organisms exchange substances with their environment Flashcards
1
Q
surface area to volume ratio
A
small organisms have a very large surface area in comparison to their volume (divide volume by surface area) whilst large organisms have a small surface area to volume ratio
2
Q
gas exchange across single-celled organisms
A
diffuse directly into or out of the cell across the cell surface membrane
3
Q
structure of fish gills
A
- four layers of gills on each side of head, supported by arches
- gills are made of stacks of gill filaments
- lamellae at right angles to gill filaments
4
Q
process of gas exchange in fish
A
- fish open mouth to enable water to flow over it then close
- increases pressure
- water passes over lamellae and oxygen diffuses into blood
- CO2 diffuses out and into water and flows back out of gills
- through counter-current mechanism
5
Q
counter-current exchange principle
A
- maintains a steep concentration gradient across entire length of lamellae
- water and blood flow in opposite direction
- water always has more O2 than blood
6
Q
why can’t fish use their bodies for gas exchange?
A
waterproof, impermeable membrane with a small surface area
7
Q
structures of dicotyledonous plants
A
stomata, spongy mesophyll and pallisade layer
8
Q
stomata
A
- site of gas exchange
- pores formed by two guard cells
9
Q
reduction of water loss in plants
A
stomata close at night when photosynthesis would not be occuring
10
Q
spongy mesophyll
A
- irregularly shaped cells
- air spaces to allow diffusion between stomata and photosynthesisng cells
- help maintain concentration gradient
11
Q
pallisade layer
A
- pallisade cells which contain chloroplasts
- site of photosynthesis
12
Q
adaptations of leaf for gas exchange
A
- thin and flat for short diffusion path and large SA:V
- stomata under leaf
- air spaces in mesophyll allow gases to move around leaf for photosynthesis
13
Q
why can’t insects use their bodies for gas exchange?
A
they have a waterproof chitin exoskeleton and a small SA:V to conserve water
14
Q
structures and function of insect gas exchange
A
spiracles- holes on body’s surface that can open and close with use of valves
tracheae- large tubes extending through all body tissues
tracheoles- smaller branches dividing of tracheae
15
Q
process of gas exchange in insects
A
- gases move in and out of tracheae through spiracles
- maintains a concentration gradient
- contraction of muscles in tracheae allows mass movement of air in and out
16
Q
adaptations of insects for gas exchange
A
- tracheoles have thin walls so short diffusion distance
- highly branched for large surface area
- tracheae provide tube full of air so fast diffusion into tissues
17
Q
xerophytic plants
A
plants that are adapted to survive in environments with limited water
18
Q
adaptations of xerophytic plants
A
- curled leaves to trap moisture to increase local humidity and therefore reduce WP gradient
- hairs to trap moisture
- sunken stomata to trap moisture
- thicker cuticle to reduce evaporation
- longer root network to reach more water
19
Q
gross structure of the human gas exchange system
A
alveoli, bronchioles, bronchi, trachea and lungs
20
Q
alveoli
A
- large number of alveoli
- thin walls
- extensive capillary network
21
Q
bronchioles
A
- narrower than bronchi
- muscle and elastic fibres
- air into alveoli
22
Q
bronchi
A
- supported by rings of cartilage
- ciliated epthelium
- narrow
- one in each lung
- air into bronchioles
23
Q
trachea
A
- wide tube supported by cartilage
- lined with ciliated epithelium cells
- carries air to bronchi
24
Q
lungs
A
25
respiration
chemical reaction to release energy in the form of ATP
26
breathing
movement of air into and out of the lungs (scientific word is ventilation)
27
what is gaseous exchange humans?
diffusion of oxygen from air in the alveoli into the blood and of carbon dioxide from the blood into the air in the alveoli
28
inhalation (inspiration)
- the external intercostal muscles contract whereas the internal muscles relax, as a result this causes the ribs to raise upwards
- the diaphragm contracts and flattens
- the intercostal muscles and diaphragm cause the volume inside the thorax to increase, thus lowering the pressure
- the difference between the pressure inside the lungs and atmospheric pressure creates a gradient, thus causing the air to be forced into the lungs
29
exhalation (expiration)
- the internal intercostal muscles contract whereas the external muscles relax therefore lowering the rib cage
- the diaphragm relaxes and raises upwards
- this action in combination decreases the volume inside the thorax, therefore increasing the pressure
- forces the air out of the lungs
30
alveolar epithelium and capillary diffusion
- the exchange of oxygen and carbon dioxide occurs between the alveoli and the capillaries in the lungs
- oxygen and carbon dioxide are exchanged in a process of simple diffusion
- the air in the alveoli contains a high concentration of oxygen
- the oxygen diffuses from the alveoli and into the blood capillaries, before being carried away to the rest of the body for aerobic respiration
- the blood in the capillaries has a relatively low concentration of oxygen and a high concentration of carbon dioxide
- the carbon dioxide diffuses from the blood and into the alveoli and is then exhaled.
