Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

AQA A Level Biology > Paper 3B > Flashcards

Paper 3B Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is osmoregulation?

A

The homeostatic control of water potential in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Key points of osmoregulation

A
  • The balance of water and mineral ions/salts- Controlled by the kidneys
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

T or F, - Your kidneys are located just below your belly button

A

F

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

T or F, - Your kidneys clean the blood and control the water levels

A

T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

T or F, - The kidneys work alongside the large intestine

A

F

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

T or F, The ureter carries urine from the kidneys to the bladder

A

T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Draw the diagram of a kidney

A

check notes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the nephron?

A

The filtering unit of the kidney which performs the job of filtering and fluid balance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Description/function of medulla

A

Inner region made up of loops of Henle, collecting ducts and blood vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Description/function of loop of henle

A

Long hairpin loop extending from the cortex and into the medulla

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Description/function of convoluted tubule

A

A series of loops surrounded by blood capillaries, walls are made up of epithelial cells with microvilli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Description/function of Renal vein

A

Returns blood to the heart via the vena cava

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Description/function of glomerulus

A

A many branched knot of capillaries from which fluid is forced out of the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Description/function of ureter

A

A tube that carries urine to the bladder

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Description/function of cortex

A

Outer region made up of renal capsules (Bowman’s capsules), convoluted tubules and blood vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Description/function of renal artery

A

Supplies the kidney with blood from the heart via the aorta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Description/function of bowman’s capsule

A

A cup shaped structure at the start of the nephron, surrounding a mass of blood capillaries (glomerulus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Description/function of collecting duct

A

A tube with several distal convoluted tubules from several nephrons empty, increases in width as it empties into the pelvis from the kidneys

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

A series of stages occur throughout the nephron in the formation of urine, what are they?

A
  1. Ultrafiltration2. Reabsorption3. Maintenance of a gradient of sodium ions4. Reabsorption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What forms in ultrafiltration?

A
  • Formation of the glomerular filtrate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where does ultrafiltration occur?

A
  • At the glomerulus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is ultrafiltration the result of?

A
  • Result of hydrostatic pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe the process of ultrafiltration

A
  1. Blood enters artery2. Branches into afferent arteriole3. Enter the Bowman’s capsule4. Divide and forms the glomerulus5. Capillaries merge – efferent artieriole6. Leaves via the renal veinThe diameter of the afferent arteriole is greater than the efferent arteriole, the blood is under higher pressure, so it forces anything that is small enough out, forming the filtrate1. Hydrostatic pressure builds up 2. Pores allow some substances out
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

In ultrafiltration, what leaves the blood and what remains in?

A

Out:- Water- Glucose- Urea- Mineral ionsIn:- Red blood cells- Proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How is the Bowman’s capsule adapted?

A

The movement of this filtrate out of the glomerulus is resisted by:- Capillary epithelial cells- Connective tissue (lining capillaries)- Epithelial cells of the renal capsule- Low hydrostatic pressure- Low water potential of the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How are podocytes and gaps in the epithelial cells good adaptations for the bowman’s capsule?

A
  1. Podocytesa. Specialized epithelial cells, form gaps, shorter diffusion pathway2. Gaps in the epithelial cellsa. Shorter diffusion pathways, easy passage of molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

The kidneys produce urine by filtration of the blood and ____ _____ of useful substances

A

selective reabsorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is selective reabsorption?

A

Selective reabsorption: The reabsorption of certain molecules back into the blood, this includes glucose, some ions, and water via co-transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is reasbosbred into the kidneys and what is left?

A

Around 85% of the filtrate is reabsorbed back into the blood, this includes useful ions and glucose, while it leaves waste and urea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How does reabsorption occur, steps and location

A
  1. Co-transporta. Proximal convoluted tubule2. Counter current mechanisma. Loop of Henle3. Anti-diuretic hormonea. Collecting duct
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How does co-transport occur?

A
  1. Sodium ions are actively transported out of the cell2. Lowers Na+ concentration inside the cell3. Na+ diffuses from the lumen into the cell carrier protein (facilitated diffusion)4. Pull with it another molecule such as glucose (co-transport)5. Molecule concentration increases6. Molecule diffuses into the blood alongside some water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the loop of henle responsible for?

A

Responsible for the reabsorption of water from the collecting duct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Key points of loop of henle

A
  • Concentrates the urine- Determines the concentration of the urine- Acts as a counter-current multiplier
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What are the two regions of the kidney?

A

Ascending and descending

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the counter-current multipleier in the loop of henle?

A
  • Allows salts to be transferred from the ascending limb to the descending limb- This arrangement is called the counter-current multiplier
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is the difference between the ascending and descenidn gparts of the loop of henle?

A
  • Descending o Into the medullao Narrowo Thing wallso Highly permeable to water- Ascendingo Back to the cortexo Widero Thicker wallso Impermeable to water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

In the counter current multiplier, why is it important the two liquids are in opposite flow?

A
  • Two liquids in opposite direction past one anothero Filtrate in collecting duct meets interstitial fluid with an even lower water potential- Increases the efficiency of salt transfer between the ascending and descending limb- Maintains a water potential gradient- Exists the length of the collecting duct- Results in 8% of water entering the fluid and then the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Describe the process of the counter current multipler

A
  1. Water leaves the filtrate via osmosis and enters the interstitial space and then the blood capillaries in it2. The water potential lowers (more negative) as it moves into the medulla3. At the same time, Na+ ions are actively transported out ascending limb4. Decrease water potential in the medulla between the two limbs, increasing the concentration and the rate of osmosis5. As the filtrate moves up the ascending at the base, Na+ ions diffuse6. Water cannot leave as the ascending wall is impermeable7. Therefore, the filtrate gets a higher water potential8. This maintains a gradient of water potential with the interstitial space9. The collecting duct is permeable to water so water can leave as he filtrate moves through it10. Filtrate has a much lower water potential, leaving concentrated urine to reach the bladder
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What happens at the distal convoluted tubule?

