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biological molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are monosaccharides?

A

the monomers from which larger carbohydrates are made

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2
Q

what are isomers

A

same molecular formula but atoms are arranged differently

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3
Q

what is the general formula for a monosaccharide

A

CnH2nOn

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4
Q

what are the common monosaccharides

A

glucose, galactose and fructose

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5
Q

how are disaccharides formed

A

by the condensation of two monosaccharides, joined by a glycosidic bond

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6
Q

what is a condensation reaction

A

involves the joining of 2 molecules together with the formation of a chemical bond and it involves the removal of a water molecule

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7
Q

what are the common disaccharides

A

maltose, sucrose and lactose

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8
Q

how is maltose formed

A

2 glucose molecules

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9
Q

how is sucrose formed

A

one alpha-glucose and one fructose molecule

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10
Q

how is lactose formed

A

one alpha-glucose and one galactose molecule

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11
Q

what is a hydrolysis reaction

A

reaction that breaks a chemical bond between two molecules and involves the use of a water molecule

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12
Q

what is a glycosidic bond

A

two monosaccharides bonded together as a result of a condensation reaction

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13
Q

what are polysaccharides

A

polymers formed by combining together many monosaccharides molecules. the monosaccharides are joined by glycosidic bonds that were formed during a condensation reaction

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14
Q

what are the three examples of polysaccharides

A

starch, cellulose and glycogen

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15
Q

what is the structure of starch

A

-polysaccharide of alpha-glucose
1. amylose, 1-4 glycosidic bonds- unbranched
2. amylopectin, 1-4 and 1-6 glycosidic bonds- branched

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16
Q

how is the structure of starch suited for energy storage (amylose)

A

-insoluble, so doesn’t effect water potential. water isn’t drawn into the cell by osmosis
-large and insoluble so doesn’t diffuse out of cells
-helical which makes it compact allowing it to be stored in small spaces

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17
Q

what is the structure of glycogen

A

-polysaccharide of alpha glucose monosaccharides
-1-4 and 1-6 glycosidic bonds- highly branched

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18
Q

explain how the structure of amylopectin and glycogen is related to their function

A

-insoluble in water, so doesn’t draw water into cells by osmosis
-large, insoluble polysaccharide so doesn’t diffuse out of cells
-compact so stored in small places
-highly branched so has more ends that can be hydrolysed by enzymes, more rapidly broken down into glucose monomers which are used in respiration to make ATP

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19
Q

what is the structure and function of cellulose

A

-polysaccharide of beta glucose
-1-4 glycosidic bonds, long straight unbranched chains
-walls linked in parallel by hydrogen bonds, forming microfibrils
provides strength and support to plant and algae cell walls

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20
Q

how is the structure of cellulose related to its function

A

-every other β-glucose molecule is inverted in a long, straight, unbranched chain
-many hydrogen bonds link parallel strands (crosslinks) to form microfibrils (strong fibres)
-hydrogen bonds are strong in high numbers, so provides strength to plant cell walls

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21
Q

what is the test for reducing sugars in carbohydrates

A

benedict’s test
1.grind sample with water and put the mixture into the test tube
2.add the same volume of benedict’s reagent (2cm3 of food sample, 2cm3 BR)
3.put tube in a water bath and heat for 5 minutes
4.if carbohydrates are present, solution will turn from blue to orange/brown

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22
Q

what is the test for non reducing sugars

A

1.carry out benedict’s test, solution should remain blue
2.grind sample with water, put into test tube
3.add same volume of dilute hydrochloric acid
4.place test tube in boiling water for 5 minutes, this hydrolyses any disaccharides present into monosaccharides
5.reduce acidity to retest monosaccharides- slowly add hydrogen carbonate solution and test with pH paper to check solution
6.retest by heating solution with benedict’s solution in water bath for 5 minutes
7.if non reducing sugar is present in the original sample, solution turns orange/brown

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23
Q

what is the test for starch

A

iodine test
1.add a food sample to a test tube (2cm3)
2.add two drops of yellow iodine solution to the test tube then shake or stir the mixture
3.positive result= blue, black colour

