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A Level Biology > 3 > Flashcards

3 Flashcards

1
Q

How does an organisms surface area to volume ratio effect it’s metabolic rate?

A

in smaller organisms with a higher SA:V:
- rate of heat loss increases
- higher metabolic rate and respiration
- to generate enough heat to maintain a constant body temperature

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2
Q

Why can’t insects use their bodies as an exchange surface?

A

They have a small SA:V ratio in order to conserve water

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3
Q

What are the function of spiracles in an insect?

A

holes on the surface of the body which open and close for gas exchange and to control water loss

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4
Q

What are the function of trachea in an insect?

A

Tubes which penetrate inside the body carrying air to every tissue

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5
Q

Describe water’s movement in tracheoles of insects

A

At rest - water fills the ends of the tracheoles

During flight - the water diffuses into the muscle (anaerobic respiration)

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6
Q

What are the function of the lamellae in fish

A
  • give increased surface area
  • blood and water flow across them in opposite directions (countercurrent exchange system)
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7
Q

What are the adaptations of gills?

A
  • each gill is made of many gill filaments which are covered in many lamellae providing a large surface area
  • vast network of capillaries on lamellae (remove o2 to maintain a conc gradient)
  • thin epithelium so shorter diffusion pathway between water and blood
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8
Q

How do fish maintain flow of water over gills (4m)

A
  • open mouth
  • water enters due to lower pressure
  • mouth closes
  • higher pressure forces water over gills
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9
Q

Why is the countercurrent exchange system in fish efficient?

A
  • water and blood flow over lamellae in opposite directions
  • always higher conc of o2 in water than blood
  • conc gradient of o2 is maintained along whole length of lamellae so equilibrium is not met
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10
Q

Why is the parallel flow exchange system in fish less efficient?

A
  • Only has a steep diffusion gradient INITIALLY
  • equilibrium would be met
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11
Q

What are the two ways fish can ventilate?

A

Passively and actively (more efficient)

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12
Q

Describe alveoli

A
  • lined with epithelium cells
  • walks only 1 cell thick so short diffusion pathway
  • network of capillaries
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13
Q

Describe inspiration (breathing in)

A
  • external intercostal muscles contract
  • internal intercostal muscles relax
  • ribs move up and out
  • diaphragm contracts and flattens
  • volume of thorax increases
  • pressure in thorax decreases
  • air pressure outside the lungs is greater so air moves in
    (Air moves down a pressure gradient)
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14
Q

What is tidal volume?

A

The volume of air in each breath

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15
Q

What is breathing rate

A

Number of breaths we take per minute

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16
Q

How do you calculate pulmonary ventilation rate?

A

Tidal volume x breathing rate
(Can be measured using a spirometer)

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17
Q

What’s the function of the pleural space

A

Filled with pleural liquid which prevents lungs rubbing with ribcage

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18
Q

Why is oxygen uptake a measure of metabolic rate in organisms

A

Oxygen is used in respiration which provides energy

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19
Q

What is digestion

A

The hydrolysis of large insoluble molecules into small soluble molecules

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20
Q

Where are lipids digested

A

Small intenstine

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21
Q

Where is amylase found and what is it’s function?

A

In the mouth
- turns starch into maltose and glucose
by hydrolysing the glycosidic bonds

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22
Q

What are the adaptations of villi?

A
  • many capillaries and lymph vessels = rich blood supply
  • microvilli = large surface area
  • lacteal connects to the lymph system
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23
Q

How are polysaccharides and disaccharides digested into monosaccharides?

A

By hydrolysis of the glycosidic bonds

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24
Q

What are the 3 disaccharide enzymes

A

Maltase, sucrase, lactase

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25
Q

What’s the role of bile salts?

A

To emulsify lipids and large droplets into small micelles which have a large surface area for lipase action

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26
Q

What’s the role of HCL in the stomach

A
  • destroys bacteria
  • ensures optimum pH 2 for mucus acts enzymes
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27
Q

What is the second section of the small intestine called?

A

Ileum —> digestion finishes and the products are absorbed

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28
Q

What happens in the duodenum (small intestine)?

A

Pancreatic juice, bile and Maltase is secreted

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29
Q

Where is bile produced and stored?

A

Produced in liver, stored in gall bladder

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30
Q

What’s the role of bile?

