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Alevel Biology > 5.1&5.2 > Flashcards

5.1&5.2 Flashcards

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1
Q

What do all living organisms need to maintain

A

A certain limited set of conditions in cells including temperature, pH, aqueous environment, no toxins and inhibitors

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2
Q

What happens when cells optimum condition isn’t maintained

A

Cells become inactive and die

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3
Q

What does it mean that multicellular organisms have specialised cells

A

Each cell relies on each cell, so they must communicate to coordinate their activity

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4
Q

What is the external environment of organisms

A

The constantly changing environment either air, water or soil

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5
Q

What stresses does a cold environment place on an organism

A

Greater heat loss

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6
Q

How does an organism counter cold conditions to stay active and alive

A

Changes in environment are monitored and organism changes its behaviour/physiology to reduce stress

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7
Q

What is environmental change to an organism

A

A stimulus and way in which organisms must change its behaviour/physiology is its response

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8
Q

What response is elicited if the environment changes slowly like between seasons

A

Gradual response

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9
Q

Give an example of a gradual response

A

Artic fox has thicker white coat in winter and thinner brown coat in summer, change in coat provides more insulation and camouflage in winter so it survives and in summer thin coat means it doesn’t over heat

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10
Q

Is everything in multicellular organisms exposed to the external environment

A

Not many tissues and cells exposed to external environment, they are protected by epithelial tissues and organs

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11
Q

What is the cell environment

A

Tissue fluid which bathes internal cells and tissues

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12
Q

What happens as metabolic reactions occur in cells

A

They use up substrate and create new products which can create unwanted bi-products which are toxic and these are moved out into the tissue fluid, so activity of cells alter their own environment

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13
Q

What happens as waste products build up in tissue fluid

A

May reduce cells activity so less waste produced but this response may not be good for whole organism

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14
Q

What is composition of tissue fluid maintained by

A

Blood, blood flows throughout body and transports substances to and from cells, waste/toxins accumulating in tissue fluid enter blood and carried away to prevent their accumulation in blood they are removed from body by excretion

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15
Q

Why is it important concentrations of waste products and substances in blood monitored closely

A

Ensures body doesn’t excrete too many useful substances but removes enough waste to maintain good health and that cells in body given substrate they need

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16
Q

Is multi or single celled organisms more efficient

A

Multicellular as it’s cells are differentiated so specialised cells can perform certain functions

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17
Q

What do groups of specialised cells performing a certain function become

A

Tissues and organs

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18
Q

Where may cells that monitor the blood be found

A

In different body part away from waste product and far from tissue or organ specialised to remove waste

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19
Q

What does a good communication system require

A

Go check these different parts of the body work together effectively

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20
Q

What are the features of a good communication system

A

Cover whole body, enables cells to communicate with each other, enable specific communication, enable rapid communication, enable long and short term responses

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21
Q

How do cells communicate with each other

A

By process of cell signalling

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22
Q

What is cell signalling

A

A process where one cell releases a chemical that’s detected by another cell, 2nd cell responds to signal released from 1st cell

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23
Q

What are the 2 major communication systems that rely on cell signalling

A

Neuronal system and hormonal system

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24
Q

What is the neuronal system

A

An interconnected network of neuronal that signal to each other across synapse junctions, neurones can conduct signals very quickly and enable rapid responses to stimulate that may be changing quickly

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25
Q

What is the hormonal system

A

System that uses blood to transport its signals, cells in endocrine system release signal (hormone) directly into blood , hormone is transported throughout body but only recognised by specific target cells, hormonal system enables longer-term responses to be coordinated

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26
Q

What must cell signalling molecules be to cell surface receptor

A

Complementary

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27
Q

What is homeostasis

A

Used in many living organisms to maintain conditions inside the body despite changes from external and internal factors

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28
Q

What aspects are maintained by homeostasis

A

Body temp, blood glucose concentration, blood salt concentration, water potential of blood, blood pressure, CO2 concentration

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29
Q

What does response to changes in the environment require

A

Requires complex mechanisms which may involve a series of tissues and organs that are coordinated through cell signalling

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30
Q

What is the standard response pathway to change in environment

A

Stimulus->receptor->communication pathway(cell signalling)->effector->response

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31
Q

What is needed for a response pathway to work

A

Number of specialised structures

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32
Q

What are the different aspects needed in a response pathway

A

Sensory receptors like temp receptor, on surface of skin, monitor changes in external environment, other receptors interns to monitor changes inside body, when 1 receptor detects change it sends message to effector (hormonal/nervous communication system), this acts by signalling between cells and transmuting message from receptor to effector via coordination centre (brain)

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33
Q

What is known as input and what’s output

A

Input-message from receptor to coordination centre, output-messages sent to effectors

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34
Q

Examples of effectors

A

Liver and muscle cells which bring about a response

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35
Q

What is feedback

A

When effectors respond to output from coordination centre, they bring a response that will change body internal conditions, these changes detected by recovers and had effect upon response pathway, so input changes known as feedback

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36
Q

How is constant internal environment maintained

A

Any change away from optimum must be reversed so conditions in body return to optimum

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37
Q

What is negative feedback

A

Bringing conditions back to optimum after a change

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38
Q

What happens when conditions change in negative feedback

A

Receptor detects stimulus and sends input to coordination centre which send output to effectors and effectors respond to output

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39
Q

What happens when effectors bring about a change that reverses initial change in negative feedback

