Last minute BIO Flashcards
1
Q
Table for magnification and resolution of all 3 microscopes?
A
Maximum Resolution:
Light = 0.2 um (not 3D)
TEM = 0.0002 um (not 3D)
SEM = 0.002 um (3D)
Maximum magnification:
Light = x1500
TEM = x1,000,000
SEM = x500,000
2
Q
How are organelles involved in protein production?
A
Proteins are made at the ribosomes The Ribosomes on the rough endoplasmic reticulum make proteins that are excreted or attached to the cell membrane New proteins produced at the rough endoplasmic reticulum are folded and processed (sugar chains added) by the rough endoplasmic reticulum Then they are transported from the rough ER to the golgi apparatus in vesicles At the golgi apparatus the proteins undergo further processing Proteins enter more vesicles and are secreted out of the cell
3
Q
Table for differences between Eukaryotic cells and prokaryotic cells?
A
prokaryote’s cell DNA is circular, whilst a eukaryotes is linear
In a prokaryote’s cell there is no nucleus, so DNA is free in the cytoplasm Whereas in a eukaryote, nucleus is present so it’s found within the nucleus
Small ribosomes in a prokaryote’s cell, and larger ribsomes in a eukaryotic cell
4
Q
Magnification definition and formula?
A
How much bigger the image is than the specimen Magnification = image size / object size
5
Q
Resolution definition?
A
The resolution of an optical microscope is defined as the shortest distance between two points on a specimen that can still be distinguished by the observer
6
Q
How to convert between mm, um and nm?
A
mm = 1m x 10^-3 um= 1m x 10^-6 nm = 1m x 10^-9
7
Q
Structure of glucose?
A
It’s a hexose ( 6 carbon) monosaccharide Alpha glucose: starting at top right then going clockwise C1 bonded to CH2OH O C2 bonded to H above and OH bellow C3 bonded to H above and OH bellow C4 bonded to OH above and H bellow C6 OH bellow and H above Beta: the same as alpha, except on C2 OH is above, and H is bellow
8
Q
How is glucose’s structure related to it’s function?
A
It’s the main energy source in animals as it’s structure makes it soluble, so can be transported easily, and it’s chemical bonds contain a lot of energy
9
Q
What does the disaccharide maltose consist of?
A
2 molecules of alpha glucose binded to each other via a glycosidic bond
10
Q
What does the disaccharide sucrose consist of?
A
When alpha glucose and fructose join together via a glycosidic bond
11
Q
What does the disaccharide Lactose consist of?
A
When Beta glucose is bonded to galactose
12
Q
What does starch consist of?
A
A mixture of the 2 polysaccharides of alpha glucose amylose and amylopectin
13
Q
Describe the structure of amylose?
A
A long unbranched chain of alpha glucose. The angles of glycosidic bonds give it a coiled structure Condense structure makes it good for storage as can fit more into a smaller space
14
Q
Describe the structure of amylopectin?
A
A long branched chain of alpha glucose, it’s side chains allow the enzymes that break down the molecule to get at the molecule to break the glycosidic bonds. So glucose can be released quickly
15
Q
Structure of glycogen?
A
Polysaccharide of alpha glucose (used as storage if there’s excess) , similar to amylopectin, except that it has far more side branches coming off it, so energy can be released more readily, which is good for animals
Also soluble, so won’t affect water potential of cells
16
Q
Describe the structure and function of cellulose?
A
Long unbranched chains of beta glucose, the cellulose chains are linked by hydrogen bonds to form strong fibres called microfibrils The strong fibres provide strucutral support for the cell, eg. in plant walls
17
Q
How are triglycerides synthesised?
A
By the formation of an ester bond between each fatty acid and the glycerol molecule A condensation reaction occurs, between the OH group on the glycerol (prop-tri-ol) and the OH of the carboxylic group at the end of the hydrocarbon chain.
18
Q
Why are triglycerides good energy storage molecules in animals and plants?
A
The hydrocarbon tails contain a lot of chemical energy when they are broken down They are insoluble, so don’t affect water potential of cell, causing water to move in via osmosis, they are insoluble as Triglycerides bundle together as insoluble droplets, as glycerol shields hydrophobic fatty acid chains as they all face inwards to form a sphere
19
Q
What’s the secondary structure of a protein?
A
When hydrogen bonds form between nearby amino acids This makes it coil into an alpha helix, or fold into a beta pleated sheet, this is the secondary structure
20
Q
What are reducing sugars?
A
All the monosacchardies, and the disacharides maltose and lactose
21
Q
How do you test for a reducing sugar?
A
Add benedict’s reagent and heat, will go from blue to brick red The higher the concentration of the reducing sugar, the further the colour change
22
Q
How do you test for a non reducing sugar?
A
If the test for the reducing sugar is negative, then add dilute HCl and heat in a water bath Nuetralise it with Sodium Hydrogen carbonate Now do the Benedict’s test again
23
Q
Can you test for proteins?
A
Use the Biruet test Solution needs to be alkaline, so add a few drops sodium hydroxide solution Add some copper sulphate solution, if it goes stays blue there’s no protein, if goes purple protein is present
24
Q
How do you test for lipids?
A
The emulsion test Shake the substance with ethanol then pour into water Solution will go milky if a lipid is present
25
How do you use calorimetry to measure the concentration of a glucose solution?
Create glucose concentrations using dilution factor 2 on 40m/M to create a 20, 10, 5 and 2.5 and a negative control of water You will have added benedict's reagent, so the higher the concentration gradient of glucose, the lower the absorbance as more benedict's reagent used up, as will have also remove precipitate by centrifuging it Now create a calibration curve by plotting absorbance on y axis, and concentration on x axis (use red filter) Now can use graph to find link the absorbance of a solution with an unknown concentration, with it's concentration
26
Which are the purine bases and what does this mean?
