Biology Chapter 7 Flashcards
Describe the quaternary structure of haemoglobin
4 polypeptides linked together: 2 alpha and 2 beta groups. 4 ferrous ions, one bound to each polypeptide, which can each bind to one oxygen molecule
How many oxygen molecules can be carried by one haemoglobin molecule?
4
Name 2 properties of haemoglobin which can make it efficient at transporting oxygen
Readily associates with oxygen when oxygen is plentiful
Readily releases oxygen where oxygen is needed
How does haemoglobin achieve efficiency at transporting oxygen
It changes its affinity for oxygen according to conditions. Its shape changes in high carbon dioxide to release oxygen
How does carbon dioxide concentration affect whether haemoglobin is released or attached?
Low carbon dioxide concentration = oxygen is attached
High carbon dioxide concentration = oxygen is released
Suggest why the concentration of oxygen is low in respiring tissues, while the concentration of carbon dioxide is high
Because oxygen is being used up to produce energy, and carbon dioxide is a by-product of respiration
Define ‘high affinity’
Easily takes up oxygen but gives it away less readily
Define ‘low affinity’
Releases oxygen more readily but takes up oxygen less readily
Explain how the environment can influence the type of haemoglobin an organism exhibits
When little oxygen is available from the environment, haemoglobin must be able to bind as much of it as possible
Explain how metabolic rate can influence the type of haemoglobin an organism exhibits
A high metabolic rate means the organism needs oxygen readily available; therefore, it needs a type of haemoglobin that can release oxygen readily
Why do different haemoglobins have different affinities for oxygen?
Slightly different amino acid sequences means that haemoglobins have different shapes and affinities
Define ‘loading/associating’
Haemoglobin combining with oxygen
Define ‘unloading/dissociating’
Oxygen being released from haemoglobin
Why, at very low concentrations of oxygen, is it difficult for haemoglobin to load the first oxygen molecule?
There is a close union between the 4 polypeptides of the haemoglobin molecule
What is meant by ‘partial pressure’?
The proportion of the total pressure that is contributed by a particular gas in a mixture
What is measured on the x-axis of an oxygen dissociation curve?
Partial pressure of oxygen (KPa)
What is measured on the y-axis?
Saturation of haemoglobin with oxygen (%)
Why does the graph show a steep rise in oxygen saturation of haemoglobin at higher concentrations of oxygen?
After the first oxygen molecule has bound, it is much easier for the other 3 polypeptides to binds to oxygen
What is the name given to the graph of the relationship between oxygen binding and oxygen concentration?
Oxygen dissociation curve
Explain why the graph tails off at high concentrations of oxygen
The haemoglobin molecule is saturated
How are the oxygen dissociation curves of different haemoglobins similar?
Similar S-shaped curves
How are oxygen dissociation curves different?
Different positions on the axes
The further to the left the curve…
the greater the affinity for oxygen
The further to the right the curve…
the lower the affinity for oxygen
How does the presence of carbon dioxide affect haemoglobin’s affinity for oxygen?
Reduces it
What affect does carbon dioxide have on the dissociation curve?
Shifts it to the right
What is the Bohr effect?
Where haemoglobin releases its oxygen more readily in response to a greater carbon dioxide concentration
Is pH at the gas exchange surface raised or lowered?
Raised
How does raised pH affect haemoglobin’s affinity to load oxygen?
Increases due to shape change
Why is oxygen not released before it gets to respiring tissues?
Shape change also increases affinity
Why is oxygen released at respiring tissues?
Increased carbon dioxide concentration leads to increased acidity and shape change in haemoglobin
Why might there be more oxygen unloaded at an active muscle cell than an intestinal epithelial cell during heavy exercise?
The more carbon dioxide is produced, the greater the shape change in haemoglobin and so the more oxygen is unloaded
Suggest where the dissociation curve of a native mountain dweller in the Andes where the air is thinner would lie? why?
Left
Needs ability to load oxygen at low partial pressures
Name 6 features of a transport system
- Suitable medium
- A form of mass transport
- Closed system of tubular vessels
- Mechanism for moving the medium in the vessels
- Unidirectional flow
- Means of controlling flow
What is meant by a ‘double circulatory system’?
The blood passes through the heart twice for each circuit of the body
What are the 3 types of blood vessels?
Arteries
Veins
Capillaries
The final exchange from blood into cells is rapid because…
- Large surface area
2.
