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biology > 3.3 Organisms exchange substances with their environment > Flashcards

3.3 Organisms exchange substances with their environment Flashcards

1
Q

Surface area to volume ratio

A
  • The surface area of an organism divided by its volume
  • the larger the organism, the smaller the ratio
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2
Q

Factors affecting gas exchange

A
  • diffusion distance
  • surface area
  • concentration gradient
  • temperature
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3
Q

Ventilation

A
  • Inhaling and exhaling in humans
  • controlled by diaphragm and antagonistic interaction of internal and external intercostal muscles
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4
Q

Inspiration

A
  • External intercostal muscles contract and internal relax
  • pushing ribs up and out
  • diaphragm contracts and flattens
  • air pressure in lungs drops below atmospheric pressure as lung volume increases
  • air moves in down pressure gradient
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5
Q

Expiration

A
  • External intercostal muscles relax and internal contract
  • pulling ribs down and in
  • diaphragm relaxes and domes
  • air pressure in lungs increases above atmospheric pressure as lung volume decreases
  • air forced out down pressure gradient
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6
Q

Passage of gas exchange

A
  • Mouth/nose → trachea → bronchi → bronchioles → alveoli
  • crosses alveolar epithelium into capillary endothelium

INSERT IMAGE HERE

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7
Q

Alveoli structure

A
  • Tiny air sacs
  • highly abundant in each lung – 300 million
  • surrounded by the capillary network
  • epithelium 1 cell thick

INSERT IMAGE HERE

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8
Q

Why large organisms need specialised exchange surface?

A
  • They have a small surface area to volume ratio
  • higher metabolic rate – demands efficient gas exchange
  • specialised organs e.g. lungs/gills designed for exchange
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9
Q

Fish gill anatomy

A
  • Fish gills are stacks of gill filaments
  • each filament is covered with gill lamellae at right angles

INSERT IMAGE HERE

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10
Q

How fish gas exchange surface provides large surface area?

A
  • Many gill filaments covered in many gill lamellae are positioned at right angles
  • creates a large surface area for efficient diffusion
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11
Q

Countercurrent flow

A
  • When water flows over gills in opposite direction to flow of blood in capillaries
  • equilibrium not reached
  • diffusion gradient maintained across entire length of gill lamellae
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12
Q

Name three structures in tracheal system

A
  • Involves trachea, tracheoles, spiracles

INSERT IMAGE HERE

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13
Q

How tracheal system provides large surface area?

A
  • Highly branched tracheoles
  • large number of tracheoles
  • filled in ends of tracheoles moves into tissues during exercise:
  • so larger surface area for gas exchange
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14
Q

Fluid-filled tracheole ends

A
  • Adaptation to increase movement of gases
  • when insect flies and muscles respire anaerobically – lactate produced
  • water potential of cells lowered, so water moves from tracholes to cells by osmosis
  • gases diffuse faster in air
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15
Q

How do insects limit water loss?

A
  • Small surface area to volume ratio
  • waterproof exoskeleton
  • spiracles can open and close to reduce water loss
  • thick waxy cuticle – increases diffusion distance so less evaporation
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16
Q

Dicotyledonous plants leaf tissues

A
  • Key structures involved are mesophyll layers
  • (palisade and spongy mesophyll)
  • stomata created by guard cells

INSERT IMAGE HERE

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17
Q

Gas exchange in plants

A
  • Palisade mesophyll is site of photosynthesis
  • oxygen produced and carbon dioxide used creates a concentration gradient
  • oxygen diffuses through air space in spongy mesophyll and diffuse out stomata
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18
Q

Role of guard cells

A
  • swell – open stomata
  • shrink – closed stomata
  • at night they shrink, reducing water loss by evaporation

INSERT IMAGE HERE

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19
Q

Xerophytic plants

A
  • Plants adapted to survive in dry environments with limited water (e.g. marram grass/cacti)
  • structural features for efficient gas exchange but limiting water loss
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20
Q

