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biology- year 1 > biological molecules- chapter 1 > Flashcards

biological molecules- chapter 1 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is covalent bonding

A

atoms share a pair of electrons in their outer shells, as a result the outer shell of both atoms is filled and a more stable compound (molecule) is formed

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2
Q

what is ionic bonding

A

ions with opposite charges attract one another, this electrostatic attraction is known as an ionic bond

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3
Q

what is what is hydrogen bonding

A

the electrons within a molecule are not evenly distributed but tend to spend more time at one position, this region is more negatively charged than the other.
the negative region of one polarised molecule and the positively charged region of another attract each other, a weak electrostatic attraction is formed, they collective form important forces that alter the physical properties of the molecules

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4
Q

what is a polar molecule

A

an uneven distribution of charge is said to be polarised

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5
Q

what is a polymer

A

long chain on monomer sub units

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6
Q

how are polymers formed

A

polymerisation

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7
Q

what are monomers

A

individual molecules

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8
Q

what are 3 example of polymers

A

polysaccharides, polypeptides, polynucleotides

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9
Q

what are condensation reactions

A

reactions that produce water

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10
Q

two examples of condensation reactions

A

amino acid to polypeptide
monosaccharide to polysaccharide

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11
Q

what is hydrolysis

A

addition of water, water molecules are used when breaking the bonds that link the sub units

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12
Q

what can starch be hydrolysed into

A

glucose

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13
Q

what is metabolism

A

all chemical processes that take place in living organisms

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14
Q

what is a molar solution

A

a solution that contains one mole of solute in each litre solution

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15
Q

what do carbon atoms do

A

readily form bonds with other carbon atoms which make sequences of varying lengths

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16
Q

what are carbon-containing molecules known as

A

organic molecules

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17
Q

what do carbon molecules form

A

a ‘backbone’ along which other atoms can be attached

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18
Q

what is a disaccharide

A

a pair of monosaccharides combined together

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19
Q

what are polysaccharides

A

monosaccharides that can be combined in a much larger form

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20
Q

what is the general formula of a monosaccharide

A

(CH2O)n

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21
Q

describe a monosaccharide

A

sweet tasting soluble substance

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22
Q

in a monosaccharides formula what number can n be

A

any from 3 to 7

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23
Q

give 3 examples of monosaccharides

A

glucose, galactose and fructose

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24
Q

what are the two isomers of glucose

A

alpha-glucose and beta-glucose

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25
Q

what type of sugar is glucose and the formula

A

hexose sugar, general formula C6H10O6

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26
Q

example of reducing sugars

A

monosaccharides and some disaccharides

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27
Q

what is reduction

A

a chemical reaction involving the gain of electrons or hydrogen

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28
Q

what is a reducing sugar

A

a sugar that can donate electrons (or reduce) another chemical, benedicts reagent

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29
Q

what is benedicts reagent and what happens when its heated with a reducing sugar

A

alkaline solution of copper (II) sulfate
when a reducing sugar is heated with benedicts it forms as insoluble red precipitate of copper (I) sulfate

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30
Q

how do you carry out a reducing sugars test

A
  1. add 2cm3 of food sample to be tested to a test tube. if the same isn’t in liquid form, first grind it in water
  2. add an equal volume of benedicts reagent
  3. heat the mixture in gently boiling water bath for five minutes
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31
Q

glucose+glucose=?

A

maltose

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32
Q

glucose+fructose=?

A

sucrose

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33
Q

glucose+galactose=?