A
  • Active transport of salts- Maintains optimum pH- Cells lining have microvilli and mitochondria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Define osmoregulation

A

Control of water potential within and surrounding cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Explain why our water levels vary (3 marks)

A
  • External temperature- Exercise- Fluid intake- Salt intake- Diet- Drug intake- Medication
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

How do we control water levels?

A
  • A hormone (ADH)- Secreted from the posterior pituitary gland- Acts on the DCT and CD- Concentrates the urine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Describe the process which ADH is involved in when the body is dehydrated

A
  1. Dehydration2. Decreased water potential of blood3. Osmoreceptors cells in hypothalamus detect change (lose water, so shrink)4. Stimulates neurosecretory cells in the hypothalamus5. Increased ADH production which passes to the posterior pituitary gland6. ADH secreted into the blood7. ADH makes collecting duct walls more permeable, more water is absorbed into the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Describe the process which ADH is involved in when the body has too much water

A
  1. Too much water2. Increased water potential of blood3. Osmoreceptors cells in hypothalamus detect change (gain water, so swell)4. Does not stimulate neurosecretory cells5. Decrease ADH production which passes to the posterior pituitary gland6. No ADH secreted into the blood7. Less ADH makes collecting duct walls less permeable, less water is absorbed into the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

How does ADH work?

A
  1. Binds to receptors on DCT and CD2. Activates enzyme phosphorylase inside3. Moves aquaporin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Describe the effect of ADH’s presence and absence

A

No ADH – - Not permeable- More water in fluid surrounding collecting duct- Large volume of dilute urineADH present – - More permeable- Increased water potential gradient- Small volume of concentrated urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Explain the responses which are brough about by the release of ADH (5 marks)

A
  1. Binds to complementary membrane bound receptors on DCT and CD2. ADH binds but cannot pass as it is insoluble3. Activates enzyme phosphorylase inside (through second messenger model)4. Vesicles contain water permeable channels (aquaporin)5. Vesicles fuse due to the fluidity membrane6. Walls more permeable to water and urea
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Why is osmoregulation negative feedback?

A
  1. Osmoreceptors in the hypothalamus detect rise in water potential2. Fewer impulse to the thirst center of the hypothalamus3. Fewer impulses to the pituitary gland4. Less ADH is released
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

How is aquaporin removed, and what happens because of this?

A
  1. Cell surface membrane folds inwards2. New vesicles remove the aquaporins3. Wall is less permeable4. More water passes out
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Why do you need ATP in the synapse?

A
  1. Need ATP to move vesicles in synaptic knob, and to join together acetyl and choline then put it in the vesicles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What does a cell lining the kidney have as adaptations?

A

thin membrane, large surface area, good blood supply, intrinsic proteins, and mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What is a mutation?

A

Any change in one or more nucleotide base or a change in the sequence of the bases in DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Characteristic of mutations

A

.Random.Spontaneous.Natural.Positive or negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Three types of mutations

A

.Insertion.Deletion.Substitution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Define insertion

A

A nucleotide is added to the DNA sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Define deletion

A

A nucleotide is lost from the DNA sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Define subsitution

A

One nucleotide is replaced by another nucleotide with a different base

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

What is a frame shift?

A

every amino acid after the insertion or deletion will move one place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

What will substitution affect?

A

Only one triplet code

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What will deletion and insertion affect?

A

the whole amino acid sequence, by causing a frame shift

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What is a mutagen?

A

A physical or chemical agent that changes the genetic material of an organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

What do mutagenic agents do?

A

increase the frequency of a mutation occurring above the natural

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

Name 4 things that act as mutagenic agents

A

Caffeine, x-rays, mustard gas and UV radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

What are chromosomal mutations?

A

Changes in the structure or number of whole chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

What are the two types of chromosomal mutations?

A

.Polyploidy.Nondisjunction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

What is polyploidy?

A

.Changes in whole sets of chromosomes.Cells have multiple sets of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

What form of polyploidy is very common in plants?

A

.3n = triploid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

What is non-disjunction?

A

.Homologous pairs fail to separate.Changes in number of individual chromosomes per cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

What is down’s syndrome caused by?

A

extra chromosome 21

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

Define meiosis

A

the process by which a diploid nucleus (2n) divides to produce four haploid daughter nuclei (n)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

Name the phases in meiosis

A

Interphase, prophase I, Metaphase I, Anaphase I, Telophase I, cytokinesis, Prophase II, Metaphase II, Anaphase II, telophase II and cytokinesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

What is a homogolous pair?

A

one chromatid of mum and one chromatid of dad

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

What are sister chromatids?

A

identical chromatids together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

What two forms of genetic variation are there?

A

Crossing over and independent segregation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

What is crossing over?

A

Crossing over is the exchange of alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

What is independent segregation?

A

Independent segregation is the random arrangement of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

State what happens in each phase of meiosis.

