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Biological Molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are the five biological molecules we learn about

A

-water
-carbohydrates
-proteins
-nucleic acids
-lipids

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2
Q

how do hydrogen bonds form between water molecules

A

-water=polar: O is more electronegative than H, so attracts electron density in covalent bonds more strongly. O=slightly neg. H=slightly pos
-intermolecular forces of attraction between a lone pair on O of one molecule and H on an adjacent molecule.

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3
Q

state 7 biologically important properties of water

A

-ice=less dense than water, reaches max density at 4°C
-high surface tension
-incompressible
-solvent
-high specific heat capacity
-high latent heat of vaporisation
-cohesion between molecules

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4
Q

Why is latent heat significant

A

-large amount of TE is absorbed to break hydrogen bonds and evaporate water.
-little water is required to evaporate in order for organisms to lose lots of energy- provides a COOLING effect.
-e.g sweat or transpiration

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5
Q

why is the incompressible nature of water important

A

-provides turgidity
-provides hydrostatic skeleton for some small animals, e.g earthworms

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6
Q

why does ice float on water and importance

A

-H-bonds hold molecules in fixed positions further away from each other.
-insulates water in arctic climates so aquatic organisms can survive. layer of water will freeze in extreme temps and rise to the top, reducing heat loss and preventing the whole body of water freezing.

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7
Q

high surface tension of water importance

A

-slows water loss due to transpiration in plants
-water rises unusually high in narrow tubes, lowering demand on root pressure
-some insects can ‘skim’ across the surface of water.

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8
Q

water as a solvent importance

A

polar universal solvent dissolves & transports charged
particles involved in intra & extracellular reactions e.g PO4 3- for DNA synthesis.

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9
Q

high specific heat capacity and latent heat of vaporisation importance

A

-acts as a T buffer, enables endotherms to resist fluctuations in core T to maintain optimum enzyme activity.
-cooling effect when water evaporates from skin surface as sweat/from mouth when panting.

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10
Q

define monomer

A

smaller units that join together to form larger molecules

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11
Q

examples of monomers

A

-monosaccharides (glucose, fructose, galactose, ribose)
-amino acids
-nucleotides

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12
Q

define polymer

A

molecules formed when many monomers join together

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13
Q

examples of polymers

A

-polysaccharides
-proteins
-DNA / RNA

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14
Q

what happens in condensation and hydrolysis reactions

A

-condensation= chemical bond forms between 2 molecules & a molecule of water is produced.

-hydrolysis= water molecule is used to break a chemical bond between 2 molecules e.g. peptide bonds in proteins, ester bonds between fatty acids and glycerol in lipids

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15
Q

name the elements found in carbohydrates, lipids, proteins, and nucleic acids.

A

carbohydrates & lipids= C H O
proteins= C H O N S
nucleic acids= C H O N P

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16
Q

structure of alpha and beta glucose

A

alpha= hydrogen above
beta=hydrogen below

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17
Q

properties of alpha glucose

A

-small & water soluble= easily transported in bloodstream
-complementary shape to antiport for co-transport for absorption in gut
-complementary shape to enzymes for glycolysis=respiratory substrate.

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18
Q

what bond forms when monosaccharides react

A

glycosidic

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19
Q

name 3 disaccharides and how they form

A

-maltose= glucose + glucose
-sucrose= glucose + fructose
-lactose= glucose + galactose
all have molecular formula C12H22O11

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19
Q

describe structure and function of starch

A

storage polymer of alpha glucose in plant cells
-insoluble=no osmotic effect on cells
-large=does not diffuse out of cells

made from amylose:
-1,4 glycosidic bonds
-helix with intermolecular H-bonds=compact

and amylopectin:
-1,4 & 1,6 glycosidic bonds.
-branched= many terminal ends for hydrolysis into glucose.

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20
Q

describe structure ad functions of glycogen

A

main storage polymer of alpha glucose in animal cells (also found in plants)
-1,4 & 1,6 glycosidic bonds
-branched= many terminal ends for hydrolysis
-insoluble= no osmotic effect & doesn’t diffuse out of cells
-compact

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21
Q

describe structure and function of cellulose

A

polymer of beta glucose gives rigidity to plant cell walls (prevents bursting under turgor pressure, holds stem up)
-1,4 glycosidic bonds
-straight-chain, unbranched molecule
-alternate glucose molecules are rotated 180
-H-bond crosslinks between parallel strands form microfibrils=high tensile strength.

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22
Q

how do triglycerides form

A

condensation reaction between 1 molecule of glycerol & 3 fatty acids which form ester bonds.

