weeks 10-11

Question 1

cell wall layers

Answer 1

middle lamella - contact point between 2 cell walls. Has pectin - gelatinous
primary cell wall
secondary cell wall

cellulose glycans are crosslinked with other glycans
proteins change rigidity
liginin - improves rigidity
suberin - wax, waterproofing

Question 2

cellulose microfibrils

Answer 2

made by cellulose synthase complexes in the plasma membrane
mew microfibrils are deposited outside the cell

enzyme complex is linked to microtubules in cytosol, it is pushed along during synthesis
orientation of microfibrils is parallel to microtubules, determines growth and cell shape

made in groups of 6

Question 3

stomata opening and closing

Answer 3

microtubules and cellulose microfibrils fan out radially from stomatal pore
guard cell walls are stronger next to pore than outside

To close - increase in ABA, efflux of solutes. Less negative water potential. water efflux, decrease in turgor pressure

to open - transport of solutes into guard cell lowers water potential. Water moves in, increase in turgor pressure

Question 4

stomatal density

Answer 4

long term response
reduced water decreases SD
Increased temp decreases SD

Question 5

plants used in plant physiology practical

ad/abaxial meaning

Answer 5

Arabidopsis Thaliana - smaller
Pisum sativum - pea plants

adaxial - top, facing stem
abaxial - bottom

Question 6

aquaporins
plasmolysis
turgor pressure
evapotranspiration

Answer 6

mambrane proteins that act as water channels

cell volume shrinks, plasma membrane detaches from cell wall

cell volume increases, resisted by cell wall

water taken up by roots, transported up xylem

Question 7

water potential

Answer 7

measured in megapascals
water potential = pressure potential/turgor pressure + solute potential/conc of solutes

when outside has lower water potential there is no turgor pressure
solute potential goes more negative because of volume shrinkage

if turgor pressure = 0MPa then plant wilts

Question 8

touch response in plants

Answer 8

compound leaf with many leaflets
pulvinus - group of cells at base of leaflet

ions flow out of cells on inside close to petiole
increase in water potential so water goes out
turgor pressure higher on outside to leaflets fold inwards towards petiole

Question 9

how to make plant physiology practical better

Answer 9

more samples/ peels
use waterbath to control temp
standardised light source/ one without heat
make sure all under lamp for same time
everyone should do all concentrations

Question 10

plant cell growth

Answer 10

elongationn zone - cells grow rapidly
lots of cell division in the meristem

turgor pressure drives cell wall expansion

diffuse growth - cell wall expansion dispersed around whole cell
Usually cells don’t expand isodiametrically -
tip growth
in root hairs and pollen tubes

anisotropic growth - cells expand in 1 direction

cell growth direction depends on cellulose microfibril oreintation
turgor pressure is same in all directions of the cell

random orientation in isodiametric growth
parallel orientation in anisotropic growth

microfibrils can’t change length - spacing changed by glycans

Question 11

gravitropism

Answer 11

gravity signal perception - change in localisation of amyloplasts/statoliths/starch granules

leads to change in auxin flow
differential growth - cells on bottom grow more than the upper side
acid growth hypotheses - auxin causes acidification of cell walls. Leads to loosening of cross links between microfibrils.
Strength reduced, so turgor pressure can drive cell growth

Question 12

gravitropism experiment

Answer 12

coloptile tip on 2 agar blocks
auxin accumulates in blocks
agar blocks are then placed on coleoptilea with their tips removed
coleoptile with agar block from lower half of tip shows increased differential growth

Question 13

neuron structure

Answer 13

cell body
dendrites receive messages from other cells
axon and axon terminals
myelin sheath - helps with speed of impulse transmission
axon hillock - high density of voltage gated Na+ channels, where action potentials are generated.

axons are bi-directional

Voltage gated Na+ channels cause action potentials, ligand gated ones don’t

Question 14

membrane potentials

Answer 14

leaky K+ channels determine resting membrane potential - moment by moment regulation - K+ diffuses out.

Concentration pulls K+ out, charge pulls it in - reaches equilibrium

Nernst equation for equilibrium potential:
Ek=58log conc(K+o)/conc(K+i)

Ek = -90
Ena = +60

Ions can also move via pump - long term regulation
3 Na+ out, 2 K+ in

Question 15

action potentials

Answer 15

Voltage gated sodium channels open so sodium moves in. Have ball/chain inactivation gate and an activation gate
Coming down K+ channels open so K+ moves out
K+ channels close after hyperpolarisation

Sodium equilibrium potential is not reached because some Nav are closed

depolarisation - decreases the electrochemical gradient, less positive ions coming into the cell so it returns to RMP
hyperpolarisation - less K+ leaves the cell because it is attracted to the more negative environment. Less +ve lost from cell so returns to RMP.