A

System moved closer to optimum and stimulus reduced, receptors detect reduction in stimulus and reduce input to coordination centre, output to effectors is also reduced so effectors reduce their activity, as system gets closer to optimum response is reduced

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40
Q

What is the negative feedback loop

A

Optimum condition->change away from optimum ->receptor detects change ->(input) ->communication system informs effectors->effectors react to reverse change->returns to optimum condition->optimum condition

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41
Q

Give an example of negative feedback

A

If temp rises too high in the body, response is to do something that brings body temp back to optimum resulting in stimulus reducing

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42
Q

What is the negative feedback loop for body temp

A

If temp rises:thermo-regulatory centre in hypothalamus detects change->nervous and hormonal system carry signal to skin, liver and muscles->less heat generated and more lost->temp too low: thermo-regulatory centre in hypothalamus detects change->nervous and hormonal system carry signal to skin, liver and muscles->more heat generated and less lost

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43
Q

3 steps for negative feedback to occur

A

1.change in internal environment must be detected 2.change must be signalled to other cells 3.must be an effective response that reverses change in conditions

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44
Q

Do negative feedback keep conditions 100%constant

A

Fairly constant but always some variation around the optimum

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45
Q

Why does negative feedback not keep same exact conditions

A

When stimulus occurs may take time to respond and responds may cause to much change but as long as conditions not too varied it remains acceptable

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46
Q

Why are negative feedback systems needed for temp control

A

To keep body warm enough for enzymes and cool enough to not damage proteins

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47
Q

Is positive or negative feedback more common

A

Negative

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48
Q

What is positive feedback

A

Response to increase the original change which destabilises system and usually harmful

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49
Q

Give an example of positive feedback (bad)

A

Below certain core temp enzymes less active and exergonic reactions are slower and release less heat, allowing body to cool more and slows enzymes controlled reactions more causing body temp to spiral down

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50
Q

Give an example of positive feedback (good)

A

At end of pregnancy to bring about cervix dilation, as cervix begins to stretch it causes posterior pituitary glands to secrete hormone oxytocin which increases uterine contractions which stretch cervix more causing more oxytocin secretion, once cervix fully dilated, baby can be born, birth ends oxytocin production, neurones also rely on positive feedback

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51
Q

What is the positive feedback loop

A

Optimum condition->change away from optimum->receptor detects change->(input)communication system informs effects->(output)effector reacts to increase change->change away from optimum

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52
Q

What effects does increases core temp have on body

A

Molecules have more kinetic energy, move quick and collide often, so essential chemical reactions occur quicker, affects structure of proteins (denature if temp too high), enzymes are globular w specific tertiary structure giving them specific 3D shape (complementary to substrate)

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53
Q

Why are some enzymes very temp sensitive

A

If body temp drops by 10degreesC some rate of enzyme controlled reactions half

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54
Q

What maintains heat in the body

A

Cellular reactions releasing heat but if temp drops reactions slow and less heat released allowing body to cool further (positive feedback), as body cools organism functions less

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55
Q

What is the difference between external and internal parts of the body

A

Core temp important as organs found in the centre, but external parts of body can change temp without effecting organisms overall survival

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56
Q

What are endotherms

A

Control their body temp within narrow limits and use variety of mechanisms to control body temp and largely independent of external temp

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57
Q

What are ectotherms

A

Can’t control body temp as effectively as endotherms, they rely on external sources of heat and body temp changes with external environment but using various behavioural mechanisms, some ectotherms can control their body temp in all but extreme conditions

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58
Q

What don’t ectotherms use to maintain their body temp

A

Don’t use internal energy sources to maintain body temp when cold but when active their muscles contract to generate heat from increased respiration

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59
Q

What does temp regulation in ectotherms rely on

A

Behavioural responses that alter heat exchange with environment

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60
Q

What happens if ectotherms too cold

A

They absorb heat from environment by moving to sunny area, lie on warm surface, expose large SA to sun

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61
Q

What do ectotherms do if they’re too hot

A

Avoid gaining heat by moving to shade, move underground, reduce body SA exposed to sun

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62
Q

What are advantages of ectotherms

A

Don’t use up energy to keep warm, so less food used in respiration and more energy gained from food used for growth, need to find less food, can survive long periods without food

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63
Q

Disadvantages of ectotherms

A

Less active in cold temps so at risk from predators whilst cold and unable to escape, can’t make use of available food while they’re cold

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64
Q

What are 2 examples of ectotherms and their adaption

A

Adder:(behavioural adaptation)lays in sun beside vegetation to absorb direct heat from sun, Horned lizard:(behavioural adaptation)can change shape by expanding/contracting ribcage increasing SA exposed to sun so more heat absorbed

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65
Q

What are endotherms

A

Use physiological and behavioural adaptations to control body temp and not environment

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66
Q

What does temp regulation rely on

A

Effectors in skin and muscles, as skin is organ in contact w environment many physiological adaptations to control body temp involves skin

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67
Q

What do changes taking place at skin alter

A

Amount of heat lost to environment

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68
Q

What is an exergonic reaction and where do many occur

A

Release energy in form heat, many exergonic chemical reactions occur in human body

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69
Q

What can endotherms do to stay warm

A

Increase respiration (exergonic) in muscles and liver to release heat using their energy intake to stay warm

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70
Q

What other physiological adaptations do endotherms have

A

Directing blood towards or away from skin to alter amount of heat lost to environment

