Core Processes Flashcards
Starch digestion
Begins in mouth where salivary amylase are secreted hydrolysing glycosidic bonds in starch to form maltose, also breaks food down into smaller pieces to increase SA to increase enzyme activity.
In stomach salivary enzymes are denatured.
In small intestine, pancreatic amylase secreted to hydrolyse remaining starch into maltose. Alkaline salts secreted to neutralise pH.
In ileum, membrane bound disacharidases (maltose) hydrolyse maltose into alpha glucose which can be absorbed
Protein digestion
Large folded polypeptides are denatured by the HCl in the stomach, they unfold into polypeptide chains.
Endopeptidase hydrolyses peptide bonds in polypeptides to form smaller polypeptide chains. (In stomach and ileum)
Exopeptidases hydrolyse peptide bonds to form smaller dipeptides.
Dipeptidase hydrolyses the peptide bonds to form two amino acids which can be absorbed by body
Lipid digestion
Fat globules are emulsified by bile slats to form smaller monoglycerides which increase SA
Lipases hydrolyses ester bonds which breaks them into glycerol, fatty acids, and bile salts.
These form micelles which are water soluble and can diffuse into epithileum .
They diffuse into epithelial cells and reach the SER
Triglycerides reform and are packaged into the Golgi vesicle - chylomicron
Leave via exocytosis into the lymphatic system and into the blood.
Absorption of AAs and monosaccharides
Na ions activel transported out of EC creates a concentration gradient
Na ions diffuse into EC down conc gradient through co transport protein carrying an AA/glucose
AA/glucosse pass into blood plasma by facilitated diffusion using carrier protein
Ventilation
Gases move down the trachea, bronchus, and bronchioles, gas exchange happens at alveoli which are at the ends of the bronchioles
Inspiration - external intercostal muscle and diaphragm contract, internal intercostal relax -> ribs move up and out and diaphragm down -> increase in thorax volume which decreases pulmanory pressure -> atmospheric pressure is greater so air from surroundings moves down pressure gradient into lungs
Expiration - external IM and diaphragm relax, internal IM contract -> diaphragm moves up pushing air out -> volume in lungs decreases so pulmanory pressure increases which is greater than atmospheric pressure so air moves down pressure gradient into atmosphere out of lungs
Gas exchange in fish
Water flows over gills in opposite direction to blood to maintain a conc gradient along the whole length of thr gill
Blood has lower conc of O2 so that O2 from water always moves down conc gradient into the blood
Gas exchange in insect
Spiracles on the exoskeleton (which is impermeable to gas) open which allows gas to diffuse in -> moves down trachea to tracheoles which are highly branched to increase SA -> diffuse into cells and muscle tissue
Cohesion tension theory
Xylem transports water because it forms a continuous tube through the plant.
Passive process so doesn’t use energy, only thermal energy from the sun
Water is lost in the leaf by transpiration by stomata -> reduces water potential in mesophyll cells
Water is drawn up the xylem down the water potential gradient
Xylem is under tension and because of H bonds in water, it is cohesive and moves up a continuous column, it adheres to the walls which pulls them in (tension), water is replaced by the roots
Mass flow hypothesis
Sucrose solution moves from source to sink.
Sucrose solution is co transported into sieve tube element via active transport through companion cells
This decreases water potential so water from the xylem moves in via osmosis which increases hydrostatic pressure.
This pushes the sucrose solution through the sieve tube plates down the pressure gradient
At the sink, the sucrose is actively removed from the sieve tube element via a companion cell and sucrose diffuses into sink
Increases water potential in the phloem so water moves back into the xylem via osmosis
The sugars are used in the sink for respiration
Ringing experiment
Stem bulges with fluid containing sugar above sections where the ring of bark has been removed
Shows that removal of phloem prevents downwards flow of sugar
Radioactive tracers
Radioactive isotopes in thr form of CO2 supplied to a leaf is incorporated into organic substances and can be traced around the plant
Shows that organic substances move from source to sink
Mitosis
PMAT
Prophase -> DNA is condensed into chromosomes, nuclear envelope disintegrates, centrioles form at poles of cell
Metaphase -> nuclear envelope gone, chromosomes line up at equator, spindle fibre attach to centromeres
Anaphase -> spindle fibres contract, centromere splits and one chromatid from each chromosome is pulled to opposite end
Telophase - nuclear envelope reforms, DNA uncondenses, cytoplasm pinches in middle
Binary fission
DNA and cell contents replicates
Cell elongates and DNA pulled to poles of cell
Cytoplasm divides forming 2 genetically identical daughter cells
Cell wall reforms
Viral replication
Virus attaches to host cell using attachment proteins
Virus injects nucleic acid into cell
Host cell replicates viral genome and ribosomes produce viral protein
Viral proteins assemble into new viruses
Cell lyses and releases virus
Reducing sugar test
Add excess Benedict’s reagent to sample
Heat in water bath
If it is present, a precipitate will form - red for high conc
Non reducing
Reducing test wont work so - add dilute HCl and heat in water bath to break the bonds and form monosaccharides
Add alkali NaOH to neutralise
Add excess Benedict’s reagent
Heat in water bath
Precipitate forms
Biurets tests
Add NaOH to sample, mix in copper (II) sulphate, positive purple result