The final exchange from blood into cells is rapid because…
- Large surface area
- Short diffusion pathway
- Steep diffusion gradient
Describe the thickness of muscle in the atria and why?
Thinnest layer of muscle
Only has to pump blood a short distance (to ventricles)
Describe the thickness of the right ventricle and why?
Thicker than atria, thinner than left ventricle
Pumps blood to the lungs
Describe the thickness of the left ventricle and why?
Thickest layer of muscle
Blood must be pumped to the rest of the body at high pressure
What is the advantage of having 2 separate pumps?
Blood pressure in the rest of the body can remain higher, while blood that goes to the lungs can go slowly with low blood pressure
What is the function of valves in the circulatory system?
To prevent the back flow of blood
Number of flaps in the left atrioventricular valve?
2 (bicuspid)
Number of flaps in the right atrioventricular valve?
3 (tricuspid)
Which heart chamber pumps blood into the aorta?
Left ventricle
Which blood chamber receives blood from veins?
Atria
Which 2 organs do pulmonary vessels link?
Heart and lungs
The aorta is connected to ____ to carry _____ blood to _____ except _____
Left ventricle
Oxygenated
All of the body
Lungs
The vena cava is connected to ____ to carry _____ blood from _____
Right atrium
Deoxygenated
All of the body
The pulmonary artery is connected to _____ to carry ______ blood to ______
Right ventricle
Deoxygenated
Lungs
The pulmonary vein is connected to _____ to carry _____ blood from _____
Left atrium
Oxygenated
lungs
What is the name given to the blood vessels that supply the heart itself with oxygen?
Coronary arteries
What is a myocardial infarction?
Flow through a coronary artery is reduced/prevented by blockage; oxygen supply to part of heart muscle is reduced; tissue may dies as a result (heart attack)
Suggest why it is important that oxygenated and deoxygenated blood is kept separate in the heart
To ensure that only oxygenated blood is delivered to tissues so that they have adequate oxygen for respiration
What are 4 risk factors associated with coronary heart disease?
- Smoking
- High blood pressure
- Blood cholesterol
- Diet
How does high blood pressure increase the risk of heart disease?
The heart must work harder to pump blood into higher-pressured arteries and so the arteries are more likely to suffer from an aneurysm and arteries thicken and harden, restricting blood flow
2 phases of heartbeat:
Systole (contraction)
Diastole (relaxation)
2 ways direction of blood flow is maintained:
Valves
Pressure changes
During diastole the pressure in the atria _____, the pressure in the ventricles _____ and the semi lunar valves ______
Increases
Decreases
Close
During atrial systole the atrial muscle wall _____, the blood in the atria ________________ and the ventricle muscle wall _______
Contracts
Is squeezed into the ventricles
Remains relaxed
During ventricular systole the ventricle muscle wall _______, the atrioventricular valves _____, the pressure in the ventricles _______ and the semi lunar valves ______
Contracts
Close
Increases
Open
Where is the atrioventricular valve located?
Between the atrium and ventricle on the same side of the body
Where is the semi-lunar valve located?
Aorta and left ventricle
Pulmonary artery and right ventricle
where are pocket valves located?
Veins
What is the equation for cardiac output?
Heart rate x stroke volume
What is the function of the arteries?
Carry blood from heart to arterioles
What is the function of the arterioles?
Control blood flow between arteries and capillaries
What is the function of the capillaries?
Link arterioles to vein; the smallest blood vessel
What is the function of the veins?
Carry blood from capillaries back to heart
Name the structure that helps maintain blood pressure through the ability to stretch
Elastic layer
Name the part of the vessel in which the blood travels
Lumen
Name the structure that resists pressure changes
Tough outer layer
Name the structure that reduces friction; thin
Endothelium
Name the structure that controls the flow of blood
Muscle layer
What is the pressure of blood in the arteries?
High
What is the function of the thick muscle layer?
Control of blood volume
What is the function of the thick elastic layer?
Maintains blood pressure
what is the function of the thick wall
Prevents artery bursting
Function of no valves
High pressure means backflow is not a problem
What is the pressure of blood in the arterioles?
Lower than in arteries
Function of thicker muscle wall of arterioles
Allows constriction of the arterioles to control the blood supply into the capillaries
Function of the thinner elastic layer of arterioles?
Due to lower blood pressure
What is the pressure of blood in the veins?
