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Biological molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is a monomer

A

smaller units which make up larger molecules

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2
Q

what is a polymer

A

molecules made from a large number of similar monomers joined tg

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3
Q

examples of a monomer

A
  • amino acids
  • monosacharrides
  • nucleotides
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4
Q

examples of a polymer

A
  • starch
  • glycogen
  • cellulose
  • protein
  • DNA/ RNA
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5
Q

condensation reaction

A

joins 2 molecules tg with the formation of a chemical bond

involves elimination of water molecule

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6
Q

hydrolysis

A

breaking of a chemical bond between 2 molecules

with use of water

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7
Q

what elements do carbs contain

A

carbon
hydrogen
oxygen

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8
Q

describe monosacharrides

A
  • single sugars
  • monomers of carbohydrates
  • used in respiration to provide energy + growth
  • include glucose, fructose, galactose
  • all have same formula C₆H₁₂O₆
  • are reducing sugars - positive result in benedicts test
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9
Q

2 types of glucose

A
  • alpha
  • beta
  • know how to draw structures
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10
Q

describe how disaccharides are formed + equations

A

2 monosacharrides joined tg by a glycosidic bond formed in a condensation reaction

monoS + monoS -> disacharide + H20

glucose+glucose -> maltose + H20

glucose + fructose -> sucrose + H20

glucose + galactose -> lactose + H20

C₆H₁₂O₆ + C₆H₁₂O₆ -> C12H22O11 + H20

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11
Q

how can disacharrides by hydrolysed

A
  • heating with acid or by an enzyme
  • hydrolysis equations are backwards to condensation
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12
Q

describe qualitative benedicts test and why its qualitative

A
  • all mono and disacharrides are reducing apart from sucrose

1) place small amnt sample in test tube with same volume of benedicts solution
2) heat to 95°C in water bath
3) brick red= positive result
4) solution BLUE = no reducing sugar

qualitative bc = doesnt allow u to compare results from diff samples

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13
Q

describe semi quantitative benedicts test

A
  • compare conc of reducing sugar in diff samples
  • control variables must be standardised - use same vol of benedicts for each sample, heat for same amnt time at same temp
  • resulting colour used to compare conc of reducing sugar each sample

brick red = high conc reducing sugar
orange = medium conc
green/yellow = low conc
blue = no reducing sugar

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14
Q

problem with semi quantitative benedicts test

A
  • can be subjective = difficult to judge colour
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15
Q

describe quantitative benedicts test

A
  • obtains numerical data to compare conc of reducing sugar in diff samples
  • objective test - not influenced by opinion
  • this is used to find conc of unknown sample
  • perform benedicts test on reducing sugar solutions of known concentrations
  • control variables must be standardised
  • use coloromiter to measure absorbance of each known solution
  • plot graph of known conc against absorbance value
  • repeat benedicts test with unknown sample
  • use absorbance value of unknown to find its conc on graph
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16
Q

test for non reducing sugar (sucrose)

A
  • take small sample and heat in 95°C water bath w benedicts solution to confirm negative result
  • hydrolyse another sample of sucrose by heating in water bath with dilute acid ( HCL)
  • neutralise acid with alkali when cooled
  • add same conc of benedicts solution and heat in water bath
  • positive brick red colour = non- reducing sugar initially present
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17
Q

name the polysacharrides + describe features

A

starch ( α-glucose)
gylcogen ( α-glucose)
cellulose ( β glucose)

these r polymers of glucose joined in condensation reactions
insoluble in water
non-reducing = negative result in benedicts test
can function as either storage or structural molecules

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18
Q

Describe the structure of starch and how it’s suited to its functions

A

Function = storage carbohydrate
found in plants
long, branched chains of α-glucose
linked together by glycosidic bonds
formed in condensation reactions
stored in starch grains in the cytoplasm of plant cells

-large so cannot cross the cell-surface membrane to leave the cell
- insoluble- osmotically inactive (does not draw water into a cell by osmosis which could lead to cell damage)
- helical shape forming a compact store
- branched - glucose easily released for respiration

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19
Q

test for starch

A

2-3 drops iodine
if present = blue/black colour
if not = remains orange

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20
Q

Describe the structure of glycogen and how it’s suited to its functions

A

Function = storage carb in cytoplasm of animal cells
found in mammals
long, branched chains of α-glucose
linked together by glycosidic bonds
formed in condensation reactions

  • insoluble - osmotically inactive
  • large - cant cross cell surface membrane
  • more branches than starch ( can be hydrolysed more rapidly to release glucose for respiration)
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21
Q

Describe the structure of cellulose and how it’s suited to its functions

A

found in cell wall of plants
structural molecule
provides rigidity + shape/strenght to cell
^ prevents cell from bursting
long straight chains of β glucose joined tg by glycosidic bonds in condensation

hydroxyl groups form hydrogen bonds
to produce microfibril structure
which provides strength