Question 16

refractory period and synaptic transmission

Answer 16

depolarisation spreads down the axon
The first part of the membrane repolarises
Na+ channels are activated and additional K+ channels have opened, so membrane cannot depolarise again

vesicles cause Ca+ channels to open, diffuse across synapse and cause Na+ channels to open on other side

Question 17

cockroach practical

Answer 17

sensilla - sensory hair like protrusions, each spine has a mechanosensory one at it’s base. It is a campaniform sensillum - hair like part is reduced to small dome of cuticle.
When dome is distorted, it distorts dendrite of neuron - causes impulse
can be chemosensory

Frequency in Hertz - impulses per second

more responsive on outside of tibia
more action potentials when you push spines proximally

spines normally respond vibrations, air puffs or mechanical touch from predators/prey

amplitude = top and bottom of peaks

Question 18

how to calculate standard error of the mean

Answer 18

standard deviation/ root of number of values

Question 19

cytoplasmic streaming

Answer 19

Direction was relative to the indifferent zone. Organelles moved from right to left, relative to the left side of the indifferent zone. Organelles moved from left to right, relative to the right side of the indifferent zone.

Note, chloroplasts were not the organelles that were moving.

Question 20

types of dna polymerase

Answer 20

DNA Pol I - Specialized for repair and primer removal

DNA Pol II - Functions primarily in DNA repair under stress conditions

DNA Pol III - The primary enzyme for bacterial DNA replication with high speed and fidelity

Question 21

If an individual has a Tt genotype, how many bands will there be on the electrophoresis gel once it has been run for the undigested products of PCR?

Answer 21

The digested PCR products of strong tasters would all be broken down by HaeIII into fragments of 44bp and 177bp. The digested PCR products of non-tasters would remain undigested, even when treated with HaeIII, so all fragments would by 221bp long. The digested PCR products of a Tt/’weak’ taster would have 3 bands as the T alleles would have geen cut into 2 fragments, and the t alleles would remain undigested.

However, because the PCR products were undigested, all fragments will be 221 bp long.

In the experiement, the undigested products were the control.

Question 22

chelex beads
and CaCl2

Answer 22

To help ensure DNA remains intact by binding to metal ions that promote DNA breakdown

helps dna bind to bacterial cell by neutralising it and co-precipitating with it

Question 23

G0 phase

Answer 23

cells aren’t dividing or preparing to divide
cell can be terminally differentiated in this stage

Question 24

coat proteins in movement of molecules

Answer 24

Vesicular transport is mega regulated! Coat proteins are required so vesicles are transported to the correct destination…
COP1 - Endoplasmic reticulum

COP2 - Golgi

Clathrin - plasma membrane

Question 25

RNA processing in bacteria vs eukaryotes

Answer 25

In eukaryotes, mRNA undergoes capping, splicing, and polyadenylation, while bacteria do not modify their mRNA

Question 26

stages of the calvin cycle

Answer 26

1. Carboxylation 2. Reduction 3. Regeneration

Question 27

why are stamenopiles photosynthetic + which groups are in the arhaeplastida

Answer 27

Most Stramenopiles do have plastids, but they did not come from the same endosymbiotic event as Archaeplastida, the red algae, green algae and land plants. Instead, stramenopiles like the brown algae endosymbiosed an ancient algae, so underwent secondary endosymbiosis. this can be seen by the fact that Stramenopile plastids have four outer membranes, not two. Red algae, Viridiplantae (Green algae and all plants), and a small basal group called the Glaucophytes, all evolved from a common ancestor which underwent an endosymbiotic event to take up a cyanobacteria. Brown algae are a separate group, consisting of a single class of Stramenopile protists, under the SAR supergroup. The stramenopiles independently underwent endosymbiosis, but their plastids have four outer membranes, suggesting they underwent secondary endosymbiosis with a red or green alga.

Question 28

EPSPs and IPSPs temporal and spacial summation

Answer 28

caused by opening of ligand gated ion channels can be different sizes, unlike action potentials postsynaptic potentials at the same synapse occur in rapid succession multiple at the same time and sum EPSPs and IPSPs will cancel out

Question 29

nervous systems in other animals

Answer 29

diffuse nerve net in cnidarians platyhelminthes: brain, defined nerve cord, collections of axon tracts and ganglia annelids - segmental ganglions arthropods - specialised sensory organs giant axons

Question 30

vertebrate nervous system

Answer 30

white matter on outside of spinal cord due to myelinated axons grey matter on inside due to cell bodies sensory neurons connect to dorsal root ganglion motor neurons connect to ventral root ganglion make up poriferal nervous system

Question 31

muscle contraction

Answer 31

each motor neuron innervates 1 muscle fibre Neuromuscular junctions are invaginated to have more acetylcholine receptors action potential in motor neuron causes acetylcholine release. Binds to nicotinic receptors excitatory junction potential in muscle cell = end plate potential action potential in muscle cell travels along transverse tubules Release of Ca2+ from sarcoplasmic reticulum Causes excitation-contraction coupling- transduction stage - changes electrical activity into mechanical reponse. Ca2+ binds to troponin which releases tropomyosin myosin binds to actin hydrolysis of ATP required for power stroke glutamate instead of acetylcholine in invertebrates