Low
4 adaptations of veins
Thin muscle layer = carry blood away from tissues, so fine control is not required
Thin elastic layer = low pressure
Overall thinness of wall layer = low pressure; allows veins to be flattened more easily
Valves = ensures blood flows only towards the heart
Function of capillaries
To exchange metabolic materials between the blood and the tissues
Pressure and speed of blood in the capillaries:
Pressure = very low
Speed = slow
5 adaptations of capillaries
Wall consists of lining layer = short diffusion distance
Many of them, branched = large surface area for diffusion to take place
Narrow diameter = can reach deep into tissues
Extremely narrow lumen = Red blood cells squeezed flat, decreases diffusion distance
Spaced between endothelial cells = white blood cells can escape to deal with infections
How is hydrostatic pressure produced?
High pressure is created at the arterial end of the capillaries as there is high pressure from the heart forced through smaller and smaller blood vessels
2 ways the outward pressure is resisted:
- Tissue fluid outside the capillaries generates a counteracting hydrostatic pressure
- Blood has a lower water potential
What is the overall effect of these different pressures?
Tissue fluid if pushed out of the capillaries
Summarise the 4 steps involved in the return of tissue fluid to the circulatory system
- Hydrostatic pressure in the capillaries is reduced as tissue fluid moves out
- The hydrostatic pressure is therefore lower at the venous end of the capillaries than that of the surrounding tissue fluid
- Tissue fluid is forced to re-enter the capillaries
- Osmotic forces also help to draw water back in
How is the remainder of tissue fluid transported back into the blood?
Through lymph vessels via the lymphatic system
2 adaptations of root hairs that increase their efficiency
- Large surface area
2. Thin surface layer
There is a high water potential in the _____
Soil
There is low water potential in the ____
Root
As a result, water more from the ____ into the ____ by ____
Soil
Root
Osmosis
Summarise the movement of water as it moves up the root
Water increases the water potential of a root-hair cell. As the next root-hair cell now has a lower water potential in comparison, water moves into it by osmosis, and continues in this way by osmosis
What is a likely method of transport into the xylem?
Osmosis
Movement of water up stems depends on:
- Humidity
2. The stomata being open
Water is lost by:
Evaporation
Water in then replenished from:
The xylem
Water moves by the establishment of:
A water potential gradient
Name a factor responsible for the movement of water up the stem in the xylem:
Cohesion-tension
Define ‘cohesion’
Water molecules’ stick together’ as they form hydrogen bonds between one another
What is the ‘transpiration pull’?
Water molecules are drawn up the xylem tubes as a result of evaporation from the leaves. This is aided by water’s cohesive properties
Name given to this theory of water movement
The cohesion-tension theory
Give 3 pieces of evidence to support the cohesion-tension theory
- During the day, there is more negative tension in the xylem so the tree trunk decreases in diameter. it expands again at night when there is less transpiration
- A tree can no longer draw up water from a broken xylem vessel
- When a xylem vessel is broken, air is drawn back in, rather than water leaking out
Is transpiration pull a passive or active process?
Passive
Where does the energy in this system come from?
The sun
Why does transpiration occur?
Leaves have a large surface area and stomata to facilitate photosynthesis
What are the benefits to transpiration?
Helps add to the amount of water transported in the plant, and increases the rate of solute transport
How does an increase in light intensity result in a corresponding increase in transpiration?
Photosynthesis increases with light intensity, so stomata are more likely to open, increasing water loss
How does a rise in temperature lead to an increase in transpiration?
- Increases the speed at which the water molecules are moving, which leads to increased evaporation
- Decreases the air’s water potential
What is the effect on transpiration of high humidity?
Reduces transpiration
Is the water potential of air higher in lower or higher humidity?
Higher humidity
How does a breeze increase the rate of transpiration?
It disperses the water vapour that collects near the stomata. This increases the water potential gradient
Describe the stages and results of a photometer experiment
Cutting is attached to a water-filled tube and a bubble is introduced into the end of the tube which moves up the tube, therefore allowing measurements of water loss by/rate of transpiration
Define translocation
The movement of organic substances around a plant
Where does translation take place?
In the phloem vessels
Is translocation an active process?
