Biological molecules Flashcards
1
Q
properties of water
A
- high BP : H-bonds between water mol = lots of energy needs to evaporate water + break bonds
- Less dense solid : H-Bonds fix positions of water mol further apart forming giant, rigid + open structure = ice floats
- cohesive : mol attracted to one another. Plants draw water up their roots
- adhesive : mol attracted to other materials
- water mol are strongly cohesive = water has a skin of surface tension.
2
Q
water for life
A
- solvent : bc its polar - solutes can dissolve. Cytosol of euk/prokaryotes is mainly water.
- medium for chemical reactions
- transport dissolved compounds in and out of cells
- efficient transport medium : cohesive = mol stick together in body
- cohesion + adhesion = capillary action : water can rise up against a narrow tube against the force of gravity (xylem)
- coolant : buffers temp changes during chem reactions bc of H bonds (lots of energy needed to overcome) - maintains constant temp which is imp for enzymes.
- stable environment : doesn’t change temp easily. Ice floats forming on surface of ponds/rivers to form an insulating layer above the water - prevents aquatic organisms from dyeing due to cold weather.
- surface tension is strong to support small insects (pond skaters)
- water is transparent so aquatics plants can still photosynthesise - light can pass through.
3
Q
describe glucose
A
- monosaccharide
- hexose
- polar
- soluble in water (H-bonds)
- glucose dissolved in cytosol of cells
4
Q
condensation reaction of glucose
A
- two a-glucose, two hydroxyl groups interact
- OH on C1 + C4(of other mol)
- covalent glycosidic bond formed
- water as by - product
5
Q
ribose
A
- pentose monosaccharide
- sugar present in RNA nucleotides
- deoxyribose present in DNA NT
6
Q
starch
A
- a-glucose joined by glycosidic bonds
- chemical energy store (storage mol of glucose)
7
Q
amylose
A
- polysaccharide in starch
- made of glucose
- joined by 1-4 glycosidic bonds
- angle of bond forms a helix = stabilised by H-bonds
- compact
- less soluble
8
Q
amylopectin
A
- formed by 1-6 + 1-4 glycosidic bonds
- branched structure
- 1-6 branching points every 25 glucose sub units
9
Q
glycogen
A
- storage mol in animal + fungi
- more branched than AP
- more compact
- less space needed
- animals are mobile
- more free ends where glucose can be added/removed
- speeds up storing/releasing glucose required by cells
10
Q
hydrolysis reactions
A
- addition of water
- catalysed by enzymes
11
Q
cellulose
A
- b-glucose can’t join same way as a-glucose
- OH group on C1+C4 too far apart
- alternate b-g turn upside down
- unable to coil/branch
- straight chain mol formed
12
Q
fibres from cellulose
A
- cellulose mol form H-bonds with each other
- forms microfibrils
- join to form macrofibrils
- combine to form fibres
- fibres = strong, insoluble + in cell wall
13
Q
why is cellulose important for diet
A
- hard to break down into its monomers
- forms fibres necessary for healthy digestive system
14
Q
what is a reducing sugar
A
- all monosaccharides and some disaccharides
- donate electrons
- reduce another mol
15
Q
test for reducing sugar
A
- qualitative test
- sample in BT
- if solid grind/blend in water
- add equal volume benedict’s reagent
- gently heat in water bath for 5 mins
- RS reacts with Cu2+ in BR
- reduces blue Cu2+ to brick red Cu+
16
Q
test for non-reducing
- sucrose
A
- don’t react with benedict’s
- solutions remains blue
- sucrose boiled with dilute HCl
- gives + result when warmed with BR
- sucrose is hydrolysed by the acid
- forms glucose + fructose = reducing sugars
17
Q
testing for starch
A
- potassium iodide mixed with a sample
- colour change from yellow/brown to purple/black = starch is present
18
Q
describe lipids
A
- non-polar
- not soluble in water
- macromolecules = large complex + not built from repeating units
19
Q
triglyceride
A
- combines 1 glycerole + 3 FA
- OH groups interact
- forms 3 water mol
- ester bonds between FA + G
- ## esterification = condensation
- when TG broken down, 3H2O needed = hydrolysis