Question 32

types of amoebocytes in sponges

Answer 32

a: oocytes and spermatocytes->reproduction b:myocytes->muscle cell around ostia c: archeocytes->totipotent and used for phagocytosis d: schlerocytes->secrete spicule lophocytes and spongocytes secrete collagen >SPICULES-is made of calcium/silica and is used for sponge structure and protection

Question 33

liquid nitrogen

Answer 33

breaks membranes so increased SA Liquid nitrogen freezes cells and stops processes, allowing it to be grinded into a fine powder without affecting the substrate wear gloves - frostbite

Question 34

earliest plants and myriapods and insects and vertebrates radiations

Answer 34

Exact date unknown, between 515 and 460Ma in the Cambrian 510 MA 420 Ma 360 Ma cambrian ordovician devonian-nekton jurassic/cretaceous

Question 35

cell migration in organogenesis

Answer 35

Neural crest cells develop along the neural tube, then migrate into the body to form the nerves/ teeth/ skull Mesoderm on the sides of the notochord form somites, which form vertebrae/ ribs/ vertebral column muscles

Question 36

drosophila development genes

Answer 36

1. Bicoid 2. Gap 3. Pair-rule 4. Segmentation 5. Homeotic selector 1. Establish polarity, head region 2. Establish the head/ thorax/ tail 3. Establish the segmentation of the body 4. Establish the boundaries of the segments 5. Establish organ identities

Question 37

anti-cancer drugs

Answer 37

taxol prevents spindle function tamoxifen blocks oestrogen receptor

Question 38

effect of cholera

Answer 38

Beta subunits bind to receptor, alpha subunits enter the cell cytoplasm alpha subunit Modifies G protein that activates adenylyl cyclase cAMP rises persistently in gut cells, continuously activating PKA Cl- channel into the intestinal lumen is activated by phosphorylation, inhibiting Na+/H+ Water follows Cl- into the intestinal lumen

Question 39

effect of adrenaline on skeletal muscle

Answer 39

Adrenaline binds to GPCR, which changes shape and activates G protein, which activates adenylyl cyclase, which catalyses the synthesis of cAMP from ATP cAMP activates PKA, which phosphorylates and activates PK, which phosphorylates and activates GP GP catalyses the depolymerisation of glycogen by phosphorylating the terminal glucose The phosphorylated glucose undergoes glycolysis to produce ATP for muscle contraction

Question 40

CCK

Answer 40

peptide hormone triggers digestion of lipids and proteins by releasing bile secreted by mucosal cells of duodenum stimulates pancreatic acinar cells related G protein is heterotrimeric 7 transmembrane helices

Question 41

2nd messengers

Answer 41

cAMP activates PKA; Ca2+ activates CDPK, or with DAG activates PKC

Question 42

types of RNA pol

Answer 42

Eukaryotes: RNA poly. I transcribes ribosomal RNA RNA poly. II transcribes mRNA RNA poly. III transcribes tRNA prokaryotes - They have one RNA polymerase with two forms One form is a core polymerase that synthesises RNA. 4 subunits- 2 alpha, 2 beta One form is a Holoenzyme that recognises and binds DNA promoters, has an additional sigma factor Polymerase acts from promoter to transcription unit to terminator in transcription SIGMA unit binds to promoter

Question 43

splicing

Answer 43

Intron-exon junctions recognised by snRNPs snRNPs cluster with associated proteins, form a spliceosome Spliceosome cleaves the 5' end of the intron Spliceosome uses the 3' end of the first exon to displace the intron and bind to the second exon

Question 44

acetylcholine and noradrenaline in gut function

Answer 44

Noradrenaline reduces the blood flow to the gastrointestinal system by causing an inhibitory affect on the enteric nervous system, thus reducing gut function. Acetylcholine increases peristalsis and the amplitude of digestive contractions by causing an increase in the [Ca2+] of muscle cells there. Noradrenaline reduced gut function by reduced blood flow, acetylcholine increases gut function by increasing [Ca2+], which is used by sliding filaments in muscle contraction. Remember that acetylcholine is part of the parasympathetic nervous system, which as a function of 'rest and digest'

Question 45

annelids

Answer 45

dorsal vessel moves blood to anterior end ventral does opposite

Question 46

diatoms

Answer 46

middle is raphe outside is striae

Question 47

plant virology practical

Answer 47

Nicotiana tobacum -> classic mosaic and chlorosis Nicotiana benthomiana -> mosaics, chlorosis, and extremely stunted growth Chenopodium aconitifalius -> mild chlorosis/mosaic

Question 48

trichonympha and cnidaria sub-groups what is in gel for agarose electrophoresis

Answer 48

metamonad- excavata Anthozoa = sea anemones, corals, sea fans Hydrozoa = hydroids, hydra, Portuguese man o war Cubazoa = box jellies Scyphozoa = jellyfish SYBR Green Dye - to highlight the location of DNA fragments without the small and insignificant ones appearing

Question 49

types of transport repeating organs

Answer 49

targeting to ER is transmembrane targeting to nucleus is gated movement in plants: myosin xi, in mammals and yeast myosin v in monoplacophorans polyplacophorans are dorsoventrally flattened bivalves are flattened laterally