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biology > topic 1A: biological molecules > Flashcards

topic 1A: biological molecules Flashcards

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1
Q

monomers and polymers definition

A

MONOMERS
-smaller molecular units which can create larger molecules (e.g. monosaccharides, amino acids and nucleotides)

POLYMERS
-large, complex molecules composed of long chains of monomers joined together (e.g. polysaccharide, polypeptide and polynucleotide)

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2
Q

condensation and hydrolysis reaction

A

CONDENSATION
-joins two monomers together, with the formation of a chemical bond and involves the elimination of a molecule of water.

HYDROLYSIS
-separates two monomers by breaking a chemical bond and involves the addition of a water molecule.

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3
Q

monsachharides + examples

A

the monomers which form larger carbohydrates e.g. glucose, fructose and galactose

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4
Q

carbohydrates contain the elements…

A

-C (carbon)
-H (hydrogen)
-O (oxygen)

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5
Q

hexose sugar

A

a monosaccharide with six carbon atoms in each molecule e.g glucose

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6
Q

isomers

A

same molecular formula but different structure with atoms arranged in a different ways

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7
Q

draw alpha glucose molecule

A

H
OH

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8
Q

draw beta glucose molecule

A

OH
H

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9
Q

disaccharides + formulas

A

-two monosaccharides join together by a condensation reaction, forming a glycosidic bond (e.g. maltose, lactose and sucrose) releasing a water molecule

FORMULAS
-(2 alpha) glucose + glucose ->maltose + water (glycosidic bond)
-glucose + galactose -> lactose + water
-glucose + fructose -> sucrose + water

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10
Q

polysaccharides + examples

A

polysaccharides are formed when more than 2 monosaccharides join together by a condensation reaction, releasing a water molecule for each glycosidic bond
e.g. starch, glycogen and cellulose

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11
Q

starch function

A

-a main energy store in plant cells

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12
Q

starch structure + formation

A

-made up of a polysaccharides of alpha glucose by a condensation reaction

-coiled structure and branched
-amylose: 1-4 glycosidic bonds so a long, unbranched chain of alpha glucose, the angles of the glycosidic bonds creates a coiled and compact structure

-amylopectin: 1-6 glycosidic bonds so a long, branched chain of alpha glucose, its side branches allows starch to hydrolyse and release glucose rapidly

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13
Q

starch structure related to function

A

-coiled structure - due to the angle of the glycosidic bond, therefore this makes it compact for more storage in cell

-branched chains: can be hydrolysed quickly so that glucose can be released quickly

-insoluble in water: no osmotic effect so this doesnt affect the water potential

-large, insoluble polysaccharide molecule: cant leave cell and cross cell membrane

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14
Q

glycogen function

A

-main energy store in animal cells

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15
Q

glycogen structure

A

-polysaccharides of alpha glucose by a condensation reaction
-1-4 and 1-6 glycosidic bonds loads more side branches coming of it
-very compact molecule

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16
Q

glycogen structure related to function

A

-branched: rapid hydrolysis to release glucose for respiration to make ATP for energy release
-compact: good for storage, so it can store more glycogen in a smaller space
-large, insoluble so cant leave cell or cross cell membrane
-insoluble: no osmotic effect so it doesnt affect water potential

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17
Q

cellulose function

A

provides strength and structural support to plant / algal cell walls

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18
Q

cellulose structure

A

-polysaccharide of beta glucose
-1-4 glycosidic bonds so forms straight cellulose chains
-the long, unbranched cellulose chains are linked in parallel together by hydrogen bonds to form microfibrils (strong fibres) which provide structural support and strength for plant cells

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19
Q

cellulose structure related to function

A

-hydrogen bonds form between chains: forms microfibrils (strong fibres) which create collective strength to the cell wall making it rigid
-straight and unbranched

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20
Q

reducing sugar test + positive result + explain colour changes

A

reducing sugars: monosaccharides, maltose and lactose
1. add benedicts solution (blue) to sample
2. heat in a boiling water bath
3. positive result: green to yellow to orange to red precipitate

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21
Q

test for starch + positive result

A

METHOD
-add iodine in a potassium iodide solution to the test sample

POSITIVE RESULT
-the solution will change from orange to blue/black

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22
Q

non reducing sugar method + positive result

A

non reducing sugars = sucrose

  1. do benedicts test and if it stays blue (negative result) then carry out this test
  2. heat in a boiling water bath with acid to hydrolyse into reducing sugars
  3. neutralise with alkali
  4. heat in a boiling water bath with benedicts solution
  5. positive result: green to yellow to orange to red precipitate
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23
Q

