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ocr a level biology > module 2 - biological molecules > Flashcards

module 2 - biological molecules Flashcards

1
Q

WATER - how does hydrogen bonding occur between water molecules?

A
  • water molecules made up of one O, two H atoms
  • both polar as H atom has partial + charge, O atom has partial charge
    -means O atom attracted to H atoms in neighbouring molecules
    attraction between consequent number of neighbouring water molecules is called hydrogen bonding
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2
Q

what are some properties of water?

A
  • low density solid form (ice)
  • cohesion
  • high latent heat of vaporisation
  • high specific heat capacity
  • good solvent properties
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3
Q

how does a low density solid form of water relate to living organisms?

A
  • this is achieved because crystalline structure of ice allows it to be less dense than the liquid arrangement
  • this means that an insulating layer of ice is provided in cold, aquatic habitats
  • polar bears rely on ice in their habitat in order to live, example
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4
Q

how does cohesion relate to living organisms?

A
  • achieved because the hydrogen bonds between water molecules are attracted to each other and flow together
  • useful for water movement upwards on xylem vessels
  • surface tension is a product of cohesion, some small organisms rely on this to move around on water surfaces
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5
Q

how does a high heat of vaporisation relate to living organisms?

A
  • extra input of energy is required to change the state of water from liquid to gas
  • thermoregulation is a key feature in allowing an organism to cool through water evaporating from the body when produced by sweating or panting
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6
Q

how does high specific heat capacity relate to living organisms?

A
  • extra input of energy is required to increase the temperature of water
  • this allows thermal stability within organisms and also aquatic environments
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7
Q

how do good solvent properties relate to living organisms?

A
  • polar water molecules attract and dissolve other polar molecules and ions
  • this is essential in water transportation of dissolved solutes like in blood or phloem
  • this also allows essential chemical reactions which take place in water
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8
Q

CARBOHYDRATES - describe what is meant by a ‘monomer’

A
  • simplest carbohydrate unit
  • also known as a monosaccharide
  • examples : glucose, ribose
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9
Q

describe what is meant by a ‘polymer’

A
  • long carbohydrate molecule formed of many monomers joined together
  • also known as polysaccharide
  • monosaccharides bond together to form polysaccharides in essential condensation reactions
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10
Q

describe a condensation reaction of carbohydrates

A
  • when two monosaccharides bond together to form a disaccharide, it involves the synthesis (formation) of a glycosidic bond
  • the glycosidic bond forms water as a by-product, hence it is called a condensation reaction
  • involves elimination of a molecule of water
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11
Q

describe a hydrolysis reaction of carbohydrates

A
  • the product of the condensation reaction can be reversed to reform the two monosaccharides
  • this reaction breaks the glycosidic bond that existed in the polysaccharide
  • this reaction involves the intake of water, is therefore called a hydrolysis reaction
  • involves addition of a water molecule
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12
Q

what are the chemical elements that make up carbohydrates? -

A
  • contain only carbon, oxygen, hydrogen atoms
  • store chemical energy in their bonds, this is used up by organisms
  • also have structural and storage functions in addition to providing energy
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13
Q

describe the ring structure and properties of glucose as an example of a hexose monosaccharide

A
  • hexose sugar with 6 carbon atoms
  • formula : C6H12O6
  • has a ring structure and can be formed as two isomers, alpha-glucose and beta-glucose
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14
Q

describe the structure of ribose as an example of a pentose monosaccharide

A
  • pentose sugar with 5 carbon atoms
  • formula : C5H10O5
  • also has a ring structure
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15
Q

how is glycogen structured?

A
  • made up of alpha-glucose monomers
  • consists of 1,4 and 1,6 glycosidic bonds
  • branched molecule
  • helical
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16
Q

what is the function of glycogen and how does its properties suit its function?

A
  • FUNCTION : carbohydrate storage in animals
  • PROPERTIES : insoluble, its branching allows it to be compact, as well as increasing the number of points at which glucose could be released by hydrolysis
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17
Q

how is amylose (starch) structured?

A
  • made up of alpha-glucose monomers
  • consists of 1,4 glycosidic bonds
  • is NOT branched
  • helical
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18
Q

what is the function of amylose and how does its properties allow it to perform its function?

A
  • FUNCTION : carbohydrate storage in plants
  • PROPERTIES : insoluble, its helices allow it to be compact
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19
Q

how is amylopectin (starch) structured?

