ORGANISMS EXCHANGE SUBSTANCES WITH THEIR ENVIRONMENT Flashcards
(124 cards)
1
Q
What are 6 things all living things need to survive?
A
- Glucose (for energy)
- Oxygen (for aerobic respiration)
- Water
- Fats (for membranes & store of energy)
- Minerals (for enzyme action & maintaining water potential)
- Proteins (for growth & repair)
2
Q
How does size affect the need for a transport system?
A
- Several cell layers
- If oxygen & nutrients diffused in they would be used by outer cell layers
- Increased distance from nutrients & oxygen & the cells requiring them
3
Q
How does level of activity affect the need for a transport system?
A
- Active animals require more oxygen for respiration
- Sedatory animals do not
4
Q
How does surface area to volume ratio affect the need for a transport system?
A
- Large multi-celluar organisms have small surface area for their volume
- Surface area of large animals not large enough to supply all nutrients needed by inner cells
5
Q
What is the relationship between surface area and volume?
A
- Larger the organism, smaller the SA:V ratio
- Outer surface is not large enough to exchange materials eg nutrients
- More specialised exchange system is needed
6
Q
What is the rate of diffusion proportional to?
A
Length of diffusion path
7
Q
What do plants need carbon dioxide and oxygen for?
A
- They need CO2 for photosynthesis, which produces O2 as a waste gas
- They need O2 for respiration, which produces CO2 as a waste gas
8
Q
How do gases move in and out of plants?
A
- Through leaves via diffusion, through pores in epidermis called stomata (stoma)
- When concentration of CO2 inside plant is low, it will diffuse in from air through pores
- If concentration of O2 is high inside plant, it will diffuse from plant cells through pores into the air
9
Q
How are leaves adapted for diffusion?
A
- Thin: decreases distance the gases have to travel between air & cells (shorter diffusion pathway)
- Air spaces between cells: increases speed of diffusion from air to cells
- Lots of stomata: let gases in & out
10
Q
What is stomata’s structure and function?
A
- Small pores on underside of leaf
- Each stoma is surrounded by 2 guard cells, which control the opening & closing of the stoma
- When CO2 levels are low inside the plant, guard cells gain water & become turgid. They curve out, opening the stoma to allow gases in & out
- Water also evaporates through stomata
- High CO2 levels cause guard cells to lose water & become flaccid (droopy/inelastic), closing the stoma
11
Q
How is the stomata controlled?
A
- Guard cells are sensitive to light, CO2 & water loss
- Cells expand in response to light & low CO2 levels, & collapse in response to water loss
12
Q
What happens when the stomata is open vs closed?
A
Open:
- Evaporation draws water out of the leaf
- Gas exchange can occur to keep photosynthesis & respiration running
Closed:
- Evaporation or gas exchange cannot occur
13
Q
What are adaptations of a plant to reduce water loss?
A
- Waxy cuticle
- Stomata on underside of leaf
- Most stomata closed at night
- Deciduous plants lose leaves in winter
14
Q
What are xerophytes?
A
Plants that have adapted by altering their physical structure
- Usually have special means of storing & condensing water (eg cacti)
- Often have few or no leaves, which reduces transpiration
15
Q
What are examples of xerophyte adaptations to reduce/prevent excessive water loss?
A
- Thick waxy cuticle: stops uncontrolled evaporation through leaf cells
- Small leaf surface area: less surface area for evaporation
- Low stomata density: smaller surface area for diffusion (fewer places for water to escape)
- Sunken stomata: maintains humid air around stomata
- Stomata hairs (trichores): maintains humid air around stomata
- Rolled leaves: maintains humid air around stomata & protects stomata from wind (more wind=increased rate of diffusion & evaporation)
- Extensive roots: maximise water uptake
16
Q
What are adaptations of a cactus to reduce/prevent excessive water loss?
A
- Absence of leaves
- Ability to store water in stems
- Shallow root systems
- Waxy skin to seal in moisture
- Spines for shade
17
Q
What is a single circulatory system in fish?
A
Heart -> gills -> body -> heart
- Low activity & don’t need to maintain temp so less energy is needed
- Blood pressure reduced as passed through gill capillaries (slows body flow)
- Limits rate of delivery of O2 & nutrients to cells & removal of waste
18
Q
How does the structure of gills in fish relate to their function?