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71
Q

What are the physiological adaptations of skin when endotherms too hot

A

Sweat glands secrete fluid onto skin surface as it evaporates it uses heat from blood as latent heat of vaporisation, hairs lie flat to reduce insulation and allow greater heat loss, vasodilation of arterioles and precapillary sphincters direct blood to skin surface so more heat radiated away from body

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72
Q

What are the physiological adaptations of skin when endotherms too cold

A

Less sweat secreted so less evaporation means less heat loss, hairs stand erect to trap hair which insulates the body, vasoconstriction of arterioles and precapillary sphincters leading to skin surface, blood diverted away from surface of skin and less heat lost

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73
Q

What are the physiological adaptations of gaseous exchange system when endotherms too hot/cold

A

Hot-some animals pant, increasing evaporation of water from surface of lungs and airways, evaporation uses heat from blood as latent heat of vaporisation- cold-less panting so less heat lost

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74
Q

What are the physiological adaptations of liver when endotherms too hot/cold

A

Hot-less respiration occurs so less heat released, cold-increase respiration in liver cells means more food energy converted to heat

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75
Q

What are the physiological adaptations of skeletal muscles when endotherms too hot/cold

A

Hot-fewer contractions so less heat released, cold-spontaneous muscle contractions (shivering) to release heat

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76
Q

What are the physiological adaptations of blood vessels when endotherms too hot/cold

A

Hot-dilation to direct blood to extreme do more heat lost, cold-constriction to limit blood flow to extremities, so blood not cooled too much (can lead to frostbite)

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77
Q

What are the behavioural adaptations of endotherms when too hot

A

Move to shade, move body to reduce SA exposed to sun, remain inactive and spread limbs out to allow greater heat loss, wet skin to use evaporation to cool body

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78
Q

What are the behavioural adaptations of endotherms when too cold

A

Lie in sun, increase SA of body exposed to sun, move to generate heat in muscles or curl in ball to reduce SA and heat loss, remain dry

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79
Q

Advantages of endotherms

A

Can maintain constant body temp despite external environment, remains active in low external temp so take advantage of prey and escape predators, inhabit colder parts of planet

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80
Q

Disadvantages of endotherms

A

Use a lot of their energy to maintain body temp, need more food, low proportion of food and nutrient energy used for growth and many overheat in hot weather

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81
Q

What detects temp change in endotherms and what happens after

A

Receptors in hypothalamus detect change in temp and send out different impulses to reverse change, some receptors quick to prevent further temp change (neural system transmits output from hypothalamus to make response rapid) other responses are long term (hormonal system)

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82
Q

What will hypothalamus bring about if core body temp too low

A

Change in skin to reduce heat loss, release heat via muscle contractions, increase metabolic to release heat form exergonic reactions

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83
Q

What will hypothalamus bring about if core body temp too high

A

Change skin to increase heat loss, less muscle contractions, decreased metabolism (example of negative feedback)

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84
Q

What monitors blood temp and detects change in core body temp

A

Thermoegulatroy centre in hypothalamus

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85
Q

What receptors can detect temp change early to counter it

A

Peripheral temp receptors in skin as extremities get cooler before the core of the body

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86
Q

What happens if thermoregultary centre signals to brain external environment is too hot/cold

A

Brain can initiate behavioural mechanisms for maintaining body temp live moving into shade

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87
Q

What is excretion

A

Removal of metabolic waste from body

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88
Q

What products are excreted

A

All products formed in excess by chemical processes occurring in cells so they don’t build up and inhibit enzyme activity or become toxic

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89
Q

What are the main excretory products

A

CO2 from respiration, Nitrogen containing compounds like urea and bile pigments found in faeces

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90
Q

What are the excretory organs

A

Lungs, liver, kidneys, skin

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91
Q

How is the lungs an excretory organ

A

Every cell in body produces CO2 due to respiration, CO2 passes from respiring cells to bloodstream where transported most in form of hydrogencarbonate ions to lungs, in lungs CO2 diffuses to alveoli to be excreted as we exhale

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92
Q

How is the liver an excretory organ

A

Directly involved in excretion, has many metabolic roles and some substances produced passed to bile for excretion with faeces like pigment bilirubin, liver also converts excess amino acids to urea, amino acids broken down in process of deamination, nitrogen containing part of molecule then combines with CO2 to make urea

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93
Q

How is the kidneys an excretory organ

A

Urea passed to bloodstream to be transported to kidneys, urea transported in solution (dissolved plasma) in kidneys urea removed from blood to become part of urine, urine stored in bladder before excreted via urethra

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94
Q

How is the skin an excretory organ

A

Excretion not primary function but sweat containing substances like salts, urea, water, uric acid and ammonia. Urea, uric acid and ammonia are all excretory products, loss of water and salts important in homeostasis (maintains body temp and water potential of blood)

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95
Q

Why is it fatal to let metabolic products to build up

A

Some products like CO2 and ammonia are toxic, they interfere with cell processes by altering pH, so normal metabolism prevented, other metabolic products can act as inhibitors and reduce essential enzyme activity

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96
Q

What is the order head downwards of lungs, kidneys, urethra, bladder, ureter and liver

A

Lungs-liver-kidney-ureter-bladder-urethra

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97
Q

How is most CO2 transported in blood

A

As hydrogencarbonate ions, this also forms hydrogen ions

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98
Q

What is the equation for the production of hydrogencarbonate ions

A

CO2 + H2O -> H2CO3 (carbonic acid), carbonic acid then dissociates to release hydrogen ions. H2CO3 -> H+ + HCO3-

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99
Q

Where does the production of hydrogencarbonate ions occur and with the help of what

