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Last minute BIOOOOOOO > Last minute BIO > Flashcards

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

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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

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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

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4
Q

Magnification definition and formula?

A

How much bigger the image is than the specimen Magnification = image size / object size

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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

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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

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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

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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

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9
Q

What does the disaccharide maltose consist of?

A

2 molecules of alpha glucose binded to each other via a glycosidic bond

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10
Q

What does the disaccharide sucrose consist of?

A

When alpha glucose and fructose join together via a glycosidic bond

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11
Q

What does the disaccharide Lactose consist of?

A

When Beta glucose is bonded to galactose

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12
Q

What does starch consist of?

A

A mixture of the 2 polysaccharides of alpha glucose amylose and amylopectin

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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

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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

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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

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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

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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.

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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

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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

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20
Q

What are reducing sugars?

A

All the monosacchardies, and the disacharides maltose and lactose

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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

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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

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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

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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

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25
Q

How do you use calorimetry to measure the concentration of a glucose solution?

A

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

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26
Q

Which are the purine bases and what does this mean?

A

Adenine and Guanine, contain 2 carbon - nitrogen rings joined together

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27
Q

Which are the pyrimidine bases and what does this mean?

A

Cytosine, and thymine, only contain 1 carbon-nitrogen ring, so are smaller than a purine base

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28
Q

What do nucleotides join together to form and what between?

A

Polynucleotides, phophodiester bond forms between the phosphate group of one nucleotide, and the sugar of another forming a sugar phosphate backbone

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29
Q

Describe how 2 polynucleotide strands join together to form a helix?

A

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

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30
Q

How can you purify DNA?

A

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

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31
Q

Describe the process of DNA self replicating?

A

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

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32
Q

Describe the first stage of protein synthesis - transcription?

A

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

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33
Q

Describe how the second step of protein synthesis occurs Translation?

A

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

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34
Q

What’s a cofactor?

A

Non protein substance, that attaches to an enzyme allowing it to work

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35
Q

Example of a inorganic cofactor?

A

Chloride ion, helps amylase enzyme bind to starch Aren’t affected during the reaction

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36
Q

What can an organic cofactor be known as?

A

Coenzymes, usually are sources from vitamins

They participate in the reaction, so are changed Often act as carries, moving chemical groups between different enzymes

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37
Q

What’s a cofactor known as if it’s tightly bound to an enzyme, and an example?

A

Prosthetic group

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38
Q

The 6 steps in cell division?

A

Interphase Prophase (Mitosis) Metaphase (Mitosis) Anaphase (Mitosis) Telophase (Mitosis) Cytokenesis

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39
Q

What occurs during interphase?

A

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)

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40
Q

Describe what occurs in the first step of mitosis, prophase?

A

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

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41
Q

What occurs in the second step of mitosis, metaphase?

A

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

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42
Q

What occurs in anaphase, the 3rd of mitosis?

A

Centromers divide Separating each pair of sister chromatids, the spindles contract pulling the chromatids to the opposite ends of the cell

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43
Q

What occurs in telophase, the 4th step of mitosis?

A

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)

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44
Q

Describe cytokenesis in mitosis?

A

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

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45
Q

What occurs in prophase 1, the first step of meiosis?

A

(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

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46
Q

What occurs in metaphase 1, the second step of meiosis?

A

The homologous pairs line up across the centre of the cell, and attach to the spindle fibres by their centromers

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47
Q

What happens in anaphase 1, the third step of meiosis?

A

The spindles contract, separating the homologous pairs, one chromosome goes to each end of the cell

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48
Q

What occurs in telophase 1, the 4th step of meiosis?

A

Nuclear envelope forms around each group of chromosomes, and then cytokinesis occurs and 2 haploid daughter cells are produced (still double stranded)

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49
Q

What happens in meiosis 2?

A

All the same steps as mitosis Produces 4 genetically different haploid daughter cells (single stranded chromosomes) = gametes

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50
Q

Describe chromatids crossing over in Prophase 1?