A
  • neutralises HCL so enzymes in small intestine don’t stop working
  • emulsifies fats into micelles
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31
Q

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels (5m)

A
  • Micelles contain bile salts and fatty acids
  • release fatty acids to lining of the ileum
  • Fatty acids absorbed by diffusion
  • Triglycerides reformed in cells
  • Vesicles move to cell membrane
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32
Q

Describe the role of enzymes in the digestion of proteins in a mammal

A
  • hydrolysis of peptide bonds
  • endopeptidase produces shorter polypeptides
  • exopeptidase produces amino acids
  • dipeptidase produces amino acids
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33
Q

What are the advantages to lipid droplet and micelle formation?

A
  • droplets increase surface area for lipase action
  • so faster hydrolysis of lipids
  • micelles carry fatty acids and glycerol through membrane
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34
Q

Explain how cells lining the ileum of mammals absorb glucose by co transport with sodium ions

A
  • maintains diffusion gradient for sodium ions to go from ileum cell to blood
  • sodium moving in by facilitated diffusion brings glucose with it
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35
Q

How are the chambers in the heart adapted (atria & ventricles)?

A

Atria: thin walled and elastic so they can stretch when filled with blood

Ventricles: thick muscular walls pump blood under high pressure

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36
Q

In the heart why is the left ventricle thicker than the right

A

Because it has to pump blood all the way around the body

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37
Q

How are arteries adapted?

A
  • thick walls to withstand high pressure.
  • Muscular and elastic to control blood flow
38
Q

How are veins adapted?

A
  • thin walls due to lower pressure
  • have valves to prevent back flow of blood.
  • have less muscular and elastic tissue bc they don’t control blood flow
39
Q

In the heart why are two pumps needed (left and right)

A
  • to maintain blood pressure around the whole body
  • when blood passes through narrow capillaries of lungs the pressure drops so would not be flowing strongly enough around the whole body
  • so it is returned to the heart to increase pressure
40
Q

Describe atrial systole (1)

A
  • atria contracts which decreases volume and increases pressure inside atria
  • pressure in atria > pressure in ventricles
  • AV valves open
  • blood is pushed into ventricles
  • semilunar valves stay closed
41
Q

Describe ventricular systole (2)

A
  • ventricles contract from the bottom up which decreases volume and increases pressure inside ventricles
  • Semi lunar valves forced open
  • pressure in ventricles > Atria
  • blood is pushed out of heart through arteries
42
Q

Describe diastole (3)

A
  • atria and ventricles relax which increases volume and decreases pressure inside chambers
  • blood from veins fill atria and flows to ventricles
  • AV valves open
  • pressure inside atria > ventricles
  • SL valves shut
43
Q

What are the nodes involved in heart contraction and where are they

A
  • Sinoatrial node (SAN) = wall of right atrium
  • atrioventricular node (AVN) = in between the two atria
44
Q

What does myogenic mean

A

The hearts contraction is initiated from within the muscle itself rather than by nerve impulses

45
Q

Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs

A
  1. Renal vein
  2. Vena cava to right atrium
  3. Right ventricle to pulmonary artery
46
Q

Explain how an arteriole can reduce the blood flow into capillaries

A
  • muscle contracts
  • narrows lumen
47
Q

What blood vessel carries blood at the lowest pressure ?

A

Vena cava

48
Q

Explain why different enzymes are required in digestion

A
  • substrates all have different shapes
  • enzymes have a specific primary structure giving a specific tertiary structure
  • therefore an active site with a specific shape
  • only substrates that are complementary can bind to the active site
  • to form an enzyme substrate complex
49
Q

Explain the role of the heart in the formation of tissue fluid

A
  • contraction of ventricles produces high blood pressure
  • this forces water out of blood capillaries
50
Q

Explain the advantage of the Bohr effect during exercise

A
  • increases dissociation of oxygen
  • for aerobic respiration at the cells
51
Q

Explain the effect of increasing CO2 concentration on the dissociation of oxyHb

A
  • decreases Hbs affinity for O2
  • by decreasing blood pH
  • increases rate of O2 unloading
  • curve shifts right
52
Q

How does binding of 1 molecule of o2 to Hb make it easier for the second to bind

A

-binding of first oxygen changes tertiary structure of Hb
- which creates another binding site

