Topic 3 - Organisms exchange substances with their environment Flashcards
why do single celled organisms use diffusion, and diffusion alone, to provide their nutrients ?
As the diffusion pathway is short
What do Multicellular organisms require to provide all of their cells with the nutrients they need??
transport systems and specialised exchange surfaces
Why do organisms with higher metabolic rates need an increased diffusion rate?
They exchange more mterials
What happens to the SA:V ratio as the object becomes bigger?
The ratio of surface area: volume ratio falls
Small organisms has a ____ SA:V ratio and exchange ____ with the _____
.Large
.Directly
.Surface
Larger organisms has a ____ SA:V, and they need _______ exchange surfaces to meet the organisms demands
.Smaller
.Specialist
Give an example of a larger organisms specialist exchange surface
Mass transport system, to deliver and remove material
Sphere surface area formula
4 x Pi x r^2
Sphere volume formula
(4/3) x Pi x r^3
If a gas exchange surface is efficient at gas exchange, what else is it efficient at?
an efficient water loss surface
How do insects limit water loss?
.Rigid exoskeleton – chitin, waterproof cuticle
.Small SA:V ratio – minimises water loss area
.Spiracles – open and close to prevent water loss
What is the tracheal system?
The tracheal system is a system of tubes in insects that supply muscles with oxygen directly
Trachea divide into
tracheoles
Tracheoles branch throughout
the body tissues of the insect
What are spiracles and what do they do?
Spiracles are tiny pores at the end of the trachea
Allow respiratory gases in and out of the insect
Valves control the opening/closure of the spiracle
When open, water can evaporate out of the spiracle
Closed most of the time
Only open to allow gas exchange
Limitations of the tracheal system?
.Relies on diffusion rather than a transport system
.For diffusion to be adequate the diffusion distance must be short
.This limits the size that insects can grow to
Describe and explain the diffusion gradients in the tracheal system
.During respiration, O2 is used
.O2 at tracheole ends falls
.Creates a diffusion gradient
.O2 diffuses from atmosphere along the tracheas and tracheoles to the cells
.CO2 is produced by respiring cells
.Diffusion gradient in opposite direction
.CO2 diffuses out of the tracheoles and into the atmosphere
Describe and explain muscle contractions in the tracheal system
.Abdominal pumping
.Contraction of insect muscles
.Trachea ‘squeezed’ and reduced in volume
.Some air will be expelled from the trachea
.Common in larger insects
.Uses energy
Describe and explain water in the tracheoles
.Anaerobic respiration produces lactate
.Lactate is water soluble so lowers water potential of muscles cells
.Water moves into muscle cells from tracheoles
.Volume in the tracheole ends decreases, drawing air in
What is a dicotyledonous?
.(dye coto lee denous)
.Flowering plants
.The seed bears two cotyledons (seed leaves)
What gases are important in plants?
CO2 and O2
Photosynthesis equation
6CO2 + 6H2O C6¬H12O6 + 6O2
Aerobic respiration equation
C6¬H12¬O6 + 6O2 6CO2 + 6H2O + ATP
Why do plants leaves have a large SA?
greater surface for diffusion to take place
Why are plants leaves thin?
Short diffusion pathway
Why are plants leaves membranes selectively permeable?
Control what goes in and out of the cell
Why do plants leaves have a large diffusion gradient?
Increased rate of diffusion
What reactions happen in a plant at night?
Respiration
\What reactions happen in a plant in the day?
Respiration and photosynthesis
What parts make up a plant leaf?
- Waxy cuticle
- Upper epidermis
- Palisade mesophyll cells
- Spongy mesophyll cells
- Sub-stomatal air space
- Lower epidermis cells
- Stomata
- Guard cells
- Sheath
- Phloem
- Xylem
How does a stomata facilitate efficient exchange?
Small pores, allow gases in and out, all cells are close to a stomatal pore therefore there is a short diffusion pathway
How do the air spaces facilitate efficient exchange?
Interconnected air spaces throughout the mesophyll layer so gases can move around mesophyll cells
How does the spongy mesophyll layer facilitate efficient exchange?
Large surface area of mesophyll cells allow for maximum diffusion
What happens to the stomata during the day? Why?
Open during the day, as photosynthesis is occurring it needs to allow the CO2 in and O2 out and water vapour out
What happens to the stomata during the night? Why?
Closed during the night, no photosynthesis so no need for CO2
Name the parts of a plant cell
- Nucleus
- RER
- Ribosomes
- Cell wall
- Golgi apparatus
- Chloroplast
- Mitochondria
- Cell membrane
- Vacuole
- Amyloplast (produces and stores starch)
- SER
Where are gills found?
Behind the fishes head
What are gills made up of?
Gill filaments
How are gill filaments arranged?
Stacked up in piles
What are perpendicular to the gill filaments?
Gill lamellae
What do gill lamellae do?
Increase gill SA
Describe the movement of water in a fishes gas exchange system
.Water is taken in through the mouth, forced over the gills, and out through the opening on each side of the body
What is countercurrent flow?
.The flow of water over the gill lamellae and the flow of blood within them are in opposite directions, this is known as countercurrent flow
Why is countercurrent flow important in fish?
.This means the maximum possible gas exchange can be achieved, if the water and blood flowed in the same direction, far less gas exchange would take place
How does countercurrent flow work?
- Blood that is already well loaded with oxygen meets water which has its maximum concentration of oxygen, therefore diffusion of oxygen from the water to the blood takes place
- Blood with little oxygen in it meets water which has had most, but not all, oxygen removed, so diffusion of oxygen from the water to the blood takes place
What does countercurrent exchange principle mean for the diffusion gradient?
a diffusion gradient for oxygen uptake is maintained across the entire width of the gill lamellae
In countercurrent flow, how much oxygen from the water is absorbed into the blood of the fish?
about 80% of the oxygen available in the water is absorbed into the blood of the fish
What would happen if there was parallel flow in fish?
.If the flow of water and blood had been the same in the same direction (parallel flow), the diffusion gradient would only be maintained across part of the length of the gill lamellae and only 50% of the available oxygen would be absorbed by the blood
Why are gills good exchange surfaces?
.High SA
.Good blood supply
.countercurrent flow
Why do plants rely on the transpiration stream? How is it made?