Adenine and Guanine, contain 2 carbon - nitrogen rings joined together
27
Which are the pyrimidine bases and what does this mean?
Cytosine, and thymine, only contain 1 carbon-nitrogen ring, so are smaller than a purine base
28
What do nucleotides join together to form and what between?
Polynucleotides, phophodiester bond forms between the phosphate group of one nucleotide, and the sugar of another forming a sugar phosphate backbone
29
Describe how 2 polynucleotide strands join together to form a helix?
There's hydrogen bonding between the bases
Complementary base pairing, A-T, C-G
2 Hydrogen bonds form between A-T
3 Hydrogen bonds form between C-G
The 2 antiparallel strands twist to form the DNA doubel helix
30
How can you purify DNA?
Via a precipitation reaction
Break up cells of sample using a blender
Make a solution of detergent, salt and distilled water
Add the broken up cells to a beaker containing the solution and heat in a water bath
The detergent in the mixture breaks down the cell membranes, and the salt binds to the DNA causing it to clump together, and warm temperature prevents the stops the enzymes in the cells working properly so DNA not broken down
Put beaker in a ice bath, and then filter
Transfer to a testube and protease enzymes to the filterered mixtures, which will break down any proteins
Dribble cold ethanol down side of tube so it forms a layer on top, causing DNA to form a white precipitate
31
Describe the process of DNA self replicating?
DNA helicase breaks down the hydrogen bonds between the 2 polynucleotide DNA strands, the helix unzips to form 2 separate strands
Each original strand acts as a template for a new strand, free floating DNA nucleotide bases join to the exposed bases on each original template strand by complementary base pairing
The nucleotides of the new strand are joined together by the enzyme DNA polymerase, this forms the sugar phosphate backbone,
Hydrogen bonds form between the bases on the original and new strand, the strands twist to form a double helix
Each new DNA molecule contains one strand from the original DNA molecule and one from new strand so it's semi conservative
32
Describe the first stage of protein synthesis - transcription?
RNA polymerase attaches to the DNA at the beginning of a gene
The hydrogen bonds break between the 2 DNA strands break, separating the strands, and the DNA molecule uncoils at that point
One of the strands is then used as a template to make an mRNA copy
The RNA polymerase lines up free RNA nucleotides alongside the template strand, complementary base pairing means that the mRNA strand ends up being a complementary copy of the DNA strand (except T is replaced by U)
Once the RNA nucleotides have paired up with their specific bases on the DNA strand they are joined together to form an mRNA molecule
The RNA polymerase moves along the DNA, separating the strands, and assembling the mRNA strand
The hydrogen bonds reform between the uncoiled strands of DNA and coil back into a double helix once the RNA polmerase passes by
When RNA polymerase reaches a stop codon, it stops making mRNA and detaches from the DNA
The mRNA moves out of the nucleus through a nuclear pore, and attaches to a ribosome in the cytoplasm
33
Describe how the second step of protein synthesis occurs Translation?
A second tRNA molecule attaches to itself to the next codon in the same way
rRNA in the ribosomes catalyses the formation of a peptide bond between the 2 amino acids attached to the tRNA, this joins them together and the first tRNA molecule moves away
Process repeats untill a polypeptide chain is formed and the stop codon is reached
34
What's a cofactor?
Non protein substance, that attaches to an enzyme allowing it to work
35
Example of a inorganic cofactor?
Chloride ion, helps amylase enzyme bind to starch Aren't affected during the reaction
36
What can an organic cofactor be known as?
Coenzymes, usually are sources from vitamins
They participate in the reaction, so are changed Often act as carries, moving chemical groups between different enzymes
37
What's a cofactor known as if it's tightly bound to an enzyme, and an example?
Prosthetic group
38
The 6 steps in cell division?
Interphase Prophase (Mitosis) Metaphase (Mitosis) Anaphase (Mitosis) Telophase (Mitosis) Cytokenesis
39
What occurs during interphase?
The cell carries out normal functions, but also prepares to divide Cell's DNA is replicated, to double it's genetic content, the organelles are also replicated so it has spare ones ATP content is increased (provides energy for cell division)
40
Describe what occurs in the first step of mitosis, prophase?
Chromosomes condense Centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called spindle Nuclear envelope breaks down and chromosomes lie free in the cytoplasm
41
What occurs in the second step of mitosis, metaphase?
The chromosomes line up along the middle of the cell (laying sideways), and become attached to the spindle by their centromers Metaphase checkpoint, checks to see that all chromosomes are attached to the spindle before it can continue
42
What occurs in anaphase, the 3rd of mitosis?
Centromers divide Separating each pair of sister chromatids, the spindles contract pulling the chromatids to the opposite ends of the cell
43
What occurs in telophase, the 4th step of mitosis?
The chromatids reach the opposite poles of the spindle, and uncoil becoming long and thin again, so they're now called chromosomes again A nuclear envelope forms around each group of chromosomes so there are now 2 nuclei Cytokenesis occurs next 9 (not part of mitosis)
44
Describe cytokenesis in mitosis?
The cytoplasm divides, a cleavage furrow forms to divide the cell membrane Produces 2 daughter cells which are genetically identical to each other and the original cell
45
What occurs in prophase 1, the first step of meiosis?
(DNA has already been replicated in interphase) Chromosomes condense, and arrange themselves into homologous pairs Crossing over occurs Centrioles start moving to opposite ends of the cells, forming the spindle fibres Nuclear envelope breaks down
46
What occurs in metaphase 1, the second step of meiosis?
The homologous pairs line up across the centre of the cell, and attach to the spindle fibres by their centromers
47
What happens in anaphase 1, the third step of meiosis?
The spindles contract, separating the homologous pairs, one chromosome goes to each end of the cell
48
What occurs in telophase 1, the 4th step of meiosis?
Nuclear envelope forms around each group of chromosomes, and then cytokinesis occurs and 2 haploid daughter cells are produced (still double stranded)
49
What happens in meiosis 2?
