Processes Flashcards
Cardiac cycle
Atrial systole:
atria muscles contract decreasing volume and therefore increasing pressure, pressure of atria> pressure of ventricles causing atrioventricular valve to open, ventricles fill with blood
Ventricular systole:
atria relax, ventricles contract, pressure in ventricles is higher than pressure in atria causing AV valve to be forced shut, when pressure in ventricles> pressure in aorta the semilunar valve opens and blood leaves the heart via the aorta
Diastole:
muscles in ventricles relax, pressure in aorta > pressure in ventricles causing semilunar valve to shut, AV valve opens and atria and ventricles slowly fill (both atria and ventricles are relaxed)
Heart beat initiation
SAN in the wall of the right atrium contains pacemaker cells, these pacemaker cells initiate a wave of excitation (depolarisation) which passes through both atria causing the muscles in the wall of the atria to contract (atrial systole), a layer of nonconducting tissue between the atria and ventricles means the ventricles don’t contract straight away. When the wave of excitation reaches the AVN a slight delay is imposed to allow the ventricles to fully fill first and then passes the excitation down the septum along the Bundle of His. The bundle of His then splits of into purkyne fibres allowing the ventricles to contract (ventricular systole) from apex upwards
Transport of CO2 in the blood
CO2 can be transported in the blood 3 ways:
-as CO2 in blood plasma
-as carbaminohaemoglobin (Hb + CO2)
-As HCO3- ions:
In RBC:
CO2 + H2O —– H2CO3 ( catalysed by carbonic anhydrase)
H2CO3—– HCO3- + H+
The H+ ions will lower the pH so react with Hb to form haemoglobin acid and is said to act as a buffer
Chloride shift:
the HCO3- ions move out of RBC (by transport proteins) so Cl- moves into the cell (by transport proteins) to balance electrochemical gradient
Fetal haemoglobin vs adult haemoglobin
fetal haemoglobin must have a higher affinity for oxygen at low pO2 e.g. in placenta
O2 transferred from adult to fetal haemoglobin (in the placenta)
The fetus receives (sufficient) oxygen for respiration
This maintains O2 concentration gradient;
phloem loading and unloading
Phloem loading:
2 Ways:
Apoplast:
H+ ions in the companion cells are actively transported (require ATP) out of cell into cell wall creating a H+ ions concentration gradient, cotransporter proteins then facilitated diffusion of H+ ions back into companion cell along with sucrose (move against concentration gradient). The sucrose then diffuses into the sieve tube element through plasmodesmata
symplast: through the cytoplasm and plasmodesmata) which is a passive process as the sucrose molecules move by diffusion
This then lowers the water potential causing water to move by osmosis into the sieve tube element increasing hydrostatic pressure at source , as assimilates are removed at sink and water potential increase water leaves meaning low hydrostatic pressure at sink. Therefore phloem sap move by mass flow down pressure gradine allowing unloading of sucrose
Process of transpiration stream- needs editing
transpiration occurs at leaves and stem in which water vapour evaporates of surface of spongy mesophyll down water potential gradient. This causes water to move by osmosis out of top of xylem replace lost water reducing hydrostatic pressure at the top of the xylem. At the roots high hydrostatic pressure as solutes actively pumped in. Water molecules have strong cohesive and adhesive forces allowing a continuous column to be created and water to move by mass flow.
how is insulin produced
glucose enters the beta cell by facilitated diffusion through glucose transporter, respiration occurs producing ATP, ATP then causes ATP sensitive K+ channels to shut causing the cell to depolarise causing the voltage gated Ca+ channels to open, calcium causes insulin containing vesicles to move towards cell surface membrane and leave cell by exocytosis
saltatory conduction
The propagation of nerve impulses along axons occurs due to local currents that cause each successive section of the axon to reach the threshold potential. In sections of the axon that are surrounded by a myelin sheath, depolarisation (and the action potentials that this would lead to) cannot occur, as the myelin sheath stops the diffusion of sodium ions and potassium ions. Action potentials can only occur at the nodes of Ranvier (small uninsulated sections of the axon). The local circuits of current that trigger depolarisation in the next section of the axon membrane exist between the nodes of Ranvier. This means the action potentials ‘jump’ from one node to the next, a process known as saltatory conduction.
Resting potential
Na+/K+ ions pump moves Three sodium ions out of the axon for every two potassium ions that are pumped in. This helps to maintain a resting potential of -70mV due to the more negative charge on the inside compared to the positive outside of the axon.
Action potential
a stimulus causes Na+ ion channels in membrane to open allowing Na+ into the axon causing inside to be more positive and outside to be more negative, the membrane is depolarised. Depolarisation causes more Na+ channels to open causing it to further depolarise. The Na+ channels then shut and the K+ channels open allowing K+ out the cell. The K+ channels take a while to close again so membrane becomes hyperpolarised.
Because the area before has depolarised the next area is triggered to open Na+ ion channels and become depolarised.
saltatory conduction
The myelin sheath is formed from Schwann cells
In sections of the axon that are surrounded by a myelin sheath, depolarisation (and the action potentials that this would lead to) cannot occur, as the myelin sheath stops the diffusion of sodium ions and potassium ions
Action potentials can only occur at the nodes of Ranvier (small uninsulated sections of the axon)
The local circuits of current that trigger depolarisation in the next section of the axon membrane exist between the nodes of Ranvier. The presence of Schwann cells means the action potentials ‘jump’ from one node to the next, this is known as saltatory conduction
DNA sequencing
-DNA wanting to be sequenced is extracted and mixed with DNA primers (short single stranded sequences of complementary bases- DNA polymerase can only bind to double stranded) , DNA polymerase, terminator bases (dideoxynucleotides) and free nucleotides.
-PCR is used:
-heat to 95 to break H bonding between base pairs
-cooled to 50 to allow primer to anneal
-heat again to 65 for optimum temp for DNA polymerase to build complementary strand of DNA using free nucleotides
-When a terminator base is incorporated into DNA, synthesis is terminated and a short strand of DNA is produced with a terminator base with a marker on it at the end
-This process is repeated many times until all possible DNA chains are produced
-We no have many different lengths of DNA
-The new complementary DNA can be separated out from the template strand
-the new complementary DNA is separated by chain size using a type of electrophoresis called capillary tube
-a laseer beam detects the position and colour of each chain and is inputted into a computer which can give you the original DNA sequence
Next generation sequencing
any method of sequencing that has replaced sangrias method of sequencing e.g. nanoporation
Bioinformatics
Bioinformatics is the storage retrieval and analysis of data from biological studies and can include lots. It is a very large data base.
Studies may be:
-DNA sequences, RNA sequences, protein structure
-could compare genotype to phenotypes and look at prevalence of disease
-computer modelling of protein structure from the base sequence
-allows for comparisons of data (sequences)
-allows large amount of data to be accessed by researchers around the world
how a resting potential is set up and maintained