.Plants rely on the transpiration stream to transport water from their roots to their leaves
.The transpiration stream is created as water is evaporated from the surface of the leaf
What are xerophytes?
Plants adapted to living in areas with a short supply of water
How do plants prevent water loss?
A thick cuticle, rolled up leaves, sunken stomata, hairs on leaves, reduced SA:V ration
How does a a thick cuticle prevent water loss?
Waxy cuticle acts as a waterproof barrier
How do rolled up leaves prevent water loss?
Stomata on lower epidermis protected/trap still air
Traps water vapour so high water potential
No water potential gradient between plant and air
How does a sunken stomata prevent water loss?
Traps still, moist air next to the lead surface
Lower water potential gradient
How does having hairs on leaves prevent water loss?
Traps still, moist air next to leaf surface
Lower water potential gradient
How does having a reduced SA:V ratio prevent water loss?
Slower rate of diffusion
Still able to photosynthesise
Respiration equation
C6H12O6 + O2 CO2 + H2O + ATP
Name components of the lungs
- Lung
- Nasal cavity
- Bronchiole
- Alveoli
- Intercostal muscles
- Ribs
- Diaphragm
- Lung
- Bronchus
- Trachea
- Bronchus
Features of lungs
Lobed structures
Features of trachea
Flexible airway supported by cartilage rings
.Muscular walls lined with ciliated epithelium and goblet cells
Features of bronchi
Trachea splits into two bronchi
.Large bronchi are supported by cartilage rings
.Lined with ciliated epithelium and goblet cells
Features of bronchioles
.Subdivisions of bronchi
.Muscular walls lined with epithelium cells
.Can constrict to control air flow
Where are alveoli and what are they?
Alveoli are located at the end of bronchioles. They are the site of gas exchange in mammals. Tiny air sacs (100-300 um).
Why are lungs on the inside?
If they were on the outside they would dry out and get damaged
How many alveoli do we have?
300 mil
How much SA does the alveoli have?
70m^2
What are alveoli lined with?
epithelial cells
Why are alveoli good surfaces for gas exchange?
- Short diffusion pathway (one cell thick), large SA, constant concentration gradient maintained through good blood supply, red blood cells slowed down and flattened against capillary wall
What is breathing/ventilation?
the constant movement of air into and out of the lungs
What is respiration?
the chemical process of using glucose and oxygen to produce carbon dioxide and ATP while releasing energy
Define inspiration
pressure outside the lungs is greater than inside, air moves in
Define expiration
pressure inside the lungs is greater than outside, air forced out
Muscles involved in ventilation/breathing?
- Internal intercostal muscles
- External intercostal muscles
- Diaphragm
How does a bell jar work?
.The rubber sheet moves down, the volume in the bell jar increases so the pressure in the bell jar decreases, the pressure inside the bell jar is greater than outside, air moves in via the balloons and inflates them
Explain how inspiration works?
.External intercostal muscles contract, internal intercostal muscles relax
.Rib cage pulled up and out
.Increases volume of thorax
.Diaphragm muscles contract and diaphragm moves down
.Increases volume in thorax further and reduces pressure inside
.Atmospheric pressure is now greater than pulmonary pressure
.Air is forced into lungs
Explain how expiration works?
.External intercostal muscles relax, internal intercostal muscles contract
.Rib cage pushed down and in
.Decreased volume of thorax
.Diaphragm muscles relax and diaphragm moves up
.Decreases volume in thorax further and increases pressure inside
.Atmospheric pressure is now less than pulmonary pressure
.Air is forced out of the lungs
Is inspiration passive or active?
Active
Is expiration passive or active?
Passive
Define tidal volume
The volume of air inhaled and exhaled in normal breath
Define expiatory reserve volume
Volume of a maximum exhalation after normal exhalation
Define residual volume
Volume remaining in the lune after maximum exhalation
Define inspiratory reserve volume
Additional volume that can be inhaled after inhalation of tidal volume
Define vital capacity
maximum volume of exhalation after lungs are maximally filled
Pulmonary ventilation rate equation with units
Pulmonary ventilation rate (dm3min-1) = tidal volume (dm3) x breathing rate (min-1)
Name the 4 main lung diseases we need to know about
Pulmonary fibrosis, tuberculosis, asthma, emphysema
Describe pulmonary fibrosis
.Scaring forms on the epithelium lining of the lungs
.This causes the lining to thicken
.This reduces the amount of oxygen able to diffuse across the membrane and into the blood
also
.The volume of air entering the lungs is also reduced
.A healthy lung is elastic allowing it to spring back into shape, expelling air
.Fibrosis reduces the elasticity of the lungs, making it more difficult to breathe out
.This inhibits ventilation
Symptoms of pulmonary fibrosis
Shortness of breath, especially when exercising
Chronic, dry cough
Pain and discomfort in the chest
Weakness and fatigue
How does pulmonary fibrosis cause shortness of breath, especially when exersizing?
.Fibrosis tissue occupies space in the lung
.This reduces the air space available
.less air=less oxygen
.oxygen in high demand during exercise, breathing more, but can’t get the oxygen needed
How does pulmonary fibrosis cause a chronic, dry cough?
.The fibrosis tissue causes an obstruction in the lung
.The body attempt to remove it by coughing, but it won’t move
.So you are always coughing
How does pulmonary fibrosis cause pain and discomfort in the chest?
The mass of fibrosis tissue causes pressure, leading to pain
.Discomfort leads to more coughing which causes more scaring
How does pulmonary fibrosis cause weakness and fatigue?
.Respiration reduced due to lack of oxygen
Describe tuberculosis?
.Formation of small hard lumps called tubercles in lungs
.Stimulation of the white blood cells to fight these results in scar tissue
.Can lay dormant
Cause of tuberculosis
A bacteria
Symptoms of tuberculosis
Persistent cough Fatigue Loss of appetite High temperature Chest pains Fever Coughing up blood
Describe asthma
The cells of the epithelial lining secrete larger quantities of mucus than normal
The muscles surrounding the bronchioles contract and so constricts the airways
How many people does asthma affect?