A

lactose

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34
Q

what bond is formed in condensation reaction

A

glycosidic bond

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35
Q

what is it good that polysaccharides are insoluble

A

makes them suitable for storage

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36
Q

what is cellulose good

A

not used for storage but gives structural support to plant cells

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37
Q

how is starch found

A

found in many parts of the plants in the form of small granules or grains

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38
Q

how is starch formed

A

joining of between 200 and 100000 a-glucose molecules by glycosidic bonds in a condensation reaction

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39
Q

how do you carry out the non-reducing sugars test

A
  1. add 2cm3 of food sample to 2cm3 of hydrochloric acid and place in a water bath. this hydrolyses the disaccharides present
  2. add sodium hydrogencarbonate to neutralise the acid, and check with pH paper
  3. test with 2cm3 of benedicts reagent, place in a water bath for 5 minutes. any change in colour is a positive result
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40
Q

what is the test for starch

A

add iodine solution to food sample
blue-black if there’s starch present

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41
Q

what type of chains are in starch

A

branched or unbranched

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42
Q

what does it mean in starch is the chains are unbranched

A

they’re wound into a tight coil that makes the molecules very compact

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43
Q

why is it good that starch is insoluble

A

doesn’t affect water potential, so water isn’t drawn into the cells by osmosis

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44
Q

why is it good that starch is insoluble

A

cannot diffuse out of cells

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45
Q

why is it good that starch is compact

A

a lot can be stored in a small space

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46
Q

what is release when starch is hydrolysed and why is this good

A

a-glucose
good because it is easily transported and ready for use in respiration

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47
Q

why is starch good branched

A

has many ends, each can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly

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48
Q

where is glycogen found

A

in animals and bacteria cells but never plant

49
Q

what is glycogens structure

A

similar to starch but has shorter chains and is more highly branched

50
Q

where is glycogen stored

A

as small granules mainly in muscles and liver

51
Q

why is it good that glycogen is insoluble

A

so it doesn’t draw water into the cells by osmosis and cannot leave by diffusion

52
Q

why is it good that glycogen is compact

A

so a lot can be stored in a small space

53
Q

why is it good that glycogen is more highly branched than starch

A

so has more enzymes to act on simultaneously, it is more readily broken down to be used in respiration

54
Q

what is cellulose made of

A

b-glucose monomers

55
Q

what are the chains like in cellulose

A

straight unbranched chains which run parallel to each other allowing hydrogen bonds to form cross-linkages between chains

56
Q

why is cellulose strong

A

a lot of hydrogen bonds

57
Q

why is it good that cellulose molecules are grouped together

A

forms microfibrils which are arranged in parallel groups called fibers- which provide more strength

58
Q

how does cellulose stop a plant cell from bursting

A

exerts an inward pressure that stops any influx of water

59
Q

how to plant cells become semi rigid

A

plant cells are turgid and push against one another, making non-woody parts semi rigid

60
Q

why is it important for plant cells to be semi rigid

A

important in maintaining stems and leaves in a turgid state so that they can provide the maximum surface area for photosynthesis

61
Q

what do lipids contain

A

carbon, hydrogen and oxygen

62
Q

are lipids soluble or insoluble

A

insoluble in water
soluble in organic solvents such as alcohol and acetone

63
Q

what are the main groups of lipids

A

triglycerides (fats and oilds) and phospholipids

64
Q

what is the role of lipids is cell membranes

A

phospholipids contribute to the flexibility of membranes and the transfer of lipid-soluble substances across them

65
Q

what is the role of lipids as a source of energy

A

when oxidised, lipids provide more than twice the energy as the same mass of carbohydrates and release water

66
Q

why are lipids good for waterproofing

A

are insoluble in water
both plants and insects have waxy lipid cuticles while mammals produce an oily secretion from the sebaceous glands in the skin

67
Q

why are lipids good for insulation

A

fats are slow conductors of heat and when stored beneath the body surface help to retain body heat
they also act as electrical insulators in the myelin sheath around nerve cells.