53
Q

Explain how a reduced tidal volume affects the exchange of CO2 between blood and alveoli

A
  • less CO2 exhaled
  • so reduced concentration gradient
  • more CO2 stays in blood
54
Q

Describe the pathway taken by an O2 molecule from an alveolus to the blood

A

alveolar epithelium to epithelium of capillary

55
Q

Describe the structure of the human gas exchange system and how we breathe in and out

A
  • trachea, bronchi, bronchioles, alveoli
  • breathing in: diaphragm & external IC muscles contract
  • volume increase and pressure decrease in thorax
  • breathing out: diaphragm relaxes & internal IC muscles contract
56
Q

Give 3 ways an insects tracheal system is adapted for gas exchange

A
  • tracheoles have thin walls so short diffusion pathway
  • highly branched/ large number of tracheoles so short diffusion pathway & large surface area
  • trachae provide tubes full of air so fast diffusion
57
Q

Explain how water from tissue fluid is returned to the circulatory system 4m

A
  • plasma proteins remain
  • reduces water potential of blood
  • water moves to blood by osmosis
  • returns to blood by lymphatic system
58
Q

What’s the function of micelles? 5m

A
  • they include bile salts and fatty acids
  • they make the fatty acids more soluble in water
  • they release fatty acids to the lining of the ileum
  • they maintain high conc gradient of fatty acids to lining
  • fatty acids are absorbed by diffusion
59
Q

Describe the mechanism for the absorption of amino acids in the ileum (5m)

A
  • Facilitated diffusion of amino acid
  • co-transport
  • sodium ions actively transported from cell to blood
  • creating sodium ion conc
  • facilitated diffusion of amino acids into blood.
60
Q

Describe the transport of carbohydrates in plants 5m

A
  • sucrose is actively transported into phloem
  • by companion cells
  • lowers WP in phloem and water enters by osmosis
  • producing higher hydrostatic pressure
  • mass flow to respiring cells
61
Q

Compare fish vs mammal circulation

A

Fish) - heart contains deoxygenated blood
- single circulation

Mammal) - heart contains deoxygenated and oxygenated blood
- double circulation system

62
Q

Describe the complete digestion of starch by a mammal

A
  • hydrolysis of glycosidic bonds
  • starch to maltose by amylase
  • maltose to glucose by Maltase
  • membrane bound
63
Q

How do larger organisms exchange

A
  • need a specialised surface for gas exchange eg lungs
  • because they have a smaller SA:V ratio and a long diffusion pathway
  • and they have a higher demand for oxygen
64
Q

What are the adaptations of xerophytic plants

A
  • stomata in pits/grooves which trap water vapour so less evaporation of water
  • thick waxy cuticle which increases diffusion distance so less evaporation
  • rolled leaves which trap water so less evaporation
  • hairs which trap water so less evaporation
65
Q

How does gas exchange occur in the alveoli?

A
  • o2 diffuses from alveoli down it’s conc gradient
  • across the alveolar epithelium
  • across the capillary endothelium and into the blood
66
Q

How would lung disease effect someone

A

. Scar tissue in lungs: - thicker tissue and less elastic so diffusion distance is increased so rate of diffusion decreased
. Faster ventilation rate to get enough oxygen into lungs
. Lungs can expand and recoil less so can’t hold as much air so reduced tidal volume and forced vital capacity

67
Q

How can asthma effect someone

A

Asthma attack can cause constriction of airways so narrow diameter so airflow in/out of lungs is reduced (FEV reduced)
Less o2 enters the blood so less gas exchange

68
Q

What is FEV

A

Max volume of air that can be breathed out in 1 second

69
Q

Describe the role of endopeptidases

A
  • hydrolyse peptide bonds within a protein
  • breaking it into 2 or more smaller peptides
70
Q

Describe the role of exopeptidases

A
  • hydrolyse peptide bonds at the ends of protein molecules
  • removing a single amino acid
71
Q

Describe role of dipeptidases (type of exopeptidases)

A
  • hydrolyse peptide bonds between to amino acids
    so that they can cross the cell membrane
72
Q

Explain why the combined actions of endo and exopeptidases are more efficient than exopeptidases on their own

A
  • endopeptidases hydrolyse internal peptide bonds
  • increasing surface area for exopeptidases
73
Q