A
  • made up of alpha-glucose monomers
  • consists of 1,4 and 1,6 glycosidic bonds
  • branched molecule
  • NOT helical
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20
Q

what is the function of amylopectin and how does its properties allow it to perform its function?

A
  • FUNCTION : carbohydrate storage in plants
  • PROPERTIES : branching increases the number of points at which glucose could be released by hydrolysis
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21
Q

how is cellulose structured?

A
  • made up of beta-glucose monomers
  • consists of 1,4 glycosidic bonds
  • is NOT branched
  • is NOT helical
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22
Q

what is the function of cellulose and how does its properties allow it to perform its function?

A
  • FUNCTION : structural strength in plant cell walls
  • PROPERTIES : insoluble, cross-links of hydrogen bonds between chains make it structurally strong
23
Q

LIPIDS - what are lipids and what are their general properties?

A
  • lipids are made up of carbon, oxygen and hydrogen atoms just like carbohydrates
  • however, they are non-polar, mostly insoluble in water
  • also vary in structure a lot depending on the lipid
24
Q

describe the structure, properties of triglycerides and how they relate to their roles in living organisms

A
  • STRUCTURE : has an ester bond attaching a glycerol molecule and three fatty acids together
  • PROPERTIES : compact and insoluble
  • ROLES : energy storage and insulation
25
Q

describe the structure, properties of phospholipids and how they relate to their roles in living organisms

A
  • STRUCTURE : a hydrophilic head consisting of a phosphate and glycerol and a hydrophobic tail consisting of fatty acids
  • PROPERTIES : hydrophilic head and hydrophobic tail
  • ROLES : key component of membrane structure
26
Q

describe the structure, properties of cholesterol and how they relate to their roles in living organisms

A
  • STRUCTURE : hydrophilic portion consisting of a hydroxyl group and then main body which is hydrophobic
  • PROPERTIES : small, has both hydrophilic and hydrophobic portions
  • ROLES : useful in membrane stability and steroid hormones
27
Q

describe the synthesis and breakdown of triglycerides by the formation of ester bonds

A
  • glycerol + 3 fatty acids —> triglyceride + 3 water molecules
  • is a condensation reaction in the forward direction, a hydrolysis reaction in the reverse direction
  • condensation reaction for each fatty acid takes place with one of OH groups in glycerol —> forms an ester bond
28
Q

PROTEINS - describe the general structure of an amino acid

A
  • central carbon atom
  • an amine group
  • a carboxyl group
  • a hydrogen atom
  • an R group —> this is different for each of the 20 amino acids found in organisms
29
Q

how is a dipeptide synthesised and broken down by the formation & breakage of peptide bonds?

A
  • peptide bond formed between two amino acids results in a dipeptide
  • amino acid monomers which join together are another example of condensation reactions
  • therefore, breaking peptide bonds results in a hydrolysis reaction
30
Q

how is a polypeptide synthesised and broken down by the formation and breakage of peptide bonds?

A
  • polypeptide is the result of many amino acids bonded together
  • generally formed during translation by ribosomes
  • not to be confused with a protein, which is more complex than a polypeptide and more than a linear chain of amino acids
31
Q

describe the primary structure of a protein

A
  • sequence of amino acids that make up its polypeptide chains
  • polypeptide is produced during translation
32
Q

describe the secondary structure of a protein

A
  • refers to specific 3D shape that the protein takes due to hydrogen bonding between the amino acids
  • this is where specific and complex shapes which make up a protein are formed due to certain bonds
  • hydrogen bonds, produces an alpha-helix coiled shape or a beta-pleated folded sheet
33
Q

describe the tertiary structure of a protein

A
  • is the 3D arrangement of the entire polypeptide chain of a protein, including all its secondary structures
  • is where specific and complex shapes which make up a protein are formed due to certain bonds and interactions
  • hydrogen bonds & ionic bonds
  • disulfide bridges may be formed
  • hydrophobic interactions may take place
  • produces very specific 3D shape
34
Q

describe the quaternary structure of a protein

A
  • refers to the arrangement of multiple polypeptide chains, or subunits, in a protein complex
  • is when two or more polypeptides subunits make up a protein
  • can also consist of prosthetic groups
35
Q

what is a prosthetic group?