A
- Have numerous folds = large surface area
- Rows of gill filaments have many lamellae = increases surface area
- Lamellae has lots of blood capillaries & thin surface layer of cells to speed up diffusion
19
Q
What is the process of the countercurrent flow system in fish?
A
- Water (containing oxygen) enters fish through mouth & passes out through gills
- Blood flows through lamellae in one direction & water flows over in the opposite direction
- It maintains a large concentration gradient between water and blood
- The concentration of oxygen in water is always higher than in blood, so as much oxygen as possible diffuses from water into the blood
20
Q
How is a concentration gradient constantly maintained in gas exchange in fish?
A
- As blood flows in opposite direction to water, it always flows next to water that’s given up less of its oxygen
- Blood is absorbing more oxygen as it moves along
- Even when blood is high saturated having flowed past most of the length of the lamellae, there’s still a concentration gradient & it continues to absorb oxygen from water
- Equilibrium is never reached, diffusion is constantly taking place
21
Q
What is an open circulatory system in insects?
A
Blood is not always held in vessels
- Blood circulates through body cavity & bathes tissues & organs allowing for diffusion of substances
22
Q
What are spiracles in insects?
A
Small openings running into the body where air (and water) enters & leaves
They can be opened (during period of high demand for oxygen) or closed (when the insect is inactive) by sphincters to control water loss
23
Q
What is tracheae in insects?
A
Large tubes which lead off from spiracles, carries air into body
Lined with chitin for mechanical strength
Impermeable = no gas exchange occurs
24
Q
What are tracheoles in insects?
A
Single elongated cells which run between tissues, come off tracheae branches
No chitin lining so are permeable = allows gas exchange
Lots of tracheoles = large surface area for diffusion
Moisture allows oxygen to diffuse into liquid before diffusing into tissues
25
What is the process of gas exchange in insects?
1. Air moves into tracheae through spiracles
2. Oxygen travels down concentration gradient towards cells
3. Tracheae branch into tracheoles which go to individual cells, meaning oxygen diffuses directly into the respiring cells
4. Carbon dioxide from cells moves down it's own concentration gradient towards spiracles to be released into the air
5. Insects use rhythmic abdominal movement to move air in & out of spiracles
26
What is tidal ventilation in insect gas exchange?
As air goes in & out of tracheoles in same way, not all of the oxygen is absorbed from the air taken in
27
What are limitations of gas exchange in insects?
- Rely on diffusion to get oxygen to every cell, so their size is limited. As they get larger, it's harder for oxygen to diffuse to every cell
- Tidal ventilation: some air taken in never reaches gas exchange surface & not all air makes it out of the body, meaning only some of the oxygen that comes into the body makes it into the cells
28
What is the structure of the human gas exchange system?
1. As you breathe in, air enters trachea
2. Trachea splits into two bronchi - one bronchus leading to each lung
3. Each bronchus then branches off into smaller tubes called bronchioles
4. Bronchioles end in small 'air sacs' called alveoli (where gases are exchanged)
5. The ribcage, intercoastal muscles & diaphragm work together to move air in & out
29
What is trachea in human gas exchange?
Flexible airway supported by rings of cartilage to prevent it from collapsing
Wall is made of muscle lined epithelial goblet cells, which produce mucus which traps dirty particles & bacteria that's breathed in
30
What are bronchi in human gas exchange?
Two divisions of trachea, each leading to one lung
| Also produce mucus and supported by cartilage
31
What are bronchioles in human gas exchange?
Series of branches subdivisions of bronchi
| Walls made of muscle, allowing them to constrict so they can control the flow of air in & out of alveoli
32
What are alveoli in human gas exchange?
Air sacs at the end of bronchioles, which contain collagen & elastic fibres, allowing them to stretch as they fill with air
- Huge number of alveoli in lungs = large surface area for exchanging oxygen & carbon dioxide
- Surrounded by network of capillaries
33
What is the role of alveoli in human gas exchange system?
- Oxygen diffuses out of alveoli, across alveolar epithelium & capillary endothelium & into haemoglobin in the blood
- Carbon dioxide diffuses into alveoli from blood & is breathed out
34
How does the structure of alveoli relate to its function?