A

Interphase – The cell is synthesising DNA and checking it (2 chromatid per chromosome)Prophase I – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks downMetaphase I – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeresAnaphase I – The pair of chromosomes are split as each is pulled to opposite poles in the cell by the spindle fibres contracting – the homologous chromosomes are separated from each other but the chromosome stays tgtherTelophase I & Cytokinesis – The cells form two nucleus, one for each set of new chromosomes, and pull apart while forming a membrane to produce two daughter cellsProphase II – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks downMetaphase II – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeresAnaphase II – The sister chromatids are split as each chromatid is pulled to opposite poles in the cell by the spindle fibresTelophase II & cytokinesis – The cells form two nucleus, one for each set of new chromatids, and pull apart while forming a membrane to produce two more daughter cells each (4 cells now altogether)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

What is a genotype?

A

The genetic makeup of an organism, the genes and alleles that they have

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

What is a phenotype?

A

Observable characteristics, genotype + environment = phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

What are the causes of genetic variation?

A

.Mutations, sexual reproduction, meiosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

How does crossing over work?

A

Homologous pairs line up, chromatids of each pair become twisted, section of chromatid breaks off and re-joins chromatid of the other homologous chromosome, sections have different alleles, new combination of linked alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

With crossing over, what happends to the amount of possible versions of allele combinations?

A

No crossing over = 2 versionsWith crossing over = 4 possible versions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

Who discovered independent segregation? When?

A

.Gregor Mendel (19th Century)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

What is independent segregation?

A

the random segregation of chromosomes during anaphase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

What did Gregor Mendel say about independent segregation?

A

.Genes are inherited independently of one another.BUT genes close together have a high likelihood of being inherited together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

Independent segregation key points

A

.Homologous pairs line up along the equator randomly.Combination of chromosomes pulled to each pole is random.Daughter cells produced are genetically different

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

The formula for the number of combinations of genes after independent segregation

A

2^n

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

The formula for the number of combinations of genes after fertilisation after independent segregation

A

(2^n)^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

Why does the formula (2^n)^2 not work for crossing over?

A

Crossing over is completely random

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

What is the ‘n’ in the formula (2^n)^2?

A

number of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

What is the first ‘2’ in the formula (2^n)^2?

A

possible number of routes the chromosomes could go to (pulled to two poles)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

Draw a labelled diagram for the nitrogen cycle

A

Check your notes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

Nitrogen molecules are made up of a triple bond, is this hard or easy to break up?

A

Hard

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

____ which is the only biological enzyme which can break the nitrogen triple bond

A

nitrogenase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

Nitrogen oxides turns back into nitrogen gas though the enzyme of _____________

A

nitrate reductase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

.Limited availability of nutrient ions in a usable form and so the flow of nutrients within an ecosystem is not linear, but mostly …

A

… cyclical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

All nutrient cycles have one simple sequence at heart, which is:

A
  • The nutrient is taken up by producers as simple, inorganic molecules- The producer incorporates the nutrient into complex organic molecules- When the producer is eaten, the nutrient passes into consumers (animals)- The complex molecules containing the nutrient are passed along the food chain as each consumer is eaten by the next- When the producers and consumers die, their complex molecules are broken down by saprobiontic microorganisms (decomposers) that release the nutrient in its original simple form, the cycle is then complete
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

________ are the driving force in the nutrient cycles which ensure the nutrients are released for reuse.Without them, nutrients would remain locked up as part of complex molecules that cannot be taken up and used again by plants

A

Saprobionts

99
Q

.Living organisms use nitrogen to …

A

… manufacture proteins, nucleic acids and other nitrogen-containing compounds

100
Q

__% of the atmosphere is nitrogen

A

78

101
Q

.Few organisms can absorb nitrogen gas _____

A

directly

102
Q

How does nitrogen enter the living component of the ecosystem?

A

.Plants take up most of the nitrogen they require in the form of nitrate ions (NO3 -) from the soil.These ions are absorbed, using active transport, by the roots

103
Q

.Animals obtain nitrogen-containing compounds by …

A

… eating and digesting plants

104
Q

.Nitrate ions are very soluble and easily leach (wash) through the soil, beyond the reach of plant roots.In natural ecosystems, the nitrate concentrations are restored largely by …

A

… the recycling of nitrogen containing compounds

105
Q

.In agricultural ecosystems, the concentration of soil nitrate can be further increased by …

A

… the addition of fertilisers

106
Q

.When plants and animals die, the process of __________ begins

A

decomposition

107
Q

The release of nitrate ions by decomposition is most important as, in natural ecosystems, there are

A

very few nitrate ions available from other sources

108
Q

.There are 4 main stages in the nitrogen cycle: _______, _______, ______ ______ __ _______, each of which involces __________________ __________________

A

ammonification, nitrification, nitrogen fixation and denitrification, each of which involves saprobiontic microorganisms

109
Q

What is the process of ammonification?

A

.Ammonification is the production of ammonia from organic nitrogen-containing compounds.In nature, these compounds include urea (from the breakdown of excess amino acids) and proteins, nucleic acids and vitamins (found in faeces and dead organisms).Saprobiontic microorganisms, mainly fungi and bacteria, feed on faeces and dead organisms materials, releasing ammonia, which then forms ammonium ions in the soil.This is where nitrogen returns to the non-living component of the ecosystem

110
Q

What is the process of nitrification?