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22
Q

what are the types of lipids

A
  • triglycerides
  • phosphlipids
  • made up of carbon, hydrogen + oxygen
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23
Q

what are triglycerides

A

lipids
have 3 fatty acids joined to 1 glycerol molecule
joined in 3 condensation reactions
loses 3 water molecules
forms 3 ester bonds

fatty acid = R- COOH
COOH = carboxylic acid

fatty acids can be saturated ( no double bonds between c atoms) or unsaturated

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24
Q

how can lipids be hydrolysed

A
  • heat with acid
  • use enzyme lipase at optimum temp + pH
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25
Q

describe features of triglycerides

A
  • high proportion of C-H bonds - release 2x energy as carbs during respiration
  • high ratio of H : O atoms = release water when respired (metabolic water) - important for organisms in dry deserts
  • non-polar = insoluble in water = osmotically inactive= good storage compounds
  • reduce water loss in waxy cuticle in plants+ insects
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26
Q

describe what a phospholipid is

A

lipid
1 glycerol + 2 fatty acids
has 1 phosphate group (which replaces a fatty acid)
all joined by condensation reactions
has ester bonds

has polar hydrophilic head ( attracts water)
and non-polar hydrophobic tail ( repels water)

phosphlipids form phospholipid bilayer due to hydrophobic tails repelled from water

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27
Q

test for lipids

A
  • place sample in tube w ethanol
  • shake mixture so fat dissolves
  • add to water in another test tube + mix contents
  • white emulsion of fat droplets = lipid present
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28
Q

compare + contrast triglycerides + phospholipids

A

BOTH :
- insoluble in water
- contain glycerol
- contain ester bonds
- contain C, H, O but phospholipids also contain phosphate group

DIFFERENCES:
- triglyerides = 3 fatty acids
phospholipids= 2 fatty acids + phosphate

  • triglycerides = hydrophobic
    phospholipids = have both hydrophobic + hydrophilic region
29
Q

what is the monomer of proteins

A

amino acids

2 AA = dipeptide
2+ AA = polypeptide

structure amino acid :
NH2 + R group attatched to CHCOOH

30
Q

what elements do proteins contain

A

carbon
hydrogen
oxygen
nitrogen
sometimes sulfur

31
Q

what do all amino acids have

A
  • amine group (NH2)
  • carboxylic acid group (COOH)
  • joined tg by peptide bonds in condensation reactions
32
Q

how are proteins hydrolysed

A

heat w acid
enzyme : protease

33
Q

describe primary structure of a protein

A

sequence of AA in the polypeptide chain - determining specific shape of protein

34
Q

describe secondary structure of a protein

A

folding or coiling of polypeptide chain
as a result of hydrogen bonds between AA

alpha helix
beta pleated sheet

35
Q

describe tertiary structure of a protein

A
  • further folding + coiling of secondary structure due to H bonds, ionic bonds + disulfide bonds forming between AA

specific structure
tertiary structure of enzyme determines shape of active site + its function

36
Q

what are globular proteins

A

soluble
consist of highly folded + coiled polypeptide chain

compac, complex tertiary structure

e.g enzymes/ antibodies

37
Q

describe quaternary structure of a protein

A
  • protein consisting of 1+ polypeptide chain
  • held tg by ionic, hydrogen and sometimes disulfide bonds
38
Q

denaturation of proteins

A

denaturation = alteration in tertiary structure of protein

high temps above optimum, extreme pH cause
H + I bonds to break
(disulfide bonds not broken at same temp as H + I )
so a change in tertiary structure (bonds may form in diff location)
causes non functional protein

39
Q

test for proteins

A
  1. add biuret reagent
  2. purple/lilac colour= protein present
  3. blue = no protein
40
Q

name properties + roles of water in biology

A
  • metabolite in reactions e.g condensation/hydrolysis, photosynthesis, + is metabolic product of respiration - important for organisms in dry areas
  • solvent - used to transport nutrients (glucose in blood , sucrose in phloem) + remove excretory products
  • high heat capacity - absorbs large amnt heat b4 rising in temparature - energy absorbed by H bonds- regulates temp by : minimising temp increase in cells + prevent dangerous fluctuations in aquatic habitats
  • large latent heat of vaporisation - provides cooling effect with little loss of water through evaporation- helps animals maintain constant body temp ( high amnt heat energy removed via sweat) + has cooling effect in plants via transpiration
  • cohesive forces between water molecules due to H bonding support water columns in plants to allow transport (internal support) + also produce surface tension where water meets air , enabling insects to walk on water surface (external support)

-provides buoyancy for aquatic organisms

41
Q

role of sodium ion

A

co- transport of glucose + AA across cell membrane

42
Q

role of iron ion

A

component of Hb which transports Oxygen

43
Q

role of hydrogen ion

A

helps determine pH + affects protein structure + activity

44
Q

role of phosphate ion

A

important as structural component in
DNA, RNA + ATP

45
Q

enzyme

A

biological catalyst
protein

46
Q

enzymes relation to activation energy

A
  • lowers activation energy
  • increasing rate of reaction
  • they do this by forming
    enzyme-substrate complexes
47
Q

activation energy

A

minimum amnt of energy required for a reaction to take place

48
Q

lock and key model

A
  • substrate (molecule) thats complementary in shape to active site binds
  • to form enzyme-substrate complex
  • ## suggests active site shapes fixed + rigid
49
Q