All the same steps as mitosis Produces 4 genetically different haploid daughter cells (single stranded chromosomes) = gametes
50
Describe chromatids crossing over in Prophase 1?
Homologous pairs have come together and pair up, the chromatids twist around each other, and bits of chromatids swap over The chromosomes still contain the same genes, but have different alleles
51
Describe the independent assortment of chromosomes?
Each homologous pair of chromosomes in your cells is made up of one chromosome from your mum (maternal), and one from your dad (paternal) When the homologous pairs line up in metaphase 1, and are separated in anaphase 1, it's random which chromosome from each pair ends up in which daughter cell So all 4 daughter cells have different combinations of maternal and paternal chromosomes
52
Describe what happens during inspiration?
The external intercostal and diaphragm muscles contract
Causing the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax
As the volume of the thorax increases, the lung pressure decreases, causing air to flow into the lungs
Active process so required ATP
53
Describe what happens during expiration?
The external intercostal and diaphragm muscles relax
Causing the ribcage to move downwards and inwards the diaphragm becomes curved again
The thorax volume decreases, causing causing the air pressure to increase above atmospheric pressure
Air is forced out of the lungs
Normal expiration is a passive process (doesn't require energy),
Forced expiration does require energy (internal intercostal muscles contract to pull the ribage down and in)
54
Describe how the gills are usually ventillated in bony fish?
The fish opens it's mouth, which lowers the floor of the buccal cavity
The volume of the buccal cavity increases, decreasing the pressure so water is sucked in
When the fish closes it's mouth the floor of the buccal cavity raises, the volume inside decreases and the pressure increases, water is forced out of the cavity and across the gill fillaments
Each gil is covered by a tiny bony flap called the operculum which when the pressure increases opens on each side of the head and allows water to leave the gills
55
Describe how insects exchange gases?
Insects have microscopic air-filled pipes called tracheae which they use for gas exchange
Air moves into the trachea through pores on the insects surface called spiracles
Oxygen travels down the concentration towards the cells, whilst CO2 from the cells moves down it's own concentration gradient towards the spiracles to be released
The trachea branch off into smaller tracheoles which have thin permeable walls and go to individual cells. The tracheoles also contain fluid in which oxygen dissolves in
The oxygen then diffuses from this fluid into body cells, CO2 diffues in the opposite direction
Insects use abnominal movents to change the volume of their bodies, and move air in and out of the spiracles. (wing movements can pump their thorax's too)
56
Out of the trachea, bronchi, larger bronchiole, smaller bronchiole, and smallest bronchiole and aleveoli, which contain cartilage, smooth muscle, elastic fibres, goblet cells, epithelium?
Cartilage:
Trachea has C shaped
Bronchi has smaller pieces
The rest have none
Smooth muscle:
All have smooth muscle apart from smallest bronchiole and alveoli
Elastic fibres:
ALL
Goblet cells:
Only trachea, bronchi and largest bronchioles
Epithelium:
Trachea, bronchi, larger and smaller bronchioles all have cilitated epithelium, smallest bronchiole and alveoli don't have any
57
Describe pressure filtration in the capillary bed?
At the start of the capillary bed nearest the arteries the hydrostatic pressure inside the the capillaries is greater than the hydrostatic pressure in the tissue fluid.
The difference in hydrostatic pressure, forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid
As fluid leaves the hydrostatic pressure reduces in the capillaries and so the pressure is much lower at the end of the capillary bed near the venules
Oncotic pressure is present in the capillaries and is generated by plasma proteins, which lowers the water potential
Near the venule end of the capillaries water will re enter the capillaries via osmosis as it has a lower water potentia than the tissue fluidl, due to fluid loss and a high oncotic pressure
58
Blood contains red blood cells, white blood cells, platelets, proteins, water and dissolved solutes what does tissue fluid and lymph contain?
Tissue fluid:
Very few proteins and white blood cells
water
dissolved solutes
```
lymph:
White blood cells
water
dissolved solutes
only antibody proteins
```
59
Describe the cardiac cycle?
1. Ventricles relax and atria contract:
When the atria contract, their volume decreases and their pressure increases, pushing their blood into ventricles via the atrioventricular valves. There's a slight increase in ventricular volume and pressure
2. Ventricles contract, atria relax:
The ventricles contract (decreasing their volume) and increasing their pressure.
The pressure become higher in the ventricles than in the atria, forcing the atrioventricular valves shut to prevent back-flow
The high pressure in the ventricles opens up the semi-lunar valves, and blood is forced into the pulmonary artery and the aorta
3. Ventricles relax and atria relax:
The higher pressure in pulmonary and aorta causes the semi-lunar valves to close, preventing backflow.
The atria fill with blood increasing their pressure, due to higher pressure in vena cava and pulmonary vein.
As the ventricles continue to relax their pressure falls bellow that off atria, causing the atrioventricular valves to open and blood flows passively (without a contraction), into the ventricles from the atria
Cycle happens again
60
Describe how cardiac muscle controls the regular beating of the heart?
Process starts in the sino-atrial node (SAN), which is in the wall of the right atrium
The SAN sends out regular waves of electrical activity which goes to the atrial walls
Causing the right and left atria to contract at the same time
A band of non conducting collagen tissue prevents the waves of electrical activity being passed directly from the atria to the ventricles
Instead these waves of electrical activity are transferred from the SAN to the atrioventricular node (AVN)
The AVN is responsible for passing the waves of electrical activity on to the bundle of His, but there's a slight delay before the AVN reacts to make sure the ventricles contract after the atria have been emptied
The bundle of His, is a group of muscle fibres responsible for conducting the waves of electrical activity to the finer muscle fibres in the right and left ventricle walls called the Purkyne tissue
The Purkyne tissue carries the waves off electrical activity to the muscular walls of the right and left ventricles, causing them to contract at the same time fr,om bottom up
61
Describe one full heartbeat on a electrocardio graph?