Adaptations of xerophyte

A
  • Adaptations to trap moisture to increase humidity → lowers water potential inside plant so less water lost via osmosis:
  • sunken stomata
  • curled leaves
  • hairs
    –
  • thick cuticle reduces loss by evaporation
  • longer root network
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21
Q

Digestion

A
  • Process where large insoluble biological molecules are hydrolysed into smaller soluble molecules
  • so they can be absorbed across cell membranes
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22
Q

Locations of carbohydrate digestion

A
  • Mouth → duodenum → ileum
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23
Q

Locations of protein digestion

A
  • Stomach → duodenum → ileum
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24
Q

Endopeptidases

A
  • Break peptide bonds between amino acids in the middle of the chain
  • creates more ends for exopeptidases for efficient hydrolysis

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25
Q

Exopeptidases

A
  • Break peptide bonds between amino acids at the ends of polymer chain

INSERT IMAGE HERE

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26
Q

Membrane-bound dipeptidases

A
  • Break peptide bond between two amino acids
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27
Q

Digestion of lipids

A
  • Digestion by lipase (chemical)
  • emulsified by bile salts (physical)
  • lipase produced in pancreas
  • bile salts produced in liver and stored in gall bladder
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28
Q

Lipase

A
  • Produced in pancreas
  • Breaks ester bonds in triglycerides to form:
  • monoglycerides
  • glycerol
  • fatty acids
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29
Q

Role of bile salts

A
  • Emulsify lipids to form tiny droplets and micelles
  • increases surface area for lipase action – faster hydrolysis
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30
Q

Micelles

A
  • Water soluble vesicles formed from fatty acids, glycerol, monoglycerides and bile salts
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31
Q

Lipid absorption

A
  • Micelles deliver fatty acids, glycerol and monoglycerides to epithelial cells of ileum for absorption
  • cross via simple diffusion as lipid-soluble and non-polar
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32
Q

Lipid modification

A
  • Smooth ER reforms monoglycerides/fatty acids into tryglycerides
  • golgi apparatus combines tryglycerides with proteins to form vesicles called chylomicrons
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33
Q

How lipids enter blood after modification?

A
  • Chylomicrons move out of cell via exocytosis and enter lacteal
  • lymphatic vessels carry chylomicrons and deposit them in bloodstream
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34
Q

How are glucose and amino acids absorbed?

A
  • Via co-transport in the ileum

INSERT IMAGE HERE

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35
Q

Haemoglobin (Hb)

A
  • Quaternary structure protein:
  • 2 alpha chains
  • 2 beta chains
  • with 4 associated haem groups in each chain containing Fe2+
    –
  • transports oxygen
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36
Q

Affinity of haemoglobin

A
  • The ability of haemoglobin to attract/bind to oxygen
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37
Q

Saturation of haemoglobin

A
  • When haemoglobin is holding the maximum amount of oxygen it can hold
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38
Q

Loading/unloading of haemoglobin

A
  • Binding/detachment of oxygen to haemoglobin
  • also known as association and disassociation
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39
Q

Oxyhaemoglobin dissociation curve

A
  • oxygen is loaded in regions with high partial pressures (alveoli)
  • unloaded in regions of low partial pressure (respiring tissue)

INSERT IMAGE HERE

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40
Q

Oxyhaemoglobin dissociation curve shifting left

A
  • Hb would have a higher affinity for oxygen
  • load more at the same partial pressure
  • becomes more saturated
  • adaptation in low-oxygen environments
  • e.g. llamas/in foetuses
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41
Q

Cooperative binding

A
  • Hb’s affinity for oxygen increases as more oxygen molecules are associated with it
  • when one binds, Hb changes shape meaning others bind more easily
  • explaining S shape of curve
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42
Q

How carbon dioxide affects haemoglobin?