- Thin exchange surface: alveolar epithelium = one cell thick meaning there's a short diffusion pathway to speed up rate of diffusion
- Large surface area: large number of alveoli = large surface area for gas exchange
- Have good blood supply
- They are moist
35
What is the process of inspiration (breathing in) in the human gas exchange system ?
1. External intercoastal muscles & diaphragm muscles contract, causing ribcage to move up & out, diaphragm flattens which increases volume of thoracic cavity
2. As volume of thoracic cavity increases, lung pressure decreases
3. Air flows from area of high pressure to low pressure (down pressure gradient) so air flows down trachea & into lungs
4. This is an active process (requires energy/ATP)
36
What is the process of expiration (breathing out) in the human gas exchange system?
1. External intercoastal muscles & diaphragm relax, ribcage moves down & in, diaphragm becomes curved again
2. Volume of thoracic cavity decreases causing air pressure to increase
3. Air is forced down pressure gradient & out of lungs
Normal expiration = passive process, doesn't require energy/ATP
Forced expiration = external intercoastal muscles relax, internal intercoastal muscles contract, ribcage further down & in. Movement of muscles is opposing
37
How does the structure of trachea in human gas exchange relate to its function?
Smooth muscle:
- Contracts & relaxes to allow diameter of airways to be controlled
- During exercise, muscle relaxes to make airways wider which reduces resistance to air flow & aids ventilation
- Muscles contract to narrow airway when challenged with foreign material
38
What are essential feature of exchange surfaces?
- Large surface area to volume ratio, to speed up rate of exchange
- One cell thick, to keep diffusion pathways short
- Partially permeable, to selectively diffuse material
39
What is pulmonary ventilation and how do you calculate it?
Total volume of air that is moved into lungs during one minute (dm3min-1)
Pulmonary ventilation (dm3min-1) = tidal volume (dm3) x ventilation rate (min-1)
40
What is tidal volume?
Volume of air in each breath
41
What is ventilation rate?
Number of breaths per minute
42
What is forced expiratory volume?
Maximum volume of air that can be breathed out in 1 second
43
What is forced vital capacity?
Maximum volume of air possible to breathe forcefully out of lungs after deep breath in
44
What is the mouth's function during human digestion & absorption?
Mechanically break down food
45
What is the oesophagus' function during human digestion & absorption?
Contracts & moves food down to stomach from mouth
46
What is the stomach's function during human digestion & absorption?
Stores food & releases it to intestines
47
What is the liver's function during human digestion & absorption?
Produces bile to digest fats/vitamins, bile ducts carry bile to gall bladder for storage or to small intestine for use
48
What is the gall bladder's function during human digestion & absorption?
Stores bile until needed for digestion
49
What is the pancrea's function during human digestion & absorption?
Makes enzymes which break down sugars, fats & starches
50
What is the small intenstine's function during human digestion & absorption?
Walls make enzymes which work with enzymes from liver & pancreas to absorb nutrients from food into bloodstream
51
What is the large intestine's function during human digestion & absorption?
Absorb water & salts from non-digested material & get rid of any left over waste products
52
What is the rectum's function during human digestion & absorption?
Stores bodily waste until it can be released through anus
53
How are carbohydrates digested?
- Amylase is produced by salivary glands & small intestine, breaking down starch into maltose
- Glycosidic bonds are hydrolysed
Membrane-bound disaccharides: enzymes attached to cell membrane of epithelial cells lining ileum to help break down disaccharides into monosaccharides
54
How are lipids digested?
- Lipase is produced by pancreas & hydrolyses ester bonds in triglycerides
Bile salts: produced by liver & emulsify lipids which cause them to form small droplets (increases surface area of lipid for lipases to work on)
55
What are micelles?
- Water soluble formed from fatty acids, glycerol & monoglycerides
- Products of lipase digestion that remain in association with the bile salts to form structures
- Travel to the ileum where, upon contact with the surface of ileum epithelium cells, they are broken down
56
How are proteins digested?
- Broken down by combination of different proteases (or peptidases) which are enzymes that catalyse the conversion of proteins to amino acids by hydrolysing peptide bonds between amino acids
57
What are endopeptidases in protein digestion?