A

.Some bacteria obtain their energy from chemical reactions involving inorganic ions.One such reaction is the conversion of ammonium ions to nitrate ions.This is an oxidation reaction and so releases energy.It is carried out by free-living soil microorganisms called nitrifying bacteria.This conversion occurs in two stages:1. Oxidation of ammonium ions to nitrite ions (NO2-)2. Oxidation of nitrite ions to nitrate ions (NO3-).Nitrifying bacteria require oxygen to carry out these conversions and so they require a soil that has many air spaces.To raise productivity, it is important for farmers to keep soil structure light and well aerated by ploughing.Good drainage also prevents the air spaces from being filled with water and so prevents air being forced out of the soil

111
Q

What is the process of nitrogen fixation?

A

.The process by which nitrogen gas is converted into nitrogen containing compounds.It can be carried out industrially and also occurs naturally when lightning passes through the atmosphere .By far, the most important form of nitrogen fixation is carried out by microorganisms, of which there are two main types:• Free-living nitrogen-fixing bacteria. These bacteria reduce gaseous nitrogen to ammonia, which they then use to manufacture amino acids, nitrogen rich compounds are released from them when they die and decay• Mutualistic nitrogen-fixing bacteria. These bacteria live in nodules on the roots of plants such as peas and beans, they obtain carbohydrates from the plant and the plant acquires amino acids from the bacteria

112
Q

What is the process of denitrification?

A

.When soils become waterlogged, and have a low oxygen concentration, the type of microorganism present changes.Fewer aerobic nitrifying and nitrogen-fixing bacteria are found, and there is an increase in anaerobic denitrifying bacteria.These convert soil nitrates into gaseous nitrogen.This reduces the availability of nitrogen-containing compounds for plants.For land to be productive, the soils on which plants grow must be kept well aerated to prevent the build-up of denitrifying bacteria.The delicate balance can be easily upset by human activities

113
Q

Describe and explain the nitrogen cycle

A

The basic outline of the nitrogen cycle is that plants use nitrogen to form complex nitrogen-containing organic molecules, these are either passed along to consumers up the food chain where they die or the producer dies itself. Saprobiontic microorganisms, mainly fungi and bacteria, feed on faeces and dead organism’s materials, this releases ammonia in the process of ammonification, which then forms ammonium ions in the soil. Free-living soil microorganisms called nitrifying bacteria convert ammonium ions into nitrate ions in the process of nitrification. Which occurs in two stages (oxidation of ammonium ions to nitrite ions (NO2-) and oxidation of nitrite ions to nitrate ions (NO3-)) which required oxygen. These nitrate ions can then be absorbed back into the plant or go through the process of denitrification (anaerobic denitrifying bacteria converting soil nitrates into gaseous nitrogen) which turns them into nitrogen in the atmosphere. Here they can go through the process of nitrogen fixation by free-living bacteria (where they are reduced form gaseous nitrogen to ammonia) or mutualistic bacteria (where bacteria on the nodules on the roots of plants obtain carbohydrates from the plant while the plant acquires amino acids from the bacteria, thereby putting nitrogen back into the producer). And so the cycle starts again.

114
Q

Basics of phosphate cycle

A

.Phosphorus is found in the lithosphere and does not have a gaseous phase.Phosphorus is usually found as phosphate ions PO4-3.These are found in rocks

115
Q

.Phosphorous must be recycled as it is required by all living things, give some examples of when phosphorous is required

A

.It is used in phospholipids, nucleic acids and ATP

116
Q

Draw a diagram of the phosphate cycle

A

Check notes

117
Q

What is the lithosphere?

A

earths crust

118
Q

Where are sedimentary rock deposits, where phosphate ions are, found?

A

.These have their origins in the sea but are brought to the surface by the geological uplifting of rocks

119
Q

How does phosphate get from the rocks to the soil/water then to plants?

A

.The weathering and erosion of phosphate rich rocks helps phosphate ions to become dissolved and so available for absorption by plants which incorporate them into their biomass

120
Q

How do phosphate ions pass from plants back to the water or soil?

A

.The phosphate ions pass into animals which feed on plants.Excess phosphate ions are excreted by animals and may accumulate in waste material such as guano formed from the excretory products of some sea birds.On the death of plants and animals, decomposers such as certain bacteria and fungi break them down releasing phosphate ions into the water or soil

121
Q

How are sedimentary rocks formed in the phosphate cycle?

A

.Some phosphate ions remain in parts of animals, such as bones or shells, that are very slow to breakdown.Phosphate ions in excreta, released by decomposition and dissolved out of rocks, are transported by streams and rivers into lakes and oceans where they form sedimentary rocks thus completing the cycle

122
Q

Describe and explain the phosphorous cycle

A

The phosphorous cycle starts with phosphorus, in the form of PO43-, in the lithosphere (earth’s crust) specifically in rocks. This rock can be eroded and so the phosphate dissolves into a body of water or soil, where they are absorbed by plants. These plants can die and decompose or be eaten by animals, which then die and decompose. This decomposed organic material is either eroded, which sends the phosphate ions back into the body of water or soil, or deposited which forms rocks and thus the cycle starts again.

123
Q

Describe and explain the carbon cycle

A

Carbon dioxide in the atmosphere is absorbed by plants for photosynthesis. The carbon compounds found in plants either get turned into fossil fuels and burnt, which releases CO2 back into the atmosphere, or the plants respire, which releases CO2 back into the atmosphere, or the plant feeds animals which then respire and so CO2 is released back into the atmosphere. Thus the cycle continues.

124
Q

Draw the carbon cycle diagram

A

check notes

125
Q

What is mutualism?

A

the way two organisms of different species exist in a relationship in which each individual benefits from the activity of the other

126
Q

Give an example of mutualism

A

For example, a bird and a flower, or an insect and a flower

127
Q

Mycorrhizae is pronounced …

A

… my-corr-eye-ziy

128
Q

What are mycorrhizas and how is their relationship with plants mutualistic?