-
20
Q
saturated FA
unsaturated FA
A
- no double bonds = saturated : all C atoms form max number of bonds with H
- double bond = unsaturated causes mol to kick/bend so can’t pack close togethor
- makes them liquid at R.T
21
Q
phospholipids
A
- modified TG
- PO43- in cytoplasm of every cell
- have extra e- so negatively charged
- soluble in water
- 2 FA + phosphate head
- non polar end (FA) and charged head (phosphate)
22
Q
phospholipid interaction with water
A
- hydrophobic (FA) repel water
- hydrophilic interact with water (phosphate)
- surfactants : layer on water surface where heads in water + tails stick out
- bilayer arrangement = forming cell membranes
23
Q
sterols
A
- lipid
- in cells
- complex OH mol
- dual hydrophilic/phobic
- OH is polar, rest is hydrophobic
24
Q
cholesterol
A
- is a sterol
- in liver and intestines
- role in CM formation
- positioned between phospholipids
- adds stability
- regualtes fluidity
- keeps fluid @ low temp and stops too fluid @ high temp
- manufactures vitD, steroid hormones + bile
25
role of lipids
- form CM
- hormone production
- electrical insulation for impulse transmission
- waterproofing (plants leaves + feathers)
- thermal insulation : reduce heat loss (penguins)
- cushioning to protect vital organs : heart + kidneys
- buoyancy : aquatic animals (wales)
26
test for lipids
- emulsion test
- mix sample with ethanol
- mix sol with water
- shake
- if white emulsion layer forms on top of sol = lipid present
- clear = negative
27
amino acid structure
- when amine and CA groups connected to central C react
- OH on CA of one Aa reacts with H in amine group(NH2) of anther Aa
- peptide bond
- forms polypeptide (many amino acids)
- water produced as a by products
- condensation reaction
28
forming polypeptide
- several Aa joined by peptide bonds
| - catalysed by peptidyl transferase in ribosomes
29
primary structure
- sequence of Aa
- controlled by info in DNA
- peptide bonds
30
secondary structure
- O ,H + N atoms of Aa interact
- H-bonds form within amino acid chain
- pulls into coiled alpha helix
OR
- polypeptide chains can lie parallel forming beta pleated sheet
31
tertiary structure
- folding of protein into final shape
interactions:
- hydrophilic + phobic interactions between polar + non-polar R-groups
- hydrogen bonds - weakest
- ionic bonds - between oppositely charged R-groups
- disulphide bonds - strongest covalent + only between R-groups with sulphur
32
quaternary
- interactions of sub-units
- identical or different sub units
- enzymes : 2 identical
- insulin : 2 diff subunits
- Hb : 4 subunits
33
breakdown of peptides
- hydrolysis
- protease catalyses reverse reaction
- water mol breaks peptide bond
- reforms amine + CA groups
34
globular proteins
- compact
- water soluble
- spherical
- formed when proteins fold into tertiary structure
-
35
insulin
- globular protein
- hormone regulates BGC
- soluble (transp in blood)
- precise shape to fit onto specific receptor
36
conjugated proteins
- globular proteins with a prosthetic group
- metal ions/mol from vitamins
- Haem groups = prosthetic groups : contain Fe2+
- Catalase + Hb
37
Hb
- quaternary + conjugated protein
- four poly petides , 2 alpha and 2 beta sub-units
- each sub unit has a prosthetic haem group
- Fe2+ combine irreversibly with O2 allow it to transport
38
catalase
- enzyme
- conjugated protein
- catalyse reactions
- quaternary protein with 4 prosethic haem groups
- Fe2+ allows catalse to react with H2O2 and speed up breakdown
39
fibrous proteins
- long , strong
- insoluble
- high proportion of Aa with hydrophobic R-groups
- organised structure
- not 3-D
- keratin, elastin + collagen
40
Keratin
- fibrous
- hair, skin , nail
- sulphur amino acids - cysteine
- strong disulphide bonds
41
elastin
- fibrous proteins
- quaternary protein
- in elastic fibres
- walls of BV + alveoli
- flexibility to expand + elastic recoil
- made of tropoelastin
42
collagen
- fibrous protein
- connective tissue
- skin, tendons + ligaments + NS
- 3 polypeptides wound in a long strong rope
- flexible
