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Biological Molecules 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
relate the stucture of triglycerides to their function
-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.
25
describe the structure and function of phospholipids
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
26
are phospholipids and triglycerides polymers
no, they are macromolecules. -not made from a small repeating unit.
27
structure and function of cholesterol
-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.
28
general structure of an amino acid
- COOH carboxyl -R variable side group -NH2 amine group
29
how do polypeptides form
condensation reactions between amino acids form peptide bonds (-CONH-) 4 levels of protein structure
29
define primary and secondary structure of a protein
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
30
describe the 2 types of secondary protein structure
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
31
define tertiary structure of protein and bonds present
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
32
define quaternary structure of a protein
-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
32
describe structure and function of globular proteins
-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
structure of haemoglobin
-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
structure and function of fibrous proteins
-can form log chains or fibres -insoluble in water -useful for structure and support e.g collagen in skin
35
functions of collagen
component of bones, cartilage, connective tissue, tendons
36
functions of elastin
provides elasticity to connective tissue, arteries, skin, lungs, cartilage, ligaments
37
functions of keratin
structural component of hair, nails, hooves/claws, horns, epithelial cells of outer layer of skin.
38
how to test for proteins in a sample
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
how to test for lipids in a sample
- dissolve solid samples in ethanol - add an equal volume of water and shake - pos result= milky white emulsion
40
how to test for reducing sugars
-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
benedicts test for non-reducing sugars
- 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
describe the test for starch
- add iodine solution -pos= colour change from orange to blue-black
43
What elements do lipids contain
C H and less O, P in phospholipid
44
Are lipids polar
Non polar
45
What are triglycerides made of
3 fatty acids and 1 glycerol
46
How do triglycerides form
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
What bonds involved with lipids
Ester bond
48
Are saturated lipids solid or liquid
Solid
49
Are unsaturated lipids solid or liquid
Liquid
50
Are unsaturated lipids found in animal or plant
Plant
51
Are saturated lipids found in animal or plant
Animal
52
What 2 components do phospholipds have
Hydrophilic head (phosphate) Hydrophobic tail (fatty acid)
53
What is cholesterol made of
4 carbon based rings
54
Shape of cholesterol
Small and narrow to sit between fatty acid tails of phospholipids
55
Is cholesterol hydrophobic or hydrophilic
Hydrophobic
56
Function of cholesterol
Regulate membrane fluidity and strength
57
What problems does too much cholesterol cause
Gailstones Atherosclerosis
58
Where are lipids important
Energy yield Energy storage Insulation Hormonal communication
59
Describe triglycerides
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
Chemical formula of a fatty acid
RCOOH
61
How do fatty acids vary
Length of hydrocarbon chain (R group) Fatty acid chain (R group) may be saturated. Unsaturated fatty acuds can be mona or poly unsaturated
62
Phosphate ion
PO4 3-
63
What does amphipathic mean and are phospholipids amphipatic
They have hydrophobic and hydrophilic parts. Yes
64
How many fatty acid tails do phospholipids have
2
65
How many fatty acid tails do triglycerides have
3
66
Is phosphate present in triglycerides
No
67
Is phosphate present in phospholipids
Yes
68
Are phospholipids polar
They have a polar phosphate head
69
Are triglycerides polar
No
70
How many water moleculea released when phospholipids and triglycerides form
3
71
Function of phospholipids
Cell membrane component
72
Function of triglycerides
Energy storage
73
Esterification
Condensation reaction Water molecule released
74
When does an ester bond form
The OH hydroxyl group of the glycerol binds with the COOH carboxyl group of the fatty acid
75
Why do triglycerides make good energy storage
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
How much energy per gram do lipids have
37K
77
Are triglycerides hydrophobic or hydrophilic and significance of this
Hydrophobic they do not cause osmotic water uptake in cells so more can be stored.
78
When are triglycerides used as insulation
Myelin sheath. Increases speed of transmission of nerve impulses. Adipose tissue layer below the skin which acts as insulation against heat loss.
79
Why are lipids buoyant
Low density of fat tissue in animals
80
When are triglycerides used as protection
Adipose tissue in mammals contains stored triglycerides and this tissue helos protect organs from risk of damage.
81
Are phospholipids hydrophobic or hydrophilic
Hydrophilic phosphate head Hydrophobic fatty acid tails. =Amphipatic So form bilayers or monolayers in water
82
What happens when phospholipids come in contact with water
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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