10% of world population
Kills 2000 people in the UK each year
Cause of asthma
Localised allergic reaction Common allergens include: .Pollen .Animal fur .Faeces of house dust mites Allergens stimulate WBC found in the lining of the bronchi and bronchioles to release histamine Histamine causes: .Inflammation Lining of airways becomes inflamed
Symptoms of asthma
Difficulty breathing
Wheezing
Tightness in chest
Coughing
Describe emphysema
Loss of elasticity preventing expansion and contraction
Common in smokers
The lungs have been permanently stretched
So no longer able to expel all of the air from the alveoli
Some alveoli burst, the surface area of alveoli reduced, little gas exchange occurs
Cause of emphysema
smoking
symptoms of emphysema
Shortness of breath
Chronic cough
Bluish skin
Name the parts of the digestive system
- Tongue
- Salivary gland
- Lobe of liver
- Gall bladder
- Traverse limb of the large intestine
- Ascending limb of the large intestine
- Salivary gland
- Oesophagus
- Stomach
- Pancreas
- Small intestine
- Descending limb of the large intestine
- Rectum
- Anus
What is digestion?
Digestion is the process in which large molecules are hydrolysed by enzymes into small molecules which can be absorbed and assimilated.
What does the oesophagus do?
The oesophagus carries food from the mouth to the stomach
What is the stomach?
a muscular sac with an inner layer that produces enzymes
What is the role of the stomach?
to store and digest food, especially proteins. It has glands that produce enzymes which digest proteins
What is the ileum?
a long muscular tube
What happens in the ileum?
Food is further digested in the ileum by enzymes that are produced by its walls and by glands that pour their secretions into
How is the ileum adapted for its purpose of absorbing the products of digestion into the blood stream?
The inner walls of the ileum are folded into villi, which gives them a large surface area. The surface area of these villi is further increased by millions of tiny projections, called microvilli, on the epithelial cells of each villus.
What does the large intestine do?
Absorb water
Most of the water that is absorbed is water from the secretions of the many digestive glands
What happens in the rectum?
rectum is the final section of the intestines. The faeces are stored here before periodically being removed via the anus in a process called egestion
Where are the salivary glands?
Near the mouth
What does the salivary glands do?
They pass their secretions via a duct into the mouth. These secretions contain the enzymes amylase, which hydrolyses starch into maltose
What is the pancreas?
a large gland situated below the stomach
What does the pancreas do?
The secretion contains proteases to hydrolyse proteins, lipase to hydrolyse lipids and amylase to hydrolyse starch
What are the two stages of digestion in humans?
- Physical breakdown
2. Chemical digestion
What is physical breakdown and why does it happen?
If food is large it is broken down by means of structures like the teeth into smaller pieces. This not only makes it possible to ingest the food but also provides a large surface area for chemical digestion. Food is churned by the muscles in the stomach wall and this also physically breaks it up.
What happens in chemical digestion?
Hydrolyses large insoluble molecules into smaller soluble ones
What carries out chemical digestion?
Enzymes
How do all enzymes function?
Hydrolysis
What is hydrolysis
the splitting up of molecules by adding water to the chemical bonds that hold them together
How does one molecules hydrolysis from enzymes usually work?
Usually one enzyme hydrolyses a large molecule into sections, and these sections are then hydrolysed into smaller molecules by one or more additional enzymes
What are the different types of digestive enzymes and their reactions?
- Carbohydrase’s hydrolyse carbohydrates to monosaccharides
- Lipases hydrolyse lipids (fats and oils) into glycerol and fatty acids
- Proteases hydrolyse proteins to amino acids
Where is the enzyme amylase produced?
The mouth and pancreas
What does amylase do?
Amylase hydrolyses the alternate glyosidic bonds of the starch molecules to produce the disaccharide maltose
What does the disaccharade maltase do?
maltose is in turn hydrolysed into the monosaccharide a-glucose by it
What is maltase produced by?
The lining of the ileum
What is the full process of carbohydrate digestion in humans?
- Saliva enters the mouth from the salivary glands and is thoroughly mixed with food when chewing
- Saliva contains salivary amylase, this starts hydrolysing any starch in the food to maltose. It also contains mineral salts which help to maintain the pH at around neutral.
- The food is swallowed and enters the stomach, where the conditions are acidic, this acid denatures the amylase and prevents further hydrolysis of the starch
- After a time the food is passed into the small intestine, where it mixes with the secretion from the pancreas called the pancreatic juice
- The pancreatic juice contains pancreatic amylase, this continues the hydrolysis of any remaining starch to maltose, alkaline salts are produced by both the pancreas and intestinal wall to maintain the pH at around neutral so that the amylase can function
- Muscles in the intestine wall push the food along the ileum, its epithelial lining produces the disaccharide maltase, the maltase hydrolyses the maltose from starch breakdown into a-glucose.
What is the optimum pH for amylase?
Neutral
Why is maltase referred to as a membrane bound disaccharidase?
It is not released into the lumen of the ileum but is a part of the cell surface membranes of the epithelial cells that line the ileum
Where is sucrose found?
in many natural foods, especially fruits.
Where is lactose found?
in milk and hence any milk products
What does sucrase do?
hydrolyses the single glyosidic bond in the sucrose molecule, this hydrolyses produces the two monosaccharides glucose and fructose.
What does lactase do?
hydrolyses the single glyosidic bond in the lactose molecule, this hydrolysis produces the two monosaccharides glucose and galactose.
What are lipids hydrolysed by?
Enzymes called lipases
What are lipases?
enzymes produced in the pancreas that hydrolyse the ester bond found in triglycerides to form fatty acids and monoglycerides
What is a monoglyceride?
a glycerol molecule with single fatty acid molecule attached
What is emulsification and why does it happen?
Lipids (fats and oils) are firstly split up into tiny droplets called micelles by bile salts, which are produced by the liver
.This process is called emulsification and increases the surface area of the lipids so that the action of lipases is sped up
What are proteins hydrolysed by?
a group of enzymes called peptidases (proteases)
What do endopeptidases do?
hydrolyse the peptide bonds between amino acids in the central region of the peptide molecule forming a series of peptide molecules
What do exdopeptidases do?
hydrolyse the peptide bonds on the terminal amino acids of the peptide molecules formed by the endopeptidases. In this way they progressively release dipeptides and single amino acids
What do dipeptidases do?
hydrolyse the bond between the two amino acids of a dipeptide. Dipeptidases are membrane bound, being part of the cell surface membrane of the epithelial cells lining the ileum
What helps maintain the neutral pH for amylase?