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24
Q

what are fatty acids made up of

A

hydrocarbon chain that is attached to a carboxyl group

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25
Q

what are the roles of lipids

A
  1. source of energy
  2. waterproofing- lipids are insoluble in water (mammals produce an oily secretion and plants + insects have waxy, lipid cuticles that conserve water
  3. insulation- fats are slow conductors of heat
  4. protection- fats stored around delicate organs
26
Q

what are triglycerides made up of

A

3 fatty acids combined with one glycerol molecule

27
Q

how is an ester bond formed

A

formed from the condensation reaction between glycerol and a fatty acid

28
Q

what are the different types of fatty acids

A
  1. saturated
  2. mono-unsaturated
  3. polyunsaturated
29
Q

what is a saturated fatty acid

A

no double bonds between their carbon atoms
- all carbon atoms are linked to max possible number of hydrogen atoms

30
Q

what is a mono-unsaturated fatty acid

A

one double bond between carbon atoms

31
Q

what is a polyunsaturated fatty acid

A

more than one double bond between carbon atom, cannot pack together so closely, making them liquid at room temperature e.g. oils
- double bonds cause the chain to bend

32
Q

what are the properties of triglycerides

A

-large because of the long hydrocarbon chains of their 3 fatty acids
-non polar because their non polar region is much larger than its polar region. this makes triglycerides insoluble in water, as a result their storage does not affect osmosis in cells or the water potential of them

33
Q

what are the functions of triglycerides

A

-high ratio of energy storing carbon-hydrogen bonds to carbon atoms in hydrocarbon chain, so used in respiration to release more energy
-triglycerides have low mass to energy ratio, making them good storage molecules because much energy can be stored in a small volume. this is beneficial to animals as it reduces the mass that they have to carry around
-high ratio of hydrogen to oxygen atoms, triglycerides release water when oxidised and therefore provide an important source of water, especially for organisms living in dry deserts

34
Q

what is the structure of a phospholipid

A

2 fatty acids attached to one molecule of glycerol through ester bonds
-instead of a third fatty acid there is instead a phosphate group

35
Q

what are the properties of phospholipids

A

the phospholipid is made up of 2 parts
-hydrophilic head, which interacts with water but not fat. this is the polar end of the molecule and it attracts water
-hydrophobic tail, which orients itself away from water but mixes readily with fat. this is the non polar end of the molecule and it repels water.
polar molecules- when placed in water, they position themselves so that he hydrophilic heads are close to the water and the hydrophobic tails are as far away from the water as possible

36
Q

what are the functions of phospholipids

A

-in an aqueous environment, phospholipid molecules form a bilayer within cell surface membranes. the bilayer separate spaces into an inside and outside space, and as a result they control the movement of molecules.
-hydrophilic phosphate head of the phospholipid molecules help to hold at the surface of the cell surface membrane
-phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell surface membrane- these glycolipids are important in cell recognition

37
Q

what are the three structures that phospholipids can form in water

A

monolayer, bilayer and micelles

38
Q

how are triglycerides and phospholipids soluble in water

A

alcohols e.g. ethanol, have both a non polar and polar region. as a result ethanol is able to mix with non polar and polar substances, triglycerides and phospholipids are non polar substances, so they are able to dissolve in alcohols

39
Q

what is the test for lipids

A

emulsion test:
1. take a completely dry and grease free test tube
2. to 2cm3 of the sample being tested, add 5cm3 of ethanol
3. shake tube throughly to dissolve any lipids
4. add 5cm3 of water and shake gently
5. milky white emulsion indicates presence of lipids
6. as a control, repeat the procedure using water instead of the sample; final solution should remain clear

40
Q

what are amino acids

A

the monomers from which proteins are made

41
Q

what is the structure of an amino acid

A

-amino group
-carboxyl group
-R group
amino acids are the basic monomer units which combine to make a polymer, called a polypeptide

42
Q

describe how amino acids join together

A

condensation reaction, removing a water molecule. between the carboxyl of one amino acid and the amine group of another, forming a peptide bond

43
Q

how are dipeptides and polypeptide formed

A

dipeptide- condensation of 2 amino acids
polypeptide- condensation of many amino acids, in a process called polymerisation

44
Q

what is the primary structure of a protein

A

sequence of amino acids in the polypeptide chain, joined by peptide bonds
-determines the proteins shape and function

45
Q

what is the secondary structure of a protein

A

folding of the polypeptide chain
-weak hydrogen bonds between the hydrogen (amino group) and the oxygen (carboxyl group) cause the polypeptide chain to be twisted into a 3D shape, such as a coil, known as an alpha-helix
-when a polypeptide chain lies next to a second polypeptide chain, hydrogen binds are then formed between between the hydrogen and oxygen forming a beta pleated sheet