Tiny peak ( P wave) from contraction (depolarisation of the atria
Then there's the QRS complex, (trough, peak, trough) formed via contraction of the ventricles
T wave (peak) caused by relaxation of the ventricles
62
Describe how a high partial pressure of CO2 makes haemoglobin more ready to offload oxygen?
Most of the CO2 from respiring tissues diffuses into red blood cells, here it reacts with water to from carbonic acid, catalysed by the enzyme carbonic anyhydrase ( The rest of the CO2 binds to haemoglobin and is taken to the lungs)
The carbonic acid dissociates to H+ ions and HCO3(-) ions
This increase in H+ ions causes oxyhaemoglobin to unload it's oxygen, so it can take up H+ ions. This forms a compound called haemoglobinic acid (also stops H+ ions increasing acidity)
The HCO3- ions diffuse out of the red blood cells and are transported in the blood plasma. To compensate for the loss of HCO3- ions from the red blood cells Cl- ions diffuse into the red blood cells
This is the chloride shift and prevent any possible pH change
When the blood reaches the lungs the low concentration of CO2 causes some of the HCO3- and H+ to recombine into CO2 and water
The CO2 then diffuses into the alveoli and is breathed out
63
Describe the symplast pathway?
Water goes through the living parts of cells- the cytoplasm
The cytoplasms of neighbouring cells connect through plasmodesmata (small channels in the cell walls)
So water moves through the sympoast pathway via osmosis
64
Describe the apoplast pathway?
Water goes through the non living parts of cells - the cell walls
Water can just diffuse between the cell walls
Water moves an area of high hydrostatic pressure, to an area of low hydrostatic pressure this is an example of mass flow
However, when the water in this pathway reaches the endodermis cells, it's pathway is blocked by a waxy Casparian strip, which forces the water to take the symplast route
Water moves into the xylem
65
Describe how Xerophytes are adapted to live in dry climates?
Can have stomata that are sunk into pits so are shielded from the wind, decreasing their transpiration rate
Can have a layer of hairs on the epidermis, that traps moist air around the stomata, which reduces the water potential gradient between the leaf and the air, decreasing the transpiration rate
Can roll their leaves traps moist air, reduces surface area for water to be lost, and shields from the wind
Can have a thick waxy layer on the epidermis, reducing water loss by evaporation
Can close their stomata at hottest points in day, where transpiration rates would be highest
66
What is translocation?
The movement of dissolved substance to where they are needed in the plant, it moves them from a source to a sink
67
Describe the mass flow hypothesis for phloem transport?
Active transport is used to load the solutes into the sieve tubes of the phloem at the source
This lowers the water potential inside the sieve tube elements, so water enters the tubes by osmosis from the xylem and companion cells
This creates a high pressure inside the sieve tube tubes at the source of the phloem
At the sink end solutes are removed from the phloem to be used up, this increases the water potential inside the sieve tubes, so water also leaves the tubes by osmosis
Lowering the pressure in the sieve tube elements at the sink end
So a pressure-gradient is formed from the source end to the sink end, and this gradient pushes the solutes to where they are needed
68
Describe exactly how substances enter the phloem at the source via active loading?
In the companion cell, ATP is used to actively transport hydrogen ions (H+) out of the cell and into the surrounding tissue cells
This sets up a conc gradient there are more H+ ions in the surrounding cells than in the companion cells
A H+ ion binds to a co-transporter protein in the companion cell membrane, and re-enters the cell down the concentration gradient
A sucrose molecule binds to the co-transporter protein at the same time. The movement of the H+ ion is used to move the sucrose into the companion cell against it's concentration gradient
Sucrose molecules are then transported out of the companion cells and into the the sieve tube elements via the same process
69
Describe how sensory receptors convert stimulus energy into nerve impulses?
When a Nervous system receptor is in it's resting state, there's a difference in charge between the inside and the outside of the cell - so there's a voltage across the membrane which is known as potential difference
This potential difference is generated by ion pumps and ion channels
The potential difference when a cell is at rest is called the resting potential
When a stimulus is detected, the cell membrane is excited and becomes more permeable, allowing more ions to move in and out of the cell - altering the potential difference
The change in potential difference due to a stimulus is called the generator potential
A bigger stimulus excites the membrane more, causing a bigger movement of ions and a bigger change in potential difference = larger generator potential
If the generator potential is large enough (reaches the threshold level) it will trigger an action potential (nerve impulse) along a neurone
70
Describe the mechanoreceptor pacinian corpuscles?
They detect mechanical stumuli, eg pressure and vibrations
They are found in your skin, and contain the end of a sensory neuron called a sensory nerve ending, which is wrapped in lots of layers of connective tissue called lamellae
When a Pacinan corpuscle is stimulated, the lamellae are stimulated, the lamellae are deformed, and press on the sensory nerve ending
Causing deformation of the stretch mediated sodium channels in the sensory neurons cell membrane
So the Sodium ion channels open and the sodium ions diffuse into the cell, creating a generator potential which if passes the threshold will cause an action potential
71
What do dendrons / dendrites do?
Carry nerve impulses towards the cell body
72
What do axons do?
Carry nerve impulses away from the cell body
73
Structure of a sensory neuron in direction of the impulse?
Connects to receptor cells via dendrites, which then goes on to one long dendron which connects to the cell body
Then one short axon carries impulses from the cell body to the CNS
74
Describe the structure of a relay neuron in direction of the impulse?
Have many short dendrites that carry nerve impulses from the sensory neurons to the cell body
And many short axons that carry nerve impulses from the cell body to motor neurons
75
Describe the structure of a motor neuron in the direction of the impulse?
Have many short dendrites that carry nerve impulses from the CNS, to the cell body
And one long axon, which carries the nerve impulses from the cell body to effector cells
76
Describe how neuron cell membranes are polarised at rest?