A

Occurs in red blood cells under enzyme carbonic anhydrase but also occurs in blood plasma

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100
Q

What can hydrogen ions effect and how

A

pH of cytoplasm in red blood cells, hydrogen ions interact with bonds in haemoglobin, changing its 3D shape reducing affinity of haemoglobin for oxygen and affecting oxygen transport

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101
Q

What happens to hydrogen ions in red blood cells to ensure they don’t effect oxygen transport

A

They combine with haemoglobin to form haemoglobinic acid

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102
Q

What happens to CO2 that’s not directly converted to hydrogencarbonate ions

A

Combines directly with haemoglobin to form carbaminohaemoglobin

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103
Q

What do haemoglobinic acid and carbaminohaemoglobin have in common

A

Both unable to combine with oxygen which reduces oxygen transport further

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104
Q

How does excess hydrogen ions in blood plasma effect blood plasma and how is this combatted

A

Excess hydrogen ions reduce pH of plasma and maintaining plasma pH is essential as changes could alter structure of proteins in blood that help transport substances around the body but proteins in blood act as buffers to resist pH change

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105
Q

If change of pH due to excess hydrogen ions in blood plasma is small what happens

A

Extra hydrogen ions detected by respiratory centre in medulla oblongata in brain causing an increased breathing rate to help remove excess CO2

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106
Q

What happens when blood pH drops below 7.35

A

Can cause headaches, drowsiness, restlessness, tremors and confusion, also rapid heart rate and changes in blood pressure (respiratory acidosis)

107
Q

What can cause a lowering in blood pH

A

Disease or lung conditions like emphysema, chronic bronchitis, asthma, severe pneumonia, blockage of airway due to swelling, foreign object or vomit can also induce acute respiratory acidosis

108
Q

What does the body do with excess amino acids as they can’t store them

A

Amino acids have almost as much energy as carbohydrates, so, wasteful to excrete amino acids, instead they’re transported to the liver and deaminated

109
Q

What do the amino groups initially form after deamination and then what happens

A

Very soluble and highly toxic compound, ammonia which is then converted to less soluble and toxic compound, urea which is transported to kidneys for excretion

110
Q

What happens to the deaminated amino acid

A

It becomes keto acid which is used directly in respiration to release energy or converted to carbohydrate or fat for storage

111
Q

What is the deamination equation

A

Ammonia+carbon dioxide-> keto acid + ammonia

112
Q

What’s the equation for formation of urea

A

Ammonia+ carbon dioxide -> urea + water

/2NH3 + CO2 -> (NH2)2CO + H2O

113
Q

What are liver cells called

A

Hepatocytes

114
Q

What do hepatocytes do

A

Carry out 100s of metabolic processes

115
Q

What does liver have an important role in and what does this mean

A

In homeostasis, so it’s essential liver has good blood supply

116
Q

What does livers internal structure ensures

A

As much blood as possible flows past as many hepatocytes as possible, enables hepatocytes to remove excess substances form blood and return substances to blood to ensure concentrations are maintained

117
Q

What 2 sources supply liver with blood

A

Hepatic artery and hepatic portal vein

118
Q

How does the hepatic artery supply liver with blood

A

Oxygenated blood from heart travels from arrow via hepatic artery to liver

119
Q

What does the hepatic artery supply the liver with

A

Oxygen for aerobic respiration, liver cells very active as they do many metabolic processes, many processes require ATP so important to have good supply of oxygen for respiration

120
Q

How does the hepatic portal vein supply liver with blood

A

Deoxygenated blood from digestive system enters liver via hepatic portal vein

121
Q

What does the hepatic portal vein supply the liver with

A

Rich with digestive products, concentrations of various substances uncontrolled as entered body from digestive products in intestines and blood may also contain toxic compounds absorbed from intestines (important these substances don’t circulate body until their concentration adjusted)

122
Q

Where does blood leave liver from

A

Via hepatic vein which rejoins inferior vena cava and blood returns to body’s normal circulation

123
Q

What is the 4th vessel connected to the liver

A

Bile duct

124
Q

What is bile

A

A secretion from the liver which has function in digestion and excretion

125
Q

What does the bile duct do and what is role of bile

A

Carries bile from liver to gall bladder where urs stored till required to aid fat digestion in small intestines, bile also contains some excretory products like bile pigment bilirubin which leaves body with faeces

126
Q

What is important about liver structure

A

That cells, blood vessels and chambers arranged to get greatest amount of contact between blood and liver cells

127
Q

How is the liver divided

A

Into lobes which are further divided into lobules, lobules are cylindrical

128
Q

What happens as hepatic portal vein and hepatic artery enter liver

A

They split into smaller and smaller vessels, these vessels run between and parallel to lobules and known as inter lobular vessels

129
Q

What enters the lobules

A

At intervals branches from hepatic artery and hepatic portal vein enter lobules

130
Q

What happens with the blood from the hepatic portal vein and hepatic artery enter the lobules

A

The 2 blood vessels mix and pass along a special chamber called sinusoid which is lined with liver cells

131
Q

What happens as blood flows along sinusoid

A

It’s in close contact with liver cells, these cells able to remove substances from blood and return other substances to blood

132
Q

What are Kupffer cells

A

Specialised macrophages move about with sinusoids, there primary function appears to be breakdown and recycling of old red blood cells

133
Q

What is a product of red blood cel breakdown

A

Bilirubin

134
Q

Where does the bile made to the liver go

A

Released into bile canaliculi which joins together to form bile duct which transports bile to gall bladder