A

.Mycorrhizas are beneficial fungi growing in association with plant roots.They exist by taking sugars and amino acids from plants ‘in exchange’ for moisture and nutrients gathered from the soil by the fungal strands.The mycorrhizas greatly increase the absorptive area of a plant, acting as extensions to the root system.They hold water close to the roots making the plant more drought tolerant.Phosphorus is often in very short supply in natural soils.It would require a vast root system for a plant to meet its phosphorus requirements unaided.Mycorrhizas are crucial in gathering this element in uncultivated soils.Neither fungi nor plants could survive in many uncultivated situations without this mutually beneficial arrangement.Mycorrhizas also seem to confer protection against root diseases

129
Q

Describe how the relationship between mycorrhizae and plants can be described as a mutualistic one. (4 marks)

A

 Mycorrhizae gain glucose Amino acids Plants gain increased drought resistance Larger root surface area So increase absorption of water and minerals

130
Q

What can farmers do to increase productivity?

A

 Reduce energy loss Shorten food chains Use fertilisers

131
Q

List the things that plants need to grow:

A

.Water.Light.Carbon dioxide.Mineral ions

132
Q

• Most farming is an intensive process.• Farmland is used repeatedly, sometimes several times a year, to rear animals or grow crops.• Plants take up the nutrients and are then harvested.Referring to the nitrogen cycle, explain the effect this would have on the ecosystem.

A
  1. Ammonification is reduced as less plants and dying and decaying• In natural ecosystems, dead matter remains and it is allowed to decompose.• On farmland mineral ions are continually removed from the soil, leaving it deficient.
133
Q

How do farmers counteract reduced ammonification?

A

farmers apply fertiliser to their crops

134
Q

What are the two types of fertilisers?

A

Organic and inorganic (natural and artificial)

135
Q

Describe organic fertiliser

A

• Dead and decaying plant and animal matter• Animal excreta such as manure and slurry• Bone meal

136
Q

Describe inorganic fertiliser

A

• Mined from rock• Converted to suitable form• Blended to suit a particular crop• Includes:- Nitrogen- Phosphorous- Potassium

137
Q

The best yields are achieved when a combination of …

A

… the 2 types of fertilisers are applied

138
Q

describe and explain the shape of the graph for fertiliser use (incerasing volumes of fetilser)

A

The yield increases until an optimum mass is reach and then it decreases, this is because increasing the nitrogen content of the soil increases the productivity of the crop. After an optimum amount of nitrogen is supplied the yield decreases, this is due to the water potential. Increased nitrates in the soil reduce the water potential which will eventually draw water out of the plant by osmosis.

139
Q

What do plants need nitrogen for?

A

Plants need nitrogen for amino acids, DNA nucleotides and ATP which are all essential for plant growth

140
Q

• Outline a method that would scientifically test the effect of nitrogen on plant growth.• Include independent, dependent and control variables.

A
  1. Gather 11 plant seeds of the same species2. Place them in equal volumes of soil in separate pots3. Make up 11 batches of fertiliser, one with 0% nitrogen, one with 10% nitrogen, etc. all the way up to one with 100% nitrogen4. Fertilise each plant with different fertilizers but of the same volume (labelling each pot with the fertiliser used)5. Water the plants throughout the week6. Measure how much each plant grew at the end7. Draw a conclusion from your resultsIV = the concentration of nitrogen in the fertiliserDV = the growth of the plantsCV = temperature, light intensity, water for watering, volume of soil, volume of fertiliser, type of plant, humidity, concentration of other things in the fertiliser (keep the ratio of other aspects of the fertiliser the same)
141
Q

What is leaching?

A

.Rainwater dissolves soluble nutrients and washes them deep into the soil.The plant roots are unable to reach and absorb them.The leached nutrients then find their way into watercourses and drinking water

142
Q

What a can excessive nitrates lead to?

A

.Excessive nitrates can prevent efficient O2 transport in babies and has links to stomach cancer.It can also lead to eutrophication

143
Q

What is eutrophication? Include a description and explanation of the process in detail

A

.Watercourses tend to contain low levels of nitrates.This limits the growth of algae and bacteria.Farmers apply fertilisers to their fields.Rainfall dissolves the nutrient ions.These dissolved nutrient ions are leached into watercourses.Nutrient content is no longer a limiting factor for algae and bacteria.Both populations grow.Algae grow on the water surface, forming an algal bloom.The algae absorb light and prevent it from reaching the bottom of the water body.Light is now a limiting factor for plants below the surface.The algae and plants below the surface die.The lack of dead organic matter is no longer a limiting factor for saprobionts.Their population increases.Their growing population requires more oxygen.Oxygen concentration reduces.More nitrates are released from the decaying organisms.Oxygen is now the limiting factor for organisms that aerobically respire.They die.Now less competition for anaerobically respiring organisms.Their population increases.They continue to decompose dead material releasing further nitrates and toxins (hydrogen sulphide).They water becomes putrid

144
Q

.Nutrients are ____ through ecosystems

A

cycled

145
Q

Give three physical things which are recycled and converted into different forms in an ecosystem

A

.Carbon, nitrogen and phosphorus

146
Q

Nutrient cycles have the same key stages, what are they?

A
  • Nutrients absorbed as simple inorganic molecules by the producer- Producer converts it into complex organic molecules- Nutrient passed on during feeding relationships- After death, consumer broken down by saprobionts- Nutrient released back into the soul in its simplest form
147
Q

Why do living things need nitrogen?