How does a change in amino acid sequence affect enzyme

A
  • tertiary structure of active site changes shape
  • enzyme ineffective
50
Q

why are enzymes effective in small quantities + why can they be used repeatedly

A

never used up/ can be resused
as theyre a catalyst

51
Q

Induced fit model

A
  • this is how Ea is lowered
  • believes active site slightly changes shape

1) presence of substrate causes a slight change in shape of active site
2) active site moulds around substrate so substrate can bind to AS
3) AS + substrate now
complementary in shape
4) so they form an enzyme-substrate complex
5) this lowers activation energy of reactions

52
Q

describe how hydrolysis + condensation reaction affects enzyme-substrate complexes

A

HYDROLYSIS:
- strain on substrate molecule
- distorts bond
- lowers Ea , making it easier to break bond

CONDENSATION:
- pulls molecules close tg
- making them more likely to react
- makes them in the right orientation

53
Q

Factors which affect the rate of enzyme reactions

A
  • susbtrate concentration
  • enzyme concentration
  • temperature
  • pH
54
Q

how does substrate conc affect enzyme reactions

A

increased substrate conc:
- increases rate of reaction
- as collisions between substrate + enzyme are more likely
- rate of reaction levels out as all enzymes AS are occupied by substrate
- so enzyme conc is limiting rate of reactions
- to increase rate of reaction at higher substrate concs u need to add more enzyme

insufficient substrate:
- slower reaction
- due to fewer collisions between enzyme + substrate
- so less enzyme-substrate complexes are formed
- all substrate has been converted to product

55
Q

how does enzyme conc affect enzyme reactions

A
  • when conc of substrates in excess
  • then an increase in enzyme conc increases rate of reaction
  • more enzyme molecules so more AS available
  • increases number of collisions between AS and substrate
  • to form more enzyme-substrate complexes
56
Q

how does temperature affect enzyme reactions

A

low temp:
- rate reations slowed down
-not enough KE for successful collisions between enzyme + substrate to occur

increased temp :
- molecules have more KE
- so more collisions between AS of enzyme + substrate molecules
- more enzyme-substrate complexes formed
- increases rate of reaction up to optimum temp when rates at maximum
- increasing temp above this causes tertiary structure of enzyme to denature as hydrogen + ionic bonds broken
- so rate of reaction decreases as substrate unable to bind to altered active site as its no longer complementary
- less enzyme substrate complexes

57
Q

how does pH affect enzyme reactions

A
  • enzymes have a optimum pH at which the rate of reaction is at its maximum
  • extreme pH can cause denaturation
  • change in pH alters ionic charges of acidic groups
  • Hydrogen + ionic bonds broken , altering tertiary structure of AS so substrate cant bind
58
Q

what are enzyme inhibitors and what types are there

A

slow down rate of enzyme catalysed reactions

  1. competitive inhibitors
  2. Non-competitive inhibitors
59
Q

how do competitive inhibitors work

A
  • have similar structure to complementary substrate molecule
  • so it competes with it to bind to AS
  • decreases rate of reaction as substrate cant bind when inhibitor molecule occupying AS
60
Q

how can competitive inhibition be reduced

A

addition of more substrate
high substrate conc= outcompetes inhibitor molecules for attachment to AS

61
Q

how do Non- competitive inhibitors work

A
  • not similar in structure to substrate
  • binds at a position on enzyme other than the AS , to form enzyme-inhibitor complex
  • altering tertiary structure of enzymes AS
  • so substrate cannot attach to altered AS as no longer complementary
  • no enzyme-substrate complexes formed
    -reduced rate of reaction

A high conc of substrate cant reduce this inhibition

62
Q

what does ATP stand for

A

Adenine Triphosphate

63
Q

what is ATP

A

an immediate energy source for biological processes

64
Q

what does a molecule of ATP consist of

A
  1. ribose
  2. adenine
  3. 3 phosphate groups

ATP is a derivative of a nucleotide

65
Q

how does ATP release energy

A
  1. hydrolysed to release energy
  2. then resynthesised
  3. the hydrolysis of ATP into ADP (adenine diphosphate) and inorganic phosphate group (Pi) is catalysed by enzyme: ATP hydrolase

ATP → ADP + Pi

66
Q

what can the inorganic phosphate group (Pi) released during hydrolysis of ATP, be used for

A
  • to phosphorylate other compounds to make them more reactive

e,g glucose phosphorylated during respiration to form glucose phosphate ( makes glucose more reactive)

67
Q

how is ATP resynthesised

A

condensation of ADP + Pi
this reactions catalysed by enzyme :
ATP synthase
energy released from photosynthesis / respiration enables ATP resynthesis

ADP + Pi → ATP

68
Q

what processes use ATP

A
  • protein synthesis ( translation)
  • axtive transport
  • contraction of muscles
  • cell division
  • synthesis reactions e.g DNA synthesis
69
Q

what term is used to describe the different structures of α-glucose
and β glucose

A

isomerism

BIOLOGY (6 decks)

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