A

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

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51
Q

Describe the independent assortment of chromosomes?

A

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

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52
Q

Describe what happens during inspiration?

A

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

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53
Q

Describe what happens during expiration?

A

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)

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54
Q

Describe how the gills are usually ventillated in bony fish?

A

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

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55
Q

Describe how insects exchange gases?

A

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)

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56
Q

Out of the trachea, bronchi, larger bronchiole, smaller bronchiole, and smallest bronchiole and aleveoli, which contain cartilage, smooth muscle, elastic fibres, goblet cells, epithelium?

A

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

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57
Q

Describe pressure filtration in the capillary bed?

A

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
Q

Blood contains red blood cells, white blood cells, platelets, proteins, water and dissolved solutes what does tissue fluid and lymph contain?

A

Tissue fluid:
Very few proteins and white blood cells
water
dissolved solutes

lymph: 
White blood cells 
water 
dissolved solutes 
only antibody proteins
59
Q

Describe the cardiac cycle?

A
  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
Q

Describe how cardiac muscle controls the regular beating of the heart?

A

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
Q

Describe one full heartbeat on a electrocardio graph?

A

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
Q

Describe how a high partial pressure of CO2 makes haemoglobin more ready to offload oxygen?

A

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
Q

Describe the symplast pathway?

A

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
Q

Describe the apoplast pathway?

A

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
Q

Describe how Xerophytes are adapted to live in dry climates?

A

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
Q

What is translocation?

A

The movement of dissolved substance to where they are needed in the plant, it moves them from a source to a sink

67
Q

Describe the mass flow hypothesis for phloem transport?

A

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
Q

Describe exactly how substances enter the phloem at the source via active loading?

A

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
Q

Describe how sensory receptors convert stimulus energy into nerve impulses?

A

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
Q

Describe the mechanoreceptor pacinian corpuscles?

A

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
Q

What do dendrons / dendrites do?

A

Carry nerve impulses towards the cell body

72
Q

What do axons do?

A

Carry nerve impulses away from the cell body

73
Q

Structure of a sensory neuron in direction of the impulse?

A

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
Q

Describe the structure of a relay neuron in direction of the impulse?

A

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
Q

Describe the structure of a motor neuron in the direction of the impulse?

A

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
Q

Describe how neuron cell membranes are polarised at rest?

A

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
Q

Describe the process of a neuron cell membrane becoming depolarised when stimulated and an action potential being generated?

A

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
Q

Describe exactly in 3 main steps how neurotransmitters transmit nerve impulses between neurones?

A

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
Q

Describe the process of adrenaline acting as the first messenger on cells?

A

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
Q

Function of the cortex in the adrenal glands?

A

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
Q

Describe the function of the medulla in the adrenal glands?

A

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
Q

Describe what islets of langerhan are and their function?

A

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
Q

Describe how the hypothalamus controls body temperature in mammals?

A

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
Q

Describe how beta cells from the ilsets of langerhan in the pancrease releasing the hormone insulin, lowers the blood glucose concentration?

A

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
Q

Describe how alpha cells from the islets of langerhans in the pancreas releasing glucagon raises the blood glucose concentration?

A

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
Q

Describe how Beta cells secrete insulin when they are depolarised?

A

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
Q

What does the growth hormone gibberellin stimulate?

A

Seed germination
Stem elongation
Side shoot formation
Flowering

88
Q

How do gibberelins stimulate seed germination?

A

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
Q

What chemical inhibits gibberellins and therfore seed germination?

A

The hormone abscisic acid

90
Q

Describe how leave loss is controlled by hormones?

A

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
Q

Explain how plant hormones are involved in stomatal closure?

A

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
Q

How does Ethene make fruit ripen?

A

Stimulates hormones, that break down cell walls and chlorphyll, and convert starch into sugars

93
Q

What does the nervous system split up into?

A

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
Q

What does the peripheral nervous system split up into?

