Biological Molecules Flashcards
1
Q
Water
A
- polar molecule
- water molecules are attracted to each other and form ‘hydrogen bonds’
- high specific heat capacity
- thermal E. weakens H bonds instead of increasing particles’ eK
- a buffer against rapid temp. changes which is good for enzymes
2
Q
Water 2
A
- high latent heat of vaporisation
- ^ allows organisms to cool without losing a large vol. of water e.g. sweating
- a good solvent as it transports dissolved substances through xylem
- water in blood plasma is vital in transferring heat around the body
- the ‘universal solvent’ due to its polarity
3
Q
Water 3
A
- contains dissolved oxygen for aquatic organisms to carry out respiration
- cohesion causes surface tension which also acts as a habitat for insects
- cohesion allows long columns of water to travel in xylem tubes
- less dense when a solid (ice)
- reactant/product in metabolic reactions
e.g. photosynthesis/aerobic respiration
hydrolysis/condensation
4
Q
Carbohydrates - Monosaccharides
A
- examples; glucose, galactose & fructose
- soluble in water due to number of hydroxyl groups (OH)
- ^ hydrophilic molecules
- ‘ribose’ = pentose sugar
‘glucose’ = hexose sugar - αlpha & βeta are ‘isomers’ of glucose
- C1 hydroxyl BELOW = ALPHA
C1 hydroxyl ABOVE = BETA
5
Q
Disaccharides
A
- examples; maltose, sucrose & lactose
- produces a water molecule as H atom from one mono. bonds with hydroxyl group from the other (condensation)
- glucose molecules are chemically bonded by glycosidic bond
- maltose forms a 1, 4 glycosidic bond
- adding water breaks glycosidic bond (hydrolysis)
- sucrose = glucose + fructose
lactose = glucose + galactose
6
Q
Polysaccharides
A
- glucose = store of chemical energy
- glucose is hydrophilic so it causes water to move into cell if cell contains a lot of it by osmosis
- ^ why plants store glucose as starch
- starch = amylose + amylopectin
- polymers are too large to diffuse through plasma membrane
- enzymes are used to break glycosidic bones in starch
7
Q
Amylose & Amylopectin
A
- amylose = thousands of α glucose molecules joined by 1, 4 glyco. bonds
- amylose twists into a compact helix with H bonds forming between neighbouring chains
- hydrolysis takes place to release glucose if cell needs it
- amylopectin branches after 25-30 glucose molecules
- branch forms 1, 6 glycosidic bond joined to main chain
- enzymes are at ends of branches & work rapidly due to excessive amount
8
Q
Glycogen
A
- the glucose storage molecule in animals (liver + muscle)
- insoluble; so cannot diffuse out of cell
- similar to amylopectin, however, it’s more branched it’s so more compact
- many free ends allow enzymes to convert glycogen back to glucose rapidly
- ^ good for animals when they rapidly require energy for respiration e.g. predator chase
9
Q
Cellulose
A
- polymer of beta glucose
- unbranched polysaccharide
- forms straight chains
- hydroxyl groups points in different directions when side-by-side
- every 2nd β glucose molecule flips to form 1, 4 glycosidic bonds
- H bonds between neighbouring chains give cellulose strength
10
Q
Cellulose 2
A
- cellulose chains grouped together are called microfibril
- many microfibril = macrofibril
- many macrofibril = cellulose fibre
- c. fibres form plant cell wall
11
Q
3.5 Lipids
A
- molecules in fats/oils
- major source of energy in human diet
- stores energy e.g. ‘adipose tissue’ under skin for insulation & around internal organs for protection
- used for waterproofing and membrane structure
12
Q
Triglycerides
A
- non-polar/hydrophobic
- 1 glycerol molecule + 3 fatty acids (3x)
- fatty acid = carboxylic group bonded to hyrdrocarbons
- saturated fatty acids contain single covalent bonds between carbon (C)
- unsaturated fatty acids contain at least one double covalent bond between C
- polyunsaturated = more than one double carbon bond
13
Q
Triglycerides 2
A
- glycerol = 3 hydroxyl groups + carbon + hydrogen (at ends of carbon)
- glycerol + fatty acid = ester bond (esterification aka. condensation)
- lipase needs 3 water molecules to break ester bonds (hydrolysis)
- a lot of energy can be released from triglycerides
14
Q
Phospolipids
A
- polar/hydrophilic
- 1 glycerol molecule bonded to 2 fatty acids + phosphate (negative)
- heads are hydrophilic
tails are hydrophobic - ^ these create a phospholipid bilayer
15
Q
Cholesterol
A
- sterols are not fats/oils but complex alcohol molecules
- has a hydrophilic hydroxyl group which interacts with phospholipids heads
- rest of molecule is hydrophobic which interacts with fatty acid tail
- helps control fluidity of plasma membrane
- produces bile in liver
- makes vitamin D & steroid hormones
- ^ these hormones can pass through plasma membranes