The outside of the membrane is more positively charged compared to the inside, as there more positive ions outside than in = polarised as difference in charge
Resting potential = -70mV
The resting potential is created and maintained by Sodium Potassium pumps (SOPI, 2 Sodium out, 3 Potassium in)
Sodium can't diffuse back in, as there are no ion channels for it, but there are potassium ion channels so the K+ ions diffuse back out
Making it more positive on the outside than the inside
77
Describe the process of a neuron cell membrane becoming depolarised when stimulated and an action potential being generated?
The stimulus excites the neuron cell membrane, causing Na+ ion channels to open, to membrane has become more permeable to Na+ ions, so they diffuse into the neuron down a electrochemical gradient. making the inside of the neuron less negative
If the potential difference reaches the threshold (around -55mV), voltage gated Na+ channels open. More Na+ ions diffuse into the neurone.
This is positive feedback
At a potential difference of around -+30mV, the Na+ ion channels close and voltage gated K+ ion channels open. The membrane is now more permeable to K+, so they diffuse out down a concentration gradient.
This is repolarisation- and is a negative feedback process
Hyperpolarsiation - K+ ion channels are slow to close, so there is a slight overshoot, where too many K+ ions diffuse out of the nueron, the potential becomes more negative than the resting potential (less than 70mV)
Resting potential - the ion channels are reset, the SOPI pumps returns the membrane to it's resting potential
78
Describe exactly in 3 main steps how neurotransmitters transmit nerve impulses between neurones?
An action potential arrives at the synaptic knob of the presynaptic neurone
The action potential stimulates voltage gated Ca2+ in the presynaptic neuron to open
Ca2+ diffuses into the synaptic knob
The influx of calcium ions into the synaptic knob, causes the synaptic vesicles to move to the presynaptic membrane, they then fuse with the presynaptic membrane
The vesicles release the neurotransmitter into the synaptic cleft via exocytosis
The nuerotransmitter diffuses across the synaptic cleft and binds to specific receptors on the post synaptic membrane
Causing Na+ ion channels in the postsynaptic neuron to open
The influx of Na+ in the postsynaptic membrane causes depolarisation. An action potential on the postsynaptic membrane is generated if the threshold is achieved
Neurotransmitter is removed from synaptic cleft so the response doesn't keep happening
79
Describe the process of adrenaline acting as the first messenger on cells?
Adrenaline binds to specific receptors on the cell membrane
When adrenaline binds it activates an enzyme in the membrane called adenylyl cyclase
Activated adenylyl cyclase, catalsyes the production of a second messenger called cyclic AMP (cAMP) from ATP
cAMP activates a cascade of enzyme controlled reactions, which makes more glucose available to the cell, by catalysing the breakdown of glycogen into glucose
80
Function of the cortex in the adrenal glands?
Secretes steroid hormones such as cortisol and aldosterone when you are stressed
Effects of these are:
Stimulating the breakdown of proteins and fats into glucose, increasing the amount of energy available so the brain and muscles can respond to the situation
Increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys
Supressing the immune system
81
Describe the function of the medulla in the adrenal glands?
Secretes catechloamine (modified amino acid) hormones such as adrenaline and noradrenaline when you stressed
Effects are:
Increase in heart and breathing rate
Cuasing cells to break down glycogen into glucose
Constricting some blood vessels, so that blood is diverted to the brain and muscles
82
Describe what islets of langerhan are and their function?
They are areas of the pancreas that contain endocrine tissue, and are found in clusters around blood capillaries, so they can secrete hormones directly into the blood
They are made up of Alpha cells that secrete a hormone called glucagon
And beta cells which secrete a hormone called insulin
Which both help to control blood glucose concentration
83
Describe how the hypothalamus controls body temperature in mammals?
The hypothalamus (part of the brain) receives information about the temperature from thermoreceptors ( the ones in the hypothalamus detect internal temperature, and the ones in the skin (peripheral thermoreceptors detect external temperature
Thermoreceptors send impulses along sensory neurons to the hypothalamus, which sends impulses along motor neurons to effectors to restore the temperature back to normal (eg . vasodialtion or vasoconstriction)
84
Describe how beta cells from the ilsets of langerhan in the pancrease releasing the hormone insulin, lowers the blood glucose concentration?
Insulin binds to specific receptors on the cell membranes of liver cells and muscle cells
It increases the permeability of cell membranes to glucose so the cells take up more glucose
Insulin also activates enzymes that convert glucose to glycogen
Cells are able to store glycogen in their cytoplasm as an energy source
The process of forming glycogen from glucose is called glycogenesis
It also increases the rate of respiration of glucose, especially in muscle cells
85
Describe how alpha cells from the islets of langerhans in the pancreas releasing glucagon raises the blood glucose concentration?
Glucagon binds to specific receptors on the cell membranes of liver cells
Glucagon activates enzymes that break down glycogen into glucose
The process of breaking down glycogen is called glycogenolysis
Glucagon also promotes the formation of glucose from fatty acids and amino acids, which is called gluconeogenesis
Glucagon also decreases the rate of respiration of glucose in cells
86
Describe how Beta cells secrete insulin when they are depolarised?
When blood glucose concentration is high more glucose enters the beta cells via facilitated diffusion
More glucose in a Beta cell causes the rate of respiration to increase, making more ATP
The rise in ATP triggers the K+ ion channels in the Beta cell plasma membrane to close
This means K+ ions can't can't get through the membrane, so they build up inside the cell
This makes the inside of the cell less negative, as there more K+ ions within the cell- so the plasma membrane is depolarised
Depolarisation triggers calcium ion channels in the membrane to open, so calcium ions diffuse into the beta cell
This causes vesicles containing insulin to fuse with the beta cell plasma membrane, releasing insulin via exocytosis
87
What does the growth hormone gibberellin stimulate?
