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Biology HL > Biological molecules (CQC) > Flashcards

Biological molecules (CQC) Flashcards

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1
Q

what does the adhesive nature of water allow?

A

it is used too carry mineral ions- this is especially useful in transpiration due to the capillary action for continuous transpirational pull, as water molecules stick together, this allows for mineral ions to enter the plant as well. This adhesive nature of water also helps for evaporation; when water evaporates the adhesive property causes water to be drawn out of the nearest xylem vessel to replace it, keeping cell walls moist allowing CO2 absorption for photosynthesis

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2
Q

what does the cohesive nature (binds with other water molecules) of water allow?

A

this is caused by hydrogen bonding between water molecules. this leads to a high surface tension, benefiting aquatic animals as it means the water can support them without the surface tension breaking (providing a habitat).

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3
Q

what does the high specific heat capacity of water allow?

A

this means the temperature remains stable providing a thermally stable environment as lots of energy is needed to break the hydrogen bonds to cause small increases in temperature

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4
Q

what does the high boiling point of water allow?

A

remains liquid from 0-100 degrees celsius, so has a high availability for organisms

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5
Q

what does the high latent heat of evaporation in water allow for?

A

large amounts of energy are needed to evaporate water (by breaking the hydrogen bonds between molecules) meaning it has a cooling effect (sweat)

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6
Q

why can water act as a solvent and what is this useful for?

A

due to the polarity of water it acts as a medium for metabolic reactions and allow transport of polar substances such as soluble glucose molecules in blood plasma

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7
Q

What does the buoyant nature of water allow?

A

the density of living organisms is close to the density of water, so they float, therefore, requiring less energy to stay afloat

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8
Q

why does water have a high viscosity?

A

pure water has a higher velocity than organic solvents as hydrogen bonds cause internal friction . if there are solutes this increases further

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9
Q

why is the transparency of water useful?

A

this allows for photosynthesis for underwater plants and vision for animals

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10
Q

why can glucose and amino acids dissolve in water?

A

glucose and amino acids can dissolve in water as they are polar molecules which dissolve in water. some have charged side groups (R) which enhance their solubility in water

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11
Q

hydrophilic vs hydrophobic.

A
  • polar molecules that dissolve in water are hydrophilic
  • non-polar molecules that do not dissolve in water are hydrophobic; when non polar molecules are added to water they join (clump) together and form larger groups
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12
Q

why is the polar nature of water useful?

A

it forms shells around polar and charged molecules so it can act as a solvent, this is important in organisms as most enzymes catalyse chemical reactions in water and many hydrophilic substances can dissolve in water to be transported
when water forms hydrogen bonds with polar molecules negatively and positively charged ions dissolve as the partially negative pole of the water is attracted to the positively charged ions and the positive pole is attracted to the negatively charged ions

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13
Q

monosaccharides, disaccharides

A

carbohydrate monomers are called saccharides (a sugar)
- Monosaccharides: General formulae (CH2O)n (where n= 3-7)
- Disaccharides: pairs of monosaccharides joined by glycosidic bonds (covalent)- they are strong and so require enzymes to break them (e.g. amylase, maltase, sucrase)

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14
Q

Polysaccharides

A

polysaccharides are polymers formed of many monosaccharide molecules. these are formed together by glycosidic bonds formed when a condensation reaction occurs between the monomers.
they are very large molecules that are insoluble. this makes them suitable for storage or support for plants (such as cellulose)

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15
Q

Glycoproteins (polysaccharides)

A

glycoproteins are composed of polypeptides with carbohydrate attached. in most cases, the carbohydrate is an oligosaccharide (a short chain of monosaccharides linked by glycosidic bonds.)

Glycoproteins are a component of plasma (cell) membranes in animal cells and are positioned with the attached carbohydrate facing outwards. By displaying distinctive glycoproteins, cells allow other cells to recognise them. the glycoprotein on the surface of one cell is recognised by receptors on the surface of another cell.

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16
Q

ABO proteins (polysaccharides)

A
  • red blood cells have glycoproteins in their membranes that do not have a known function, but that affect blood transfusion. any of three possible types of oligosaccharide can be present on the glycoprotein. the oligosaccharides are O, A and B. one or two of these types of glycoproteins are present in every persons blood, but not all three.
  • if blood containing glycoprotein A is transfused into a person who does not produce it themselves, the blood will be rejected. Similarly blood containing glycoprotein B is rejected if a person does not produce it themself. However, glycoprotein O does not cause rejection problems, because it has the same structure as A and B with one monosaccharide less, so it is not recognised as foreign
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17
Q

how are monosaccharides joined?