Saliva contains mineral salts that maintain the neutral pH for amylase
How is protease kept at the right pH?
Stomach produces hydrochloric acid which provides an acidic pH for protease
What allows amylase to function after the stomach, how?
Alkaline salts are produced by the pancreas and intestinal wall to neutralise stomach acid and allow amylase to function
.Bile salts produced by the liver and released/stored in the gall bladder also helps as it is alkaline
Describe the structure of bile salts
.One end is soluble in fat (lipophilic) but not in water (hydrophobic)
.The other side is insoluble in fat (lipophobic) but soluble in water (hydrophilic)
Describe the process of the absorption of triglycerides
.Lipid mixed with bile salts
.This forms micelles
.Monoglycerides and fatty acids releases
.Monoglycerides and fatty acids are absorbed through the membrane of the ileum
.Monoglycerides and fatty acids are converted back to triglycerides in the endoplasmic reticulum
.Triglycerides are packaged into chylomicrons
.Chylomicrons released by exocytosis
.Chylomicrons go into lymphatic vessels and then into the blood stream
What are chlymicrons?
Small milky globules
.A small fat globule composed of proteins (1-2%) and lipid
.They transport fat from the intestines to the liver and to adipose (fat) tissue
.After a fatty meal, the blood is so full of chylomicrons that it looks milky
.The chylomicrons are synthesised in the mucosa (the lining) of the intestine
Define mass transport
the bulk movement of materials from exchange surfaces to the cells throughout the organism
What do efficient transport systems have?
- A suitable transport medium o Normally liquid but can be a gas o Materials (oxygen, waste) can dissolve - Closed system of tubular vessels o Contains or holds the medium o Forms branching to all parts of the organism o Ensures medium is close to cells - Mechanisms for movement of tissue fluid o Generates pressure o Enables the medium to move
What is the circulatory systems transport medium, tubular vessels and mechanisms for movement of tissue fluid?
Blood, veins/arteries/capillaries and heart
What type of muscle is the heart?
A cardiac muscle
What is the heart?
An organ in the circulatory system
The heart is myogenic, what does this mean?
It naturally contracts and relaxes
Describe our circulatory system
Double
How is the heart apart of a double circulatory system?
Blood passes the heart twice, through two different circuits
In the circulatory system, what is circuit one?
links the heart and the rest of the body
In the circulatory system, what is circuit two?
links the heart with the lungs
Name the parts of the heart
- Right atrium
- Right ventricle
- Left atrium
- Left ventricle
- Pulmonary artery
- Aorta
- Superior vena cava
- Inferior vena cava
- Pulmonary vein
- Septum
- SAN node
What is the SAN node
the hearts pace maker, initiates an electrical wave of electricity
How do the coronary arteries maximise mass transport?
- Coronary arteries supply the heart with the oxygen it requires, the oxygen is needed so that the heart can contract and pump blood around the bod
How does the wall thickness of the heart maximise mass transport?
left ventricle wall is much thicker to produce necessary pressure, since it is thicker it can contract much stronger, this increases the pressure so the blood can travel around the entire body
How do the valves of the heart maximise mass transport?
open and close between atriums and ventricles as well as ventricles and vessels to help produce necessary pressure and prevent backflow. This also generally builds pressure in the blood
What are the 3 heart valves and where are they?
- Semi-lunar valves (between ventricle and vessel)
- Left atrioventricular valve (tricuspid valve) between left atrium and left ventricle
- Right atrioventricular valve (bicuspid valve) between right atrium and right ventricle
Describe the opening and closing of valves?
- Pressure is higher where concave (as ventricle fills with blood)
- Pushes the flexible, fibrous tissues together
- Tissues form a tight fit with no gap
- Prevents the backflow of blood (back into the atrium)
- Pressure is higher above the valve
- Pushes the flexible fibrous tissues apart
- Causes opening for blood to travel (from high to low pressure) into the ventricle
What causes the hearts beat sound?
The opening and closing of valves
Advantages of biological valve replacements
Cows are in high supply
Fairly well tested
Fewer long term issues
Disadvantages of biological valve replacements
Unethical to use cows
Not suitable for all
Can need replacing
What is systole?
contraction
What is diastole?
relaxation
What happens in ventricular systole?
ventricle completely full, forces tricuspid and bicuspid valves to close, forces semi-lunar valve to open, pushes blood out of the heart
What happens in atrial systole?
pushes last bit of blood into ventricle, ventricular diastole occurs in this stage
What happens in ventricular and atrial diastole?
They relax, makes up the majority of the cycle, blood movement is aided by gravity
What is haemoglobin
A respiratory pigment used to transport oxygen
What type of molecule is haemoglobin?
A protein
Why is haemoglobin needed?
as oxygen has a low solubility in water
Describe the structure of haemoglobin
Each haemoglobin has beta polypeptides, alpha polypeptides and four haem groups (1 per polypeptide chain) which contain a ferrous ion (Fe2+)
Each haem group carries one O2 molecule
What is haemoglobin called when it is combined with oxygen?
oxyhaemoglobin
What must haemoglobin do to be efficient?
- Readily associate with oxygen at the exchange surface
2. Readily dissociate with oxygen at the tissues
Define affinity
the attractive force binding atoms in molecules, chemical attraction
What is high affinity with haemoglobin?
high attractive force, readily associates with O2
What is low affinity with haemoglobin?
take up less O2 (lower association) but release more readily (easily disassociation)
In the body, where is oxygen affinity high and low?
High in exchange surfaces (lungs) and low in respiring tissues (muscles)
How does affinity change?
1. The environment: .How much oxygen is available .Partial pressure of oxygen 2. Metabolic rate: .How much oxygen is required by the organism
What is partial pressure of oxygen?
.The amount of gas present in a mixture of gases
.Measured in kilopascals (kPa)
If the environment has a low concentration (partial pressure) of oxygen:
- Need haemoglobin to hold onto oxygen
- High affinity for oxygen
- Hold onto oxygen tightly
BUT - Means oxygen will not be used up as readily
- Organisms have a low metabolic rate
If the environment has a high concentration (partial pressure) of oxygen:
- Oxygen is readily available
- Do not need to hold on to oxygen
- Low affinity for oxygen
SO - Oxygen dissociates easily
How does partial pressure differ throughout the body?