31
spirometry
measures air volumes- spirometry measures the volume of air that is exchanged between the lungs and the atmosphere
32
digestion
large biological molecules are hydrolysed to smaller molecules that can be absorbed across cell membranes
33
pulmonary ventilation rate
tidal volume x breathing rate
34
tidal volume
the normal volume of air in each breath (norm=0.5dm3)
35
breathing rate
number of breathes per minute
36
digestion of carbohydrates location
mouth and small intestine
37
what hydrolyse carbohydrates?
amylases and membrane-bound disaccharides
38
role of amylase
hydrolyses polysaccharides into disaccharides by hydrolysing glycosidic bonds
39
role of membrane-bound disaccharides
sucrase, maltase and lactase hydrolyse disaccharides (e.g sucrose, maltose and lactose) into monosaccharides
40
digestion of lipids location
small intestine
41
what hydrolyse lipids?
lipase and bile salts (emulsification)
42
role of bile salts
emulsify lipids, forming micelles, to provide a larger surface area for lipase action
43
role of lipase
hydrolyses ester bonds between monoglycerides and fatty acids
44
what are micelles?
micelles are water soluble vesicles that contain bile salts and fatty acids/monoglycerides
45
digestion of proteins location
stomach and small intestine
46
what hydrolyse proteins?
membrane-bound dipeptidases, endopeptidases and exopeptidases
47
role of endopeptidases
hydrolyse peptide bonds between amino acids in the middle of a polymer chain
48
exopeptidases
hydrolyse peptide bonds between amino aicds at the end of a polymer chain
49
membrane-bound dipeptidases
hydrolyse peptide bonds in a dipeptide into two amino acids
50
wall of ileum structure
- covered in villi
- thin walls surrounded by capillary network
- epthilial cells have microvilli
51
absorption of monosaccharides and amino acids
- sodium ions actively transported out of the epithelial cell into blood
-reduces sodium ion concentration in epithelial
- sodium ions can the diffuse from lumen down their concentration gradient into epithelial cell
- does this through a co-transporter protein
- glucose or amino acids are actively transported
- glucose moves by facilitated diffusion from the epithelial cell to the blood
52
why do fatty acids and monoglycerides not require co-transport?
they are non-polar so can diffuse across the membrane of the epithelial cells
53
absorption of fatty acids and monoglycerides
- micelles contain bile salts and fatty acids/monoglycerides
- bring them to the lining of the ileum
- fatty acids/monoglycerides are absorbed by diffusion
- maintains a higher concentration gradient of fatty acids
- triglcyerides are reformed in golgi
- vesicles move to cell membrane
54
haemoglobin structure
- quaternary structure
- four polypeptide chains
- 2 alpha-globin and 2 beta-globin chains
- each chain has a prosthetic haem group
- haem group contains Fe2+ ion
- subunits held together by disulphide bonds
- hydrophobic R group face inwards and hydrophillic R groups outwards so they are water soluble
55
role of haemoglobin
allow oxygen molecules to bind to haem groups, forming oxyhaemoglobin, where they are carried around body to respiring cells
56
how many oxygen molecules can haemoglobin hold?
4
57
affinity
the ability of haemoglobin to attract or bind to oxygen
58
saturation of haemoglobin
haemoglobin is holding 4 oxygen molecules
59
loading/association of haemoglobin
binding of oxygen to haemoglobin
60
unloading/dissociation
oxygen unbinds from haemoglobin
61
oxyhaemoglobin dissociation curve
oxygen is loaded in regions with a high partial pressure of oxygen (alveoli) and unloaded in regions with low partial pressures of oxygen (respiring cells). this is shown by a sigmoid curve.
62
co-operative binding
- hard for first molecule of O2 to bind to haemoglobin
- when it does, this changes the shape of haemoglobin
- this makes it easier for further oxygen molecules to bind
- it is hard for the 4th molecule to bind because it id harder to find a binding site
63
the bohr effect
when high carbon dioxide concentrations cause the oxyhaemoglobin curve to shift to the right because affinity decreases
64
high pCO2 (respiring cells)=curve shifts to the...
right because affinity decreases so oxygen can be unloaded
65
low pCO2 (alveoli)=curve shifts to the...
left because affinity increases so oxygen can be loaded
66
animals with low affinity for oxygen
have faster metabolisms
67
effects of altitude on affinity for oxygen
high affinity so loads more oxygen
68
features of mammilian circulatory system
closed- blood remains within blood vessels
double- blood passes through heart twice in each circuit
69
gross structure of the human heart
right side:
- right atrium and ventricle
- vena cava
- pulmonary artery
left side:
- left atrium and ventricle
- aorta
- pulmonary vein
70
features of cardiac muscle
myogenic and never fatigues
71
coronary arteries function
supply cardiac muscle with oxygenated blood
72
atrioventricular valves
between atria and ventricles
73
semilunar valves
between ventricles and arteries
74
function of valves
open when pressure is higher behind valve and open when its lower on front to keep blood flowing unidirectionally to prevent blackflow
75
cardiac cycle stages
diastole, atrial systole and ventricular systole
76
what happens during atrial diastole?