A
  • When carbon dioxide dissolves in liquid, carbonic acid forms
  • decreases pH causing Hb to change shape
  • affinity decreases at respiring tissues
  • more oxygen is unloaded
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43
Q

Bohr effect

A
  • High carbon dioxide partial pressure
  • causes oxyhaemoglobin curve to shift to the right
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44
Q

Oxyhaemoglobin dissociation curve shifting right

A
  • Hb has lower affinity for oxygen
  • unloads more at the same partial pressures
  • less saturated
  • present in animals with faster metabolisms that need more oxygen for respiration
  • e.g. birds/rodents
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45
Q

Closed circulatory system

A
  • Blood remains within blood vessels
46
Q

Name different types of blood vessels

A
  • Arteries, arterioles, capillaries, venules and veins
47
Q

Structure of arteries

A
  • Thick muscular layer
  • thick elastic layer
  • thick outer layer
  • small lumen
  • no valves
48
Q

Capillary endothelium

A
  • Extremely thin
  • one cell thick
  • contains small gaps for small molecules to pass through (e.g. glucose, oxygen)
49
Q

Capillaries

A
  • Form capillary beds
  • narrow diameter (1 cell thick) to slow blood flow
  • red blood cells squashed against walls shortens diffusion pathway
  • small gaps for liquid/small molecules to be forced out
50
Q

Arterioles

A
  • Branch off arteries
  • thickest muscle layer to restrict blood flow
  • thinner elastic layer and outer layer than arteries as pressure lower
51
Q

Tissue fluid

A
  • Liquid bathing all cells
  • contains water, glucose, amino acids, fatty acids, ions and oxygen
  • enables delivery of useful molecules to cells and removal of waste
52
Q

Tissue fluid formation

A
  • At arteriole end, the smaller diameter results in high hydrostatic pressure
  • small molecules forced out (ultrafiltration)
  • red blood cells/large proteins too big to fit through capillary gaps so remain
53
Q

Reabsorption of tissue fluid

A
  • Large molecules remaining in capillary lower its water potential
  • towards venule end there is lower hydrostatic pressure due to loss of liquid
  • water reabsorbed back into capillaries by osmosis
54
Q

Role of the lymph in tissue fluid reabsorption

A
  • Not all liquid will be reabsorbed by osmosis as equilibrium will be reached
  • excess tissue fluid (lymph) is absorbed into lymphatic system and drains back into bloodstream and deposited near heart
55
Q

Cardiac muscle

A
  • Walls of heart having thick muscular layer
  • unique because it is:
  • myogenic – can contract and relax without nervous or hormonal stimulation
  • never fatigues so long as adequate oxygen supply
56
Q

Coronary arteries

A
  • Blood vessels supplying cardiac muscle with oxygenated blood
  • branch off from aorta
  • if blocked, cardiac muscle will not be able to respire, leading to myocardial infarction (heart attack)
57
Q

Structure of the heart

A

INSERT IMAGE HERE

58
Q

Adaptation of left ventricle

A
  • Has a thick muscular wall in comparison to right ventricle
  • enables larger contractions of muscle to create higher pressure
  • ensures blood reaches all body cells
59
Q

Veins connect to the heart

A
  • Vena cava – carries deoxygenated blood from body to right atrium
  • Pulmonary vein – carries oxygenated blood from lungs to left atrium
60
Q

Arteries connected to the heart

A
  • Pulmonary artery – carries deoxygenated blood from right ventricle to lungs
  • Aorta – carries oxygenated blood from left ventricle to rest of the body
61
Q

Valves within the heart

A
  • Ensure unidirectional blood flow
  • semilunar valves are located in aorta and pulmonary artery near the ventricles
  • atrioventricular valves between atria and ventricles
62
Q

Opening and closing of valves

A
  • Valves open if the pressure is higher behind them compared to in front of them.
  • AV valves open when pressure in atria > pressure in ventricles
  • SL valves open when pressure in ventricles > pressure in arteries
63
Q

The Septum

A
  • Muscle that runs down the middle of the heart
  • separates oxygenated and deoxygenated blood
  • maintains high concentration of oxygen in oxygenated blood
  • maintaining concentration gradient to enable diffusion to respiring cells
64
Q

Cardiac output

A
  • Volume of blood which leaves one ventricle in one minute.
  • heart rate = beats per minute

ADD IMAGE HERE

65
Q

Stroke volume

A
  • Volume of blood that leaves the heart each beat
  • measured in dm^3

[CHECK UN/ADDITION OF FORMULA]