Seed germination
Stem elongation
Side shoot formation
Flowering
88
How do gibberelins stimulate seed germination?
Triggering the breakdown of starch into glucose in the seed
| The plant embryo in the seed can then use the glucose to respire a release the energy it needs to grow
89
What chemical inhibits gibberellins and therfore seed germination?
The hormone abscisic acid
90
Describe how leave loss is controlled by hormones?
Auxins inhibit leave loss, and are produced by young leaves so as they get older are more likely to fall off
Ethene stimulates leaf loss, and is produced by ageing leaves, as the leaf gets older more ethene is produced, causing layer of cells called the abscission layer to form at the bottom of the leaf stalk.
This separates the leaf from the rest of the plant, the abscission layer expands breaking cell walls, and causes the leaf to fall off
91
Explain how plant hormones are involved in stomatal closure?
Need to be able to close stomata to reduce water loss
This is done using guard cells found each side of the stomatal pore
When they are filled with water, they are turgid and the pore is forced open, when they lose water they become flaccid and the pore is closed
Absisic acid (ABA) triggers stomatal closure by binding to receptors on the guard cell membranes which causes specific ion channels to open, this allows Ca2+ ions in, this increase then causes K+ ion channels to open so they leave the cell, raising the water potential of the cells, so water then leaves the guard cells via osmosis
So the guard cells become flaccid and the stomata close
92
How does Ethene make fruit ripen?
Stimulates hormones, that break down cell walls and chlorphyll, and convert starch into sugars
93
What does the nervous system split up into?
The central nervous system - made up of the brain and the spinal cord
The peripheral nervous system - made up of the nuerons that connect the CNS to the rest of the body
94
What does the peripheral nervous system split up into?
The somatic nervous system - controls conscious activities such as running
The autonomic nervous system - controls unconscious activities such as digestion
95
What does the autonomic nervous system split up into?
The sympathetic nervous system - gets the body readu for "fight or flight" by sympathetic neurons releasing the neurotransmitter noradrenaline
The parasympathetic nervous system - Calms the body down "rest and digest" by parasympathetic neurons releasing the neurotransmitter acetlycholine
96
Where it's found and it's functions for the hypothalamus?
Found just beneath the middle part of the brain
Automatically maintains body temperature at the normal level, and produces hormones that control the pituitary gland
97
Where it's found and it's functions for the Pituitary gland?
Found just beneath the hypothalamus
It is controlled by the hypothalamus, and it releases hormones and stimulates other glands such as the adrenal glands
98
Where it's found and it's functions for the Cerebrum?
Largest part of the brain (all of the top) and is split into the 2 halves called the cerebral hemispheres
Has a thin outer layer called the cerebral cortex which is highly folded
It is involved in vision, hearing, learning and thinking
99
Where it's found and it's functions for the medulla oblongata?
Found at the base of the brain, and at the top of the spinal cord
It automatically controls breathing rate and heart rate
100
Where it's found and it's functions for the Cerebellum?
It is found beneath the back of the cerebrum and it also has a folded cortex
It's important for muscle coordination, posture and coordination of balance
101
Describe the knee jerk reflex?
Stretch receptors in the quadricep muscle detect that the muscle is being stretched
A nerve impulse is passed along a sensory neuron which communicates directly with a motor neuron in the spinal cord
The motor neuron carries the nerve impulse to the effector (the quadricep muscle), causing it to contract so the lower leg moves forward quickly, so you maintain balance
102
Describe how the nervous system and hormonal system coordinate in the fight or flight response?
Nerve impulses from sensory neurons arrive at the hypothalamus activating both the hormonal system and the sympathetic nervous system
The pituitary gland is stimulated to release a hormone called ACTH, this causes the cortex of the adrenal to release steroidal hormones
The sympathetic nervous system is activated, triggering the release of adrenaline from the medulla region of the adrenal gland
103
How does the nervous system help to control heart rate?
The sinoatrial node (SAN) generates electrical impulses that cause the cardiac muscle to contract
The rate at which the SAN fires is unconsciously controlled by a part of the brain called the medulla
Stimuli of high and low pressure are detected by baroreceptors (pressure receptors) in the aorta and vena cava
Oxyen level (Co2 and pH aswell help), is detected by chemorecptors in the aorta, the carotid artery and in the medulla
104
Steps that occur if a high blood pressure is present/ or high blood O2, low CO2 conc, and high pH level?
Baroreceptors detect high blood pressure, chemoreceptors detect chemicals
Impulses are sent to the medulla oblongata, which sends impulses along the vagus nerve. This secretes acetlycholine, which binds to receptors on the SAN.
Effector is the cardiac muscle- heart rate slows down to reduce blood pressure back to normal
105
Steps that occur if low blood pressure is present/ or low O2 blood conc, high CO2 or low pH?
Baroreceptors detect low blood pressure/ or chemoreceptors detect chemicals
Impulses are sent to the medulla, which sends impulses along the accelerator nerve. This secretes noradrenaline, which binds to receptors on the SAN
Effector is the caridac muscle, Heart rate speeds up to increase blood pressure back to normal
106
How to use the student's t test to compare heart rate before and after exercise?
Identify null hypothesis , that the means for the 2 sets of data are the same
Calculate the mean and standard deviation for both sets of data
Calculate the t test by using the formula (Mean 1 - Mean 2) / The square root of (standard deviation(1)^2/number of values in that table) + (standard deviation(2)^2/number of values in that table)
So all of bottom row is square rooted
Calculate the degrees of freedom by doing the total value of n then - 2
Look up values for t crit in a table of critical values at the 95% confidence level, if the t test is larger than the t crit we can be 95% sure there has been a significant change, so it's not down to chance
107
What are thick myofilaments made up of?
The protein myosin
108
What are thin myofilaments made up of?
The protein actin
109
What happens to band length when during muscle contraction?
A band stays the same
I band gets shorter
H zone gets shorter
110
What is the actin-myosin binding site in resting muscles blocked by?