A

when two monosaccharides join by a glycosidic bond. this is an anabolic process which requires energy in the form of ATP. when two monosaccharides join together this is called a condensation reaction, this is because water is formed as a by-product

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18
Q

monomers and polymers

A

many organic molecules are made up of individual molecules called monomers. the Caron atoms of these monomers readily form bonds with other carbon atoms to form longer chains of repeating monomer units called polymers. carbohydrates and proteins are made up of polymers
in carbohydrates the monomer is a sugar called a saccharide. a single monomer is called a monosaccharide.

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19
Q

carbohydrate general formula

A

CnH2nOn

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20
Q

properties of monosaccharides

A
  • they are soluble; this means they easily dissolve in plasma and so are easily transported
  • they are stable; this means they can be used for food storage (e.g. glycogen, starch)
  • yields energy when oxidised: this means it is used as a substrate for respiration
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21
Q

how are disaccharides separated?

A

when water is added to a disaccharide it will break the glycosidic bond and release the monosaccharides. this is called hydrolysis

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22
Q

Starch

A

Found in: plants only
Monomer: α-glucose
Structure: chains of α-glucose molecules linked by glycosidic bonds between -OH group on carbon 1 and carbon 4 of adjacent glucose in condensation reactions. wound into tight coils. Unbranched.
Function: energy storage

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23
Q

Glycogen

A

Found in: animals and some fungi
Monomer: α-glucose
Structure: chains of α-glucose molecules linked by glycosidic bonds in condensation reactions. shorter chains and more branched
Function: energy storage

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24
Q

Cellulose

A

Found in: plants only; major component of cell walls
Monomer: β-glucose
Structure: unbranched straight chain of β-glucose molecules.
Function: energy storage and rigidity

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25
Q

Lipids

A
  • contain carbon, hydrogen and oxygen
  • insoluble in water
  • are soluble in organic solvents
  • main groups are called triglycerides
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26
Q

Uses of lipids

A
  • Insulation- slow conductors of heat (thermal insulators)
  • Waterproofing- Insoluble in water and hydrophobic e.g. oils from glands in skin
  • Protection- stored around organs as shock absorbers
  • Energy source- release energy when oxidised (twice as much energy per gram compared to carbohydrates)
  • Plasma membranes- flexible and allow substances across
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27
Q

forming triglycerides

A
  • When triglycerides form from fatty acids and glycerol it is a condensation reaction as water is formed as a by-product
  • when triglycerides are broken down using water it is a Hydrolysis reaction
  • they are made up of three fatty acids and glycerol. ester bonds form between the fatty acids and glycerol
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28
Q

Saturated and unsaturated lipids

A

Saturated- no carbon-carbon double bonds between the carbon atoms in the fatty acid chain

Mono-unsaturated- one double bond between carbon atoms in the fatty acid chain

Poly-unsaturated- more than one double bond between carbon atoms in the fatty acid chain

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29
Q

Cis vs Trans fatty acids

A

Trans- hydrogens on opposite sides of the two carbon atoms that are bonded. They do not bend at the double bond and so have a high melting point (produced by hydrogenation of oils). they are solid at room temperature

Cis- hydrogens on the same sides of the two carbon atoms that are double bonded- they do bend at the double bond and so have a lower melting point. they are liquid at room temperature

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30
Q

Coronary heart disease and lipids

A
  • what risks are there for CHD
    - Can cause atherosclerosis (narrowing of (lumen of) arteries)
    - CHD/ formation of clots/heart attack/heart failure/ thrombosis/stroke
    - hypertension (high blood pressure) obesity/overweight
    - which is linked to diabetes
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31
Q

What things are made out of proteins?

A
  • hormones
  • antibodies
  • enzymes
  • receptors for hormones
  • muscle tissue
  • channels in cell membranes
  • catalysts
32
Q

Amino Acids

A

NH2-CHR-COOH
1. NH2- amine group
2. CHR- central carbon atom with a hydrogen bond and an R-group
3. COOH- carboxyl group

33
Q

What are proteins?

A

Proteins are large polymers made up of the monomers amino acids. these contain the elements carbon, hydrogen, oxygen, nitrogen and sometimes sulphur. The NH2 represents an amine group, COOH represents a carboxyl group and the R represents a carbon containing side chain, which can contain sulphur and is used in bonding. the twenty amino acid groups that are common in all organisms differ only in their R groups. these join together to make long chain polymers called polypeptides.

