1. Biological Molecules Flashcards
Uses of carbohydrates
- Respiratory substrates in cells
- Form structural components in plasma membranes and cell walls
Uses of lipids
- Bilayer of plasma membranes
- Hormones
- Respiratory substrates
Uses of proteins
- Form cell structures
- As enzymes
- As chemical messengers
- As components of the blood
Uses of nucleic acids
Carry the genetic code for the production of proteins. (in viruses & all living organisms-> evidence for evolution)
Def and examples of monomers
The smaller units from which larger molecules are made.
eg. 1️⃣ Monosaccharides
2️⃣ Amino acids
3️⃣ Nucleotides
Polymers
Molecules made from a large no. of monomers joined tgt.
Condensation reaction
Joins 2 molecules tgt
w/ the FORMATION of a chemical BOND &
involves the ELIMINATION of a molecule of WATER.
Hydrolysis
BREAKS a chemical BOND between 2 molecules &
involves the USE of a WATER molecule.
Monosaccharides
- def
- general formula
- examples
- the monomers from which larger carbohydrates are made
- (CH2O)n
- 1️⃣ Glucose
2️⃣ Galactose
3️⃣ Fructose
Condensation reaction between 2 monosaccharides
- Glycosidic bond
- Water
Formation of polysaccharides by condensation- examples
α-glucose -> glycogen
-> starch
β-glucose -> cellulose
Examples of disaccharides
- M𝘢𝘭tose- 2 x glucose (p𝘢𝘭)
- S𝘶crose- gl𝘶cose + fr𝘶ctose
- Lactose- Glucose + galactose
General formula of monosaccharides
(CH2O)n
α-glucose
CH2OH–O
H
What is an isomer?
Same molecule (same no. of atoms), different arrangement
Organisms that move use lipids rather than carbohydrates as an energy source. Suggest why.
Lipids provide more than twice as much energy as carbohydrate when oxidised.
This means the same amount of energy can be provided for less than half the mass.
Therefore, it is a lighter storage product- major plus if the organism is motile (able to move around).
The points where one collagen molecule ends and the next begins are spread out throughout the fibre, rather than all being in the same position along it.
Explain how this arrangement of collagen molecules is necessary for the efficient functioning of a tendon.
The junctions between adjacent collagen molecules- points of weakness.
If they are all at the same point in a fibre
-> a major weak point
=> the fibre might break
What is a DNA molecule?
- double helix
- 2 polypeptide chains
- held tgt by H bonds
- between specific complementary base pairs
What kind of reactions can the hydrolysis of ATP be coupled to?
Energy-requiring reactions within cells.
What are the roles of lipids?
- Source of energy
- releases > 2x energy than carbohydrates when oxidised + produces water
- Waterproofing
- insoluble in water
- Insulation
- retain body heat ∵ slow conductors of heat
- electrical insulators- myelein sheath around nerve cells
- Protection around delicate organs
Advantages of triglycerides
- Source of energy
- ↑ energy-storing CH bonds : C atoms
- Good storage molecules
- ↓ mass : energy (↑ energy stored in small vol–> ↓ mass
- Insoluble in water
- x affect H2O potential ∵ large & non-polar
- Source of water
- ↑ H : O atoms –> release water when oxidised
Why did many scientists initially doubt that DNA was the genetic code?
- chemically simple w/ few components
- proteins in chromosomes believed to contain genetic info ∵ proteins showed ↑ variation
Describe 3 roles of RNA.
- transfer genetic info from DNA to ribosomes
- proteins –> ribosomes
- protein synthesis
What is a metabolic pathway?
A series of reactions in which each step is catalysed by an ezyme.
What is end-product inhibition?
- non-competitive
- negative feedback loop of end product inhibiting action of first enzyme in the metabolic pathway
- if conc of end product ↑, inhibition of first enzyme ↑
∴ ↓ end products produced –> conc back to normal
Suggest how the cross-linkages between the amino acids of polypeptide chains increase the strength and stability of a collagen fibre.
- prevents individual polypeptide chains from sliding past one another
–> gain strength ∵ act as a single unit
Explain why changing certain amino acids that are not part of the active site also prevents the enzyme from functioning.
- changed a.a. may be one that forms H bonds w/ other a.a.
- if new a.a. X form H bonds,
- tertiary structure changes- including a.s.
- substrate will no longer fit
Suggest a possible purpose of enzyme Y in the mammalian stomach.
- milk = only food in diet of young mammals
- enzyme coagulates milk–> remains in stomach for longer –> ↑ time for enzymes to act on + broken down & absorbed
- if liquid–> passes thru stomach ↑ quickly–> only partially digested
Suggest why enzymes are attached to the inner membrane of an organelle ‘in a very precise sequence’.
- product of one reaction acts as substrate for next reaction
- sequence ↑ chance of each enzyme coming into contact w/ substrate
- ↑ efficient production of end product
Suggest an advantage of end-product inhibition being non-competitive rather than competitive.
- level of end product X fluctuate w/ changes in level of substrate
- non-comp X competing for a.s.
- X affected by substrate conc.
Role of iron ions
- haemoglobin- 4 polypeptide chains w/ Fe2+ in the centre
- binds to O2 (temprarily becomes Fe3+ until O2 is released)
Role of hydrogen ions
Affects enzyme-controlled reactions
- conc. of H+
Role of sodium ions
co-transport of glucose & amino acids across cell surface membrane alongside Na+
Roles of phosphate ions
- bonds between phosphate group STORE ENERGY in ATP
- phosphate groups in DNA & RNA –> nucleotides join to form polynucleotides
Structure of glycerol
—H
l
H-C-OH
l
H-C-OH
l
H-C-OH
l
H