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23
Q

compare saturated and unsaturated fatty acids

A

saturated:
-single C-C bonds only
-straight-chain lots of contact points
-higher melting point=solid at room T
-found in animal fats

unsaturated:
-contain C=C bonds
-‘kinked’ molecule have fewer contact points
-lower melting point=liquid at room T
-found in plant oils

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24
Q

relate the stucture of triglycerides to their function

A

-high energy:mass ratio= high caloric value from oxidation (energy storage)
-insoluble hydrocarbon chain = no effect on water potential of cells & used for waterproofing
-slow conductor of heat= thermal insulation e.g adipose tissue.
-less dense than water = buoyancy of aquatic animals.

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25
Q

describe the structure and function of phospholipids

A

amphithatic: glycerol backbone attatched to 2 hydrophobic fatty acid tails & 1 hydrophilic polar phosphate head.
-forms phospholipid bilayer in water = component of membranes
-tails can splay outwards = waterproofing e.g for skin

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26
Q

are phospholipids and triglycerides polymers

A

no, they are macromolecules.
-not made from a small repeating unit.

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27
Q

structure and function of cholesterol

A

-steroid structure of 4 hydrocarbon rings. Hydrocarbon tail on one side, hydroxyl group (-OH) on the other.
-adds stability to cell surface phospholipid bilayer by connecting molecules & reducing fluidity.

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28
Q

general structure of an amino acid

A
  • COOH carboxyl
    -R variable side group
    -NH2 amine group
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29
Q

how do polypeptides form

A

condensation reactions between amino acids form peptide bonds (-CONH-)
4 levels of protein structure

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29
Q

define primary and secondary structure of a protein

A

primary- sequence, number & type of amino acids in the polypeptide, determined by sequence of codons on mRNA.
secondary- weak negatively charged N and O interact with weak positively charged H to form hydrogen bonds

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30
Q

describe the 2 types of secondary protein structure

A

a-helix:
-all N-H bonds on same side of protein chain
-spiral shape
-H-bonds parallel to helical axis

B-pleated sheet:
-N-H & C=O groups alternate from one side to the other

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31
Q

define tertiary structure of protein and bonds present

A

3D structure formed by further folding
-Disulphide bridges: strong covalent S-S bonds between molecules of the amino acid cysteine.
-Ionic bonds: relatively strong bonds between charged R groups (pH changes cause these bonds to break)
- hydrogen bonds: numerous & easily brokenn

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32
Q

define quaternary structure of a protein

A

-functional proteins may consist of more than one polypeptide.
-precise 3D structure held together by the same types of bond as tertiary structure
-may involve addition of prosthetic groups e.g metal ions or phosphate groups

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32
Q

describe structure and function of globular proteins

A

-spherical & compact
-hydrophilic R groups face outwards & hydrophobic R groups face inwards = usually water soluble.
-involved in metabolic processes e.g enzymes such as amylase, insulin, haemoglobin.

33
Q

structure of haemoglobin

A

-globular conjugated protein with prosthetic group
-2 a-chains, 2 B-chains, 4 prosthetic haem groups.
-water soluble so dissolve in plasma
-Fe2+ haem group forms coordinate bond with O2
-tertiary structure changed so it is easier for subsequent O2 molecules to bind.

34
Q

structure and function of fibrous proteins

A

-can form log chains or fibres
-insoluble in water
-useful for structure and support e.g collagen in skin

35
Q

functions of collagen

A

component of bones, cartilage, connective tissue, tendons

36
Q

functions of elastin

A

provides elasticity to connective tissue, arteries, skin, lungs, cartilage, ligaments

37
Q

functions of keratin

A

structural component of hair, nails, hooves/claws, horns, epithelial cells of outer layer of skin.

38
Q

how to test for proteins in a sample

A

Biuret test confirms presence of peptide bond
-add equal volume of sodium hydroxide to sample at room temperature.
-add drops of dilute copper (II) sulfate solution. swirl to mix
-pos result=colour change from blue to purple
-neg result=remains blue

39
Q

how to test for lipids in a sample

A
  • dissolve solid samples in ethanol
  • add an equal volume of water and shake
  • pos result= milky white emulsion
40
Q

how to test for reducing sugars

A

-add an equal vol of benedicts solution to a sample
-heat the mixture in an electric water bath at 100 degrees for 5 mins
-pos result= colour change from blue to orange and brick red precipiate forms.