- Act to hydrolyse peptide bonds WITHIN a protein
- Eg: trypsin & chymotrypsin are synthesised in pancreas & secreted into small intestine
- Eg: pepsin is released into stomach by cells in stomach lining, only works in acidic conditions (provided by the hydrochloric acid in the stomach)
58
What are exopeptidases in protein digestion?
- Act to hydrolyse peptide bonds at the ENDS of protein molecules, they remove single amino acids from proteins
- Eg: dipeptidases (specifically dipeptides), they act to separate the 2 amino acids that make up a dipeptide by hydrolysing peptide bond between them
- Dipeptidases are often located in cell-surface membrane of epithelial cells in small intestine
59
Where are the products of digestion absorbed?
Across ileum epithelium into the bloodstream
60
How are monosaccharides absorbed?
- Glucose: absorbed by active transport & with sodium ions via co-transporter protein (same as galactose)
- Fructose: absorbed via faciliated diffusion through different protein
61
How are monoglycerides & fatty acids absorbed?
- Micelles help move them towards epithelium
- As micelles constantly break up & reform they can 'release' monoglycerides & fatty acids, allowing them to be absorbed
- Monoglycerides & fatty acids are lipid-soluble so diffuse directly across epithelium
62
How are amino acids absorbed?
- Via co-transport
- Sodium ions actively transported out of ileum epitheial cells into blood creating sodium ion concentration gradient
- They then diffuse from lumen or ileum into epithelial cells through transporter proteins, carrying amino acids with them
63
What is the structure of haemoglobin?
- Large protein with quaternary structure, each with polypeptide chain (4) which all have a haem group containing an iron ion
- Has high affinity for oxygen (each molecule can carry 4 oxygen molecules)
64
What is partial pressure of oxygen?
Measure of oxygen concentration (pO2)
65
How does haemoglobin saturation depend on the partial pressure of oxygen?
- Oxygen loads onto haemoglobin to form oxyhaemoglobin when there's a high pO2
- Oxyhaemoglobin unloads its oxygen when there's a low pO2
- Oxygen enters blood capillaries at alevoli (at high pO2) so oxygen unloads onto haemoglobin to form oxyhaemoglobin
- When cells respire, they used up oxygen (lowers pO2), red blood cells deliver oxyhaemoglobin to respiring tissues, where it unloads its oxygen
66
What is the dissociation curve?
Shows how saturated haemoglobin is with oxygen at any given pO2
67
How does the dissociation curve work?
- Where pO2 is high, haemoglobin has high affinity for oxygen, so has a high saturation of oxygen
- Where pO2 is low, haemoglobin has low affinity for oxygen, meaning it releases oxygen rather than combining with it
- Graph is 's-shaped' as when haemoglobin combines with it's first oxygen molecule, it's shape alters to make it easier for other molecules to also join. As haemoglobin gets saturated, it's harder for more oxygen molecules to join, so the graph has a steep area in middle (where it's easy for oxygen to join) and shallow areas at each end (where oxygen is harder to join)
68
What is the bohr effect?
- Haemoglobin gives up more oxygen more readily at higher partial pressure of carbon dioxide
- When cells respire they produce carbon dioxide, raising the pCO2
- This increases rate of oxygen unloading - so dissociation curve shifts right
- Saturation of blood with oxygen is lower for given pO2, meaning more oxygen is released
69
What is the circulatory system?
Specialised transport system to carry raw materials from specialised exchange organs to their body cells, made up of heart and blood vessels
70
What is a double circulatory system and what are its benefits?
Blood passes through heart twice on a single circuit
| Benefits: able to deliver nutrients at faster rate & has a larger capacity to get oxygen
71
What are the 2 types of double circulatory system?
Pulmonary: carries deoxygenated blood to lungs to pick up oxygen
Sytemic: carries oxygenated blood to body tissues
72
What is the role of arteries in the circulatory system?
- Carry blood from heart to rest of body
- Divide into smaller vessels (arterioles), which form a network throughout the body. Blood is directed to different areas of demand in the body by muscles inside arterioles, which contract to restrict or allow full blood flow
73
What is the structure of arteries and how does it relate to its function?
- Walls are thick & muscular & have elastic tissue to stretch & recoil as heart beats, maintaining high pressure
- Inner lining (endothelium) is folded, allowing artery to stretch which also helps maintain high pressure
- All except pulmonary carry oxygenated blood
74
What is the role of veins in the circulatory system?