.High at exchange surfaces
.Low at muscles, where it has been used to respire
How does haemoglobin change how it works in different pO2 levels?
Low pO2, difficult to attach the first O2
Medium pO2, changed shape means it can easily associate (disrupt bonds in the structure)
High pO2, fewer binding sites so difficult to fully saturate
What is an oxygen dissociation curve
Relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen
Drawn an oxygen dissociation curve
IDK Chec your notes
Describe oxygen dissociation curve
The higher the pO2 the more saturation of haemoglobin with oxygen. At low pO2, the rate of increase of saturation of haemoglobin with oxygen is low, then it speeds up as pO2 increases, before again slowing as pO2 reaches large values.
Explain oxygen dissociation curve
At low pO2, the rate of increase of saturation of haemoglobin with oxygen is low as it is initially difficult to attach the first O2. The rate of increase of saturation of haemoglobin with oxygen increases as the changed shape of the haemoglobin means it can easily associate (disrupt bonds in the structure). The rate of increase of saturation of haemoglobin with oxygen slows again as pO2 reaches large values, because the fewer binding sites make it difficult to fully saturate.
What does a shift to the left on an oxygen dissociation curve mean?
= higher O2 affinity
High saturation at lower PP
What does a shift to the right on an oxygen dissociation curve mean?
= lower O2 affinity
High saturation at higher PP
What is the Bohr Effect?
Haemoglobin has a reduced affinity for oxygen in the presence of carbon dioxide. The greater the concentration of carbon dioxide, the more readily the haemoglobin releases it
Why does the behaviour of haemoglobin change in different regions of the body?
The Bohr Effect
Describe and explain the behaviour of haemoglobin at the gas exchange substance (lungs)?
- At the gas exchange surface (lungs), the level of carbon dioxide is low because it diffuses across the exchange surface and is expelled from the organism. The affinity of haemoglobin for oxygen is increased, which, coupled with the high concentration of oxygen in the lungs, means that oxygen is readily loaded by haemoglobin. The reduced carbon dioxide level has shifted the oxygen dissociation curve to the left.
Describe and explain the behaviour of haemoglobin at rapidly respiring tissues (muscles)?
- In rapidly respiring tissues (muscles), the level of carbon dioxide is high. The affinity of haemoglobin for oxygen is reduced, which, coupled with the low concentration of oxygen in the muscles, means that oxygen is readily unloaded from the haemoglobin into the muscle cells. The increased carbon dioxide level has shifted the oxygen dissociation curve to the right.
Why is it that the greater the concentration of carbon dioxide, the more readily haemoglobin releases its oxygen?
Because dissolved carbon dioxide is acidic and the low pH causes haemoglobin to change shape.
Describe and explain the loading, transporting and unloading of oxygen
- At the gas exchange surface carbon dioxide is constantly being removed
- The pH is raised due to the low level of carbon dioxide
- The higher pH changes the shape of haemoglobin into one that enables it to load oxygen readily
- This shape also increases the affinity of haemoglobin for oxygen, so it is not released while being transported in the blood to the tissues
- In the tissues, carbon dioxide is produced by respiring cells
- Carbon dioxide is acidic in solution, so the pH of the blood within the tissues is lowered
- The lower pH changes the shape of haemoglobin into one with a lower affinity for oxygen
- Haemoglobin releases its oxygen into the respiring tissues
Explain the statement, ‘The more active a tissue, the more oxygen is unloaded’
The higher rate of respiration the more carbon dioxide the tissues produce - the lower pH the greater the haemoglobin shape change the more readily oxygen is unloaded the more oxygen is available for respiration
Why is the loading, transporting and unloading of oxygen important?
This means that there is a flexible way of ensuring that there is always sufficient oxygen for respiring tissues.
Why is the blood returning to the lungs usually only 75% saturated?
In humans, haemoglobin normally becomes saturated with oxygen as it passes through the lungs. In other words, most of the haemoglobin molecules are loaded with their maximum four oxygen molecules. When this haemoglobin reaches a tissue with a low respiratory rate, only one of these molecules will normally be released. The blood returning to the lungs will therefore contain haemoglobin that is still 75% saturated with oxygen.
If a tissue is very active (an exercising muscle) then how many oxygen molecules are usually unloaded from each haemoglobin?
3 oxygen molecules are usually unloaded from each haemoglobin molecules.
In plants, what is water absorbed through?
By the roots through extensions called root hairs
In flowering plants, the vast majority of water is transported through …
hollow, thick walled tubes called xylem vessels.
The main force that pulls water through the xylem vessels in the stem of the plant is …
the evaporation of water from leaves – a process called transpiration.
The energy for transpiration is supplied by the ___ and is therefore _______.
Sun
Passive
Describe the movement of water out through the stomata
The humidity of the atmosphere is usually less than that of the air spaces next to the stomata.
As a result, there is a water potential gradient from the air spaces through the stomata to the air.
Provided the stomata are open, water vapour molecules diffuse out of the air spaces into the surrounding air.
Water lost by diffusion from the air spaces is replaced by water evaporating from the cell walls of the surrounding mesophyll cells.
By changing the size of their stomatal pores, plants can control …
Their rate of transpiration
Water is lost from mesophyll cells by __________ from their _________ to the __________ of the leaf.
Evaporation
cell wall
air spaces
Water lost from the mesophyll cells is replaced by water reaching the mesophyll cells from the _____ either via _________ or via the _________
xylem
cell walls
cytoplasm
In the case of the cytoplasmic route, the water movement occurs because:
- Mesophyll cells lose water to the air spaces by evaporation due to heat supplied by the sun
- These cells now have a lower water potential and so water enters via osmosis from neighbouring cells
- The loss of water from these neighbouring cells lowers their water potential
- They, in turn, take in water from their neighbours by osmosis
What is the main factor that is responsible for the movement of water up the xylem, from the roots to the leaves?