A

.Nitrogenous bases (DNA).Amino acids, protein

148
Q

.Few organisms can use gaseous nitrogen, how do plants get nitrogen?

A

.Plants use nitrate ions (NO3-) from the soil.They are taken up via active transport

149
Q

How do animals get nitrogen?

A

.Animals get their nitrogen from consuming plants

150
Q

Why are plants unable to use nitrogen straight from the air?

A

Nitrogen gas is unreactive and is not easily converted into other compounds

151
Q

Nitrate ions are extremely soluble, how could this be problematic to plants?

A

Washed away from plant roots by rain water

152
Q

.Microorganisms play a huge role in cycling nitrogen, why?

A

During decomposition, microorganisms replenish the nitrate concentration in the soil

153
Q

Draw the nitrogen cycle

A

check notes or google it

154
Q

what 3 ways can nitrogen fixation occur?

A
  1. Nitrogen gas can be ‘fixed’ into ammonia by humans using the Haber process, this is then used in the production of fertilisers2. A small amount of nitrogen is fixed to nitrate by lightning3. Microorganisms that carry out this process, either free living or mutualistic
155
Q

How does free living nitrogen fixing bacteria work?

A

Nitrogen fixing bacteria reduce: nitrogen gas  ammoniaThen used to manufacture amino acidsNitrogen rich compounds are released from the bacteria when they die

156
Q

How does mutualistic nitrgen fixing bacteria work?

A

.The nitrogen fixing bacteria live in colonies inside the cells of root nodules of leguminous plants such as clovers or peas.The bacteria get carbohydrates from the plant while giving the plant proteins.The nitrogen in the plant proteins is passed on to animals through food chains – feeding

157
Q

What does ammonification do?

A

Organic N containing compounds  ammonia

158
Q

Give examples of Organic N containing compounds

A

Urea, nucleic acids, proteins and vitamins

159
Q

When living organisms excrete waste or die, their nitrogen is returned to the soil in the form of what and how?

A

ammonium compounds by saprobionts (bacteria and fungi)

160
Q

What do saprobionts do in the nitrogen cycle?

A

Saprobionts break down proteins in detritus to form ammonium ions (ammonification or deamination), this is where nitrogen return to the non-living component of the ecosystem

161
Q

What is nitrification?

A

.Plants can only take up nitrogen in the form of nitrate.Ammonium compounds are oxidised into nitrates by nitrifying bacteria in two stages1. First forming nitrite ions (NO2-)2. Then forming nitrate ions (NO3-)

162
Q

Is nitrification oxidation or reduction?

A

This is an oxidation reaction and so releases energy

163
Q

Nitrifying bacteria are chemosynthetic bacteria, which means what?

A

they use the energy released by nitrification to live

164
Q

Nitrifying bacteria require oxygen to carry out these conversions so the soil needs many air spaces.Farmers can increase the aeration of soils by:

A
  • Ploughing- Good drainage
165
Q

What is denitrifcation?

A

.The anaerobic denitrifying bacteria convert.nitrate  nitrogen gas.which is then lost to the air

166
Q

Where is denitrification found?

A

waterlogged soil

167
Q

What does denitrifcation represent?

A

This represents constant loss of ‘useful’ nitrogen from soil, and explain why fertilisers and nitrogen fixation by the nitrifying bacteria are so important

168
Q

Why must phosphorus be recycled?

A

as it is required by all living things

169
Q

What are the uses of phosphorus?

A

.ATP and ADP.Phospholipids.Nucleic acids

170
Q

Describe the phosphorus cycle

A
  1. Phosphorus is trapped in sedimentary rock2. The rocks are formed in the sea but are raised to the surface by geological activity3. Weathering and erosion release the phosphate ions4. These ions are able to dissolve and are taken up by plants5. They are then passed to animals during feeding6. When organisms excrete or die they are broken down by bacteria and fungus which are able to release the phosphates7. These phosphates end up in the soil or dissolved in water8. Some phosphates are fixed into hard tissues such as bones and shells, these take a very long time to break down9. Some of the phosphates remaining in the water are eventually combined into sedimentary rock
171
Q

What is a mutualistic relationship?

A

.Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits from the activity of the other

172
Q

Examples of mutualistic relationships

A

.Birds in the crocodile mouth.Clownfish in the coral anemone.Fish on the shark

173
Q

What are mycorrhizae?

A

beneficial fungus grown in association with plant roots

174
Q

What does mycorrhizae do?

A
  1. The mycorrhizas greatly increase the absorptive area of a plant, acting as extensions to the root system, they hold water close to the roots making the plant more drought tolerant, mycorrhizas also seem to confer protection against root diseases
175
Q

How is the relationship between a plant and mycorrhizae mutualistic?

A
  1. This relationship is mutualistic as the mycorrhizae takes sugars and amino acids from plants in exchange for moisture and nutrients gathered from the soil by the fungal strands
176
Q

Why are mycorrhizae so important?

A
  1. Phosphorus is in short supply in natural soils, it would require a vast root system for a plant to meet its phosphorus requirements unaided, mycorrhizas are crucial in gathering this element in uncultivated soils, neither fungi nor plants could survive in many uncultivated situations without this mutually beneficial agreement
177
Q

why do single celled organisms use diffusion, and diffusion alone, to provide their nutrients ?

A

As the diffusion pathway is short

178
Q

What do Multicellular organisms require to provide all of their cells with the nutrients they need??