135
Q

What happens when blood reaches end of sinusoid

A

Concentrations of many components have been modified and regulated

136
Q

What is at the centre of each lobule

A

A branch of the hepatic vein known as intra-lobular vessel

137
Q

What happens at intra-lobular vessel

A

Sinusoids empty into this,

138
Q

What joins to form hepatic vein and what’s hepatic veins function

A

Branches of hepatic vein, from different lobules, join together to form hepatic vein, which drains blood form liver

139
Q

What is the structure of liver cells (hepatocytes)

A

Appear unspecialised, they have simple cuboid shape with many microvilli on surface

140
Q

What is the function of hepatocytes

A

Many metabolic functions include protein synthesis, transformation and storage of carbohydrates, synthesis of cholesterol and bile salts, detoxification and many other processes

141
Q

What does hepatocytes function mean about their cytoplasm

A

Cytoplasm must be very dense and specialised in number of certain organelles it contains

142
Q

What functions does the liver carry out

A

Control of blood glucose, amino acid and lipid levels, synthesis of bile, plasma proteins and cholesterol, synthesis of red blood cells in foetus, storage of vitamins A,D and B12, iron, glycogen, detoxification of alcohol and drugs, hormone breakdown, destruction of red blood cells

143
Q

What form does liver store sugars as

A

Glycogen

144
Q

How much glycogen can liver store

A

100-120g which is 8%of weight of fresh liver

145
Q

What does glycogen form in hepatocytes and what is glycogen broken down to

A

Forms granules and glycogen broken down to release glucose into blood as required

146
Q

What are examples of substances the liver must detoxify

A

Hydrogen peroxide produced in the body, alcohol consumed as part of our diet pr drugs/medicines take for health or recreational use

147
Q

How are toxic substances rendered harmless in liver

A

By oxidation, reduction, methylation or combination with other molecules, liver cells contain many enzymes that make them less toxic

148
Q

What is role of catalase in liver

A

Converts hydrogen peroxide to oxygen and water, catalyse has high turn over number

149
Q

What is cytochrome P450 role in liver

A

A group of enzymes used to breakdown drugs including cocaine and various medicinal drugs, also used in other metabolic reactions like electron transport in respiration, their role in metabolising drugs can interfere with other metabolic roles and cause unwanted side effects of some medicinal drugs

150
Q

What does alcohol do to nerve activity and respiration

A

Depresses nerve activity, also contains a chemical potential energy used for respiration

151
Q

How is alcohol broken down in hepatocytes

A

Broken down by enzyme dehydrogenase, resulting compound is ethanal which is dehydrogenated further by ethanal dehydrogenase to produce final product of acetate which combines with CoA to form acetyl CoA which enters aerobic respiration

152
Q

What happens to hydrogen atoms released from alcohol

A

They combine with coenzyme NAD, to form reduced NAD

153
Q

What is the equation for the breakdown of alcohol in the liver

A

Ethanol->(ethanol dehydrogenase and reduced NAD)->ethanal->(ethanal dehydrogenase and 2 reduced NAD)-> Ethanoic acid->acetyl CoA->respiration

154
Q

What is required to oxidise and breakdown fatty acids needed for respiration

A

NAD

155
Q

What happens when liver has to detoxify too much alcohol

A

It uses up NAD stores and has insufficient amount left to deal with fatty acids, these fatty acids then convert back to lipids and stored as fat in hepatocytes causing liver to become enlarged, known as fatty liver which causes alcohol related hepatitis or cirrhosis

156
Q

Why can’t we store excess amino acids

A

Amino group makes them toxic

157
Q

Why is it wasteful to excrete amino acids and so what happens

A

They contain a lot of energy so it’s wasteful, so excess amino acids undergo treatment in liver to remove and excrete amino components

158
Q

What is the 2 processes of breaking down amino acids in liver

A

Deamination followed by ornithine cycle

159
Q

What is the equation to remove and excrete amino components

A

Amino acid->(deamination)->ammonia+keto acid->(ornithine cycle)->urea

160
Q

What does deamination do

A

It removes amino group and produces ammonia

161
Q

What is the issue with production of ammonia in liver

A

It’s very soluble and toxic so it can’t accumulate,

162
Q

What product does deamination also produce

A

Organic compound, keto acid, which enters respiration directly to release its energy

163
Q

What is the equation of the breakdown of amino acids in liver

A

amino acid+oxygen->keto acid + ammonia

164
Q

What must happen to ammonia due to its toxicity

A

Must be converted to less toxic form very quickly

165
Q

What happens in ornithine cycle

A

Ammonia and CO2 combine with amino acids to form urea

166
Q

What is the ornithine cycle in detail

A

Ammonia and CO2 combine with amino acid ornithine to produce citrulline which is converted to arginine by addition of further ammonia, arginine then reconverted to ornithine by urea removal

167
Q

Why does ammonia turn to urea and then what happens to urea

A

as it’s less soluble and toxic than ammonia so can be passed back to blood and transported to kidneys, in kidneys urea filtered out of blood and concentrated in urine which is stored in bladder till released from body