Cohesion-tension
Describe the movement of water up the stem
- Water evaporates from mesophyll cells due to heat from the sun leading to transpiration
- Water molecules form hydrogen bonds between one another and hence tend to stick together, this is known as cohesion
- Water forms a continuous, unbroken column across the mesophyll cells and down the xylem
- As water evaporates from the mesophyll cells in the leaf into the air spaces beneath the stomata, more molecules of water are drawn up behind it as a result of this cohesion
- A column of water is therefore pulle dup the xylem as a result of transpiration. This is called the transpiration pull.
Why is it called cohesion-tension?
There is cohesion between the water molecules through hydrogen bonds and transpiration pull puts the xylem under tension, that is, there is a negative pressure within the xylem, hence the name cohesion-tension theory.
What evidence can be used to support the cohesion-tension theory?
- Change in the diameter of tree trunks according to the rate of transpiration. During the day, when transpiration is at its greatest, there is more tension in the xylem. This pulls the walls of the xylem vessels inwards and causes the trunk to shrink in diameter. At night, when transpiration is at its lowest, there is less tension in the xylem and so the diameter of the trunk increases.
- If a xylem vessel is broken and air enters it, the tree can no longer draw up water. This is because the continuous column of water is broken and so the water molecules can no longer stick together.
- When a xylem vessel is broken, water does not leak out, as would be the case if it were under pressure. Instead air is drawn in, which is consistent with it being under tension.
Transpiration pull is a _______ process and therefore does not require _____________ to take place.
Passive
Metabolic energy
the xylem vessels through which the water passes are ____ and so cannot actively move the water.
dead
Why is it important that the xylem has no end walls?
means that the xylem forms a series of continuous, unbroken tubes from root to leaves, which is essential to the cohesion-tension theory of water flow up the stem.
Energy is still needed to drive the process of transpiration, what sort of energy is it and where does it come from?
this energy is in the form of heat that evaporates water from the leaves and it ultimately comes from the sun.
It’s difficult to measure how much water leaves a plant, so what do you do instead?
Measure how much is absorbed
The rate of water loss in a plant can be measured using a potometer, describe the steps involved:
- A leafy shoot is cut under water. Care is taken not to get water on the leaves.
- The photometer is filled with water, taking care not to get any air bubbles in it
- Using a rubber tube, the leafy tube is fitted to the potometer under water
- The potometer is removed from under the water and all joints are sealed with waterproof jelly
- An airbubble is introduced into the capillary tube
- The distance moved by the air bubble in a given time is measured a number of times and the mean is calculated
- Using this mean value, the volume of water lost is calculated
- The volume of water lost against the time in minutes can be plotted on a graph
- Once the air bubble nears the junction of the reservoir tube and the capillary tube, the tap on the reservoir is opened and the syringe is pushed down until the bubble is pushed back to the start of the scale on the capillary tube. Measurements are then continued as before
The potometer experiment can be repeated under different conditions to see the effect, give examples of different conditions
different temperatures, humidity, light intensity, or the differences in water uptake between different species in the same conditions
In the potometer experiment, why is the leafy shoot cut under water rather than in air?
As xylem is under tension, cutting the shoot in the air would lead to air being drawn into the stem, breaking the continuous stream of water, if cut under water, the continuous stream of water is maintained
In the potometer experiment, why are all joints sealed with waterproof jelly?
Sealing prevents air being drawn into the xylem and stopping water flow up it and also stop water escaping, leading to inaccurate results
What assumption is made in the potometer experiment?
That all water taken up is transpired
Why might the potometer experiment not be representative of actual plants transpiration rates?
- An isolated shoot is much smaller than the whole plant
Conditions in the lab may be different than those in the wild
What is each root hair cell?
Each root hair is an extension of a root epidermal cell
What are root hair cells used for?
the exchange surfaces in plants responsible for the absorption of water via osmosis and mineral ions by active transport
Why do xylem vessels vary in appearence?
depending on the type and amount of thickening on their cell walls.
As xylem vessels mature, what happens?
As they mature, their walls incorporate a substance called lignin and the cells die.
The lignin often forms rings or spirals around the vessel
How are xylems adapted to cope with negative pressure?
They have thick walls to prevent the vessels collapsing
Why is it advantageous that xylems are dead?
- Living cells have a cell surface membrane and cytoplasm, and water movement would be slowed as it crossed this membrane/cytoplasm
What is another feature of ligning, apart from its strength?
Water proofing
Xylems are thickened in spirals, why is this adventageous?
- Allows the vessels to elongate as the plant grows, uses less materials and is therefore less wasteful, allows stems to be flexible
Define translocation
the process by which organic molecules and some mineral ions are transported from one part of a plant to another
In flowering plants, the tissue that transports biological molecules is called ______
phloem
Describe the make up of the phloem
Phloem is made up of sieve tube elements, long thin structures arranged end to end
Their end walls are perforated to form sieve plates
Cells called ______________ are associated with the sieve tube elements
Companion cells
The plant transports sugars made in photosynthesis from ______ to _____
Sources
Sink
What are sources?
the site of production of sugar in the plant
What are sinks?
the places where sugar is used directly or stored for future use
Where are the sinks in the plant? What does this mean for translocation?
Sinks can be anywhere in the plant, so the translocation of molecules in the phloem can be in either direction
What sort of things can the phloem transport?
The phloem can transport organic molecules like sucrose or amino acids, as well as inorganic ions such as potassium, chloride, phosphate and magnesium ions
What mechanism of translocation is currently favoured?
the mass flow theory
How many phases can the mass flow theory be broken down into?
3
What is the first phase of the mass flow theory?
Transfer of sucrose into sieve elements from photosynthesising tissue
Describe and explain the first phase of the mass flow theory
- Sucrose is manufactured from the products of photosynthesis in cells with chloroplasts
- The sucrose diffuses down a concentration gradient by facilitated diffusion from the photosynthesising cells into companion cells
- Hydrogen ions are actively transported from companion cells into the spaces within cell walls using ATP
- These hydrogen ions then diffuse down a concentration gradient through carrier proteins into the sieve tube elements
- Sucrose molecules are transported along with the hydrogen ions in a process known as co-transport
- The protein carriers are therefore also known as co-transport proteins
What is the second phase of the mass flow theory?
