Paper 2 recall Flashcards
Where are electron carries in photosynthesis located?
The thylakoid membrane
Where are protons pumped to and from in the chemiosmotic theory of photosynthesis?
They move from the stroma into the thylakoid intermembrane space
How are the electrons in chlorophyll replaced after photoionisation?
Photolysis of water splits to release electrons
What are all the products of the light dependent stage?
Oxygen, NADPH and ATP
What are some of the adaptations of chlorophyll for photosythesis?
Contain DNA and ribosomes to make proteins and enzymes, selectively permeable allows H+ gradient established, thylakoid membrane has large SA for chlorophyll, electron carriers and enzyme attachment and grana maximises light absorption
How is GP reduced to TP in photosynthesis?
Glycerate 3-phosphate is reduced to triose phosphate as NADPH is oxidised to NADP and energy is supplied from ATP
How is RuBP regenerated?
Most TP reforms Ribulose BiPhosphate using ATP
How is TP converted to pyruvate in glycolysis?
It is oxidised and NADH formed, each TP also synthesises two ATP per molecule so net gain 2 ATP for the whole of glycolysis
What happens in the link reaction?
The pyruvate is oxidised to acetate, CO2 is lost from the molecule and two hydrogens to form 1 NADH, acetate then combines with coenzyme A to form acetylcoenzyme A
What are the raw products for one Kreb cycle?
2 CO2, 3NADH, 1 FADH and one ATP
How are electrons released at the ETC of oxidative phosphorylation?
The Hydrogen atoms of NADH and FADH are released and they split to release electron which enter the carrier proteins and protons
How is the release of energy from electrons controlled?
As they move through the electron carriers, they move into lower energy levels so down an energy gradient, this causes gradual releases of energy that allow all the energy to be used
What are lipids and proteins converted to for use in respiration?
Glycerol becomes phosphorylates then becomes TP, fatty acids are converted to Acetyl Coenzyme A and proteins are converted to intermediates of the Krebs cycle
How is NAD regenerated in anaerobic respiration?
The pyruvate becomes reduced
What happens to lactate once oxygen becomes available again?
It is oxidised back to pyruvate which can then be further oxidised to release energy or converted into glycogen in the liver
What are saprobionts?
Organisms that break down the complex materials of dead organisms into simple structure that can be used by plants
What is biomass?
Total mass of living material in a specific area at a given time (mass of carbon easier measure due to water varying)
Why is so much of the suns energy NOT used to synthesise organic substances by plants?
90% of the sun energy reflected back by clouds and dust, not all wavelengths of light absorbed by plants, light may not fall on chlorophyll molecule and other factors such as CO2 may limit the rate of photosynthesis leading to 1-3% of the suns energy harnessed
What is the Gross Primary Production?
Total quantity of chemical energy store in plant biomass in a given area or volume in a given time
What is NPP used for?
Growth and reproduction
Why is energy transfer between trophic levels low?
Not all of the organism consumed, some parts not digested (faeces), energy lost in excretion (urine) and heat losses from respiration
How have nitrogen fertilisers reduced species diversity?
Soils favour the growth of grasses, nettles and other rapidly growing species, these out-compete many other species
What is IAA?
Indoleacetic acid (a plant growth factor)
How does IAA affect roots?
Inhibits cell elongation
What is the proposed explanation for IAA increasing plasticity of cell walls?
Acid growth hypothesis, active transport of H+ ions from the cytoplasm into spaces in the cell walls causing cell wall to become more plastic allowing the cell to elongate by expansion
What is the peripheral nervous system?
Pairs of nerves that originate from either the brain or the spinal cord
What are the features of a reflex?
Rapid, short lived, localised and involuntary
What does the coordinator neurone do?
Links the sensory neurone to the motor neurone in the spinal cord
How does the Pacinian Corpuscle act as a transducer?
Converts the change in the form of energy by the stimulus into nerve impulses that can be understood by the body
What are the features of rod cells?
Abundant, only see black and white, many connected to one bipolar cell, low light intensity, night vision, single impulse so low visual acuity, found at the peripheries
What are the features of cone cells?
Three different types (different sensitivities to wavelengths), own bipolar cell connected, only respond to high light intensity (iodopsin broke down), multiple impulses so good visual acuity, found only at the fovea
How does the heart beat?
