biology exam revision

light independent inputs and outputs

18ATP, 12 NADPH, 6 carbon dioxide

18ADP + Pi, 12 NADP+, 1 glucose, 6 water

aerobic respiration

1 glucose, 6 oxygen

30 or 32 ATP, 6 carbon dioxide, 6 water

light dependent inputs and outputs

12 water, 12 NADP+, 18ADP + Pi

6 oxygen, 12 NADPH, 18ATP

overall photosynthesis

12 water, 6 carbon dioxide

6 water, 1 glucose, 6 oxygen

lactic acid fermentation

1 glucose

2 lactate, 2ATP

ethanol fermentation

1 glucose

2 ethanol, 2ATP, 2 carbon dioxide

ELISA

Antibodies complementary to pathogenic antigens are plated. Sample is added - if that pathogen is present in the sample, its antigens will bind to the antibody. A detection antibody with an enzyme is added, which will bind to the antigen-antibody complex if it is present. A substrate is added, releases a signal if the antigens are present

Howea Palms

Howea belmoreana - original, neutral pH

Howea forsteriana - diverged, higher pH

Attenuation

RNA polymerase transcribes leader region, as repressor is not bound to operator. Ribosome reads mRNA and two tryptophan codons, stops if tRNA with tryptophan does not arrive. This allows mRNA to form an antiterminator hairpin loop, so transcription continues, operon is expressed.

CRISPR steps

Exposure: Cas 1 and 2 find PAM on viral DNA and cut upstream of it to get protospacer, insert it into CRISPR array

Expression: Spacer and half repeat on either side is transcribed, forming guide RNA which binds to Cas9

Extermination: CRISPR-Cas9 searches for PAM. Binds to the PAM and unwinds DNA. If section upstream of PAM is complementary to gRNA, it will cut the DNA leaving blunt ends

Recombinant plasmids

Plasmid vector with two reporter genes is chosen. One has recognition site. Gene of interest and plasmid are cut with same restriction endonuclease, creating complementary sticky ends which allow them to join. Gene of interest is inserted into a reporter gene, disrupting it.

Insulin production

Bacteria are exposed to ampicillin - transformed will live as they have plasmids and so can express ampicillin resistance. Then exposed to tetracycline - insulin subunit gene is inserted into tetracycline resistance so recombinant plasmid bacteria will die. The plasmids are extracted from them, and a lac Z gene is added, then they are taken up by bacteria again.

Purpose of Lac Z

Produces beta-galactosidase, which forms a fusion protein with insulin subunit to prevent bacteria consuming it. Also acts as a reporter gene - turns blue in presence of X-gal. So blue bacteria contain recombinant plasmids and are producing insulin.

C4 adaptations

PEP carboxylase performs initial carbon fixation in mesophyll cell. Rubisco completes in bundle sheath cell, which is further from stomata - lower oxygen, higher carbon concentration

CAM adaptations

PEP carboxylase performs initial carbon fixation at night - carbon is stored in vacuole. In day, stomata close, carbon is released, creating high carbon concentration for Rubisco to act on.

Complement proteins three actions

Opsonisation - bind to surface

Chemotaxis - attract phagocytes

Membrane attack complex - punch holes, lysis

Inflammation

Initiation - tissue damage causes release of cytokines from macrophages and histamine

Vasodilation - Histamine binds to blood vessel receptors, increasing permeability

Migration - Phagocytes are attracted by cytokines

Frameshift

As codons are read in groups of three nucleotides, the deletion of one or two nucleotides changes the order of nucleotides in following codons. This can create a different sequence of amino acids

Steps in sympatric speciation

Variation in population creates different phenotypes. Selection pressures act differently on different phenotypes, causing genetic divergence. This creates isolating mechanisms, preventing interbreeding