68
Q

why are lipids good for protection

A

fat is often stored around delicate organs

69
Q

what is a triglyceride

A

has 3 fatty acids and a glycerol combined

70
Q

what bond does each fatty acid form with the glycerol

A

ester bond in a condensation reaction

71
Q

what does saturated mean

A

no carbon-carbon double bonds, all the carbon atoms are linked to the maximum possible hydrogen atoms

72
Q

what does mono unsaturated mean

A

single double bond

73
Q

what does polyunsaturated mean

A

more than one double bond

74
Q

why is it good that triglycerides have a high ratio of energy-storing carbon

A

hydrogen bonds to carbon atoms so is an excellent source of energy

75
Q

why is it good that triglycerides have a low mass to energy ratio

A

makes them good storage molecules

76
Q

why is it good that triglycerides are large, non polar molecules

A

insoluble in water, means their storage does not affect osmosis in cells

77
Q

why is it good that triglycerides have a high ratio of hydrogen to oxygen atoms

A

they release water when oxidised and therefore provide an important source of water

78
Q

what is a phospholipid

A

one fatty acid molecule is replaced by a phosphate molecule

79
Q

what do fatty acid molecules do

A

repel water (hydrophobic)

80
Q

what do phosphate molecules do

A

attract water (hydrophilic)

81
Q

what two parts make up a phospholipid

A

hydrophilic head and hydrophobic tail

82
Q

what does the hydrophilic head do

A

interact with water but not with fat

83
Q

what does a hydrophobic tail do

A

orientates itself away from water but readily mixes with fat

84
Q

why is a phospholipid said to be polar

A

as it has two ends that behave differently

85
Q

why is it good that phospholipids are polar

A

means that in an aqueous environment, phospholipid molecules for a bilayer within cell-surface membrane
this forms a hydrophobic barrier is formed between the inside and outside of a cell

86
Q

why is it good that phospholipids have hydrophilic phosphate ‘heads’

A

help to hold at the surface of a cell-surface membrane

87
Q

why is the structure of phospholipids good

A

allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane
glycolipids are important in cell recognition

88
Q

what is the test for lipids

A
  1. take a completely dry and grease free test-tube
  2. add 2cm3 of sample to 5cm3 of ethanol
  3. shake the tube thoroughly to dissolve any lipid in the sample
  4. add 5cm3 of water and shake gently
  5. cloudy-white colour is a positive result
89
Q

why is the positive result cloudy

A

due to any lipid in the sample being finely dispersed in the water to form an emulsion light passing through is refracted as it passes from oil droplets to water droplets making it appear cloudy

90
Q

what is the structure of an amino acid

A

basic monomer unit that combines to make a polypeptide which are then combined to form proteins

91
Q

what are the 4 different chemical groups atatched to an amino acid

A

amino group (-NH4)
carboxyl group (-COOH)
hydrogen atom (-H)
R group- a variety of different chemical groups

92
Q

how is a peptide bond formed

A

condensation reaction- water is made by combining an –OH from the carboxyl group of one amino acid with an –H from the amino group of another amino acid
the two amino acids then become linked by a new peptide bond between the carbon atom or one amino acid and the nitrogen atom of the other

93
Q

how are amino acids joined together

A

by polymerisation then the resulting chain is called a polypeptide

94
Q

what forms the primary structure of any protein

A

the sequence of amino acids

95
Q

what is the sequence of amino acids determined by

A

DNA

96
Q

what does the primary structure then determine

A

determines the subsequent shapes and functions- any change can lead to a change of shape

97
Q

what groups are either side of the peptide bond

A

both -NH and -C=O groups on either side

98
Q

what charge does the -NH group have

A

positive charge

99
Q

what charge does the O from the -C=O group have

A

negative charge

100
Q

what bond does the -NH and -C=O group form

A

hydrogen bonds

101
Q

what do the -NH and -C=O groups cause

A

causes the long peptide chain to be twisted into a 3-D shape, such as the coil known as an a-helix

102
Q

what can the a-helix be twisted to and folded to give

A

the complex and specific 3D structure of proteins where the bonds that occur depend on the primary structure of the protein

