bio the end

Question 1

Table for magnification and resolution of all 3 microscopes?

Answer 1

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

Question 2

Table for differences between Eukaryotic cells and prokaryotic cells?

Answer 2

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

Question 3

Describe the structure of amylose?

Answer 3

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

Question 4

Describe the structure of amylopectin?

Answer 4

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

Question 5

How do you test for a reducing sugar?

Answer 5

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

Question 6

How do you test for a non reducing sugar?

Answer 6

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

Question 7

Can you test for proteins?

Answer 7

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

Question 8

How do you test for lipids?

Answer 8

The emulsion test Shake the substance with ethanol then pour into water Solution will go milky if a lipid is present

Question 9

Which are the purine bases and what does this mean?

Answer 9

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

Question 10

Which are the pyrimidine bases and what does this mean?

Answer 10

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

Question 11

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

Answer 11

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

Question 12

How can you purify DNA?

Answer 12

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

Question 13

What’s a cofactor?

Answer 13

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

Question 14

What can an organic cofactor be known as?

Answer 14

Coenzymes, usually are sources from vitamins

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

Question 15

What occurs during interphase?

Answer 15

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)

Question 16

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

Answer 16

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

Question 17

What occurs in the second step of mitosis, metaphase?

Answer 17

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

Question 18

What occurs in anaphase, the 3rd of mitosis?

Answer 18

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

Question 19

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

Answer 19

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)

Question 20

Describe cytokenesis in mitosis?

Answer 20

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

Question 21

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

Answer 21

(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

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

Function of the cortex in the adrenal glands?5

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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

Answer 28

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

Question 29

Describe how Beta cells secrete insulin when they are depolarised?

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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

Question 32

what does glycolysis do in general?

Answer 32

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

Question 33

What occurs in phosphorylation in glycolysis?

Answer 33

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

Question 34

What occurs in the oxidation stage of glycolysis?

Answer 34

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

Question 35

What takes place in the link reaction?

Answer 35

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

Question 36

What occurs in the Kreb’s cycle?

Answer 36

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

Question 37

Calvin cycle explained (LIR)?

Answer 37

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

How well did you know this?

Question 38

Explain the ornithine cycle?

Answer 38

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