A

transport systems and specialised exchange surfaces

179
Q

Why do organisms with higher metabolic rates need an increased diffusion rate?

A

They exchange more mterials

180
Q

What happens to the SA:V ratio as the object becomes bigger?

A

The ratio of surface area: volume ratio falls

181
Q

Small organisms has a ____ SA:V ratio and exchange ____ with the _____

A

.Large.Directly.Surface

182
Q

Larger organisms has a ____ SA:V, and they need _______ exchange surfaces to meet the organisms demands

A

.Smaller.Specialist

183
Q

Give an example of a larger organisms specialist exchange surface

A

Mass transport system, to deliver and remove material

184
Q

Sphere surface area formula

A

4 x Pi x r^2

185
Q

Sphere volume formula

A

(4/3) x Pi x r^3

186
Q

If a gas exchange surface is efficient at gas exchange, what else is it efficient at?

A

an efficient water loss surface

187
Q

Define mass transport

A

the bulk movement of materials from exchange surfaces to the cells throughout the organism

188
Q

What do efficient transport systems have?

A
  • A suitable transport mediumo Normally liquid but can be a gaso Materials (oxygen, waste) can dissolve- Closed system of tubular vesselso Contains or holds the mediumo Forms branching to all parts of the organismo Ensures medium is close to cells- Mechanisms for movement of tissue fluido Generates pressureo Enables the medium to move
189
Q

What is the circulatory systems transport medium, tubular vessels and mechanisms for movement of tissue fluid?

A

Blood, veins/arteries/capillaries and heart

190
Q

What type of muscle is the heart?

A

A cardiac muscle

191
Q

What is the heart?

A

An organ in the circulatory system

192
Q

The heart is myogenic, what does this mean?

A

It naturally contracts and relaxes

193
Q

Describe our circulatory system

A

Double

194
Q

How is the heart apart of a double circulatory system?

A

Blood passes the heart twice, through two different circuits

195
Q

In the circulatory system, what is circuit one?

A

links the heart and the rest of the body

196
Q

In the circulatory system, what is circuit two?

A

links the heart with the lungs

197
Q

Name the parts of the heart

A
  1. Right atrium2. Right ventricle3. Left atrium4. Left ventricle5. Pulmonary artery6. Aorta7. Superior vena cava8. Inferior vena cava9. Pulmonary vein10. Septum11. SAN node
198
Q

What is the SAN node

A

the hearts pace maker, initiates an electrical wave of electricity

199
Q

How do the coronary arteries maximise mass transport?

A
  1. Coronary arteries supply the heart with the oxygen it requires, the oxygen is needed so that the heart can contract and pump blood around the bod
200
Q

How does the wall thickness of the heart maximise mass transport?

A

left ventricle wall is much thicker to produce necessary pressure, since it is thicker it can contract much stronger, this increases the pressure so the blood can travel around the entire body

201
Q

How do the valves of the heart maximise mass transport?

A

open and close between atriums and ventricles as well as ventricles and vessels to help produce necessary pressure and prevent backflow. This also generally builds pressure in the blood

202
Q

What are the 3 heart valves and where are they?

A
  • Semi-lunar valves (between ventricle and vessel)- Left atrioventricular valve (tricuspid valve) between left atrium and left ventricle- Right atrioventricular valve (bicuspid valve) between right atrium and right ventricle
203
Q

Describe the opening and closing of valves?

A
  • Pressure is higher where concave (as ventricle fills with blood)- Pushes the flexible, fibrous tissues together- Tissues form a tight fit with no gap- Prevents the backflow of blood (back into the atrium)- Pressure is higher above the valve- Pushes the flexible fibrous tissues apart- Causes opening for blood to travel (from high to low pressure) into the ventricle
204
Q

What causes the hearts beat sound?

A

The opening and closing of valves

205
Q

Advantages of biological valve replacements

A

Cows are in high supplyFairly well testedFewer long term issues

206
Q

Disadvantages of biological valve replacements

A

Unethical to use cowsNot suitable for allCan need replacing

207
Q

What is systole?

A

contraction

208
Q

What is diastole?

A

relaxation

209
Q

What happens in ventricular systole?

A

ventricle completely full, forces tricuspid and bicuspid valves to close, forces semi-lunar valve to open, pushes blood out of the heart

210
Q

What happens in atrial systole?

A

pushes last bit of blood into ventricle, ventricular diastole occurs in this stage

211
Q

What happens in ventricular and atrial diastole?

A

They relax, makes up the majority of the cycle, blood movement is aided by gravity

212
Q

What is haemoglobin

A

A respiratory pigment used to transport oxygen

213
Q

What type of molecule is haemoglobin?

A

A protein

214
Q

Why is haemoglobin needed?

A

as oxygen has a low solubility in water

215
Q

Describe the structure of haemoglobin

A

Each haemoglobin has beta polypeptides, alpha polypeptides and four haem groups (1 per polypeptide chain) which contain a ferrous ion (Fe2+)Each haem group carries one O2 molecule

216
Q

What is haemoglobin called when it is combined with oxygen?

A

oxyhaemoglobin

217
Q

What must haemoglobin do to be efficient?

A
  1. Readily associate with oxygen at the exchange surface2. Readily dissociate with oxygen at the tissues
218
Q

Define affinity

A

the attractive force binding atoms in molecules, chemical attraction

219
Q

What is high affinity with haemoglobin?

A

high attractive force, readily associates with O2

220
Q

What is low affinity with haemoglobin?

A

take up less O2 (lower association) but release more readily (easily disassociation)

221
Q

In the body, where is oxygen affinity high and low?