41
Q

benedicts test for non-reducing sugars

A
  • negative result= remains blue
    -hydrolyse non-reducing sugars e.g sucrose into their monomers by adding 1 cm3 of HCl. Heat in a boiling water bath for 5 mins.
    -neutralise mixture using sodium carbonate solution
    -proceed with benedicts test
42
Q

describe the test for starch

A
  • add iodine solution
    -pos= colour change from orange to blue-black
43
Q

What elements do lipids contain

A

C H and less O, P in phospholipid

44
Q

Are lipids polar

A

Non polar

45
Q

What are triglycerides made of

A

3 fatty acids and 1 glycerol

46
Q

How do triglycerides form

A

3 condensation reactions between glycerol and 3 fatty acids lead to release of 3 water molecules and formation of 3 new covalent ester bonds

47
Q

What bonds involved with lipids

A

Ester bond

48
Q

Are saturated lipids solid or liquid

A

Solid

49
Q

Are unsaturated lipids solid or liquid

A

Liquid

50
Q

Are unsaturated lipids found in animal or plant

A

Plant

51
Q

Are saturated lipids found in animal or plant

A

Animal

52
Q

What 2 components do phospholipds have

A

Hydrophilic head (phosphate)
Hydrophobic tail (fatty acid)

53
Q

What is cholesterol made of

A

4 carbon based rings

54
Q

Shape of cholesterol

A

Small and narrow to sit between fatty acid tails of phospholipids

55
Q

Is cholesterol hydrophobic or hydrophilic

A

Hydrophobic

56
Q

Function of cholesterol

A

Regulate membrane fluidity and strength

57
Q

What problems does too much cholesterol cause

A

Gailstones
Atherosclerosis

58
Q

Where are lipids important

A

Energy yield
Energy storage
Insulation
Hormonal communication

59
Q

Describe triglycerides

A

Non polar
Hydrophobic
Glycerol=alcohol
Fatty acids contain a methyl group at one end of a hydrocarbon chain known as the R group and at the other end is carboxyl.

60
Q

Chemical formula of a fatty acid

A

RCOOH

61
Q

How do fatty acids vary

A

Length of hydrocarbon chain (R group)
Fatty acid chain (R group) may be saturated.
Unsaturated fatty acuds can be mona or poly unsaturated

62
Q

Phosphate ion

A

PO4 3-

63
Q

What does amphipathic mean and are phospholipids amphipatic

A

They have hydrophobic and hydrophilic parts. Yes

64
Q

How many fatty acid tails do phospholipids have

A

2

65
Q

How many fatty acid tails do triglycerides have

A

3

66
Q

Is phosphate present in triglycerides

A

No

67
Q

Is phosphate present in phospholipids

A

Yes

68
Q

Are phospholipids polar

A

They have a polar phosphate head

69
Q

Are triglycerides polar

A

No

70
Q

How many water moleculea released when phospholipids and triglycerides form

A

3

71
Q

Function of phospholipids

A

Cell membrane component

72
Q

Function of triglycerides

A

Energy storage

73
Q

Esterification

A

Condensation reaction
Water molecule released

74
Q

When does an ester bond form

A

The OH hydroxyl group of the glycerol binds with the COOH carboxyl group of the fatty acid

75
Q

Why do triglycerides make good energy storage

A

Long hydrocarbon chains containing lots of C-H bonds with little oxygen (so highly reduced) when get oxidised during cellular respiration the binds break, releasing lots of energy to produce ATP. The breaking of these bonds also releases metabolic water = useful

76
Q

How much energy per gram do lipids have

A

37K

77
Q

Are triglycerides hydrophobic or hydrophilic and significance of this

A

Hydrophobic they do not cause osmotic water uptake in cells so more can be stored.

78
Q

When are triglycerides used as insulation

A

Myelin sheath. Increases speed of transmission of nerve impulses.
Adipose tissue layer below the skin which acts as insulation against heat loss.

79
Q

Why are lipids buoyant

A

Low density of fat tissue in animals

80
Q

When are triglycerides used as protection

A

Adipose tissue in mammals contains stored triglycerides and this tissue helos protect organs from risk of damage.

81
Q

Are phospholipids hydrophobic or hydrophilic

A

Hydrophilic phosphate head
Hydrophobic fatty acid tails.
=Amphipatic
So form bilayers or monolayers in water

82
Q

What happens when phospholipids come in contact with water

A

Form monolayers or bilayers where the hydrophilic head touch water and the hydrophobic tail face in. Hydrophobic core created= acts as a barrier to water soluble molecules.

Biology (13 decks)

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