34
Q

Types of R groups

A

The type of R group determines the properties of the proteins. They can be:

  • Hydrophilic or Hydrophobic. Hydrophilic R groups can be polar or charged, acidic or basic
35
Q

Dipeptides

A

two amino acid monomers can join together to form a dipeptide. the process involves a condensation reaction whereby a water molecule is removed. the water is made by combining an OH from the carboxyl group and one amino acid with an H from the amino group of the other amino acid. A new peptide bond is formed which links the two.

this bond can be broken by Hydrolysis to form two amino acids again. Polypeptides are formed by condensation of many amino acids

36
Q

Protein Structure

A

Primary structure: the specific sequence and number of the amino acids in the polypeptide chain

Secondary structure: formed when the long chain of polypeptides fold into a 3D shape (e.g. alpha-helix or beta pleated sheet).

tertiary structure: the alpha-helices fold to give specific 3D tertiary structures

quaternary structure: when more than one tertiary polypeptide chains link

37
Q

What would happen if the amino acid sequence changed?

A

The primary structure would change, leading to a different secondary and tertiary structure and different folding and bonding. therefore the protein will be a different shape and so may no longer function.

38
Q

how does temperature affect the shape of a protein?

A

denaturation; causes h-bonds/ionic bonds/disulphide bonds to break; therefore the polypeptide chain forms in a different way

39
Q

what are the bonds present in proteins?

A
  • hydrogen bonds
  • disulphide bonds
  • ionic bonds
40
Q

how does pH affect the shape of the protein?

A

denaturation; pH mainly affects ionic bonds, causing them to break, therefore the polypeptide chain folds in a different way.

41
Q

Amino acid polarity

A

Amino acids may be polar or non polar depending the on the side chain. polar amino acids have hydrophilic R groups whereas non polar amino acids have hydrophobic R groups. (non polar amino acids tend to be found in the centre of a structure and are used to stabilise the structure. Polar amino acids tend to be located on the proteins surface)- for water soluble proteins.
The active site of an enzyme depends on the location and distribution of polar and non polar amino acids as hydrophobic and hydrophilic interactions can play a role in substrate binding to active site.

42
Q

Globular proteins

A

they have a tertiary structure and a rounded shape. they mainly have metabolic functions (catalysts) or transport.
they are mostly soluble in water.
they are sensitive to temperature and pH changes.
e.g. haemoglobin, myoglobin, insulin and catalyses

43
Q

Fibrous proteins

A

they have a secondary structure and are strands- long and narrow shape. they mainly have support/ structural functions. they are mostly insoluble.
they aren’t very sensitive to temperature and pH changes
e.g. collagen, myosin, keratin and spider silk

44
Q

function of cellulose

A

important component of the primary cell wall of green plants

45
Q

function of actin

A

forms microfilaments in the cytoskeleton and the thin filaments in muscle fibrils

46
Q

function of spider silk

A

used to contain prey/ as a cocoon to protect offspring

47
Q

function of albumin

A

binds water, cations, fatty acids, bilrubin, thyroxine and pharmaceuticals

48
Q

function of collagen

A

responsible for healthy joints and skin elasticity

49
Q

function of insulin

A

the main anabolic hormone in the body, reduces glucose levels

50
Q

function of immunoglobins

A

aids in the immune system: it helps neutralise antibodies. Agglutination: antibodies glue together foreign cells for phagocytes

51
Q

function of keratin

A

fibrous protein; key structural material making up scales, hair, nails, feathers, horns claws, hooves and the outer layer of skin among vertibrates

52
Q

function of rhodopsin

A

located in the retina; converts light into electrical signals

53
Q

Conjugated proteins

A

not only composed of amino acids. formed by binding some non protein substance covalent bonds with amino acids —> the bond between the conjugated protein is not very strong. such proteins are bound by covalent bonds. it contains an amino acid part combined with a non protein like lipid/ carb

54
Q

Non conjugated proteins

A

only consist of one polypeptide chain and link tertiary structures such as collagen and insulin

55
Q

how has cryogenic microscopy increased our knowledge of protein structure?

A

They pass a beam of electrons through a specimen—> electrons will be absorbed by the denser parts of the sample, and scattered in the less dense parts—> this forms a detailed image due to the electrons having a shorter wavelength than light.