SAN emits wave of electricity which causes atria to contract, this reaches AVN which emits another wave through Purkyne fibres in Bundle of His to cause ventricles to contract from the bottom upwards
What are the 6 features of mammalian motor neurones?
A cell body, dendrons, an axon, Schwann cells, myelin sheath and nodes of Ranvier
What are dendrons?
Extensions of the cell body which subdivide into smaller branched fibres called dendrites, that carry nerve impulses towards the cell body
What is an axon?
A single long fibre that carries nerve impulses away from the body cell
What are Schwann cells?
Surround the axon to protect it, and provide electrical insulation, they also carry out phagocytosis, they wrap aourn the axon many times to form the myelin sheath
How is a potential difference established (resting potential)?
Three sodium ions actively transported out and two potassium ions actively transported in by sodium potassium pump, sodium ions channels closed but potassium ion channels open
How does hyperpolarisation occur?
Outward diffusion of potassium ions causes temporary overshoot in electrical gradient, with the inside of the axon being more negative than usual
How does depolarisation of one region on an axon transfer to the next?
Sodium ion channels are voltage gated so when one are has an increase in voltage it causes adjacent sodium ion channels to open
What factors increase the speed of action potentials along an axon?
Presence of a myelin sheath, larger diameter (less leakage) and higher temperatures (until denaturation)
How do organisms perceive the different sizes of stimuli?
By the number of impulses passing in a given time and by having different neurones with different threshold values
What are the purposes of the refractory period?
Ensure the action potentials are propagated in one direction only, produces discrete impulses (separates action potentials) and limits the number of action potentials passing along one axon
How do inhibitory synapses operate?
Neurotransmitters bind to chloride ion protein channels, causing them to open so Cl- move into post-synaptic neurone, K+ channels also open so K+ moves out, this causes hyperpolarisation, meaning threshold potentials harder to reach
What are excitatory synapses?
Synapses that generate a new action potential
What are the processes of transmission across a cholinergic synapse?
Action potential arrives at synaptic knob and Ca2+ channels open for Ca2+ to move into knob, causing synaptic vesicles to fuse with the membrane and acetylcholine released into synaptic cleft, diffuse and bind to receptors on Na+ channels, allowing Na+ to diffuse in, generating a new action potential, acetylcholinesterase then breaks it down and it diffuses back to the pre-synaptic neurone, ATP reforms acetyl choline and is stored for future use
What are the different bands in muscles?
I band is lighter as it consists only of the thin actin and A bands are darker as this is where the thick and thin bands overlap
What is the Z line?
Marks the end of the sarcomere
How are slow twitch muscle fibres adapted to aerobic respiration?
A large store of myoglobin, a rich supply of blood vessels to deliver oxygen and glucose and numerous mitochondria to produce ATP
How are fast twitch muscle fibres adapted to their role?
Thicker and more numerous myosin filaments, high concentration of glycogen, high concentration of enzymes for anaerobic respiration and a store of phosphocreatine
What structures of muscles change during contraction?
H zone, I band and Z lines all narrow
What happens in muscle contraction?
Action potential travels deep into a fibre through tubules (extensions of membrane of sarcomere), opening Ca2+ channels on the ER causing Ca2+ to diffuse out, these cause tropomyosin on actin binding sites to pull away, myosin head form crossbridge, heads change their angle to pull the actin along and release ADP, ATP attaches to head and they release actin, Ca2+ activate ATPase and ATP energy release causes head to return to original position
What happens in muscle relaxation?
Ca2+ actively transported into ER and tropomyosin block actin binding sites
What is ATP used for in muscle contraction?
The movement of the myosin heads and the reabsorption of calcium ions by the ER
What is the second messenger model?
Adrenaline binds to transmembrane protein receptors on liver cells, changing protein shape inside the membrane, this activates adenyl cyclase which converts ATP to cAMP, the cAMP acts as a second messenger and binds to protein kinase activating it, this catalyses the conversion of glycogen to glucose which moves into the blood by facilitated diffusion
What are the Islets of Langerhans and what do they produce?
They are groups of hormone producing cells, alpha cells produce glucagon and beta cells produce insulin
What can be used for gluconeogenesis?
Glycerol and amino acids
How does insulin reduce blood glucose concentration?
Changes tertiary structure of glucose channel proteins causing them to open, causes vesicles with transport proteins inside to fuse with the membrane and activates enzymes to convert glucose to glycogen and fat
What does glucagon do?