Yes, it requires energy to create a pressure difference
Explain how sucrose is transferred into sieve elements
- Sucrose is loaded into the phloem at the source (usually a photosynthesising leaf)
- Hydrogen ions are pumped out of the companion cell using ATP
- This creates a high concentration of hydrogen ions outside the companion cell
- Sucrose is loaded (moved into companion cells) by active transport, against the concentration gradient
Explain the mass flow of sucrose through sieve tube elements
Sucrose diffuses down the concentration gradient into the sieve tube elements. This lowers the water potential of the sieve tube element so water enters by osmosis
Explain how sucrose is unloaded at the phloem
- Sucrose is unloaded from the phloem into a sink (e.g root)
- Sucrose moves out by diffusion and is then converted into another substance to maintain a concentration gradient
- Water will follow by osmosis
What name is given to the hypothesis for how solutes are transported by the phloem
Mass flow hypothesis for translocation
At the source sucrose is co-transported with _____ into ______
Hydrogen ions
Companion cells (linked to sieve cells)
What does sucrose decrease in the phloem?
Water potential
What does this create?
Hydrostatic pressure that pushes fluid along the phloem
Why is sucrose required by cells?
For respiration or converted into starch for storage
What is the name given to cells that require glucose?
Sink
How is sucrose transported out of the phloem?
Companion cells actively transport sucrose out of the phloem
What does this do to the water potential in the surrounding cells?
Causes them to have a more negative water potential than the phloem, so water leaves the phloem and enters the cells, causing fluid to be pulled towards the sink
What evidence supposes the mass flow hypothesis?
- If the phloem is cut, hydrostatic pressure causes sap to seep from the cut
- Sucrose concentration is higher in the source than in the sink areas
- Low light slows translocation due to reduced sucrose production from photosynthesis
- Low oxygen slows translocation due to reduced ATP production from photosynthesis
What evidence questions the mass flow hypothesis?
- Role of the sieve plates is unknown, they may hinder movement of solutes
- Different types of solutes move at different speeds; they should all move at the same speed in mass flow
Name 2 ways evidence has been gained about the mechanism of translocation in plants:
- Ringing experiments
2. Tracer experiments
How does a ringing experiment illustrate that sugars are transported in the phloem?
Removing phloem so sugary liquid builds up above the cut and non-photosynthetic tissue below the cut die due to no sugar
How do tracer experiments show that translocation of organic molecules occurs in the phloem?
Plant kept in 14C carbon dioxide atmosphere
Sugars incorporate 14C
X-ray film responds to 14C and darkens only over locations of phloem
Suggest why a student cut the shoot and put it into the photometer under water in a photometer experiment
To prevent air bubbles
Suggest why a student would make repeat measurements in a photometer experiment
To get a reliable mean
To get concordant results
Suggest how a sieve tube cell is adapted for translocation
- End walls form sieve plates
2. No nucleus/ ribosomes so more space for material to pass
What are physical and chemical digestion and where do they take place?
Physical breakdown = large to small molecules which are possible to ingest and have a large surface area for chemical digestion. Occurs in the mouth by teeth and stomach when churned by muscles in the stomach wall
Chemical breakdown = hydrolyse large insoluble molecules into smaller, soluble ones
Describe how starch is digested by amylases and membrane-bound disaccharidases
Amylase breaks down starch (polysaccharide) into maltose (disaccharide) in the mouth with enzymes made in the salivary glands. The glycosidic bonds are hydrolysed. Attached to the cell membrane in the ileum are membrane bound disaccharidases such as sucrose
Describe digestion of lipids by lipase
Lipases breaks down lipids into fatty acids and monoglycerides. Bile salts (made in the liver, stored in the gall bladder) emulsify lipids and so increase the surface area for lipases to work on. Then, the monoglycerides and fatty acids stick to the bile salts and form micelles. Micelles help the products of lipid digestion to be absorbed
Describe digestion of proteins by endopeptidases, exopeptidases and membrane-bound dipeptidases in mammals
Endopeptidases hydrolyse peptide bond within a protein. Exopeptidases hydrolyse peptide bonds at the end of proteins by removing single amino acids. Dipeptidases are exopeptidases that work specifically on dipeptides often found in the cell-surface membrane of epithelial cells in the small intestine
Describe the structure of the ileum and explain how it is adapted for the function of absorption
- Villi and microvilli increase surface area for diffusion
- Thin walled = short diffusion pathway
- Rich blood supply = maintains concentration gradient
- Contain muscle which can move =maintains concentration gradient
Explain how triglycerides are absorbed
Micelles help to move monoglycerides and fatty acids to the epithelium. Micelles are constantly breaking up and re-forming releasing monoglycerides and fatty acids to be absorbed. They are lipid soluble so can diffuse across the epithelial cell membrane