168
Q

What is the equation for ornithine cycle

A

Ammonia+CO2 -> urea+water

169
Q

How many kidneys do we have and where are they located

A

2 kidneys 1 each side of spine just below lowest rib

170
Q

Where do the kidneys get blood from and where does it leave from

A

Renal artery and leave from renal vein

171
Q

What is kidneys role

A

Excretion, kidneys remove waste products from blood and produce urine

172
Q

Where does urine pass down Out of kidneys and to what

A

Passed down ureter and goes to bladder where it’s stored before release

173
Q

What surrounds the kidneys

A

A tough capsule

174
Q

What is the outer, middle and inner region of kidney called

A

Capsule, cortex, medulla

175
Q

What is the centre that leads to the ureter in the kidney called

A

Pelvis

176
Q

What does the bulk of each kidney have

A

Small tubules called nephrons, each kidney has around 1m nephrons

177
Q

Where does each nephron start

A

In Cortex at cup shaped structure called bowmans capsule

178
Q

What is the remainder of the nephron after bowmans capsules

A

A coiled tube that passes through cortex, forms loop down to medulla and back to cortex before joining a collecting duct that passes back down medulla

179
Q

What does the renal artery split into

A

Many afferent arterioles which each lead to capillaries called glomerulus

180
Q

Where does the blood go from the glomerulus

A

Continues to efferent arteriole which Carries blood to more capillaries surrounding the rest of the tubule and these capillaries flow into renal vein

181
Q

What is each glomerulus surrounded by and what process occur here

A

Bowmans capsule, fluid from blood pushes into Bowmans capsule by process of ultrafiltration

182
Q

How does ultrafiltration work

A

The filter is the barrier between blood in capillaries and lumen of Bowmans capsule, barrier consists of 3 layers all enabling ultrafiltration

183
Q

What is the first layer of ultrafiltration and how does it filter

A

Endothelium of capillary-narrow gaps in endothelium of capillary wall, endothelial cells have pores called fenestrations allowing blood plasma and substances dissolved in it to pass out of the capillary

184
Q

What is the second layer of ultrafiltration and how does it filter

A

Basement membrane-consists of fine mesh of collagen fibres and glycoproteins, mesh acts as filter to prevent passage of molecules with relative molecular mass above 69000, so lost proteins and all blood cells stay in capillaries of glomerulus

185
Q

What is the last layer of ultrafiltration and how does it filter

A

Epithelial cells of Bowmans capsule (podocytes)- have specialised shape, have finger like projections called major processes and on each major process is a foot process that holds cells away from capillary endothelium, projections ensure gaps between cells, fluid from blood in glomerulus can pass between these cells into lumen of Bowmans capsule

186
Q

What does Bowmans capsule lead to

A

Rest of the tubule which has 3 parts

187
Q

What are the 3 parts of the tubule after Bowmans capsule

A

Proximal convoluted tubule, loop of Henle, distal convoluted tubule

188
Q

What does fluid from many nephrons enter and where does that go

A

Enters collecting ducts which pass down medulla to pelvis at kidneys centre

189
Q

What is in a nephron

A

Afferent arteriole to glomerulus to efferent arteriole, at glomerulus ultrafiltration to Bowmans capsule which goes to proximal convoluted tubule then descending loop of Henle moving from cortex to medulla and then ascending loop of Henle back to cortex, then distal convoluted tubule to collecting duct

190
Q

What is ultrafiltration

A

Filtering of blood at a molecular level

191
Q

How does ultrafiltration work

A

Blood flows into glomerulus through afferent arteriole which is wider than efferent arteriole that carries blood away from glomerulus, difference in diameters ensures blood in glomerulus maintains higher pressure than bowmans capsule, pressure difference pushes fluid from blood to bowmans capsule surrounding glomerulus

192
Q

What is filtered out of blood in ultrafiltration

A

Blood plasma containing dissolved substances pushed under capillary pressure to bowmans capsules lumen, blood plasma contains water, amino acids, glucose, urea, inorganic mineral ions

193
Q

What does concentration of dissolved solutes in blood depend on

A

Water balance in organism

194
Q

How much glucose and amino acids found in urine and protein

A

0.0g dm-1 and almost 0 protein

195
Q

What is left in capillaries after ultrafiltration and what does this mean

A

Blood cells and proteins, proteins means negative water potential in blood which ensures some fluid retained in blood containing some water and dissolved substances

196
Q

Why is very low water potential needed in blood at capillaries

A

Helps reabsorb water at later stage

197
Q

What happens to the composition of the filtrate as it passes along tubule from bowmans capsule

A

Altered by selective reabsorption, substances absorbed back to tissue fluid and blood capillaries surrounding nephron

198
Q

What happens in proximal convoluted tubule

A

Filtrate altered by reabsorption of all sugars, most mineral ions and some water, 85% of fluid reabsorbed here and cells of tubule have highly folded surface to increase SA

199
Q

What happens in descending loop of Henle

A

Water potential of fluid decreased by action of mineral ion and water removal

200
Q

What happens in ascending limb of loop of Henle

A

Water potential increased as mineral ions removed by active transport

201
Q

What happens in collecting duct

A

Water potential decreased by water removal, final product in collecting duct is urine, process ensures urine has low water potential so urine has higher concentration of solutes than in blood and tissue fluid, urine passes to pelvis and down ureter to bladder

202
Q

What does reabsorption involve

A

Involves active transport and cotransport, cells lining proximal convoluted tubule specialised to achieve reabsorption

203
Q

How are proximal convoluted tubule specialised to achieve selective reabsorption

A

Cell surface membrane in contact with tubule fluid is highly folded into microvilli which increase SA for reabsorption, cell surface membrane also contains special cotransporter proteins that transport glucose of amino acids, in association with sodium ions from tubule to cells