Mass flow of sucrose through sieve tube elements
What is mass flow
the bulk movement of substance through a given channel or area in a specified time
Describe and explain the second phase of the mass flow theory
- The sucrose produced by photosynthesising cells (source) is actively transported into the sieve tubes
- This causes the sieve tubes to have a lower (more negative) water potential
- As the xylem has a much higher (less negative) water potential, water moves from the xylem into the sieve through tubes by osmosis, creating a high hydrostatic pressure within them
- At the respiring cells (sink), sucrose is either used up during respiration or converted to starch for storage
- These cells therefore have a low sucrose content and so sucrose is actively transported into them from the sieve tubes lowering their water potential
- Due to this lowered water potential, water also moves into these respiring cells, from the sieve tubes, by osmosis
- The hydrostatic pressure of the sieve tubes in this region is therefore lowered
- As a result of water entering the sieve tube elements at the source and leaving at the sink, there is a high hydrostatic pressure at the source and a low one at the sink
- There is therefore a mass flow of sucrose solution down this hydrostatic gradient in the sieve tubes
Is mass flow active or passive? Therefore, how can it be affected?
While mass flow is a passive process, it occurs as a result of the active transport of sugars. Therefore the process as a whole is active which is why it is affected by, for example, temperature and metabolic poisons.
What is the third phase of the mass flow theory?
Transfer of sucrose from the sieve tube elements into storage or other sink cells
Describe and explain the third phase of the mass flow theory
Sucrose is actively transported by companion cells, out of the sieve tubes and into the sink cells
Evidence Supporting the Mass Flow Hypothesis
- There is a pressure within sieve tubes, as shown by sap being released when they are cut
- The concentration is higher in leaves (source) than in roots (sink)
- Downward flow in the phloem occurs in daylight, but ceases when leaves are shaded, or at night
- Increases in sucrose levels in the leaf are followed by similar increases in sucrose levels in the phloem a little later
- Metabolic poisons/lack of oxygen inhibit translocation of sucrose in the phloem
- Companion cells possess many mitochondria and readily produce ATP
Evidence Questioning the Mass Flow Hypothesis
- The function of the sieve plates in unclear, as they would seem to hinder mass flow (it has been suggested that the have a structural function, helping to prevent the tubes from bursting under pressure)
- Not all solutes move at the same speed – they should do so if movement is by mass flow
- Sucrose is delivered at more or less the same rate to all regions, rather than going more quickly to the ones with the lowest sucrose concentration, which the mass flow theory would suggest
Describe the structure of woody stemmed plants
Woody stems have an outer protective layer of bark on the inside of which is a layer of phloem that extends all around the stem. Inside the phloem layer is xylem.
What happens in the ringing experiment
At the start of a ringing experiment, a section of the outer layers (protective layer and phloem) is removed around the complete circumference of a woody stem while it is still attached to the rest of the plant.
What observations are made in the ringing experiment
After a period of time, the region of the stem immediately above the missing ring of tissue is seen to swell.
Samples of liquid that has accumulated in this region are found to be rich in sugars and other dissolved organic substances.
Some non-photosynthetic tissues in the region below the ring (toward the roots) are found to wither and die, while those above the ring continue to grow.
What conclusions can be drawn from the observations in the ringing experiment? Why?
- The sugars of the phloem accumulating above the ring, leading to swelling in the region
- The interruption of flow of sugars to the region below the ring and the death of tissues in this region
The conclusion drawn from this type of ringing experiment is that the phloem, rather than xylem, is the tissue responsible for translocating sugars in plants
As the ring of the tissue removed had not extended into the xylem, its continuity had not been broken. If it were the tissue for translocating sugars you would not have accepted sugars to accumulate above the ring nor tissues below it to die.
What is useful for tracing the movement of substances in plants
Radioactive isotopes
describe and explain how a tracer experiment would be conducted on a plant using 14 carbon
the isotope 14C can be used to make radioactively labelled carbon dioxide (14CO2). If a plant is then grown in an atmosphere containing 14CO2, the 14C isotope will be incorporated into the sugars produced during photosynthesis. These radioactive sugars can then be traced as they move within the plant using autoradiography. This involves taking thin cross sections of the plant stem, and placing them on a piece of x-ray film. This film becomes blackened where it has been exposed to the radiation produced by the 14C in sugars. The blackened regions correspond to where phloem tissue is in the stem. As the other tissues do not blacken the film, it follows that they do not carry sugars and that the phloem alone is responsible for their translocation.
Evidence that Translocation of organic Molecules occurs in the phloem
- When phloem is cut, a solution of organic molecules flows out
- Plants provided with radioactive carbon dioxide can be shown to have radioactively labelled carbon in phloem after a short time
- Aphids are a type of insect that feeds on plants. They have needle like mouthparts which penetrate the phloem. They can therefore be used to transport the contents of sieve tubes. These contents show daily variations in the sucrose content of leaves that are mirrored a little later by identical changes in the sucrose content of the phloem
- The removal of a ring of phloem from around the whole circumference of a stem leads to the accumulation of sugars above the ring and their disappearance from below it
Describe and explain the differences in doing the ringing experiment in the summer and winter
There would be a large swelling above the ring in summer, but little if any in winter
In summer the rate of photosynthesis (and therefore production of sugars) is higher due to higher temperatures, longer daylight and higher light intensity. The translocation of these sugars leads to their accumulation, and therefore swelling, above the ring. In winter the rate of photosynthesis (and therefore production of sugars) is lower due to lower temperatures, shorter periods of daylight and lower light intensity. The less translocation of these sugars leads to not very much accumulation, and therefore less swelling, above the ring.
Squirrels strip sections of bark from branches, why might the branch die? How might it survive? Why is it unlikely a squirrel would kill a big mature tree?
If the squirrel strips away the phloem, then some parts of the branch can no longer receive sugar, so can’t respire, so will die
If the branch has enough leaves, these leaves will be able to supply the sugar needed for continued respiration, so it might survive
It is unlikely that squirrels would strip back the whole circumference of the tree, any intact phloem would be able to supply sufficient sugars to keep the tree alive
What do veins do?
carry blood towards the heart
What do Venules do?
control blood flow from capillaries to veins
What do capillaries do?
