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Biological molecules Flashcards

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AP® Biology flashcards
1
Q

What makes water polar?

A

Oxygen - slightly negative as it has a greater affinity for electrons in an O-H covalent bond
Hydrogen - slightly positive

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2
Q

Why is water being polar helpful in life?

A

It means it can act as a solvent and acts as a good transport medium - transports substances easily around organisms

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3
Q

Why is cohesion in water helpful in life?

A
  • It makes it a very good transport medium.
  • Hydrogen bonds are formed between molecules resulting in capillary action - water being drawn up a narrow tube against gravity
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4
Q

Why is water having a high specific heat capacity helpful in life?

A
  • maintains body temp.
  • maintains constant temperature in ponds/sea etc to provide a constant environment for fish
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5
Q

Why is the density of water helpful in life?

A
  • Ice floats on top of water because H bonds fix slightly further apart, creating an insulating layer for the water below - prevents all of it freezing and killing aquatic creatures
  • high density of water makes it easier for aquatic animals to swim and float
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6
Q

Elements in carbohydrates

A

carbon, oxygen, hydrogen

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7
Q

what are simple carbohydrates known as?

A

monosaccharides eg glucose

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8
Q

What are complex carbohydrates known as?

A

polysaccharides eg. starch

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9
Q

In alpha glucose, what’s the arrangement of OH and H on carbon 1?

A

OH on bottom, H on top
ABBA - alpha below, beta above

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10
Q

Name of the bond that joins 2 monosaccharides together

A

1-4 glycosidic bond

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11
Q

what reaction do 2 alpha glucose molecules go through to get maltose? (disaccharide)

A

condensation

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12
Q

What makes starch adapted to its function?

A
  • compact, spiral shape for storage
  • insoluble due to large size of molecules so no effect on water pot.
  • more ‘free ends’ on branched amylopectin so glucose can be readily hydrolysed for respiration
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13
Q

amylose properties that make it adapted to function

A
  • unbranched, spiralling structure - compact
  • made up of 1-4 glycosidic bonds between alpha glucose molecules
  • insoluble
  • 20% of starch
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14
Q

amylopectin properties that make it adapted to function

A
  • highly branched - can be hydrolysed by enzymes quicker than amylose
  • made up of 1-4 and 1-6 (every 20-30 monomers) glycosidic bonds
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15
Q

What makes glycogen adapted to its function?

A
  • compact for storage
  • more branched than starch as animals more likely to need quick burst of energy
  • insoluble due to large size, no effect on water pot.
  • ‘free ends’ as highly branched so can be readily hydrolysed for glucose
  • Shorter 1-4 chains and more 1-6 chains than starch
  • metabolically inactive
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16
Q

what makes cellulose adapted to its function?

A
  • molecules don’t spiral due to beta-glucose bonding parallel forming straight chains
  • H bonds between glucose due to this arrangement - strong, prevent spiralling
  • chains can lie close allowing H bonds to form between chains - more strength
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17
Q

function of cellulose

A
  • gives cell wall great strength
  • arrangement of macrofibrils allows water to pass through
  • keeps cells turgid
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18
Q

Test for starch

A

Iodine solution
Orange to blue/black
coils in amylose trap iodine molecules

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19
Q

test for reducing sugars

A

Benedict’s solution added, heated for 2 mins
V. low conc - blue
green, yellow, orange
Strong conc. - brick red
- semi-quantitative test

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20
Q

test for non-reducing sugars

A

test reducing sugars first
Heat solution with acid
Cool and neutralise
Heat with Benedict’s
green, yellow, orange, brick-red

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21
Q

test for proteins

A

add equal volumes of protien solution and biuret reagant
lilac solution formed - nitrogen atoms

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22
Q

test for lipids

A

Place one drop of vegetable oil in test tube and add ethanol, shake thoroughly.
Pour mixture into test tube 3/4 filled with water
- white emulsion will form on the surface because alcohol mixes with the water

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23
Q

What elements are in triglycerides?

A

carbon, oxygen hydrogen

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24
Q

what are the 2 main components for triglycerides?

A

1glycerol, 3 fatty acids

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25
Q

How is a triglyceride formed?

A
  • 3 condensation reactions occur to bond 3 fatty acids to a glycerol molecule
  • 3 ester bonds formed - the C, O, O
  • process is called esterfication
  • 3 water molecules also made
26
Q

How are triglycerides broken down?

A

Lipase breaks the ester bonds holding them together, releasing the glycerol and fatty acid molecules
- requires 3 water molecules - hydrolysis

27
Q

What makes triglycerides insoluble?

A
  • They are non-polar so it’s difficult for H bonds to form between it and water
  • so they’re hydrophobic
28
Q

why can lots of energy be released from triglycerides?