- Take blood back to heart under low pressure
- Blood flow through veins is helped by contraction of body muscles surrounding them
- All veins carry deoxygenated blood (oxygen's been used up by body cells), except for pulmonary veins which carry oxygenated blood to heart from lungs
75
What is the structure of veins and how does it relate to its function?
- Wider lumen than arteries to carry large volume of blood from all around the body to heart
- Less smooth muscle and connective tissue, making the walls of veins thinner than arteries as blood in the veins has less pressure than in arteries
- Very little elastic or muscle tissue
- Contain valves to stop blood flowing backwards
76
What is the role of arterioles in the circulatory system?
- Branch into capillaries & distribute blood flow into capillary beds
- Substances are exchanged between cells & capillaries, so they're adapted for efficient diffusion
- Always found near cells in exchange tissues, so there's a short diffusion pathway
77
What is the structure of arterioles and how does it relates to its function?
- Smooth muscle around the arterioles are able to constrict which can limit the diameter of the vessel. As the vessel constricts the diameter becomes smaller and which controls the flow of blood through the body
- Walls only one cell thick which shortens diffusion pathway
- Large number of capillaries to increase surface area for exchange
78
What is tissue fluid?
- Fluid that surrounds cells in tissues, made from small molecules that leave blood plasma eg oxygen, water & nutrients
- Cells take in oxygen & nutrients from tissue fluid & release metabolic waste into it
- In a capillary bed, substances move out of capillaries into tissue fluid, by pressure filtration
79
What is pressure filtration process in the circulatory system?
1. At start of capillary bed, nearest the arteries, the hydrostatic (liquid) pressure inside capillaries is greater than hydrostatic pressure in tissue fluid
2. Difference in hydrostatic pressure means an overall outward pressure forces fluid out of capillaries and into spaces around the cells, forming tissue fluid
3. As fluid leaves, hydrostsatic pressure reduces in capillaries - so hydrostatic pressure is much lower at venule end (closest to veins) of capillary bed
4. Due to fluid loss & increasing concentration of plasma proteins, water potential at venule end of capillary bed is lower than water potential in tissue fluid
5. Meaning some water re-enters capillaries from tissue fluid at venule end via osmosis
80
Where does excess tissue fluid go?
Drained into lymphatic system (network of tubes acts like a drain), which transports excess fluid from tissues & dumps it back into circulatory system
81
What is hydrostatic pressure?
Heart creates this at arterial end of capillaries, causes tissue fluid to move out of blood plasma - stopped by 2 other forces:
1. Pressure of tissue fluid outside capillaries
2. Lower water potential of blood
Overall effect: fluid is pushed out of capillaries - called ultrafiltration
82
Which side of the heart pumps oxygenated blood and which side pumps deoxygenated blood?
Right side = pumps deoxygenated blood to lungs
| Left side = pumps oxygenated blood to body
83
What is the role of the left ventricle?
Chamber in the heart that receives oxygenated blood from the left atrium and pumps it out of the heart to the rest of the body
- Has thicker & more muscular walls than right ventricle as it needs to contract to pump blood around body (right ventricle is only to the lungs which is nearby)
84
What is the role of the right ventricle?
Chamber in the heart that receives deoxygenated blood from the right atrium and pumps it out of the heart to the lungs for reoxygenation
85
Why do ventricles have thicker walls than atria?
As they push blood out of heart whereas atria pushes blood short distance into ventricles
86
What is the role of the atrioventricular valves?
Link atria to ventricles to stop blood flowing back into atria when ventricles contract
87
What is the role of the semi-lunar valves?
Link ventricles to pulmonary artery & aorta, and stop blood flowing back into heart after ventricles contract
88
What is the aorta?
Main artery that carries oxygenated blood away from the heart at high pressure
89
What is the atrium?
Type of chamber in the heart which receives blood directly from a vein and passes it on to a ventricle
90
What is the coronary artery?
Main artery that supplies the heart tissue with blood
91
What is the role of the left atrium?
Chamber in the heart that receives oxygenated blood from the pulmonary vein and passes it on to the left ventricle
92
What is the pulmonary artery?
Main artery that carries deoxygenated blood from the heart to the lungs for reoxygenation
93
What is the pulmonary vein?