Attaches to specific protein receptors on liver cells, activates enzymes that convert glycogen to glucose and activates enzymes for gluconeogenesis
What are the features of the kidney?
Fibrous capsule, cortex, medulla, renal pelvis, ureter, renal artery and renal vein
What is the renal pelvis?
A funnel shaped cavity that collects urine into the ureter
What does the Renal capsule consist of?
Network of capillaries known as the glomerulus and the inner layer is made up of specialised cells called podocytes
What are the blood vessels associated with each nephron?
The afferent arteriole, which form the glomerulus, which leads into the efferent arteriole before it becomes the blood capillaries surrounding the nephron before leading into the renal vein
What is formed in ultrafiltration?
The glomerular filtrate which is a solution containing water, glucose, urea and mineral ions, that move out of the glomerulus through pores in the endothelial cells
How are substances reabsorbed by the PCT?
Na+ actively transported out of endothelial cells into capillaries so Na+ facilitated diffusion into endothelial cells with glucose, amino acids or chloride ions
What ‘s the differences between the descending and ascending limb?
The descending is narrow, thin and highly permeable to water, whereas ascending is wider, thick and impermeable to water
How is ADH released?
Osmoreceptors in the hypothalamus shrink, causing the posterior pituitary gland to release ADH
What is autosomal linkage?
Any to genes that occur on the same chromosome that aren’t sex chromosomes
How does ADH increase water potential?
Binds to protein receptors on cell-surface membranes causing activation of phosphorylase which causes vesicles to move and fuse with the membrane increasing aquaporins of collecting duct and DCT also send nerve impulses to thirst centre of the brain
What is epistasis?
When the allele of one gene affects or masks the expression of another in the phenotype
What is allelic frequency?
The number of times an allele occurs within a gene pool
What are the 5 conditions for the Hardy-Weinberg equation?
No mutations arise, population is isolated, no selection pressures, large population and mating is random
What causes genetic variation?
Mutations, meiosis (independent segregation and crossing over) and random fertilisation
What are the different forms of selection?
Stabilising, directional and disruptive
What is genetic drift?
Small population have few breeding individuals, meaning smaller variety of alleles and reduced genetic diversity, however fast genetic drift can increase speed of speciation
What is sympatric speciation?
The formation of a species from reproductive isolation, yet the same area geographically, mutations leads to the evolution of genetic differences
What are the three possible consequences of base substitution?
Formation of the stop codon, meaning polypeptides made shorter, code fora different amino acid or codes for the same amino acid as the genetic code is degenerate
What are the different gene mutations?
Substitution, deletion, addition, duplication, inversion and translocation
What is translocation mutation?
When a group of bases become separated from the DNA sequence on one chromosome and insert onto a different chromosome (cancer and infertility)
What are totipotent cells?
Cell which can divide and differentiate into any type of cell (fertilised egg)
What are the various sources of stem cells in mammals?
Embryonic, umbilical cord blood, placental and adult
What are pluripotent cells and where are they found?
In the embryos and can differentiate into almost any type of cell
What are multipotent cells and where are they found?
In adults and umbilical cord blood and can differentiate into a limited number of cells
What are unipotent cells and where are they found?
Derive from multipotent stem cells and are made in adult tissue, they can only differentiate into a single type of cell
What are induced pluripotent cells?
Extracted and lab treated unipotent cells (any adult tissue), they’re self-renewing meaning they have the same applications as embryonic stem cells, but none of the ethical issues
How is transcription controlled?
Transcriptional factors move into the nucleus from the cytoplasm and bind to a specific base sequence of the DNA, mRNA is produced, when a gene is switched off, the site of the transcriptional factor is not active as it’s not bound
How does oestrogen act through second messenger models?
It’s lipid soluble so diffuses through phospholipid membrane, and binds with a site on a receptor molecule of the transcriptional factor, this causes the shape of the DNA binding site on the transcriptional factor to change shape and is now complimentary to DNA
What is epigenetics?
The influence that environmental factors have causing heritable changes in gene functions without changing the base sequences of DNA
What is the epigenome?
A second layer surrounding the DNA-histone complex made of chemical tags, this determines the shape of the complex
The epigenome of a cell is the accumulation of the signals it has received during it’s lifetime and it therefore acts like cellular memory
How can condensation of DNA to reduce transcription occur?