A
  • is when a non-protein component is part of the structure of a conjugated globular protein
  • not all globular proteins are conjugated
  • the non-protein component could be : lipids, carbohydrates, metal ions, molecules derived from vitamins
36
Q

describe the structure and function of globular proteins

A
  • STRUCTURE : shape - compact and spherical
  • bonding and structure : on outside - hydrophilic R groups, on inside - hydrophobic R groups
  • water solubility : soluble
  • conjugation : sometimes conjugated forms with presence of a prosthetic group
    -FUNCTIONS : enzymes, hormones, membrane proteins, antibodies, transport proteins, antibodies, transport proteins ( like catalase, insulin and haemoglobin)
37
Q

describe the structure and function of fibrous proteins

A
  • STRUCTURE : shape - long and linear
  • bonding and structure : often a repeated sequence of a a limited number of amino acids, organised and strong
  • water solubility : insoluble
  • conjugation : no conjugated forms
  • FUNCTIONS : structural roles ( like keratin or collagen )
38
Q

describe the structure and function of haemoglobin

A
  • water soluble globular protein which consists of two alpha and two beta polypeptide chains, each containing a haem group
  • carries oxygen in the blood as oxygen can bind to the haem (Fe2+) group and oxygen is then released as required
39
Q

describe the properties and functions of collagen

A
  • fibrous protein of great strength due to presence of both hydrogen and covalent bonds
  • molecules wrap around each other, form fibrils which form strong collagen fibres
  • forms structure of bones, cartilage and connective tissue
  • main component of tendons which connect muscles to bones
40
Q

describe the properties and functions of keratin and elastin

A
  • KERATIN : contains high amounts of cysteine, resulting in disulphide links forming between 2 polypeptide chains —> makes molecules hard and strong
  • found in fingernails, hooves and horns
  • ELASTIN : has ability to stretch and recoil, coiling of elastin molecules and cross links keep molecules together
  • found in lungs, bladder and blood vessel walls
41
Q

INORGANIC IONS - where do they occur?

A
  • occur in solution in the cytoplasm and body fluid of organisms, some in high concentrations and others in very low concentrations
42
Q

how are H+ (hydrogen) ions useful in the body?

A
  • determine PH of bodily fluids
  • higher the concentration, lower the PH
43
Q

how are Na2+ (sodium) ions useful in the body?

A
  • used in co-transport of glucose and amino acids across cell membranes , transmission of nerve impulses
44
Q

how are PO43- (phosphate) ions useful in the body?

A
  • essential components of DNA, RNA, nucleotides, ATP
45
Q

how are Ca2+ (calcium) ions useful in the body?

A
  • regulate protein channels, impulse transmission & harden body parts like teeth
46
Q

how are K+ (potassium) ions useful in the body?

A
  • plays a role in muscle contraction, nervous transmission, active transport, maintaining turgidity in plant cells
47
Q

how are NH4+ and NO3- (ammonium and nitrate) ions useful in the body?

A
  • part of nitrogen cycle, source of nitrogen for biological molecules
  • provide nitrogen for plants
48
Q

how are HCO3- (hydogencarbonate) ions useful in the body?

A
  • formed when CO2 dissolves in blood
  • important in transport of CO2 in blood, regulation of blood pH
49
Q

BIOCHEMICAL TESTS - what is benedict’s test testing for, how is it done and how are results interpreted?

A
  • reducing, non-reducing sugars
  • alkaline solution of blue copper sulphate added, solution heated
  • presence of reducing sugar : red copper oxide precipitate formed
  • absence of reducing sugar : benedict’s reagent doesn’t change colour
50
Q

what is biuret test testing for, how is it done and how are results interpreted?

A
  • proteins
    -sample of solution placed in test tube, equal amount of NaOH added , few drops of dilute copper sulphate solution added, gently mixed
  • presence of protein : solution turns lilac/indicator of peptide bonds
  • absence of protein : solution remains blue
51
Q

what is emulsion test testing for, how is it done and how are results interpreted?

A
  • lipids
  • 2ml of sample added to 5ml of ethanol, contents mixed thoroughly by shaking to ensure lipids dissolved
  • add 5ml of water & mix, solution turns cloudy indicating presence of lipid due to formation of an emulsion
52
Q

what is iodine testing for, how is it done and how are results interpreted?

A
  • starch
  • in presence of starch, colour of potassium iodide solution goes from yellow to to black/blue
53
Q

how can colorimetry be used to determine the concentration of a chemical substance in a solution?

A
  • technique used to find the concentration of a solution
  • intensity of light absorbed by a sample with an unknown concentration is measured, then compared to the absorbances for known concentrations of the same substance, using a calibration curve

ocr a level biology (7 decks)

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