Model Answers Flashcards
1
Q
Protein Structure
A
- proteins have a primary structure, formed by a sequence of amino acids joined together by peptide bonds in a condensation reaction
primary structure folds into a secondary structure of either alpha helix or beta pleated sheets, held together by hydrogen bonds - secondary structure folds into a tertiary 3D structure held together by hydrogen bonds, ionic bonds, and disulphide bonds
- some proteins may form a quaternary structure of more than one polypeptide chain
2
Q
Induced Fit (Enzymes)
A
- enzyme active site is complementary to substrate
- when substrate binds, enzyme changes shape slightly
- stresses bonds in substrate
- reducing activation energy for the reaction
- quicker rate of reaction
3
Q
Competitive Inhibitors
A
- bind to active site
- blocks active site so substrate can’t bind
- fewer enzyme-substrate complexes form
4
Q
Non-competitive Inhibitor
A
- binds to allosteric site
- changes tertiary structure
- enzyme no longer complementary to substrate
- fewer enzyme-substrate complexes form
5
Q
DNA Structure
A
- DNA is made of a polymer of nucleotides (polynucleotide)
- two molecules antiparallel to each other, coiled into a double helix
- each nucleotide made up of deoxyribose (pentose) sugar, a phosphate group, and an organic nitrogenous base (adenine, thymine, guanine, cytosine)
- adjacent nucleotides joined between the sugar and phosphate group in a condensation reaction forming a phosphodiester bond
- complementary base pairing holds two strands together due to hydrogen bonds
6
Q
DNA Replication/ Semi-conservative Replication
A
- DNA helicase breaks hydrogen bonds causing strands to separate
- both strands act as a template
- free nucleotides complementary base pair to template
- DNA polymerase joins adjacent nucleotides together forming phosphodiester bonds
- hydrogen bonds form between the old and new synthesised strand
7
Q
ATP
A
- nucleotide structure
- has a ribose sugar with adenine base and three phosphate groups attached
- phosphate groups can be hydrolysed to remove a phosphate
- this hydrolysis can be used to release energy for chemical reactions (can also be used for phosphorylation, which can make substrates more reactive)
- ATP can be resynthesised by ATP synthase during respiration and photosynthesis
8
Q
Water
A
- a metabolite in hydrolysis and condensation reactions
- a solvent so metabolic reactions can occur
- high specific heat capacity to buffer changes in temperature
- high latent heat of vaporisation provides a cooling effect
- cohesion between molecules forms a continuous column of water in the xylem
- cohesion causes surface tension for organisms to move on bodies of water
9
Q
Inorganic Ions
A
- H+ for chemiosmosis and oxidative phosphorylation
- H+ for maintaining pH
- Na+ for co-transport
- Na+ for depolarisation
- Na+ for sodium potassium pump
- K+ for sodium potassium pump
- Fe 2+ for haemoglobin
- Ca 2+ for NMJ
- Ca 2+ synaptic transmission
- Ca 2+ sliding filament
- PO4 3- for phospholipid bilayer, DNA, RNA, and ATP
- NO3 - for nitrogen cycle and nitrogen containing compounds
10
Q
Mitosis
A
- DNA replicated in S-phase of interphase
- prophase - chromosomes condense and become visible
- metaphase - chromosomes line up along the equator of the cell
- anaphase - sister chromatids pulled to opposite poles of the cell by spindle fibres
- telephase- chromosomes decondense and nuclear envelope starts to reform
- cytokinesis - cytoplasm and surface membrane splits forming two genetically identical cells
11
Q
Binary Fission
A
- bacteria are prokaryotes produced by binary fission
- DNA (and plasmids) are replicated
- cytoplasm and cell membrane divides in two
- each daughter cell receives a copy of the circular DNA
12
Q
Phospholipid Bilayer
A
- made up of phospholipids with hydrophilic (polar) phosphate heads and hydrophobic (non-polar) fatty acid tails
- bilayer limits movement of substances through membrane so only small non-polar molecules can freely diffuse through
- transmembrane proteins can act as carrier and channel proteins
- channel proteins allow facilitated diffusion of ions, and also transport molecules across the membrane using energy from ATP (in active transport)
- glycoproteins act as antigens for cell recognition, increase stability and adhesion of cells
- glycolipids also increase stability and adhesion of cells
- cholesterol increases rigidity of membrane
13
Q
Phagocytosis
A
- phagocyte recognises antigen
- pathogen is engulfed into phagosome
- lysosome fuses with phagosome forming a phagolysosome
- lysosome enzymes hydrolyse pathogen
- antigens from pathogen presented on cell surface
14
Q
Cell Mediated Immunity
A
- antigen presented by antigen presenting cell
- helper T cells with complementary receptors bind to antigen
- helper T cells activated and go through mitosis
- forms cytotoxic T cells and more helper T cells
- cytotoxic T cells produce perforins to kill cells by making holes in their cell surface membrane, water enters, and causes the cell to burst
15
Q
Comparison of Prokaryote and Eukaryote DNA
A
- prokaryotic DNA is short, eukaryotic DNA is longer
- prokaryotic DNA is circular, eukaryotic DNA is linear
- prokaryotic DNA has no introns, eukaryotic DNA has introns
- prokaryotic DNA is free floating, eukaryotic DNA is contained within the nucleus