Tropomyosin, which is held in place by troponin
111
Describe the whole process of muscle contraction being triggered by an action potential?
When an action potential from a motor neuron stimulates a muscle cell it depolaries the sarcolemma
Depolarisation spreads down the t tubules to the sarcoplasmic reticulum
This causes the sarcoplasmic reticulum to release stored Ca2+ ions into the sarcoplasm
Ca 2+ ions bind to troponin, causing it to change shape, this pulls the attached tropomyosin out of the actin-myosin binding site on the actin filament
This exposes the binding site, which allows the myosin head to bind = actin-myosin crossbridge
Calcium ions also activate the enzyme ATPase which breaks down ATP (into ADP +Pi) to provide the energy required for muscle contraction. The energy released from ATP moves the myosin head, which pulls the actin along in a rowing action
ATP also provides energy to break the actin-myosin crossbridge, so the myosin head detaches from the actin filament after it's moved
The myosin then reattaches to a different binding site further along the actin filament, a new actin-myosin cross bridge is formed and the cycle is repeated
Overall this effect causes the sarcomere to shorten and the muscle to contract
112
Describe what happens in muscle contraction when excitation stops?
When the muscle stops being stimulated, calcium ions leave their binding sites on the troponin molecules and are moved back to sarcoplasmic reticulum via active transport
The troponin molecules return to their original shape, pulling the attached tropomyosin molecules with them, this means the tropomyosin molecules block the actin-myosin binding sites again
Muscles aren't contracted and the actin filaments slide back into their relaxed positions lengthening the sarcomere
113
Describe briefly how the CP system generates energy for muscle contraction?
ATP is made by phosphorylating ADP - adding a phosphate group taken from creatine phosphate
CP is stored inside cells and this system generates ATP very quickly
CP runs out very quickly so is used for short burts of exercise (eg. tennis serve)
This system is anaerobic and alactic (no lactic acid formed)
114
Describe the neuromuscular junctions ( the synapses between neurones and muscles?
They use the neurotransmitter acetlychloine, which binds to receptors called nicotinic cholinergic receptors
Work in the same way as synapses between neurones- causing depolarisation in muscle cell which always leads to a contraction (if threshold level is reached)
Acetlycholinesterase stored in clefts on the postsynaptic membrane is released to breakdown acetlycholine after use
115
what does glycolysis do in general?
splits one molecule of glucose (6C), to form 2 smaller molecules of pyruvate (3C). Process occurs in cytoplasm of cells. It's an anaerobic process so is the first step of aerboic and anaerobic respirarion
Phosphorylation, then oxidation
116
What occurs in phosphorylation in glycolysis?
Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP. Forming 1 molecule of hexose Biphosphate and 2 molecules of ADP. Tje hexose biphosphate is then split into 2 molecules of triose phosphate
117
What occurs in the oxidation stage of glycolysis?
Triose phosphate is oxidised (loses hydrogen) forming 2 molecules of pyruvate, NAD collects thr hydrogen forming 2 reduced NAD. 4 ATP are produced, but 2 were used up in stage one sp theres a net gain of 2 ATP
118
What takes place in the link reaction?
Occurs in mitochondrial matrix. Pyruvate is decarboxylated, one carbon atom is removed in the form of CO2. NAD is reduced, it collects hydrogen from pyruvate, changing pyruvate into acetate. Acetate is combined with coenzyme A to form acetyle coenzyme A. No ATP is formed in this reaction
119
What occurs in the Kreb's cycle?
Acetyl CoA from the link reaction combines with oxaloacetate to form citrate (citric acid), this is catalysed by citrate synthase. Coenzyme A goes back to the link reaction to be used again
The 6C citrate molecule converted to 5C molecule as decarboxylation occurs removing CO2, dehydrogenation also occurs so hydrogen lost to turn NAD into reduced NAD
5C molecule then turned into a 4C molecule as decarboxylation and dehydrogenation occur producing one molecule of reduced FAD and 2 of reduced NAD. ATP is produced via direct transfer of phosphate group from an intermediate compound to ADP, this is called substrate level phosphorylation.
Citrate has now been converted to oxaloacetate
120
Describe oxidative phosphorylation in depth?
Hydrogen atoms are released from reduced NAD and reduced FAD as they're oxidised to NAD and FAD. The H atom splits into H+ and e-
The electrons move along the electron transport chain (made up of 3 electron carriers, located in the inner mitochondrial membrane), losing energy at each carrier.
The energy is used by the electron carriers to pump protons from the mitochondrial matrix into the intermembrane space
The conc of protons now higher in intermembrane space than matrix, so electrochemical gradient formed
Protons move back down the electrochemical gradient, into the matrix via ATP synthase, which bonds Pi and ADP to form ATP
In the mitochondrial matrix at the end of the transport chain, the protons, electrons and O2(from the blood), combine to form water, as O2 is the final electron acceptor
121
What are the 2 types of anaerobic respiration?
Alcoholic fermentation and Lactate fermentation.
Both take place in cytoplasm and start with glycolysis.
Doesn't use Oxygen so only has glycolysis out of aerobic respiration
122
What does lactate fermentation occur in and what does it produce?
Occurs in mammals and produces lactate (lactic acid)
Reduced NAD transfers hydrogen to pyruvate producing NAD and Lactate
NAD can then be reused in glycolysis
123
Where does alcoholic fermentation occur and what does it produce?
Occurs in yeast cells and produces ethanol
CO2 is removed from pyruvate to form ethanal, reduced NAD (from glycolysis) transfers hydrogen to ethanal to form ethanol and NAD
NAD can be reused in glycolysis
124
How do you find RQ value ( respiratory quotient), of a respiratory substrate?
Volume of CO2 released / volume of O2 consumed
125
PS1 wavelength absorbed?
700nm
126
PS11 wavelength absorbed?