Main vein that carries oxygenated blood away from the lungs and back to the heart
94
What is the renal artery?
Main artery that carries oxygenated blood to the kidneys from the heart
95
What is the renal vein?
Main vein that carries deoxygenated blood away from the kidneys back to the heart
96
What is the role of the right atrium?
Chamber in the heart that receives deoxygenated blood directly from the vena cava and passes it on to the right ventricle
97
What is the vena cava?
Main vein that carries deoxygenated blood into the right atrium of the heart
98
What is a vein?
Type of blood vessel that carries blood into the heart from other parts of the body
99
What is a ventricle?
Type of chamber in the heart which receives blood from the atrium above it and pumps it out of the heart
100
What is the process of the cardiac cycle?
1. Diastole:
- Entire heart is relaxed
- Both atria & ventricles relaxed & blood enters at low pressure through veins, pulmonary vein and vena cava into the atria
- As the blood flows in the atria, blood pressure begins to increase causing the AV valves to open allowing for blood to enter ventricles
- Semi-lunar valves remain closed
2. Atrial systole:
- Heart is full of blood & ventricles are relaxed
- Atria contracts to ensure all the blood is emptied from the atria and enters the ventricles
- This causes the pressure within ventricles to increase shutting the AV valves, to prevent the backflow of blood back to the atria
3. Ventricular systole:
- Atria relax
- Ventricles contract & pressure further increases in the ventricles above the pressure within the arteries (pulmonary arteries and aorta) causing atrioventricular valves
- Due to the pressure change, blood is able to flow out through the semi-lunar valves and allows for the blood to leave to flow into arteries
101
What is cardiac output?
Amount of blood pumped around body, depends on 2 factors:
- Stroke volume: volume of blood pumped by left ventricle in each heart beat
- Heart rate: number of times the heart beats per minute
102
How do you calculate cardiac output?
Cardiac output = stroke volume x heart rate
103
What is sino-artrial node?
- Special cardiac muscle tissue in right atrium, aka SAN or pacemaker
- Sets rhythm at which all other cardiac muscles beat
- Sends excitation wave (depolarisation) over atrial walls
104
What is an electrocardiogram?
Record of wave of electrical activity caused by atrial systole, ventricular systole and the start of ventricular diastole
105
What are the features of an electrocardiogram?
- P wave: wave of depolarisation that spreads from SAN across atria and which causes atrial systole
- PR interval: time taken for wave of depolarisation to be conducted from SAN to ventricles via AVN measured from start of P wave to start of QRS complex
- QRS complex: wave of depolarisation that spreads across ventricles and which causes ventricular systole
- T wave: repolarisation of ventricles during diastole
106
What is cardiovascular disease?
Disease associated with heart & blood vessels, usually a build-up of fatty deposits inside arteries
107
How does cardiovascular disease start with an atheroma formation?
- If damage occurs to endothelium (inner lining of artery), white blood cells & lipids from blood clump together under the lining to form fatty streaks
- Over time, more white blood cells, lipids & connective tissue builds up & hardens to form a fibrous plaque (atheroma) which partially blocks lumen of artery & restricts blood flow = blood pressure increases
108
What are the 2 types of disease which affects arteries?
- Aneurysm: balloon-like swelling of artery
1. Atheroma plaque damages & weakens arteries & narrows them which increases blood pressure
2. When blood travels through weakened artery at high pressure, it may push inner layers of artery through outer elastic layer to form swelling - aneurysm
3. Aneurysm may burst, causing haemorrhage (bleeding)
- Thrombosis: formation of blood clot
1. Atheroma plaque can burst through endothelium (inner lining) of artery
2. This damages artery wall & leaves a rough surface
3. Platelets & fibrin (protein) accumulate at site of damage & form blood clot (thrombosis)
4. Blood clot can cause blockage or artery or can become dislodged & block blood vessel
5. Debris from burst can cause another blood clot to form further down artery
109
How does a myocardial infarction (heart attack) occur?
- If coronary artery becomes blocked, an area of heart muscle will cut off from its blood supply, receiving no oxygen & causing myocardial infarction
- Heart attack can cause damage & death or heart muscle
- If large areas of heart are affected, complete heart failure can occur which is often fatal
110
How does high blood cholesterol increase risk of cardiovascular disease?