- atria and ventricular muscles are relaxed
- blood enters atria
- this increases pressure in atria
77
what happens during atrial systole?
- atria muscle contract
- increase blood pressure
- AV valves open
- blood pumped to ventricles
- volume decreases in atria
78
what happens during ventricular systole?
- ventricular muscles contract
- increases pressure
- AV valves close
- SL valves open
- blood pumped into arteries
79
structure of arteries
- thick muscle layer so constriction and dilation can control blood volume
- thick elastic layer to maintain blood pressure as walls stretch and recoil
- thick walls to prevent bursting
80
structure of atreioles
- thick muscler layer (thick than arteries) to help restrict blood flow into the capillaries
- thinner elastic layer as pressure is lower
- thinner walls as pressure is lower
81
structure of veins
- relatively thin muscle so can't control blood flow
- relatively thin elastic layer as pressure is low
- thin walls as pressure is low and helps blood flow
- has valves
82
structure of capillary beds
- no muscle or elastic layer
- wall is one cell thick to provide short diffusion distance
83
importance of capillary beds
capillaries form capillary beds as exchange surfaces. they have a narrow diameter to slow blood flow and red blood cells are squahsed against walls. this maximises diffusion.
84
tissue fluid definition
fluid containing water, glucose, amino acids, fatty acids, ions and oxygen which bathes the tissues
85
formation of tissue fluid
- high hydrostatic pressure at arteriole end
- pressure forces blood out of capillaries
- only small substances escape through gaps in capillaries
86
reabsorption of tissue fluid
- water potential of blood is lower than water potential of tissue fluid
- water moves by osmosis down concentration gradient back to blood at venule end when hydrostatic pressure decreases
- rest of tissue fluid is absorbed into the lympathic system and returns to blood
87
cardiac output
CO = stroke volume × heart rate
88
xylem
long continuous columns that transport water that also provide structural strength to stem
89
phloem
transport organic substances to all cells in a plant
90
structure of phloem
- sieve tube elements: tube to transport sucorse, have end plates for flow of solution
- companion cells: provide ATP for AT
91
cohesion-tension theory process
- water is lost from leaf due to transpiration/evaporation
- lowers water potential of leaf
- water pulled up through xylem (creating tension)
- water molecules cohere through hydrogen bonding
- forming a continuous column of water
- adhesion of water molecules to walls of xylem (capillarity)
92
mass-flow hypothesis process
mass flow from the source to the sink
- sucrose actively transported into sieve tube elements
- lowers water potential of phloem
- water from xylem moves in via osmosis
- increase in water increases hydrostatic pressure
- sucrose solution is forced out to sink
- sucrose used in respiration or as starch
93
transpiration
loss of water vapour from the stomata by evaporation
94
factors that affect transpiration
- temperature (+ve)
- light intensity (+ve)
- wind intensity (+ve)
- humidity (-ve)
95
translocation
movement of organic materials around plant
96
tracers
- plants grown in radioactively labelled carbon dioxide
- this is absorbed into plant and used in photosynthesis to creature sugars
- xray film show sections containing sugars turn black (phloem)
97
ringing experiments
- ring of bark and phloem are removed from a tree trunk
- trunk swells above the removed section
- liquid contains sugar
98
muscle in atria
thin as they only need to pump blood to ventricles so less contraction is needed
99
muscles in ventricles
thick as they pump blood to the lungs and the rest of the body, the keeps the blood at a higher pressure
100
pressure in right ventricle
low as blood is only being pumped to lungs, this prevents damage to capillaries
101
pressure in left ventricle
high as blood is being pumped to the body so there are large contractions
102
vena cava
carries deoxygentaed blood from body into right atrium
103
pulmonary vein
carries oxygenated blood from lungs left atrium
104
pulmonary artery
carries deoxygenated blood from right ventricle to lungs
105
aorta
carries oxygenated blood from left ventricle to body
106
renal vein
carries deoxygentaed blood away from kidneys to heart
107
renal artery
supplies kidney with oxygenated blood
108
evidence for mass flow
- sap is released when the stem of a plant is cut, showing there is pressure in sieve tubes
- concentration of sucrose is higher in leaves than roots
- increase in sucrose at leaves is followed by increase in sucrose at phloem
- metabolic poisons/ lack of oxygen inhibit transolcation
109
evidence against mass flow
- structure of sieve tube elements seems to hinder mass flow
- not all solutes move at the same time
- sucrose is delivered at the same rate to all regions, rather than going faster to ones with low sucrose concentration