A

High in exchange surfaces (lungs) and low in respiring tissues (muscles)

222
Q

How does affinity change?

A
  1. The environment:.How much oxygen is available.Partial pressure of oxygen2. Metabolic rate:.How much oxygen is required by the organism
223
Q

What is partial pressure of oxygen?

A

.The amount of gas present in a mixture of gases .Measured in kilopascals (kPa)

224
Q

If the environment has a low concentration (partial pressure) of oxygen:

A
  • Need haemoglobin to hold onto oxygen- High affinity for oxygen- Hold onto oxygen tightlyBUT- Means oxygen will not be used up as readily- Organisms have a low metabolic rate
225
Q

If the environment has a high concentration (partial pressure) of oxygen:

A
  • Oxygen is readily available- Do not need to hold on to oxygen - Low affinity for oxygenSO- Oxygen dissociates easily
226
Q

How does partial pressure differ throughout the body?

A

.High at exchange surfaces.Low at muscles, where it has been used to respire

227
Q

How does haemoglobin change how it works in different pO2 levels?

A

Low pO2, difficult to attach the first O2Medium pO2, changed shape means it can easily associate (disrupt bonds in the structure)High pO2, fewer binding sites so difficult to fully saturate

228
Q

What is an oxygen dissociation curve

A

Relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen

229
Q

Drawn an oxygen dissociation curve

A

IDK Chec your notes

230
Q

Describe oxygen dissociation curve

A

The higher the pO2 the more saturation of haemoglobin with oxygen. At low pO2, the rate of increase of saturation of haemoglobin with oxygen is low, then it speeds up as pO2 increases, before again slowing as pO2 reaches large values.

231
Q

Explain oxygen dissociation curve

A

At low pO2, the rate of increase of saturation of haemoglobin with oxygen is low as it is initially difficult to attach the first O2. The rate of increase of saturation of haemoglobin with oxygen increases as the changed shape of the haemoglobin means it can easily associate (disrupt bonds in the structure). The rate of increase of saturation of haemoglobin with oxygen slows again as pO2 reaches large values, because the fewer binding sites make it difficult to fully saturate.

232
Q

What does a shift to the left on an oxygen dissociation curve mean?

A

NAME?

233
Q

What does a shift to the right on an oxygen dissociation curve mean?

A

NAME?

234
Q

What is the Bohr Effect?

A

Haemoglobin has a reduced affinity for oxygen in the presence of carbon dioxide. The greater the concentration of carbon dioxide, the more readily the haemoglobin releases it

235
Q

Why does the behaviour of haemoglobin change in different regions of the body?

A

The Bohr Effect

236
Q

Describe and explain the behaviour of haemoglobin at the gas exchange substance (lungs)?

A
  • At the gas exchange surface (lungs), the level of carbon dioxide is low because it diffuses across the exchange surface and is expelled from the organism. The affinity of haemoglobin for oxygen is increased, which, coupled with the high concentration of oxygen in the lungs, means that oxygen is readily loaded by haemoglobin. The reduced carbon dioxide level has shifted the oxygen dissociation curve to the left.
237
Q

Describe and explain the behaviour of haemoglobin at rapidly respiring tissues (muscles)?

A
  • In rapidly respiring tissues (muscles), the level of carbon dioxide is high. The affinity of haemoglobin for oxygen is reduced, which, coupled with the low concentration of oxygen in the muscles, means that oxygen is readily unloaded from the haemoglobin into the muscle cells. The increased carbon dioxide level has shifted the oxygen dissociation curve to the right.
238
Q

Why is it that the greater the concentration of carbon dioxide, the more readily haemoglobin releases its oxygen?

A

Because dissolved carbon dioxide is acidic and the low pH causes haemoglobin to change shape.

239
Q

Describe and explain the loading, transporting and unloading of oxygen

A
  • At the gas exchange surface carbon dioxide is constantly being removed- The pH is raised due to the low level of carbon dioxide- The higher pH changes the shape of haemoglobin into one that enables it to load oxygen readily- This shape also increases the affinity of haemoglobin for oxygen, so it is not released while being transported in the blood to the tissues- In the tissues, carbon dioxide is produced by respiring cells- Carbon dioxide is acidic in solution, so the pH of the blood within the tissues is lowered- The lower pH changes the shape of haemoglobin into one with a lower affinity for oxygen- Haemoglobin releases its oxygen into the respiring tissues
240
Q

Explain the statement, ‘The more active a tissue, the more oxygen is unloaded’

A

The higher rate of respiration  the more carbon dioxide the tissues produce - the lower pH  the greater the haemoglobin shape change  the more readily oxygen is unloaded  the more oxygen is available for respiration

241
Q

Why is the loading, transporting and unloading of oxygen important?

A

This means that there is a flexible way of ensuring that there is always sufficient oxygen for respiring tissues.

242
Q

Why is the blood returning to the lungs usually only 75% saturated?

A

In humans, haemoglobin normally becomes saturated with oxygen as it passes through the lungs. In other words, most of the haemoglobin molecules are loaded with their maximum four oxygen molecules. When this haemoglobin reaches a tissue with a low respiratory rate, only one of these molecules will normally be released. The blood returning to the lungs will therefore contain haemoglobin that is still 75% saturated with oxygen.

243
Q

If a tissue is very active (an exercising muscle) then how many oxygen molecules are usually unloaded from each haemoglobin?

A

3 oxygen molecules are usually unloaded from each haemoglobin molecules.

AQA A Level Biology (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions