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A-level Biology > organisms and environment > Flashcards

organisms and environment Flashcards

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AP® Biology flashcards Biology 101 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
sa:v ratio
maintained concentration gradient

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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 in humans

A

Mouth / nose -> trachea -> bronchi -> bronchioles -> alveoli crosses alveolar epithelium into capillary endothelium

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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

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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

How fish gas exchange surface provides large surface area

A

fish gills stacked gill filaments covered in many gill lamellae are positioned at right angles creates a large surface area for efficient diffusion

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10
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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11
Q

Name three structures in tracheal system

A

Involves trachea, tracheoles, spiracles

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12
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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13
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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14
Q

Dicotyledonous plants leaf
tissues

A

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

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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

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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17
Q

Role of guard cells

A

swell - open stomata
shrink - closed stomata
at night they shrink, reducing water loss by evaporation

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18
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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19
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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20
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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21
Q

Locations of carbohydrate
digestion

A

Mouth -> duodenum -> ileum

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22
Q

Locations of protein digestion

A

Stomach -> duodenum -> ileum

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23
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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24
Q

Exopeptidases

A

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

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25
Q

Membrane- bound dipeptidases

A

Break peptide bond between two amino acids

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26
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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27
Q

Lipase

A

Produced in pancreas Breaks ester bonds in triglycerides to form :
monoglycerides
glycerol
fatty acids

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28
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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29
Q

Micelles

A

Water soluble vesicles formed from fatty acids, glycerol, monoglycerides and bile salts

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30
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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31
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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32
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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33
Q

How are glucose and amino acids absorbed

A

Via co-transport in the ileum

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34
Q

Haemoglobin (Hb)

A

Quaternary structure protein 2 alpha chains
2 beta chains
4 associated haem groups in each chain containing Fe2+
transports oxygen

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35
Q

Affinity of haemoglobin

A

The ability of haemoglobin to attract / bind to oxygen

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36
Q

Saturation of haemoglobin

A

When haemoglobin is holding the maximum amount of oxygen it can hold

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37
Q

Loading / unloading of haemoglobin

A

Binding/detachment of oxygen to haemoglobin
also known as association and disassociation

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38
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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38
Q

Oxyhaemoglobin dissociation curve

A

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

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39
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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40
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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41
Q

Bohr effect

A

High carbon dioxide partial pressure
causes oxyhaemoglobin curve to shift to the right

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42
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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43
Q

Capillary endothelium

A

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

44
Q

Closed circulatory
system

A

Blood remains within blood vessels

45
Q

Name different types of blood vessels

A

Arteries, arterioles, capillaries, venules and veins

46
Q

Structure of arteries

A

Thick muscular layer thick elastic layer thick outer layer small luman
no valves

47
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

48
Q

Arterioles

A

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

48
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

49
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

50
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

51
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

52
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 suppl

53
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)
Supply cardiac muscle with oxygenated blood
for continued respiration and energy production for contraction

54
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

55
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

56
Q

Arteries connected to the hear

A

Pulmonary artery - carries deoxygenated blood from right ventricle to lungs
Aorta - carries oxygenated blood from left ventricle to rest of the body

57
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

58
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

58
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

59
Q

Cardiac output

A

Volume of blood which leaves one ventricle in one minute.
heart rate = beats per minute
cardiac output= heart rate x stroke volume

60
Q

Stroke volume

A

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

61
Q

Cardiac cycle

A

Consists of diastole, atrial systole and ventricular systole

62
Q

Diastole

A

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

63
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

64
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

65
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

66
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

67
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

68
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

69
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

70
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

71
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

72
Q

Root pressure in plant transport

A

As water moves into roots by osmosis, the volume of liquid inside the root increases therefore the pressure inside the root increases
this forces water upwards

73
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

74
Q

Translocation

A

Occurs in phloem
explained by mass flow hypothesis
transport of organic substances through plant

75
Q

Sieve tube elements

A

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

76
Q

Companion cell

A

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

77
Q

Mass flow hypothesis

A

Organic substances, sucrose, move in solution from leaves (after photosynthesis) to respiring cells
source -> sink direction

78
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

79
Q

What happens to sucrose after translocation?

A

Used in respiration at the sink stored as insoluble starch

80
Q

Investigating translocation

A

Can be investigated using tracer and ringing experiments proves phloem transports sugars not xylem

80
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

81
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

81
Q

How do small organisms exchange gases

A

Simple diffusion
across their surface

81
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

82
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

83
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

84
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

85
Q

Name of gas exchange system in terrestrial insects

A

Tracheal system

86
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

86
Q

Describe structure of spiracles

A

Round, valve-like openings
running along the length of the abdomen

87
Q

How tracheal system provides short diffusion distance

A

Tracheoles have thin walls so short diffusion distance to cells

87
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

88
Q

Amylase

A

Produced in pancreas & salivary gland
hydrolyses starch into maltose

88
Q

Membrane-bound disaccharidases

A

Maltase / sucrase / lactase hydrolyse disaccharides into monosaccharides

89
Q

Enzymes involved in
protein digestion

A

endopeptidases
exopeptidases
membrane-bound dipeptidases

90
Q

Products of protein digestion

A

Large polymer proteins are hydrolysed to amino acids

91
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

92
Q

Blood vessels entering / exiting the kidney

A

Renal artery carries oxygenated blood to kidney
renal vein carries deoxygenated blood to heart

93
Q

Blood vessels entering / exiting the lung

A

Pulmonary artery carries deoxygenated blood to lung pulmonary vein carries oxygenated blood to heart

94
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

95
Q

Describe then structure of veins

A

Thin muscular layer
thin elastic layer
thin walls
valves

96
Q

Explain role of elastic layer in arteries

A

Thick elastic layer
to help maintain blood pressure
By stretching and recoiling

97
Q

Describe the elastic layer in veins

A

Thin elastic layer as pressure lower
cannot control the flow of blood

98
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

99
Q

What causes the AV valves to open

A

Higher pressure in the atria than in the ventricles

100
Q

What causes the semi-lunar valves to open

A

Higher pressure in the ventricles than in the arteries

A-level Biology (8 decks)

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