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A2 Biology > Unit 4: Section 2 and 3 - Excretion / Photosynthesis and Respiration > Flashcards

Unit 4: Section 2 and 3 - Excretion / Photosynthesis and Respiration Flashcards

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1
Q

What does the hepatic artery do?

A

Supplies the liver with oxygenated blood from the heart, so the liver has a good supply of oxygen.

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2
Q

What does the hepatic vein do?

A

Takes deoxygenated blood away from the liver

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3
Q

What does the hepatic portal vein do?

A

Brings blood from the duodenum and ileum (parts of the small intestine), so it’s rich in the products of digestion. This means any ingested harmful products are broken down straight away

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4
Q

What does the bile duct do?

A

Takes bile to the gall bladder to be stored

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5
Q

What are sinusoids?

A

Capillaries that connect the hepatic artery and the hepatic portal vein to the central vein

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6
Q

What are kupffer cells?

A

Cells attached to the walls of the sinusoids that remove bacteria and break down old red blood cells

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7
Q

What are the three layers that substances pass through during ultra-filtration?

A

Capillary wall, basement membrane and epithelium of the Bowman’s capsule

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8
Q

Where are microvilli found and what do they do?

A

They are found in the epithelium of the PCT wall, they provide a large surface area for the reabsorption of useful substances

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9
Q

What substances are reabsorbed from the filtrate back into the blood?

A

Glucose, amino acids, vitamins and some salts

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10
Q

What is urine usually made up of?

A

Water and salts, urea and other substances such as hormones or excess vitamins

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11
Q

What does urine not usually contain?

A

Proteins and blood cells (they’re too big), glucose, amino acids and vitamins

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12
Q

What happens to the amount of water that is reabsorbed by osmosis into the blood from the nephron when the water content of the blood is too low?

A

It increases

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13
Q

Where does water reabsorption take place?

A

Loop of henle, DCT and collecting duct

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14
Q

How does the hairpin countercurrent multiplier mechanism work?

A

1) Near the top of the ascending limb sodium and chlorine ions are actively pumped out into the medulla, the ascending limb is impermeable to water, so the water stays inside the tubule. This creates a low water potential in the medulla.
2) Because there’s a lower water potential in the medulla than in the descending limb, water moves out of the descending limb into the medulla by osmosis. This makes the filtrate more concentrated. The water in the medulla is then reabsorbed into the blood through the capillary network.
3) Near the bottom of the ascending limb sodium and chlorine ions diffuse out into the medulla, further lowering the water potential in the medulla.
4) All of these steps lower the water potential in the medulla, so water moves out of the collecting duct by osmosis. The water is again reabsorbed into the blood through the capillary network.

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15
Q

What cells monitor the water content of the blood?

A

Osmoreceptors

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16
Q

Where is ADH released from

A

The posterior pituitary gland

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17
Q

What can kidney failure be caused by?

A

Kidney infections - This can cause inflammation of the kidneys which can damage the cells and interfere with ultrafiltration and reabsorption

High blood pressure - This can damage the glomerulus because the capillaries can get damaged because of the high blood pressure. This means larger molecules can enter the blood

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18
Q

What problems can kidney failure cause?

A

1) Waste products like urea can build up in the blood and cause vomiting
2) Fluid starts to accumulate in the tissues because the kidneys cant remove excess water so parts of the body can swell up
3) The balance of ions in the body becomes unbalanced, salt build up may cause more water retention, and an imbalance of calcium and phosphate can lead to brittle bones
4) Long term kidney failure causes anaemia

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19
Q

How does renal dialysis work?

A

1) The patients blood is passed through a dialysis machine, the blood flows on one side of a partially permeable membrane and a dialysis fluid flows on the other
2) Waste products diffuse across the membrane into the fluid, removing them from the blood
3) Blood cells and larger molecules like proteins are prevented from leaving the blood

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20
Q

How is urine used to test for pregnancy?

A

1) A stick is used with an application area that contains antibodies for hCG (Human chorionic gondadotropin) bound to a coloured blue bead
2) When urine is applied any hCG will bind to the antibodies on the bead
3) The urine moves up the test strip, carrying the beads with it
4) The test strip has antibodies to hCG immobilised
5) If hCG is present the test strip turns blue because the immobilised antibody binds to any hCG attached to the blue beads, concentrating them in that area

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21
Q

How is urine used to test for steroids?

A

1) Urine is tested for steroids using gas chromatography
2) The urine is vaporised and passed through a column containing a liquid. Different substances move through the column at different speeds. The length of time taken for the substances in the sample to pass through the column is compared with the take taken for the steroid to pass through the column, if they are the same then a steroid is present

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22
Q

What is an autotroph?

A

An organism that can make it’s own organic molecules

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23
Q

What is a heterotroph?

A

An organism that feeds on other organisms in order to obtain it’s organic molecules

24
Q

What is the formula for photosynthesis?

A

6CO2 + 6H2O + energy —-> Glucose + 6O2

25
Q

How is ATP synthesised?

A

From ADP and inorganic phosphate, using energy from an energy releasing reaction e.g. the breakdown of glucose in respiration. The energy is stored as chemical energy in the phosphate bond

26
Q

What catalyses ADP+P=ATP

A

ATP synthase

27
Q

Why is ATP a good energy source

A

1) It only stores or releases a small amount of energy at a time, so no energy is wasted
2) It’s a small, soluble molecule so can easily be transported round the cell
3) It’s easily broken down so energy can be released easily
4) It can transfer energy to other molecules by transferring one of it’s phosphate groups
5) ATP can’t pass out of the cell, so the cell always has an immediate supply of energy

28
Q

What is phosphorylation?