What’s the function of atrioventricular valves

A

Prevent back flow of blood from ventricles to atria

74
Q

What’s the function of semilunar valves

A

Prevent backflow of blood from arteries to ventricles

75
Q

Describe the formation of tissue fluid

A
  • higher hydrostatic pressure at end of capillaries than tissue fluid
  • which forces water out of capillaries
  • large plasma proteins remain in the capillaries because they’re too large to leave
76
Q

How can high blood pressure lead to an accumulation of tissue fluid

A
  • high hydrostatic pressure
  • which increases outward pressure from arterial end of capillary
  • so more tissue fluid is formed and the lymph system is not able to drain tissues fast enough
77
Q

Describe the cohesion tension theory of water transport in the xylem 4m

A
  • water evaporates from leaves during transpiration
  • reducing wP in the cell and increasing wP gradient
  • water drawn out of xylem creating tension
  • cohesive forces between water molecules pull up water as an unbroken column
78
Q

How does light effect the rate of transpiration

A
  • faster transpiration
  • stomata open in light to let CO2 in for photosynthesis so water can evaporate faster
79
Q

How does temperature effect the rate of transpiration

A
  • faster transpiration
  • water molecules gain more kinetic energy so move faster
80
Q

How does humidity effect the rate of transpiration

A

The higher the humidity the slower the rate of transpiration
- as humidity increases more water is in the air so has a higher water potential
- decreasing the water potential gradient from leaf to air
- so water evaporates slower

81
Q

How does wind effect the rate of transpiration

A
  • wind blows away water molecules from around the stomata
  • which decreases the water potential of air around the stomata
  • which increases the water potential gradient
  • so water evaporates faster
82
Q

How is the xylem adapted for its function

A
  • cells joined with no end walls, forming a long continuous tube. Water can flow as a continuous column
  • cells contain no cytoplasm/nucleus so no obstructions and easier water flow
  • thick cell walls with lignin -> provides support and can withstand tension
  • pits in side walls - allow lateral water movement
83
Q

What two types of cells does phloem tissue have

A
  1. Sieve tube elements
    - no nucleus - easier flow of organic substances
    - sieve plate
  2. Companion cells
    - many mitochondria so high rate of respiration to make ATP for active transport of solutes
84
Q

What’s the order of AV and SL valves opening and closing in the heart

A

1 - AV valves close
2 - SL valves open
3 - SL valves close
4 - AV valves open

85
Q

What happens when the oxyHb curve shifts left

A
  • haemoglobin has higher affinity for O2
  • O2 associates more readily and dissociates less readily
86
Q

What happens when the oxyHb curve shifts right

A
  • haemoglobin has a lower affinity for O2
  • O2 dissociates more readily and associates less readily
87
Q

As partial pressure of oxygen increases what happens to saturation of haemoglobin with oxygen

A

Saturation increases because number of oxygen molecules binded to iron increases

88
Q

What is the Bohr effect

A

How changing carbon dioxide concentration effects % saturation of oxygen on a oxyhaemoglobin curve

89
Q

When does haemoglobin have a higher affinity for oxygen

A
  • at low CO2 concentrations
  • in blood passing away from the lungs
  • at higher pH
90
Q

Describe mass flow of sucrose down a phloem (5m)

A
  • sucrose moves down into the sieve tube element (STE) causing the wP to decrease
  • water moves from the xylem into the STE element by osmosis
  • causing the hydrostatic pressure in the STE to to increase
  • at the sink cell the hydrostatic pressure decreases bc of water moving out of the STE
  • sucrose moves down the hydrostatic pressure gradient and into the sink cell
91
Q

Describe the complete role of micelles in lipid digestion

A
  • lipids are digested into monoglycerides, fatty acids and glycerol by lipase and bile salts. these form micelles
  • micelles deliver these things to the epithelial cells of the ileum for absorption by diffusion
  • once in the cell these will be modified back into triglycerides inside the Golgi body and endoplasmic reticulum
92
Q

Briefly outline lipid digestion

A
  • lipase hydrolyses lipids into glycerol and fatty acids
  • bile salts (in micelles) emulsifies lipids and large droplets into fatty acids
  • micelles are then what deliver the products to the ileum for absorption by diffusion

A Level Biology (6 decks)

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