66
Q

Cardiac cycle

A
  • Consists of diastole, atrial systole and ventricular systole

INSERT IMAGE HERE

67
Q

Diastole

A
  • Atria and ventricular muscles are relaxed
  • when blood enters atria via vena cava and pulmonary vein
  • increasing pressure in atria
68
Q

Atrial systole

A
  • Atria muscular walls contract, increasing pressure further.
  • pressure atria > pressure ventricles
  • atrioventricular valves open and blood flows into ventricles
  • ventricular muscle relaxed
69
Q

Ventricular systole

A
  • After a short delay (so ventricles fill), ventricular muscular walls contract
  • pressure ventricle > atria pressure and artery pressure
  • atrioventricular valves close and semi-lunar valves open
  • blood pushed into artery
70
Q

Transpiration

A
  • Loss of water vapour from stomata by evaporation
  • affected by:
  • light intensity
  • temperature
  • humidity
  • wind
    –
  • can be measured in a lab using a potometer
71
Q

How light intensity affects transpiration?

A
  • As light intensity increases, rate of transpiration increases
  • more light means more stomata open
  • larger surface area for evaporation
72
Q

How temperature affects transpiration?

A
  • As temperature increases, rate of transpiration increases
  • the more heat there is, the more kinetic energy molecules have
  • faster moving molecules increases evaporation
73
Q

How humidity affects transpiration?

A
  • As humidity increases, transpiration decreases
  • the more water vapour in the air, the greater the water potential outside the leaf
  • reduces water potential gradient and evaporation
74
Q

How wind affects transpiration?

A
  • As wind increases, rate of transpiration increases
  • the more air movement, the more humid areas are blown away
  • maintains water potential gradient, increasing evaporation
75
Q

Cohesion in plant transport

A
  • Because of the dipolar nature of water, hydrogen bonds can form – cohesion
  • water can travel up xylem as a continuous column

INSERT IMAGE HERE

76
Q

Adhesion in plant transport

A
  • Water can stick to other molecules (xylem walls) by forming H-bonds
  • helps hold water column up against gravity

INSERT IMAGE HERE

77
Q

Root pressure in plant transport

A
  • As water moves into roots by osmosis, the volume of liquid inside the root increases
  • ∴ the pressure inside the root increases
  • this forces water upwards
78
Q

Cohesion-tension theory

A
  • As water evaporates out the stomata, this lowers pressure
  • water is pulled up xylem (due to negative pressure)
  • cohesive water molecules creates a column of water
  • water molecules adhere to walls of xylem pulling it upwards
  • this column creates tension, pulling xylem inwards
79
Q

Translocation

A
  • Occurs in phloem
  • explained by mass flow hypothesis
  • transport of organic substances through plant
80
Q

Sieve tube elements

A
  • Living cells
  • contain no nucleus
  • few organelles
  • this makes cell hollow
  • allowing reduced resistance to flow of sugars
81
Q

Companion cell

A
  • Provide ATP required for active transport of organic substances
  • contains many mitochondria

INSERT IMAGE HERE

82
Q

Mass flow hypothesis

A
  • Organic substances, sucrose, move in solution from leaves (after photosynthesis) to respiring cells
  • source → sink direction
83
Q

How is pressure generated for translocation?

A
  • Photosynthesising cells produce glucose which diffuses into companion cell
  • companion cell actively transports glucose into phloem
  • this lowers water potential of phloem so water moves in from xylem via osmosis
  • hydrostatic pressure gradient generated
84
Q

What happens to sucrose after translocation?

A
  • Used in respiration at the sink
  • stored as insoluble starch
85
Q

Investigating translocation

A
  • Can be investigated using tracer and ringing experiments
  • proves phloem transports sugars not xylem
86
Q

Tracing

A
  • Involves radioactively labelling carbon – used in photosynthesis
  • create sugars with this carbon
  • thin slices from stems are cut and placed on X-ray film which turns black when exposed to radioactive material
  • stems will turn black as that is where phloem are
87
Q

Ringing experiments

A
  • Ring of bark (and phloem) is peeled and removed off a trunk
  • consequently, the trunk swells above the removed section
  • analysis will show it contains sugar
  • when phloem removed, sugar cannot be transported
88
Q

How do small organisms exchange gases?