A

The somatic nervous system - controls conscious activities such as running

The autonomic nervous system - controls unconscious activities such as digestion

95
Q

What does the autonomic nervous system split up into?

A

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
Q

Where it’s found and it’s functions for the hypothalamus?

A

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
Q

Where it’s found and it’s functions for the Pituitary gland?

A

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
Q

Where it’s found and it’s functions for the Cerebrum?

A

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
Q

Where it’s found and it’s functions for the medulla oblongata?

A

Found at the base of the brain, and at the top of the spinal cord

It automatically controls breathing rate and heart rate

100
Q

Where it’s found and it’s functions for the Cerebellum?

A

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
Q

Describe the knee jerk reflex?

A

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
Q

Describe how the nervous system and hormonal system coordinate in the fight or flight response?

A

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
Q

How does the nervous system help to control heart rate?

A

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
Q

Steps that occur if a high blood pressure is present/ or high blood O2, low CO2 conc, and high pH level?

A

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
Q

Steps that occur if low blood pressure is present/ or low O2 blood conc, high CO2 or low pH?

A

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
Q

How to use the student’s t test to compare heart rate before and after exercise?

A

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
Q

What are thick myofilaments made up of?

A

The protein myosin

108
Q

What are thin myofilaments made up of?

A

The protein actin

109
Q

What happens to band length when during muscle contraction?

A

A band stays the same
I band gets shorter
H zone gets shorter

110
Q

What is the actin-myosin binding site in resting muscles blocked by?

A

Tropomyosin, which is held in place by troponin

111
Q

Describe the whole process of muscle contraction being triggered by an action potential?

A

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
Q

Describe what happens in muscle contraction when excitation stops?

A

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
Q

Describe briefly how the CP system generates energy for muscle contraction?

A

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
Q

Describe the neuromuscular junctions ( the synapses between neurones and muscles?

A

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
Q

what does glycolysis do in general?

A

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
Q

What occurs in phosphorylation in glycolysis?

A

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
Q

What occurs in the oxidation stage of glycolysis?

A

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
Q

What takes place in the link reaction?

A

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
Q

What occurs in the Kreb’s cycle?

A

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
Q

Describe oxidative phosphorylation in depth?

A

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
Q

What are the 2 types of anaerobic respiration?

A

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
Q

What does lactate fermentation occur in and what does it produce?

A

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
Q

Where does alcoholic fermentation occur and what does it produce?

A

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
Q

How do you find RQ value ( respiratory quotient), of a respiratory substrate?

A

Volume of CO2 released / volume of O2 consumed

125
Q

PS1 wavelength absorbed?

A

700nm

126
Q

PS11 wavelength absorbed?

A

680nm

127
Q

Non cyclic photophosphorylation ( LDR)?

A

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
Q

Cyclic photophosphorylation?

A

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
Q

Calvin cycle explained (LIR)?

A

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
Q

What are the useful substances made by the Calvin Cycle?

A

Carbs- 2 TP molecules
Lipids, using glycerol synthesised from TP and fatty acids from GP
Amino acids from GP

131
Q

Explain the step of blood reaching the site of ultrafiltration in the kidney?

A

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
Q

Explain the steps in ultrafiltration of the kidney?

A

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
Q

Explain the process absorption in the kidney?

A

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
Q

Explain the counter current multiplier mechanism in the loop of Henle?

A

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
Q

What is the water potential of the blood measured by?

A

Cells called osmoreceptors in the part of the brain called the hypothalamus

136
Q

What happens when osmoreceptors are stimulated by a low water potential in the blood?

A

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
Q

How is urine used in pregnancy tests?

A

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
Q

How are excess amino acids broken down by the liver?

A

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
Q

What are Kupffer cells?

A

Attached to walls of the sinusoids, they remove bacteria and break down old red blood cells

140
Q

Explain the ornithine cycle?

A

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
Q

Formula for volume of a sphere?

A

4/3 x pi x r^3

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