56
Q

Enzymes

A
  • they are globular proteins (specific tertiary shape)
  • they act as natural catalysts; speed up a wide range of intra and extracellular reactions
  • they provide an alternate reaction pathway that requires a lower activation energy (allowing for faster reactions at lower temperatures)
    • this is needed to ensure that metabolic processes (e.g. respiration/ digestion) happen fast enough to sustain life
57
Q

Metabolism

A

all the enzyme catalysed reactions in a living organism (anabolism+catabolism)

58
Q

Anabolism

A

the synthesis of larger molecules from small molecules by condensation reactions (e.g. protein synthesis)

59
Q

Catabolism

A

the hydrolysis of larger molecules into smaller molecules (e.g. digestion)

60
Q

activation energy

A

the minimum energy required to start a reaction

61
Q

enzyme specificity

A
  • the substrate molecule fits into the enzymes active site to produce an enzyme substrate complex
  • the bond breaks and two smaller product molecules are formed
  • the enzyme remains unchanged and is free to catalyse another reaction
62
Q

the breaking down of maltose

A
  • enzymes have active sites which have a specific shape
  • in this reaction the active site of the maltase enzyme is specific to the substrate maltose
  • the maltose binds to the enzymes active site creating an enzyme substrate complex
  • this allows the reaction to occur
  • at the end of the reaction, the product is released
63
Q

why are enzymes specific to their substrate?

A
  • the active site has a specific shape due to tertiary structure
  • the substrate is complementary on shape for active site
  • binds to form an E-S complex
64
Q

Models of enzyme action; the lock and key hypothesis

A
  • the active site has a specific chemical structure
  • the active sites shape is complementary in shape to the enzymes substrate
65
Q

models of enzyme action: the induced fit model

A
  • substrate binds to the active site
  • shape of active site changes to accommodate the substrate and improves the fit of the enzyme and substrate. the substrate also changes shape
  • the enzyme changes from inactive to active form
66
Q

what are the advantages of the induced fit model

A

the induced fit model allows for a broad specificity of some enzymes (permits some enzymes to bind to several substrates) e.g. proteases

67
Q

factors affecting enzyme activity: temperature

A

high KE means that the particles will move more. this increases the chance of successful collisions between the enzyme and the substrate, allowing enzyme substrate complexes to form. Increasing RoR. However after the optimum temperature is reached and the temperature still rises, the bonds begin to break and the enzyme active site changes shape (denatures)- RoR will slow down as less enzyme/substrate complexes will form

68
Q

factors affecting enzyme activity: pH

A

pH is a measure of hydrogen ion concentration, with each enzyme having an optimum pH at which they work. a change in pH alters the charges on the amino acids that make up the active site of the enzyme. The pH therefore interferes with the hydrogen (and ionic bonds between R groups). changing the bonding, changing the folding and so changes the tertiary structure and so the specific shape of the active site. therefore substrate and active site are no longer complementary in shape and so cannot form E/S complexes. the shape of the active site is altered.

69
Q

factors affecting enzyme activity: concentration of enzyme

A

if you increase the concentration of enzyme, when there is a limited amount of substrate, this has no effect as there is already enough active sites for all the molecules (substrate is the limiting factor)

70
Q

factors affecting enzyme activity: concentration of substrate

A

the substrate concentration will increase until Vmax when the rate of reaction is at its maximum as the enzyme will become the limiting factor

71
Q

Enzyme inhibition

A

Enzyme inhibitors are those that directly or indirectly interfere with the functioning of the active site of an enzyme and so reduce its activity. Most inhibitors make temporary attachments to the active site and are therefore called reversible inhibitors.

72
Q

competitive inhibition

A

the inhibitor binds directly to the active site; directly blocking the active site

73
Q

non-competitive inhibition

A

the inhibitor binds to the allosteric site, preventing the reaction, even if enzyme substrate complexes are formed

74
Q

Statins and enzyme inhibition

A

Statins are a drug used to treat high blood pressure.

  • Competitive inhibition of HMG-CoA reductase
  • as it is a similar shape to the HMG-CoA substrate, so it binds to the enzymes active site instead
  • less cholesterol is produced in the body
75
Q

End product inhibition (reversible reaction)

A
  1. metabolic pathway is a series of enzyme catalysed reactions
  2. allosteric enzyme catalyses first step in the chain of reactions
  3. enzyme is inhibited by the end product
  4. end product binds at the allosteric site (non competitive inhibition)
  5. end product formation stops
  6. more inhibition of enzyme as end product concentration rises/ less inhibition as end product reduces
  7. negative feedback so can be reversed
76
Q

Mechanism based inhibition

A
  • mechanism based inhibition is irreversible.
  • the inhibition becomes permanently attached to the active site via covalent bond.
  • forms enzyme inhibitor complex
77
Q

Immobilised enzymes

A
  • enzymes that aren’t mobile
  • more efficient as can be used again as they don’t become part of the reaction mixture

Biology HL (10 decks)

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