen and connect muscle to bones
  • bones are made from collagen and are reinforced with calcium phosphate which makes them hard
  • cartilage and connective tissue are made from collagen
79
Q

key features of keratin

A
  • is a fibrous protein
  • is rich in cysteine (lots of disulfide bridges and hydrogen bonding makes it strong)
  • is found where the body needs a part to be hard and strong (fingernails, hair, scales, fur etc)
  • provides mechanical strength, is an impermeable barrier to infection and is water which prevents entry of water-borne pollutants)
80
Q

key feature of elastin

A
  • is a fibrous protein
  • the cross-linking and coiling makes the structure strong and extensive
  • found in living things where they need to stretch or adapt their shape as a part of life processes (found in skin, the lungs and blood vessels)
81
Q

key features of haemoglobin

A
  • is a globular protein
  • has a quaternary structure made up of 2 α-globin chains and 2 β-globin chains (each has its own tertiary structure)
  • on the outside of each chain there is a space for a haem group (contains an iron ion) to be held
  • carries 4 O2 molecules as each molecule binds to the 4 iron ions
82
Q

key feature of insulin

A
  • is a globular protein
  • made from 2 polypeptide chains
  • soluble in water
  • the A chain begins with a section of α-helix and the B chain ends with a section of β-pleat
  • folds into tertiary structure and joined by disulfide bridges
  • binds to glycoprotein receptors to increase their uptake of glucos from the blood
83
Q

key features of pepsin

A
  • globular protein
  • an enzyme that digests proteins in the stomach
  • made of a single polypeptide chain of 327 amino acids
  • folds into a symmetrical tertiary structure
  • has 4 amoni acids with basic R groups and 43 with acidic R groups
  • held by hydrogen bonds and 2 disulfide bridges
84
Q

what are the two approaches scientists can use to predict tertiary structure

A
  • ab inito protein modelling - model built based on physical and electrical properties of the atoms in each amino acid sequence
  • comparitive protein modelling - protein threading (scans the amino acid sequence against a database of solved structures and produces a set of possible models which would match the sequence
85
Q

carbohydrate test

how to test for starch

A
  • add iodine solution to a sample
  • if starch is present, it will change from yellow-brown to blue-black
  • when dissolved in potassium iodide, the iodine (I2) forms a triiodide ione I3- which causes the colour change

iodine test

86
Q

carbohydrate test

how to test for reducing sugars

A
  • known as reducing sugars because they reucde or give electrons to other molecules
  • if you heat a reducing sugar with Benedict’s solution, it will go blue to green to yellow to orange-red
  • the solution contains Cu2+ ions (which are reduced to Cu+ ions) forming orange-red copper (I) oxide (Cu2O) precipitate
  • the intensity of the red colour is proportional to the concentration of sugar

Benedict’s test

87
Q

carbohydrate test

how to test for non-reducing sugars

A
  • hydrolyse the bond first
  • take a sample for reducing sugars to check there are none in the first place
  • take a seperate sample and boil it with hydrochloric acis to hydrolyse the sucrose into glucose and fructose
  • cool the solution and use sodium hydrogencarbonate solution to neutralise it
  • test for reducing sugars again
  • posititive result (green to yellow to orange to red) indicated the non-reducing sugars were present in the original sample
88
Q

how to test for proteins

A
  • if proteins are present, the colour will change from light blue to lilac
  • colour is formed by a complex between the nitrogen atoms in a peptide chain and Cu2+ ions

the biuret test

89
Q

how to test for lipids

A
  • take a sample and mix it thoroughly with ethanol
  • filter
  • pour solution into water in a clean test tube
  • a cloudy white emulsion indicates the presence of lipids

the emulsion test

biology - module 2 (2 decks)

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