suggest a method to measure the quantity of sugar in a solution

A

-carry out benedicts test as above, then filter and dry precipitate
-find mass

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24
Q

suggest another method to measure the quantity of sugar in a solution

A
  1. Make sugar solutions of known concentrations
    (eg. dilution series)
  2. Heat a set volume of each sample with a set
    volume of Benedict’s solution for the same time
  3. Use colorimeter to measure absorbance (of
    light) of each known concentration
  4. Plot calibration curve - concentration on x axis,
    absorbance on y axis and draw line of best fit
  5. Repeat Benedict’s test with unknown sample and
    measure absorbance
  6. Read off calibration curve to find concentration
    associated with unknown sample’s absorbance
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25
what elements are contain in lipids?
carbon, hydrogen and oxygen
26
structure of triglycecides
-contains one molecule of glycerol with three fatty acids attached to it
27
explain how glycerol is bonded with the three fatty acids
1. molecule of glycerol and a fatty acid bond by a condensation reaction which releases a water molecule and removed (this reaction repeats 3 times) 2. therefore three ester bonds and three molecules of water are released and removed
28
draw the basic structure of a fatty acid (RCOOH)
-variable R-group - hydrocarbon chain (this may be saturated or unsaturated -COOH = carboxyl group.
29
what can fatty acids be?
two type of fatty acids: the R group may be saturated and unsaturated - difference is in their hydrocarbon tails (R group) SATURATED: no double bonds in hydrobarbon chains - all carbons are fully saturated with hydrogen UNSATURATED: one or more c=c double bond in hydrobarbon chains, this causes the chain to kink/ bend
30
structure of phospholipids
-similair to a triglyceride structure -except one of the fatty acid molecules are replaced by a phosphate group, the two fatty acids are joined to the glycerol molecule by a condensation reaction
31
properties of triglycerides related to function
function: energy storage -ENERGY SOURCE: a high ratio of C-H bonds to carbon atoms in hydrocarbon chain, so used in respiration to release more energy than the same mass of carbohydrates INSOLUBLE: Hydrophobic / non-polar fatty acids so insoluble in water (clump together as droplets, tails inwards) So no effect on water potential of cell (or can be used for waterproofing)
32
properties of phospholipids related to function
Function: form a bilayer in cell membrane, allowing diffusion of lipid-soluble (non-polar) or very small substances and restricting movement of water-soluble (polar) or larger substances ● Phosphate heads are hydrophilic ○ Attracted to water so point to water (aqueous environment) either side of membrane ● Fatty acid tails are hydrophobic ○ Repelled by water so point away from water / to interior of membrane
33
test for lipid + positive result
-using emulsion test -add ethanol, then add water -POSITIVE RESULT: clear to white/milky
34
protein
a protein is a polymer made up of the monomer, amino acids
35
4 groups from the structure of an amino acid
-carboxyl group (COOH) -amine group (NH2) -R (variable group- 20 different amino acids) -hydrogen atom
36
describe how amino acids join together
the amino acids join together between the OH of carboxyl group of one and the H of amine group of another by a condensation reaction removing a water molecule, this forms a peptide bond.
37
definition of: dipeptide polypeptide protein
-formed by the condensation of two amino acids -formed by the condensation of many amino acids -1 or more polypeptide chains is a protein
38
primary structure
a specific sequence of amino acids in a polypeptide chain, joined by peptide bonds
39
secondary structure
-hydrogen bonds form between the amino acids this causes the polypeptide chain to be coiled (alpha helix) or folded (beta sheet)
40
tertiary structure and additional bonds
-the tertiary structure is where it is coiled and folded further, which leads to additional bonds forming between different parts of the polypeptide chain -hydrogen bonds, ionic bonds and disulphide bridges -hydrogen bonds: between R groups -disulphide bridges: only occur between cysteine amino acids (if there is a sulfur in R group) -ionic bonds: between charged R groups -tertiary structure creates the final 3D structure for proteins of only one polypeptide chain
41
Quaternary structure
-a Quaternary structure is a protein made up of more than one polypeptide chain (which are bounded together) -the Quaternary structure is the proteins final 3D structure -examples: haemoglobin, insulin collagen
42
test for proteins + positive + negative result
-use the biuret test -(test solution must be alkaline) add biuret reagent sodium hydroxide -then add copper (II) sulfate solution -POSITIVE RESULT: blue to purple/ lilac -NEGATIVE RESULT: no colour change, stays blue
43
relationship between protein structures and function
-the sequence of amino acids is determined by the genetic code, this effects the primary structure -the primary structure determines how the polypeptide is coiled or folded in the secondary structure -the secondary structure determines where bonds form, this affects the whole shape of the protein -the shape of a protein determines its function -altering the primary structure affects the tertiary structure shape, which affects its function
44
protein types
-globular- soluble, R group folded creates 3D shape (e.g. enzymes) -fibrous- insoluble, structural, 3D shape (e.g. collagen + keratin - structural protein)
45
enzymes
enzymes are biological catalysts which speeds up the rate of a chemical reaction by lowering the activation energy without getting used up (a tertiary structure with a specific 3D shape)
46
lock and key theory
-old and outdated model -the substrate is complementary to the enzymes active site, so the substrate binds to it - this forms an enzyme-substrate complex - the enzyme catalyses a reaction to release products - enzyme is unchanged and can be reused
47
induced fit model
-the substrate binds to a not complementary active site of an enzyme, this causes the active site to change shape slightly and to mould itself around the substrate in order to complete the fit -the enzyme is flexible causing bonds in the substrate distort the hydrogen bonds holding the enzyme -this forms an enzyme-substrate complex, the enzyme catalyses a reaction and releases products - the enzyme's active site returns to its original shape
48
enzymes properties relate to their tertiary structure - enzyme specificity
-enzymes are very specific - they only catalyse on reaction as only one substrate is complementary to the active site -the shape of the active site is determined by the tertiary structure which is determined by the primary structure (sequence of amino acids in a polypeptide chain) -if there is a mutation which affects the gene, the primary structure is affected, this changes the way the polypeptide is bonded and folded, and therefore affects the shape of the protein in its tertiary structure which alters the shape of the active site, this means that the substrate will not fit and the reaction wont be catalysed
49
factors affecting enzyme activity
-pH -temperature -enzyme concentration -substrate concentration -competitive inhibitor -non competitive inhibitor
50
temperature affecting enzyme activity
-As temperature increases to optimum, rate of reaction increases -More kinetic energy -So more enzyme-substrate complexes form -As temperature exceeds optimum, rate of reaction decreases -Enzymes denature-tertiary structure and active site change shape ○ As hydrogen/ionic bonds break ○ So active site no longer complementary ○ So fewer enzyme-substrate complexes form
51
pH affecting enzyme activity
-as pH increases/decreases above/below an optimum, rate of reaction decreases -Enzymes denature-tertiary structure and active site change shape -As hydrogen/ionic bonds break -So active site no longer complementary -So fewer enzyme-substrate complexes form
52
substrate concentration affecting enzyme activity
-As substrate concentration increases, rate of reaction increases -Substrate concentration = limiting factor (too few substrate molecules to occupy all active sites) -More enzyme-substrate complexes form -At a certain point, rate of reaction stops increasing/ levels off -Enzyme concentration=limiting factor -as all active sites saturated/occupied (at a given time)
53
enzyme concentration affecting the rate of reaction
-As enzyme concentration increases, rate of reaction increases -Enzyme concentration=limiting factor(excess substrate) -More enzymes so more available active sites -So more enzyme-substrate complexes form -At a certain point, rate of reaction stops increasing/ levels off -Substrate concentration =limiting factor (all substrates in use)
54
competitive inhibitors affecting enzyme activity
-As concentration of competitive inhibitor increases, rate of reaction decreases -competitive inhibitors molecules have a similar shape to the substrate molecule, which means it competes to bind to the active site, they block the active site so no substrate molecules can bind -so fewer enzyme-substrate complexes forms -increasing competitive inhibitors, reduces the effect of inhibitor
55
non competitive inhibitors affecting rate of reaction
- As concentration of non-competitive inhibitor increases, rate of reaction decreases -non competitive inhibitor molecules binds away from the enzyme's active site and binds to the allosteric site, this changes the tertiary structure of the enzyme so the substrate is no longer complementary to the active site of the enzyme and substrates can no longer bind to it -so fewer enzyme-substrate complexes form -increasing the substrate concentration, has no effect to the rate of reaction, as the change to active site is permanent
56
give examples of variables that could affect the rate of an enzyme- controlled reaction
-enzyme concentration / volume -Substrate concentration / volume -Temperature of solution -pH of solution -Inhibitor concentration
57
Describe how temperature can be controlled. (2)
-Use a thermostatically controlled water bath -Monitor using a thermometer at regular intervals and add hot / cold water if temperature fluctuates
58
Describe how pH can be controlled. (2)
-Use a buffer solution -Monitor using a pH meter at regular intervals
59
Why were enzyme & substrate solutions left in water baths for 10 mins before mixing? (1)
-So solutions equilibrate / reach the temperature of the water bath
60
Describe a control experiment. (2)
-Use denatured enzymes (eg. by boiling) -Everything else same as experiment, eg. same conc./ volume of substrate (at start) and enzyme, same type / volume of buffer solution, same temperature
61
Describe how the rate of an enzyme-controlled reaction can be measured
-measure time taken for reaction to reach a set point, eg. concentration / volume / mass / colour of substrate or product -rate of reaction = 1 / time; example units = s-1 -measure concentration / volume / mass / colour of substrate or product at regular intervals (or using a continuous data logger) throughout reaction -plot on a graph with time on the x axis and whatever is being measured on the y axis -draw a tangent at t = 0 (or any other time for rate at a particular point) -Initial rate of reaction = change in y / change in x; example units = cm3 s-1
62
Suggest a safety risk and explain how to reduce this risk. (2)
-Handling enzymes may cause an allergic reaction -Avoid contact with skin by wearing gloves and eye protection
63
Explain why using a colorimeter to measure colour change is better than comparison to colour standards. (2)
-not subjective -more accurate
64
Explain a procedure that could be used to stop each reaction. (1)
-boil / add strong acid / alkali to denature enzyme -put in ice to lower kinetic energy so no enzyme-substrate complexes form -add high concentration of inhibitor so there is no enzyme-substrate complexes formed
65
Explain why the rate of reaction decreases over time throughout each experiment
-initial rate is highest as substrate concentration not limiting / many enzyme-substrate complexes form -reaction slows as substrate used up and often stops as there is no substrate left

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