46
Q

what is the tertiary structure of a protein

A

the alpha-helicases of the secondary protein structure can be twisted and folded even more to give the complex and often specific 3D structure of each protein. this structure is maintained by different bonds:
-disulfide bridges, fairly string and not easily broken
-ionic bonds, formed between any carboxyl and amino groups that are involved in making peptide bonds, they are weaker than disulfide bridges and are easily broken by changes in pH
-hydrogen bonds, numerous but easily broken

47
Q

why is the 3D structure important in the tertiary structure of a protein

A

makes each protein distinctive and allows it to recognise and be recognised by other molecules

48
Q

what is the quaternary structure of a protein

A

arises from the combination of a number of different polypeptide chains

49
Q

what is the test for proteins

A

biuret test- detects peptide bonds
1. place a sample of the solution to be tested in a test tube and add an equal volume of sodium hydroxide solution at room temperature
2. add a few drops of very dilute copper (III) sulfate solution and mix gently
3. a purple colouration indicates the presence of peptide bonds and hence a protein, if no proteins present solution remains blue

50
Q

what are the two different types of proteins

A

fibrous proteins (e.g. collagen) have structural functions
globular proteins (e.g. haemoglobin) carry out metabolic functions

51
Q

how do enzymes act as biological catalysts

A

each enzyme lowers activation energy of the reaction that it catalyses, this is done to speed up the rate of reaction

52
Q

describe the induced fit model of enzyme action

A
  1. substrate binds to (not completely complementary) active site of enzyme
  2. causing active site to chained shape, so it is complemtary to substrate
  3. so enzyme substrate complex forms
  4. causing bonds in substrate to bend, lowering activation energy
53
Q

explain the specificity of enzymes

A

specific tertiary structure determines shape of active site, this is dependant on the primary structure of amino acids. active site is complementary to a specific substrate. only this substrate can bind to active site, inducing fit and forming an enzyme substrate complex

54
Q

describe and explain the effect of enzyme concentration on the rate of enzyme-controlled reactions

A
  1. as enzyme conc increases, rate of reaction increases
    - increase in enzymes means more active sites are available
    -so more enzyme substrate complexes can for,
  2. at a certain point, rate of reaction levels off, this is because all the substrates are in use, making the substrate conc a limiting factor
55
Q

describe and explain the effect of substrate concentration on the rate of enzyme co trolled reactions

A

as substrate conc increases, rate of reaction increases
-low substrate conc= limiting factor as less ESC can be formed
at a certain point, rate of reaction stops increasing
-enzyme conc= limiting factor as all the active sites are in use

56
Q

describe and explain the effect of temperature on the rate of enzyme controlled reactions

A

as temp increases up to optimum, rate of reaction increases
-more kinetic energy
-more ESC form
as temp increases above optimum, rate of reaction decreases
-enzymes denature- tertiary structure and active site change shape
-as hydrogen bonds break
-active site no longer complementary
-fewer ESC can form

57
Q

describe and explain the effect of pH on the rate of enzyme controlled reactions

A

if pH is too high or too low, this will interfere with the changes in the amino acids in the active site. this can break the hydrogen bonds holding the tertiary structure in place and therefore the active site changes shape
-enzyme therefore denatured and fewer ESC form

58
Q

describe and explain the effect of concentration of competitive inhibitors on the rate of enzyme controlled reactions

A

as conc of competitive inhibitors increases, rate of reaction decreases
-similar shape to substrate
-competes for and blocks active site
-substrate cannot bind and fewer ESC cans for
increasing substrate will out compete the inhibitors

59
Q

describe and explain the effect of concentration of non competitive inhibitor on the rate of enzyme controlled reactions

A

as concentration of non competitive inhibitors increases, rate of reaction decreases
-binds to site other than the active site (allosteric site)
-changes enzymes tertiary structure/active site
-active site no longer complementary to substrate
-fewer ESC form
increasing conc of substrate has no effect on rate of reaction as change to active site is permanent

60
Q

describe the basic function of DNA and RNA

A

DNA- holds genetic information which codes for polypeptides
RNA- transfers genetic information from the DNA to the ribosome

61
Q

describe how nucleotides join together to form polypeptides

A

-condensation reaction, removing water molecule
-between phosphate group of one nucleotide and deoxyribose/ribose of another
-forming phosphodiester bonds

AS biology (6 decks)

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