204
Q

What is the structure of the cell surface membrane in proximal convoluted tubule that’s close to tissue fluid and blood capillaries

A

Also folded to increase SA, membrane contains sodium-potassium pumps that pump sodium ions out of cell and potassium ions into cell, cell cytoplasm has many mitochondria indicating an active process is involved

205
Q

How are glucose and amino acids selectively reabsorbed

A

By movement of sodium ions and glucose into cells driven by concentration gradient created by pumping sodium ions out of cell

206
Q

How do sodium ions move into cell after they have been pumped out in reabsorption

A

By facilitated diffusion but as they move in the cotransport glucose and amino acids against their concentration gradient known as secondary active transport

207
Q

What does the movement of glucose and amino acids out of tubule to these cell mean for the water potential in cells

A

It lowers the water potential of the cell meaning water from the tubule also leaves tubule by osmosis

208
Q

What happens to larger molecules like small proteins that may have entered tubule

A

They can be reabsorbed by endocytosis

209
Q

Where does selective reabsorption occur

A

Proximal convoluted tubule

210
Q

What does the loop of Henle consist of

A

A descending limb that goes into medulla and ascending limb that goes back to the cortex

211
Q

What does the arrangement for loop of Henle allow

A

Mineral ions (Na+Cl ions) to be transported from ascending limb to descending limb, overall effect to increase concentration of mineral ions in tubule fluid which has similar effect upon concentration of mineral ions in tissue fluid, giving medulla tissue fluid very low water potential

212
Q

What happens as mineral ions enter descending loop of Henle

A

Concentration of fluid rises meaning water potential decreases and becomes more negative further descending limb goes to medulla

213
Q

What happens as fluid rises up ascending limb

A

As base Mineral ions leave fluid by diffusion but higher up limb active transport used to move minerals out

214
Q

What part of the ascending limb is impermeable to water

A

Upper portion

215
Q

What is the effect of ionic movements in descending and ascending loop of Henle

A

Creates higher water potential in ascending limb and decrease water potential in medulla, water potential of tissue fluid becomes lower at bottom of loop of Henle

216
Q

What happens as fluid passes down collecting ducts

A

Passes through tissue with decreasing water potential, so always a water potential gradient between fluid in collecting duct and that in tissue allowing water to move out of collecting duct and into tissue fluid by osmosis

217
Q

What is the arrangement of the loop of Henle known as

A

Hairpin countercurrent multiplier system, overall arrangement is to increase efficiency of transfer of mineral ions from ascending limb to descending limb to create water potential gradient in medulla

218
Q

From top of ascending limb where does the fluid go

A

Passes along short distal convoluted tubule where active transport used to adjust concentration of mineral ions, from here fluid flows to collecting duct but still has lots of water so high water potential

219
Q

Where does collecting duct carry fluid to

A

Down through medulla to pelvis, tissue fluid in medulla has low water potential that gets even lower deeper into the medulla

220
Q

What happens to water as tubule fluid passes down collecting duct

A

Water moves by osmosis from tubule fluid to surrounding tissue and then to blood capillaries by osmosis and it’s carried away

221
Q

What does the amount of reabsorbed water depend on

A

Permeability of collecting duct wall

222
Q

What is in urine by the time it reaches the pelvis

A

Very low water potential and concentration of mineral ions and urea is higher than in the blood

223
Q

What happens to glucose during loop of Henle

A

It is all reabsorbed in the proximal convoluted tubule

224
Q

What happens to sodium ions in loop of Henle

A

Diffuse into descending limb causing concentration to rise then pumped out of ascending limb so concentration falls

225
Q

What happens to urea concentration in loop of Henle

A

Concentration rises as water withdrawn from tubule, urea also actively moved into tubule

226
Q

Although sodium ions removed from tubule why does concentration still rise

A

Water is also removed from tubule and potassium ions increase concentration as water is removed, potassium ions actively transported to tubule to be removed in urine too

227
Q

What is osmoregualtion

A

The control of water potential in the body

228
Q

What does osmoregulation involve

A

Controlling levels of both salt and water in body

229
Q

Why must correct water balance between cells and surrounding fluid be maintained

A

To prevent water entering cells causing lysis or leaving cells and causing crenation

230
Q

What3 sources the the body gain water form and how is it lost

A

Food, drink and metabolism and lost by urine, sweat, water vapour in exhaled air and faeces

231
Q

What does kidney act as to control water content of body and salt concentration of body fluid

A

An effector

232
Q

On a cool day and u have drink lots of water what do kidneys produce

A

Large volume of dilute urine

233
Q

On hot day and drunk little what do kidneys produce

A

Smaller volumes of more concentrated urine

234
Q

How do kidneys alter volume of urine produced

A

By altering permeability of collecting duct wall, if need to conserve water collecting ducts more permeable and more water reabsorbed so smaller volume of urine, if don’t need to conserve water collecting duct less permeable and more urine produced

235
Q

What do cells in collecting duct walls respond to in terms of becoming more or less permeable

A

Antidiuretic hormone (ADH) in blood

236
Q

What do collecting duct membranes have for osmoregulation

A

Receptors for ADH

237
Q

How does ADH work

A

Binds to receptor and causes a chain of enzyme-controlled reactions inside the cell like cell signalling, end result of these reaction is to cause vesicles containing water permeable channels (aquaporins) to fuse with cell surface membrane making walls more permeable to water

238
Q

What happens when levels of ADH rise in the blood

A

More aquaporins inserted allowing more water to be reabsorbed by osmosis than in blood, less urine produced and has more negative water potential