- Cholesterol = one of main components of fatty deposits that form from atheromas
- Atheromas can lead to increased blood pressure & blood clots, which could block flow of blood to coronary arteries, causing myocardial infarction
111
How does a poor diet increase risk of cardiovascular disease?
- Diet in high saturated fat = higher cholesterol levels
| - Diet in high salt = increases risk of high blood pressure
112
How does smoking increase risk of cardiovascular disease?
- Nicotine & carbon monoxide increase risk, nicotine increases risk of high blood pressure
- Carbon monoxide combines with haemoglobin & reduces amount of oxygen transported in blood = reduces amount of oxygen available to tissues. If heart muscle doesn't receive enough oxygen, can lead to heart attack
- Smoking also decreases amount of antitoxins in blood (which are important for protecting cells from damage. Cell damage to coronary artery wall is more likely)
113
How does high blood pressure increase risk of cardiovascular disease?
- Increases risk of damage to artery walls so increases risk of atheroma formation
- Atheroma can also cause blood clots, which could block flow of blood to heart muscle, possibly leading to myocardial infarction
114
What is the role of xylem tissue in plants?
Transports water & mineral ions in solution, these substances move up plant from roots to leaves
115
What is the role of xylem vessels in plants?
- Part of xylem tissue that transports water & ions
- Very long, tube-like structures formed from dead cells joined end to end
- Have no end walls, making an uninterrupted tube allowing water to pass through middle easily
116
What is the cohesion tension theory in the transport in plants?
Water moves up plant against gravity, cohesion & tension help move water up plant
1. Water evaporates from stomata in leaves, lowering water potential of leaf cells
2. Creates tension which pulls more water into leaf
3. Water molecules = cohesive, meaning they stick together due to hydrogen bonds. This means a whole column of water in xylem moves upwards from roots to plants
4. Also adhesion of water molecules to walls of xylem
117
What is transpiration in the transport in plants?
Loss of water from plants surface
1. Water accumulates in spaces between cells in leaf
2. When stomata open (during day), water moves out of leaf via stomata down concentration gradient
118
What factors affect the rate of transpiration in the transport in plants?
- Temperature: higher the temperature, faster transpiration. Warmer water molecules = more energy so evaporate from cells faster. Increases concentration gradient = faster diffusion
- Light: the lighter it is means faster transpiration. Stomata open when light lets in CO2 for photosynthesis. When its dark, stomata are closed so little transpiration
- Humidity: lower the humidity, faster transpiration. If air around plant is dry, concentration gradient between leaf & air is increased, increasing transpiration rate
- Wind: the winder it is, faster transpiration. Lots of air movement blows away water molecules from around stomata which increases concentration gradient so increases transpiration rate
119
What is a potometer and how is it used?
Special piece of apparatus used to estimate transpiration rates by measuring water uptake by plant
1. Cut shoot underwater to prevent air entering xylem
2. Place shoot sealed into capillary tube
3. One air bubble is introduced
4. Record start position of air bubble in the graduated capillary tube
5. Using stopwatch, record pipette readings every 10 mins
6. Rate of bubble movement is an estimate of rate of transpiration
- Only change 1 variable (eg temp) & keep others constant
120
What is the role of the phloem in transport in plants?
Carries solutes (dissolved sugars) up or down the plant
121
What are sieve tube elements?
Living cells that form tube for transporting solutes
122
What is a companion cell?
For each sieve tube element, they carry out living functions for sieve cells
123
What is the process of translocation in the transport in plants?
Movement of solutes in phloem
- Energy required process, moves solutes from 'source to sink'
- 'Source' of a solute = where it's made, 'sink' = area where it's used up
- Enzymes maintain concentration gradient from 'source to sink' by changing the solutes at the sink. This makes sure there's always a lower concentration at the sink than the source
124
What is the mass flow hypothesis?
- Active transport is used to load sucrose into sieve tube cells from companion cells, this will lower water potential
- The high concentration of sucrose (low water potential) in sieve tube cells of phloem causes water to move in via osmosis from xylem, which raises pressure in cell
- At the sink, the sugar concentration drops as solutes are used up. This increases the water potential inside so water moves out via osmosis, this also means the pressure is decreased in the sieve tubes
- This difference in pressure causes a pressure gradient, so the movement is always from source to sink