A

Adding phosphate to a molecule

29
Q

What is photophosphorylation?

A

Adding phosphate to a molecule using light

30
Q

What is photolysis?

A

The splitting of a molecule using light

31
Q

What is the co-enzyme used in photosynthesis and what does it do

A

NADP - transfers hydrogen from one molecule to another

32
Q

What are the co-enzymes used in respiration and what do they do?

A

NAD and FAD - transfer hydrogen from one molecule to another

Co-enzyme A - Transfers acetate between molecules

33
Q

What are thylakoids?

A

Fluid filled sacks that are stacked up in the chloroplast into structures called grana

34
Q

What are the grana linked together by?

A

Bits of thylakoid membrane called lamellae

35
Q

What are primary pigments?

A

Reaction centres where electrons are excited during the LDR

36
Q

What are accessory pigments?

A

They surround the primary pigments and transfer light energy to them

37
Q

What wavelength does photosystem 1 absorb light best at?

A

700nm

38
Q

What wavelength does photosystem 2 absorb light best at?

A

680nm

39
Q

What is the stroma?

A

A gel-like substance that surrounds the thylakoids and contains enzymes, sugars and organic acids

40
Q

What happens in the LDR?

A

1) This reaction requires light
2) It takes place in the thylakoid membranes of the chloroplasts
3) Here, light energy is absorbed by photosynthetic pigments in the photosystems and converted to chemical energy
4) The light energy is used to form ATP and to reduce NADP to form reduced NADP.
5) During the process H2O is oxidised to O2

41
Q

What happens in the LIR?

A

1) This is also called the Calvin cycle
2) Doesn’t rely on energy directly (but relies on products of LDR)
3) Takes place in the stroma of the chloroplasts
4) Here the ATP and reduced NADP from the LDR supply the energy and hydrogen to make glucose from CO2

42
Q

What is the light absorbed by the photosystems used for?

A

1) Making ATP from ADP (called phosphorylation)
2) Making reduced NADP from NADP
3) Splitting water into protons, electrons and oxygen (called photolysis)

43
Q

What does non-cyclic photophosphorylation produce?

A

ATP, Reduced NADP and Oxygen

44
Q

What happens in non-cyclic photophosphorylation?

A

1) Light energy is absorbed by PSII, the light energy excites electrons in chlorophyll, the electrons move to a higher energy level, these high energy electrons move along the electron transport chain.
2) Light energy splits water into protons, electrons and oxygen. The electron produced replaces the electron that has just moved down the electron transport chain
3) The excited electrons lose energy as they move along the electron transport chain. This energy is used to transport protons into the thylakoid so that the thylakoid has a higher concentration of protons that the stroma. Protons then move down their concentration gradient out of the thylakoid via ATP synthase, the energy from this movement combines ADP to form ATP
4) Light energy is absorbed by PSI which excites the electrons to an even higher level, the electrons are then transferred to NADP, along with a proton from the stroma to form reduced NADP

45
Q

What is cyclic photophosphorylation?

A

Only use PSI, the electrons from the chlorophyll are passed back to PSI via electron carriers, no reduced NADP or oxygen produced, only small amount of ATP produced

46
Q

Where does the Calvin cycle take place?

A

In the stroma

47
Q

What happens in the first stage of photosynthesis?

A

1) CO2 enters the leaf and diffuses into the stroma
2) Here it combines with RuBP (5 carbon compound), this creates a 6 carbon compound which quickly breaks down into two molecules of glycerate 3-phosphate (3 carbon)
3) Rubisco catalyses the reaction between CO2 and RuBP

48
Q

What happens in the second stage of photosynthesis?

A

1) ATP from the LDR provides energy to turn the 3 carbon compound into a different 3 carbon compound called triose phosphate
2) This reaction also requires hydrogen ions which come from reduced NADP, this turns reduced NADP into NADP
3) This triose phosphate is then used to make useful compounds such as glucose

49
Q

What happens in the third stage of photosynthesis?

A

1) Five out of every 6 molecules of TP aren’t used to make hexose sugars, but are used to regenerate RuBP
2) Regenerating RuBP uses the rest of the ATP produced by the LDR

50
Q

How is the structure of a chloroplast adapted for photosynthesis?

A

1) The chloroplast envelope keeps the reactants for photosynthesis close to their reaction sites
2) The thylakoids have a large surface area to allow as much light energy to be absorbed as possible
3) Lots of ATP synthase molecules are present in the thylakoid membrane to produce ATP in the LDR
4) The stroma contains all the enzymes and sugars for the LIR to take place

51
Q

What is the optimum temperature for photosynthesis?

A

25 degrees

52
Q

What is the optimum carbon dioxide level for photosynthesis?

A

0.4%

53
Q

What happens during glycolysis?

A

1) Phosphorylation
- Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP
- This creates 1 molecule of hexose bisphosphate and 2 molecules of ADP
- Then, hexose bisphosphate is split up into 2 molecules of triose phosphate
2) Oxidation
- Triose phosphate loses hydrogen, forming 2 molecules of pyruvate
- NAD collects the hydrogen ions, forming 2 reduced NAD
- 4 ATP were produced, but 2 were used in stage 1, so there’s a net gain of 2 ATP

54
Q

What happens during the link reaction?

A

1) Pyruvate is decarboxylated - one carbon atom is removed from pyruvate in the form of CO2
2) NAD is reduced - it collects hydrogen from pyruvate, changing pyruvate into acetate
3) Acetate is combined with coenzyme A to form acetyl coenzyme A
4) No ATP is produced

55
Q

Page 40 diagram

A

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A2 Biology (3 decks)

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