239
Q

What happens if levels of ADH fall in the blood

A

Cell surface membrane folds inwards to create new vesicle that removes aquaporins from the membrane making walls less permeable and less water reabsorbed by osmosis into blood, more water passes down collecting duct to form more urine with higher water potential

240
Q

What does the hypothalamus contain

A

Specialised cells called osmoreceptors

241
Q

How do osmoreceptors work

A

They’re sensory receptors that detect changes to water potential of blood, cells respond to effect of osmosis and shrink, as a result they stimulate neurosecretory cells in hypothalamus

242
Q

What are neurosecretory cells

A

Specialised neurones that produce and release ADH, ADH manufactured in cell body which lives in hypothalamus

243
Q

Where does ADH go after being secretared

A

Moved down axon terminal bulb into posterior pituitary gland where it’s stored in vesicles, when neurosecretory cells stimulated by osmoreceptors they carry action potentials down their axons and cause release of ADH any exocytosis

244
Q

Where does ADH enter blood capillaries and where does it go from there

A

Enters through posterior pituitary gland and transported around the body and acts on cells of collecting ducts, once water potential of blood rises again less ADH is released

245
Q

What is half life of ADH and what does this mean

A

20mins so once ADH in blood broken down, collecting ducts receive less stimulus and become less permeable

246
Q

What is the negative feedback loop of control to bloods water potential

A

Increased water potential detected by hypothalamus->less ADH released from posterior pituitary gland-> collecting duct walls less permeable->less water reabsorbed to blood and more urine produced->decrease of water potential of blood (opposite of water potential too low in blood)

247
Q

What happens if kidneys completely fail

A

They’re unable to regulate levels of water and electrolytes (substances that form charged particles in water) in body or remove waste products like urea in blood which quickly leads to detah

248
Q

What are causes of kidney faliure

A

Diabetes mellitus (type 1/2 sugar diabetes), heart disease, hypertension and infection

249
Q

What are the 2 treatments for kidney faliure

A

Renal dialysis and kidney transplant

250
Q

How does renal dialysis work

A

Waste product, excess fluids and mineral ions removed from blood by passing it over partially permeable dialysis membrane allowing exchange of substances between blood and dialysis fluid, dialysis fluid contains correct concentrations of mineral ions, urea, water and other substances in blood plasma, any substances in excess diffuse into dialysis fluid and substances too low concentration diffuse into blood from dialysis fluid

251
Q

What are the 2 types of renal dialysis

A

Haemodialysis, peritoneal dialysis

252
Q

What is haemodialysis

A

Blood from artery or vein passed into machine that contains an artificial dialysis membrane shaped to form many artificial capillaries which cause increase SA for exchange, heparin added to avoid clotting, artificial capillaries surround dialysis fluid which flows opposite direction to blood (countercurrent) improving exchange efficiency, any bubbles removed before returned to veins

253
Q

Where does haemodialysis happens

A

In a clinic 2/3 times a week for several hours each time, some patients do it at home

254
Q

How does peritoneal dialysis(PD) work

A

Dialysis membrane in body’s own abdominal membrane (peritoneum), surgeon implants permeant tube in abdomen, dialysis solution poured through tube and fills space between abdominal walls and organs, after several hours used solution drains from abdomen

255
Q

Where is peritoneal dialysis carried out

A

At home or work and patient can walk whilst having it and must be combined with carefully controlled diet

256
Q

How does a kidney transplant work

A

Bets option for prolonging life for kidney failure, requires major surgery, surgeon implants new organ in lower abdomen and attaches to blood supply and bladder, patient given immunosuppressant to prevent immune system recognising new organ as foreign and rejecting it

257
Q

4 advantages of kidney transplant over dialysis

A

Not time consuming, feel physically fitter, improved quality of life, improved self image

258
Q

4 disadvantages of kidney transplant over dialysis

A

Must take immunosuppressive drugs, need major surgery, need regular checks for signs of infection, immunosuppressant side effects like high BP and susceptible to infection

259
Q

Why can we detect some substances in urine

A

Substances with lower molecular mass than 69000 enter nephron, so any metabolic product or substance can pass to urine from blood if it’s small enough, if substances not reabsorbed further down nephron they’re detected in urine

260
Q

What are example of things we can test for in urine

A

Glucose in diabetes diagnosis, alcohol for blood Alcohol in drivers, recreational drugs, hCG in pregnancy tests, anabolic steroids for doping in sport

261
Q

Why do pregnancy tests work

A

Once embryo implanted in uterine lining it produces a hormone called hCG, it’s relatively small glycoprotein with molecular mass of 36700 and can be found 6days after conception, pregnancy testing kits use monoclonal antibodies which bind to hCG in urine

262
Q

5 steps for how pregnancy tests work

A

1.urine poured onto test stick, 2.hCG binds to mobile antibodies attached to blue bead 3.mobile antibodies move down test stick 4.of hCG present it binds to fixed antibodies holding beads in place and blue lines form 5.mobile antibodies with no hCG attached bind to another fixed site show the test is working

263
Q

What are anabolic steroids

A

Anabolic steroids increase protein synthesis in cells causing build up of tissue especially in muscles, they are controversial as they give sporting advantages and dangerous side effects and major sporting bodies ban them

264
Q

How does testing for anabolic steroids work

A

Had life of 16hours and stay in body for many days, they’re relatively small molecules and easily enter nephron, testing involves analysis of urine in lab using gas chromatography

Alevel Biology (25 decks)

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