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
