Topic 1 Flashcards
(14 cards)
starch structure
alpha-glucose join to form:
slightly branched structure called amylopectin with 1-4 and 1-6 glycosidic bonds
coiled helix shape called amylose with 1-4 glycosidic bonds
cellulose structure
made up of beta-glucose molecules by 1-4 glycosidic bonds to form a long, straight polymer
polymers arranged parallel held by strong hydrogen bonds to form microfibrils mesh
pectin holds cell walls of adjacent together
why are proteins soluble in water
proteins fold so hydrophilic groups outside
exposed R groups are polar
can form hydrogen bonds
water is a polar solvent
globular proteins
structure examples (2)
compact, roughly spherical structure
has a tertiary and quarternary structure held by hydrogen, ionic and sulphur bonds
hydrophilic on the outside
e.g. haemoglobin, enzymes
Fibrous proteins
general structure
examples
structure of one of the examples
properties
Long, thin e.g. collagen (bone and cartilage), keratin (hair)
Collagen molecule consists of three long polypeptide chains held by crosslinking and hydrogen bonds
High tensile strength, flexibility, insoluble
DNA synthesis
- DNA helicase unwinds the double helix by breaking the hydrogen bonds between the complementary base pairs
- Forms two single strands which exposed bases act as a template for free nucleotides to form new complementary base pairings from A,T,C and G by hydrogen bonds
- DNA polymerase catalyses the condensation reaction to form covalent bonds between phosphate and deoxyribose of every new nucleotide along multiple sites of the DNA
- DNA ligase forms phosphodiester bonds to complete the phosphate-sugar backbone between two replication forks
- Process continues for the entire molecule
- A winding enzyme winds the new strands up to form two new helices
description of triplet codons
Universal code: all organisms have the same triplet codon which code for the same amino acid
Degenerate: 64 combinations of bases but only 22 so some amino acids are coded for by more than one triplet code
Non-overlapping: each triplet is only read once
protein synthesis
Transcription – DNA is used as a template to make mRNA
1. DNA helicase breaks hydrogen bonds, exposing the bases
2. Free complementary nucleotides join to the bases of the template strand (antisense DNA) and RNA polymerase joins the nucleotides together to form pre-mRNA
3. DNA strands re-join behind the building of pre-mRNA
4. Once RNA polymerase detects the stop codon, it detaches, completing production
5. Pre-mRNA is spliced where introns are removed and exons join together to form mRNA
- Introns prevent synthesis of polypeptide
6. mRNA molecules leave nucleus via nuclear pore and are attracted and attach to ribosomes in the cytoplasm
Translation – mRNA is used to make a protein
7. Ribosome attaches to mRNA molecule in cytoplasm
8. tRNA, carrying an amino acid specific to 3 base anticodon, moves to ribosome and pairs anti-codon sequence with the complementary bases on mRNA
9. Another tRNA molecule with another amino acid will pair with the next codon on mRNA
10. Amino acids join together by peptide bonds to extend polypeptide chain
11. mRNA releases tRNA which releases amino acid
12. tRNA picks up another free amino acid corresponding to its 3 base anti-codon
13. protein moves into ER and packaged into vesicles at end of RER
14. vesicles fuse with golgi apparatus which modifies proteins
15. vesicles move to cell surface membrane and leave by exocytosis
sickle cell anaemia
cause
what the heck is it
Result of point mutation, a substitution of one base in one codon changes one amino acid in a 147 amino acid chain
Haemoglobin molecules stick together to form rigid rods so they do not transport O2 efficiently and block small blood vessels
should measure the initial rate of enzyme-catalysed reactions
initial concentration of substrate will change quickly
enzymes cause large increase in reaction rates
initial rate will measure speed at correct value of independent variable
nitrate ions
to make DNA and amino acids
calcium ions
to form calcium pectate for the middle of lamellae of the cell wall which holds cells together to give a stronger cell structure
magnesium ions
to produce chlorophyll
phosphate ions
to make ADP, ATP, NAD and phospholipid