A

they’re made up of lots of carbon and hydrogen atoms

29
Q

fatty acid structure

A

An acid group at one end
A hydrocarbon chain between 2-20 carbons long

30
Q

Saturated fatty acids

A
  • no double bonds, only single
  • All possible bonds made with hydrogen
  • solids at room temp
  • straighter chains, group closer together
31
Q

unsaturated fatty acids

A
  • double bonds between 1 or more carbon atoms - less hydrogen can bond to it
  • kink in chain
  • unable to group close together
  • liquids at room temp.
32
Q

Structure of phospholipid

A

1 glycerol, 2 fatty acids, 1 phosphate group (hydrophillic)

33
Q

function of lipids

A
  • energy source - broken down to CO2 and water in respiration to release energy and ATP
  • energy store - insoluble, don’t affect water pot.
  • insulation
  • buoyancy - less dense than water, helps marine animals
  • protection - around internal organs
34
Q

cholesterol function

A
  • in biological membranes
  • in hormones eg. testosterone, oestrogen - allowing them to pass through cell membranes
  • used to make vitamin D
  • used in liver to produce bile - used in digestion of lipids by lipase
35
Q

cholesterol structure

A
  • small
  • OH group - polar - hydrophillic
  • (rest of molecule) 4 carbon rings and hydrocarbon tail - non-polar - hydrophobic
36
Q

elements in proteins

A

carbon, oxygen, hydrogen, nitrogen, sulfur (depending on the protein)

37
Q

What groups do all proteins have?

A

amino group, carboxyl (COOH), R group (differs for each amino acid)

38
Q

amino acid structure

A

amine group on left (N, H, H)
R group
Carboxyl group on right (COOH)
H R O
N C C
H H OH

39
Q

What molecule is removed when 2 amino acids join?

A

water - condensation reaction

40
Q

What bond is formed during formation of dipeptide (2 amino acids)?

A

peptide bond

41
Q
A
42
Q

functions of proteins in an organism

A
  • as enzymes
  • cell surface membrane
  • hormones eg. insulin
  • fibrous proteins - structure, provide strength
  • transport eg. haemoglobin
43
Q

primary structure of protein and why it’s important to overall structure

A
  • order of amino acids in polypeptide chain - determined by the gene that codes for it
  • the order directly impacts the bonds formed on other levels of structure
  • changing just one amino acid can change shape and function of protein
44
Q

secondary structure of proteins

A

alpha helix
- polypeptide chain twists into helix
beta pleated sheet
- polypeptide chain folds over itself

Hydrogen bonds between NH group and CO group on another amino acid hold it in place

45
Q

tertiary structure

A

polypeptides fold further into a precise 3D shape
- Hydrogen bonds between amine group and carboxyl group, between polar areas of R groups
- Ionic bonds between R groups that ionise to form charged groups that attract each other
- Disulphide bonds - between sulphur containing R groups of the amino acid cystenine - covalent bond (strong)
- Hydrophobic parts of R group point inwards, hydrophillic parts point outwards, this causes the polypeptide chain to twist

46
Q

quaternary structure of protein

A

Several polypeptide shains bonded together to form intricate shapes
- sometimes contain prosthetic group, making it a conjugated protien

47
Q

Globular proteins

A
  • Quaternary structure
  • Curl up into a ball shape - compact
  • R group folded into middle away from water
  • Soluble in water
    Eg. haemoglobin
48
Q

fibrous proteins

A
  • structural role eg. in bones, tendons
  • form long rope-like molecules
  • large proportion of amino acids with hydrophobic R groups
  • insoluble in water
49
Q

collagen

A
  • fibrous protein in tendons, ligaments, skin
  • strong molecule due to structure
  • 3 polypeptide chains wrap tightly to form triple helix
  • in polypeptides every 3rd amino acid is glycine (R group - H, smallest amino acid so chains can wrap tightly around each other)
  • hydrogen bonds form between polypeptide chains
  • polypeptide chains also joined to each other by cross-links
  • lots of collagen molecules can join together arranged staggered (no weak spots) - microfibrils, fibrils
50
Q

keratin

A
  • fibrous protein in hair, nails, skin
  • strong, insoluble in water
  • high proportion of cysteine - used to form lots of disulphide bonds (strong covalent bonds) - very strong molecules
51
Q

elastin

A
  • fibrous protein in skin, walls of arteries
  • helps make it elastic in skin and stretch and recoil in arteries
  • long strands cross-linked to each other with hydrophobic regions
  • normally hydrophobic regions on strands associate causing elastin to group together, when stretched only cross-linked parts together
52
Q

Conjugated proteins

A

Globular proteins with a prosthetic group eg. haemoglobin has a haem group

53
Q

Fibrous proteins

A

Form long strands
Insoluble - high proportion of hydrophobic R groups
Structural role
Eg. keratin, collagen

54
Q

Collagen structure

A

Fibrous protein found in skin, teeth, tendons, bones etc.
- 3 identical polypeptide chains wound into triple helix
- chains held together by hydrogen bonds
- every 3 amino acids - glycine

55
Q

high latent heat of evaporation of water - helpful in life

A

Heat energy is absorbed during the evaporation of sweat which regulates body temperature

56
Q

Why is water essential to life?

A
  • needed for chemical reactions eg. photosynthesis
  • maintains shape of cells - tugor pressure
  • transport of molecules
  • regulate body temp
57
Q

properties of polysaccharides

A
  • made up of many monosaccharides
  • large so insoluble
  • NOT sugars
58
Q

ribose structure

A
  • 5 carbons, 10 hydrogens, 5 oxygens
  • pentose sugar
59
Q

ribose function

A
  • suagr produced by body from food
  • enhances recovery of muscles
  • in RNA nucleotides
  • part of nucleic acid
60
Q
A

biology (11 decks)

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