103
Q

what bonds are included in the tertiary structure

A

disulfide- fairly strong and not easily broken
ionic- formed between any carboxyl and amino groups that are not involved in forming peptide bonds. they are weaker that disulfide bonds and are easily broken by pH changes
hydrogen- numerous but easily broken

104
Q

what do quaternary structure form

A

complex molecules containing a number of individual polypeptide chains that are linked in various ways
may also be non-protein groups associated with the molecules such as the iron-containing haem group in haemoglobin

105
Q

what is the test for proteins

A
  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 (0.05%) copper (II) sulfate solution and mix gently
  3. a purple coloration indicates the presence of peptide bonds and hence a protein. no protein, the solution remains blue
106
Q

what do enzymes do when there catalysts

A

alter the rate of reaction with no changes to themselves
can be reused repeatedly and are therefore effective in small amounts
globular proteins

107
Q

what must happen for small reactions to take place

A

-substrates must collide with sufficient energy to alter the arrangement of their atoms
-free energy of the products must be less than that of the substrates
-need to exceed the minimum amount of energy to activate the reaction. activation energy
-enzymes lower the activation energy needed to start the reaction

108
Q

what is the active site

A

the specific region of the enzymes is functional

109
Q

what is the active site made up of

A

small number of amino acids

110
Q

what does the active site form

A

small depression within the much large molecule

111
Q

what’s formed when enzymes act on substrates

A

it fits neatly in this depression and forms an enzymes-substrate complex

112
Q

in the enzyme-substrate complex what is this held in place by

A

by bonds that temporarily form between certain amino acids of the active sites and groups on the substrate molecules

113
Q

what does the induced fit model of enzyme action propose

A

-that the proximity of the substrate leads to a change in the enzymes that forms the functional active site
-the enzyme is flexible and can mould itself around the substrate
-as it changes shape the enzymes puts a strain on the substrate molecules, which distorts a particular bond or bonds in the substrate which lowers the activation energy needed to break the bond

114
Q

from measuring enzyme-catalysed reactions what are two changes most frequently measured

A

-the formation of the products of the reaction.
-the disappearance of the substrate

115
Q

for an enzyme to work what must it do

A

-come into physical contact with its substrate
-have an active site which fits the substrate

116
Q

what is the effect of temperature on enzyme action

A

-rise in temperature increases the kinetic energy of molecules
-this means that the enzyme and substrate molecules come together more often
-temperature rise also begins to cause the hydrogen and other bond in the enzyme to break
-the enzyme and active site changes shape
-at first the substrate doesn’t fit as well into the active site
-at some point the enzyme is so disrupted that it stops working all together. It has denatured
-this is a permanent change

117
Q

what is the effect of pH on enzyme action

A

-pH of a solution is a measure of its hydrogen ion concentration
-the pH of a solution is calculated using the formula pH= -log10(H+)
-a hydrogen ion concentration of 1x10-9 therefore has a pH of 9
-the pH affects how an enzyme works in the following ways:
a change in pH alters the charges on the amino acids that make up the active site of the enzyme. The substrate can no longer become attached to the active site and so the enzyme-substrate complex cannot be formed
-depending on how significant the change in pH is, it may cause the bonds maintaining the tertiary structure to break
-H+ ions affects the ionic and hydrogen bonds between –NH2 and –COOH.

118
Q

what are competitive inhibitors

A

-have a similar molecular shape similar to that of the substrate
-they compete with the substrate for the available active sites
-increasing the substrate concentration, decreases the effect of the inhibitor
-the inhibitor is not permanently bound to the active site

119
Q

what are non-competitive inhibitors

A

-attach themselves to the enzyme at a binding site which is not the active site.
-upon attaching to the enzyme the inhibitor alters the shape of the enzyme and thus its active site in such a way that substrate molecules can no longer occupy it
-an increase in substrate concentration does not decrease the effect of the inhibitor

biology- year 1 (10 decks)

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