Link arterioles to veins
What do Arteries do?
carry blood away from the heart
What do Arterioles do?
control blood flow from arteries to capillaries
Why is the tough layer of blood vessels important?
resist pressure changes from both within and outside
Why is the muscle layer of vessels importan?
contract to control flow of blood
Why is the elastic layer of vessels important?
stretches and recoils, helps to maintain pressure
Why is the lumen of vessels important?
a passage for the blood to travel through
Order of thickness muscle layer of blood vessels (thick to thin)
Ateriole, artery, vein, capillary
Order of thickness of elastic layer of blood vessels (thick to thin)
Artery, arteriole, vein, capillary
Order of lumen size of blood vessels (thick to thin)
Vein, arteriole, artery, capillary
Which blood vessels have high pressure?
Artery
Which blood vessels have valves present?
Vein
The artery elastic layer is much thicker than veins so …
it keeps the blood pressure high, stretching at systole and springing back during diastole
The arteries have no valves but the veins do as …
blood is constantly under high pressure in arteries but much lower pressure in veins so back flow is more likely
Veins have thinner muscle layers as …
they are carrying blood away from tissue therefore construction and dilation does not control flow to tissues
There are spaces between the lining cells of capillaries as …
this gives them an increased rate of diffusion, short diffusion pathway, and an increased surface area/coverage to cells
Why are thick elastic tissue good?
Stretches under pressure, when heart beats
Springs back
Evens out pressure/flow
Why are thick muscle tissue good?
Muscle contracts
Reduces diameter of lumen
Changes flow/pressure
Why is a smooth epithelium good in vessels?
Smooth, so reduces friction, lessens possible blood clots, and provides less resistance
What does the SAN do?
sends an electrical wave the septum (base), via the atrium
What is the SAN?
the hearts pace maker, initiates an electrical wave of activity
What is the AVN?
the second node for contraction, initiates an electrical wave down the septum
What are ECG’s used to measure?
heart rate
How do ECG’ measure heart rate?
They detect the electrical impulse sent from the SAN and highlight the series of electrical current change during one cycle
What are the different parts of the ECG wave?
P, Q, R, S, T
What is the p wave?
activation of the atria
What is the QRS complex?
activation of the ventricles
Draw and label a regular ECG
google it
What is the T wave>
recovery wave
When does atrial systole happen?
P wave
When does ventricular systole happen?
QRS complex
When is the delay from SAN to AVN?
Between P and R
When is ventricular diastole?
T wave
Atrial systole is a weaker contraction than …
ventricular systole
Equation for cardiac output (with units)
Cardiac output (dm3min-1) = heart rate (bpm) x stroke volume (dm3)
Heart rate is …
how many times the heart beats per minute
Stroke volume is …
volume of blood pumped at each beat
What is a cardiovascular disease?
A degenerative disease of the heart and circulatory system
4 examples of cardiovascular disease
- Strokes
- Angina
- Heart failure/attacks
- Atherosclerosis
A risk factor is …
any characteristic or exposure of an individual that increases the likelihood of developing a disease or injury (not causes)
A correlation is …
a change in one or two variables that is reflected by a change in the other
Are risk factors correlations?
Yes
Name 4 risk factors for cardiovascular disase
Smoking
High Blood Pressure
Cholesterol
Diet/Lifestyle
How is smoking a risk factor for cardiovascular disease?
Smoking cigarettes makes the walls of your arteries sticky from the chemicals, so fatty material can stick to them. If the arteries that carry blood to your heart get damaged and clogged, it can lead to a heart attack. If this happens in the arteries that carry blood to your brain it can lead to a stroke. The build-up of plaque is called atherosclerosis.
How is high blood pressure a risk factor for cardiovascular disease?
If your blood pressure is consistently too high this means that your heart has to work harder to pump blood around your body. It also makes the walls of your arteries less stretchy, causing a build-up of fat which can lead to a heart attack or stroke. The build-up of plaque is called atherosclerosis.
How is cholesterol a risk factor for cardiovascular disease?
Cholesterol joins with proteins to form lipoproteins, non-high density lipoproteins can build up fatty deposits which narrow your arteries, leading to heart attacks or strokes. The build-up of plaque is called atherosclerosis.
How is diet/lifestyle a risk factor for cardiovascular disease?
Eating unhealthy and not exercising can cause high cholesterol and a weak heart, this can lead to a heart attack or stroke. The build-up of plaque is called atherosclerosis.
What is tissue fluid?
a watery liquid that bathes all of the tissues in our body
What does tissue fluid do?
Allows the exchange of substances between the blood and cells
What does tissue fluid contain?
Molecules required:
- Glucose, amino acids, fatty acids, ions and oxygen
Waste produced:
- Carbon dioxide, urea and water
Unlike the blood, what does tissue fluid not contain?
it does not contain large products like red blood cells and plasma proteins
What is the formation of tissue fluid dependent on?
- Hydrostatic pressure
- Water potential (osmotic pressure)
What is hydrostatic pressure caused by and what does it do?
.Result of heart pumping
.Forces small molecules out
.Prevents movement of liquid in
How is tissue fluid formed?
- The hydrostatic pressure is greater than the osmotic pressure (water potential) at the arterial end (where it is narrow), which forces the fluid out of the capillary, along with some molecules, but not large molecules like proteins. This is called ultra-filtration and it lowers the water potential of the capillary. At the venous end (where it is wider), the hydrostatic pressure is lower than the osmotic pressure so fluid moves into the capillary, bringing waste products with it
What is ultra-filtration?
When hydrostatic pressure forces smaller molecules out of the capillaries, but leaves the big molecules there
What is it like at the arteriole end?
.Higher hydrostatic pressure
.Lower osmotic pressure
.Net loss of water/fluid out
.Tissue fluid is formed
What is it like at the venular end?
.Lower hydrostatic pressure
.Higher osmotic pressure
.Net movement in
.Removal of waste
What percentage of tissue fluid returns via the lymphatic system instead of the capillaries?
10%
What is the lymphatic system and what does it do?
- Is separate to the circulatory system
- Made up of lymph capillaries
- Contains accumulated tissue fluid (lymph)
- Drains back into the blood via two ducts that join veins close to the heart
Draw a diagram of the lymphaic system, both
check notes
What is lymph moved by?
- Hydrostatic pressure of the tissue fluid
- Contraction of body muscles squeezes lymph vessels
Fluid in the blood is called
plasma
Fluid surrounding the cells is called
tissue fluid
Fluid in the lymphatic system is called
lymph