680nm
127
Non cyclic photophosphorylation ( LDR)?
Light energy absorbed by PS11 (680nm), exciting electrons in chlorophyll
Electrons move to a higher energy level to an electron carrier, and then move down a transport chain to PS1
As excited electrons leave PS11, they need to be replaced so light energy splits water into H+ ions, electrons and oxygen (goes into atmosphere)
(chemiosmosis)
The excited electrons lose energy as they move down the electron transport chain
This energy is used to transport protons into the thylakoid, via protein pumps, so thylakoid has higher conc of protons than stroma, forming a gradient across the membrane
Protons move down conc gradient into stroma via enzyme ATP synthase, the energy from this movement combines ADP and inorganic phosphate, forming ATP
Light energy absorbed by PS1 (700nm), which excites the electrons to an even higher energy level
Finally electrons are transferred to NADP, along with a H+ ion to form reduced NADP
128
Cyclic photophosphorylation?
Only uses PS1
Cyclic as electrons aren't passed onto NADP, but passed back to PS1 via electron carriers
Therefore electrons recycled and repeatedly flow through
No Reduced NADP or O2 formed, little bit of ATP made
129
Calvin cycle explained (LIR)?
CO2 enters leaf through stomata, diffuses into stroma of chloroplast
Combines with RuBp, making an unstable 6C compound which splits into 2 3C compounds called GP
Rubsico enzyme catalyses reaction between CO2 and RuBp
ATP from LDR turns GP into TP, this reaction also requires H+ ions from reduced NADP in the LDR, reduced NADP is recycled back to form NADP
TP converted into many useful compounds
5 out of every 6 TP molecules aren't used to make Hexose sugars, but are regenerated to form RuBp
Regenerating RuBP uses rest of ATP produced in LDR
130
What are the useful substances made by the Calvin Cycle?
Carbs- 2 TP molecules
Lipids, using glycerol synthesised from TP and fatty acids from GP
Amino acids from GP
131
Explain the step of blood reaching the site of ultrafiltration in the kidney?
Blood from renal artery enters smaller arterioles in the cortex
Each arteriole splits into a structure called the glomerulus (bundle of capillaries looped inside a hollow ball called the bowman's capsule where ultrafiltration occurs
132
Explain the steps in ultrafiltration of the kidney?
The afferent arteriole (takes blood into the glomerulus), and the efferent arteriole (takes blood out of the glomerulus), efferent smaller in diameter, so pressure of blood in glomerulus is higher
The high pressure forces liquid and small molecules in the blood out of the capillary and into the bowman's capsule
Small substances pass through 3 layers to reach the bowman's capsule, the capillary wall, the basement membrane, and the epithelium of the bowman's capsule
Larger molecules such as proteins can't pass through into bowmans caspule, so stay in the blood
133
Explain the process absorption in the kidney?
Takes place as the filtrate flows along the Proximal convoluted tubule, the loop of Henle and the distal convoluted tubule
Useful substances leave the tubules of the nephrons and enter the capillary network that wraps around them
Epithelium of PCT has microvilli to increase SA
Useful solutes such as glucose, amino acids, vitamins and some salts reabsorbed along PCT via active transport and facilitated diffusion
Also some urea is reabsorbed via diffusion
Water enters blood by osmosis because water potential of blood lower than that of the filtrate, occurs in loop of Henle, DCT, and the collecting duct
Filtrate that remains is urine, which passes along the ureter to the bladder
134
Explain the counter current multiplier mechanism in the loop of Henle?
Near the top of the ascending limb, Na+ and Cl- ions are actively pumped out into the medulla. The ascending limb is impermeable to water, so water stays inside the tubule, but creates a low water potential in the medulla
Because there's lower water potential in the medulla than in the descending limb, water moves from the descending limb and into the medulla by osmosis. This makes the filtrate more concentrated
Water in the medulla is reabsorbed back into the blood via a capillary network
Near the bottom of the ascending limb, Na+ and Cl- ions diffuse out into the medulla further reducing the water potential, as impermeable so water can't follow
All these stages cause water to move out of the collecting duct via osmosis and into the medulla via osmosis
135
What is the water potential of the blood measured by?
Cells called osmoreceptors in the part of the brain called the hypothalamus
136
What happens when osmoreceptors are stimulated by a low water potential in the blood?
Hypothalamus sends nerve impulses to the posterior pituitary gland to release the hormone ADH
ADH makes the walls of the descending limb more permeable to water, so more water reabsorbed from these tubules into the medulla and into the blood by osmosis
137
How is urine used in pregnancy tests?
hCG is a hormone only present in pregnant woman's urine
A stick with an application area that contains monoclonal antibodies for hCG bound to a coloured bead (blue)
When urine is applied any hCG will bind to antibodies on the beads
The urine moves up the test strip with beads attached
The test strip has antibodies to hCG stuck to it (immobilised)
If there is hCG present, test strip turns blue, because the immobilised antibody binds an hCG attached to the blue beads in that area
138
How are excess amino acids broken down by the liver?
Deamination occurs- Nitrogen containing amino groups (NH2), are removed from excess amino acids, forming ammonia (NH3), and organic acids
The organic acids can be respired to give ATP, or converted to carbohydrate and stored as glycogen
Ammonia is too toxic to be excreted directly, so it's combined with CO2 in the ornithine cycle
The urea is released from the liver into the blood. The kidneys then filter the blood and remove the urea as urine
139
What are Kupffer cells?
Attached to walls of the sinusoids, they remove bacteria and break down old red blood cells
140
Explain the ornithine cycle?
Ammonia and CO2 combine to form carbonyl phosphate, which combines with ornithine to form citruline
Which then combines with aspartate and ATP to give off AMP and water, and produce arigininosuccinate, which then converts to arginine
Water is added to arginine to produce urea, and ornithine
141
Formula for volume of a sphere?
4/3 x pi x r^3