Decreased acetylation of the histones or increased methylation of DNA
How does decreased acetylation affect DNA?
Increases the positive charges on histones and therefore increases the attraction of the phosphate groups on DNA, making the association stronger and the DNA not accessible to transcription factors
How does increased methylation affect DNA?
Added to the cytosine bases to either: prevent the transcriptional factors binding to the complex or attracting proteins that condense the complex making it inaccessible
How does small interfering (si)RNA impact translation?
An enzyme cuts large double-stranded molecules of RNA into smaller siRNA, one siRNA bind with an enzyme, the siRNA guides the enzyme to mRNA by base pairing, enzymes then cut the mRNA into smaller sections so it cannot be translated
What are oncogenes?
Most are mutations of proto-oncogenes (stimulate cell division) oncogenes are permanently activated for two reasons: receptor protein on membrane permanently activated or may code for a growth factor
What do tumour-suppressor genes do?
Slow down cell division, repair mistakes in DNA and cause apoptosis
What happens in hypermethylation of tumour-suppressor genes?
Methylation occurs in a specific region of the gene, causing it to become inactive
What is bioinformatics?
The collection and analysis of complex biological data such as genetic codes, using computers to read, store and organise biological data
What is recombinant DNA?
DNA from two organisms that has been combined using technology
What are the 5 stages of making proteins from DNA technology?
Isolation, insertion, transformation, identification and growth
What are three methods of producing DNA fragments?
Conversion of mRNA to cDNA (complimentary), restriction endonuclease and synthesis is gene machine
What are sticky ends?
When restriction endonuclease cut DNA to leave staggered ends rather than straight, the two ends produced must be palindromes of one another
How does the gene machine work?
Computer is given the DNA nucleotide chain needed to produce, the computer designs a series of small overlapping single strands known as oligonucleotides, they’re assembled then joined together to make a gene, which is replicated in PCR, the gene can then be inserted into bacterial plasmid, using sticky ends which can be stored, cloned or transferred to another organism
What are the two methods of gene cloning?
In vivo, by transferring into host cells using vector
In vitro, by using PCR
What enzyme joins together sticky ends?
DNA ligase binds the phosphate sugar framework to join them as one
Why are stick ends important?
Provided the same restriction endonuclease is used, the DNA of one organism can join with the DNA of another
What is the promotor?
The binding site of mRNA polymerase on DNA and transcriptional factors binding sites
What is the terminator?
Region of DNA that released RNA polymerase and stops RNA synthesis
How is DNA inserted into the vector?
The carrier (usually plasmids) is cut with the same restriction endonuclease, DNA ligase joins them and the plasmid now had recombinant DNA
How are plasmids inserted back into bacteria?
Plasmids and bacteria are mixed in a solution containing Ca2+ ions, the ions and increasing temperature increase the permeability of membranes allowing the plasmids to pass through
What are some marker genes?
Second genes incorporated that are easily identifiable, for example, genes for antibiotic resistance, create fluorescent proteins or produces enzymes that actions can be identified
What is replica plating?
The use of antibiotic resistant genes to cut at the site and insert so they’re no longer resistant
What does the polymerase chain reaction require?
The DNA fragment, DNA polymerase, primers, nucleotides and a thermocycler
What form of DNA polymerase is used and why?
Taq polymerase, it’s collected from bacteria on volcanic vents so can withstand high temperature
What happens in PCR?
Vessel reaches 95C, causing H bonds to break, cooled to 55C causing primers to anneal, providing starting sequences for DNA polymerase, the temp is increased to 72C as this is optimum for polymerase
What are the advantages of in vitro cloning?
Rapid, doesn’t require living cells
What are the advantages of in vivo cloning?
Useful for transfer genes into another organism, no risk of contamination, very accurate, cuts out specific genes and produces transformed bacteria that can be used to produce large quantities
What are DNA probes?
Short single-stranded DNA that is radioactively labelled (P-32) or fluorescent
What happens in DNA hybridisation?
DNA heated into two complimentary single strands then cooled to allow annealing to DNA probes as well as reforming original strand
What are VNTR?
Variable number tandem repeats are DNA bases that are non-coding
What are the 5 main stages of genetic fingerprinting?
Extraction, digestion, separation, hybridisation and development
What are the uses of DNA fingerprinting?
Genetic relationships and variability, forensic science, medical diagnosis and plant and animal breeding