A
  • Simple diffusion
  • across their surface
89
Q

Why don’t small organisms need breathing systems?

A
  • They have a large surface area to volume ratio
  • no cells far from the surface
90
Q

How alveoli structure relates to its function?

A
  • Round shape & large number in – large surface area for gas exchange (diffusion)
  • epithelial cells are flat and very thin to minimise diffusion distance
  • capillary network maintains concentration gradient
91
Q

How fish gas exchange surface provides a short diffusion distance?

A
  • Thin lamellae epithelium means short distance between water and blood
  • capillary network in every lamella
92
Q

How fish gas exchange surface maintains diffusion gradient?

A
  • Counter-current flow mechanism
  • circulation replaces blood saturated with oxygen
  • Ventilation replaces water with oxygen removed
93
Q

Name of gas exchange system in terrestrial insects

A
  • Tracheal system
94
Q

Describe structure of spiracles

A
  • Round, valve-like openings
  • running along the length of the abdomen
95
Q

Describe trachea & tracheoles structure

A
  • Network of internal tubes
  • have rings of cartilage adding strength and keeping them open
  • trachea branch into smaller tubes – tracheoles
  • tracheoles extend through all tissues delivering oxygen
96
Q

How tracheal system provides short diffusion distance?

A
  • Tracheoles have thin walls so short diffusion distance to cells
97
Q

How tracheal system maintains concentration gradient?

A
  • Body can be moved by muscles to move air –ventilation
  • Use of oxygen in respiration and production of CO2 sets up steep concentration gradients
98
Q

Amylase

A
  • Produced in pancreas & salivary gland
  • hydrolyses starch into maltose
99
Q

Membrane-bound disaccharidases

A
  • Maltase/sucrase/lactase
  • hydrolyse disaccharides into monosaccharides
100
Q

Enzymes involved in protein digestion

A
  • endopeptidases
  • exopeptidases
  • membrane-bound dipeptidases
101
Q

Products of protein digestion

A
  • Large polymer proteins are hydrolysed to amino acids
102
Q

Double circulatory system

A
  • Blood passes through heart twice
  • pulmonary circuit delivers blood to/from lungs
  • systemic circuit delivers blood to the rest of the body
103
Q

Coronary arteries

A
  • Supply cardiac muscle with oxygenated blood
  • for continued respiration and energy production for contraction
104
Q

Blood vessels entering/exiting the kidney

A
  • Renal artery carries oxygenated blood to kidney
  • renal vein carries deoxygenated blood to heart
105
Q

Blood vessels entering/exiting the lung

A
  • Pulmonary artery carries deoxygenated blood to lung
  • pulmonary vein carries oxygenated blood to heart
106
Q

Blood vessels entering/exiting the heart

A
  • Vena cava carries deoxygenated blood to heart (right atrium)
  • aorta carries oxygenated blood to body
  • pulmonary artery – carries blood from the heart to the lungs
  • pulmonary vein – carries blood from the lungs into the heart
107
Q

Describe then structure of veins

A
  • Thin muscular layer
  • thin elastic layer
  • thin walls
  • valves
108
Q

Explain role of elastic layer in arteries

A
  • Thick elastic layer
  • to help maintain blood pressure
  • by stretching and recoiling
109
Q

Describe the elastic layer in veins

A
  • Thin elastic layer as pressure lower
  • cannot control the flow of blood
110
Q

Explain the role of valves in veins

A
  • Due to low pressure in veins
  • skeletal muscle usually used to flatten walls of veins for blood flow
  • valves prevent the backflow of blood
  • unidirectional flow
111
Q

What causes the AV valves to open?

A
  • Higher pressure in the atria than in the ventricles
112
Q

What causes the semi-lunar valves to open?

A
  • Higher pressure in the ventricles than in the arteries

biology (5 decks)

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