Biology AS Cells Exchange And Transport Module 2 Exchange And Transport

OCR Biology AS

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Side ASide B
Define Exchange Surface
An exchange surface is a specialised area that is adapted to make it easier for molecules...
What substances do living cells need? (6)
- oxygen for aerobic respiration- glucose as a source of energy - proteins for growth and...
What features do good exchange surfaces have in common?
- large surface area to provide more space for molecules to pass through- thin barrier to reduce...
List 4 exchange surfaces in living organisms
1) small intestine (where nutrients are absorbed)2) liver (where levels of sugars in the blood...
Define Gaseous exchange
Gaseous exchange is the movement of gases by diffusion between an organism and its environment...
How does gaseous exchange occur in the lungs?
Gases pass both ways through the thin walls of the alveoli. Oxygen passes from the air in the...
Why do the lungs have a large surface area?
The large surface area provides more space for molecules to pass through.
Why do the lungs have a barrier permeable to oxygen and carbon dioxide?
The plasma membranes that surround the thin cytoplasm of the cells form the barrier to exchange....
Why do the lungs have a thin barrier to reduce diffusion distance?
- the alveolus wall is one cell thick- the capillary wall is one cell thick- both walls consist...
Why must the lungs produce surfacant?
To reduce the cohesive forces between the water molecules. Without the surfacant,...
Why is a steep diffusion gradient needed in the lungs?
For diffusion to be rapid.
What is meant by a steep diffusion gradient?
This means having a high concentration of molecules on the supply side of the exchange surface...
How is a steep duffusion gradient maintained?
A fresh supply of molecules on one side is needed to keep the concentation there high, and...
How is a diffusion gradient maintained in the lungs?
This is achieved by the action of the blood transport system and the ventilation movements.   The...
Outline inspiration (inhaling)
- Diaphragm contacts to become flatter and pushes digestive organs down - External intercostal...
Outline expiration (exhaling)
- Diaphragm relaxes and is pushed up by displaced organs underneath- External intercostal muscles...
What 5 requirements must the airways meet?
1) larger airways must be large enough to allow sufficient air to flow without obstruciton2)...
What is the difference between the trachea and bronchi?
The bronchi are narrower
List the 4 features of the trachea and bronchi
1) Much of the wall consists of cartilage2) The cartilage is in the form of incomplete rings...
Describe the bronchioles
They are much narrower than the bronchi.Larger bronchioles may have some cartilage.The wall...
What is the role of cartilage?
Cartilage plays a structural role. It supports the trachea and bronchi, holding them open.
What is the role of smooth muscle?
The smooth muscle can contract. When it contracts it constricts the airway and makes the lumen...
What is the role of elastic fibres?
When smooth muscle contacts, it reduces the diameter of the lumen of the airway. The smooth...
What is the role of goblet cells and glandular tissue?
Goblet cells and glandular tissue secrete mucus. Mucus traps tiny particles from the air. These...
What is the role of ciliated epithelium?
This consists of ciliated cells. The cilia on these cells (hair like projections) move in a...
What is tidal volume?
Tidal volume is the volume of air moved in and out of the lungs with each breath when you are...
What is vital capacity?
Vital capacity i sthe largest volume of air that can be moved into and out of the lungs in...
What is residual volume?
Residual volume is the volume of air that always remains in the lungs, even after the biggest...
What is dead space?
Is the air in the bronchioles, bronchi and trachea.
What is inspiratory reserve volume?
Inspiratory reserve volume is how much more air can be breathed in over and above the normal...
What is expiratory reserve volume?
Expiratory reserve volume is how much more air can be breathed out over and above the amount...
How does a spirometer work?
A spirometer consists of a chamber filled with oxygen that floats on a tank of water. A person...
Why is soda lime used in measuring oxygen uptake?
Soda lime is used to absorb the carbon dioxide that is exhaled. This causes the volume of gas...
Look at spirometer trace
Define transport
Transport is the movement of oxygen, nutrients, hormones, waste and heat around the body.
What three factors affect the need for a transport system?
- size- surface area to volume ratio - level of activity
What 5 things will and effecient/effective transport system include?
- a fluid or medium to carry nutrients and oxygen around the body (blood)- a pump to create...
What sort of circulatory system to fish have?
Single circulatory system
How does a single circulatory system work in fish?
The blood flows from the heart to the gills and then on to the body before returning to the...
What sort of circulatory system do mammals have?
A double circulatory system
How does the double circulatory system work?
One circuit carries blood to the lungs to pick up oxygen. This is the pulmonary circulation....
What happens in the single circulatory system of fish?
- the blood pressure is reduced as blood passes through the tiny capillaries of the gills-...
What happens in the double circulatory system of mammals?
- the heart can increase the pressure of the blood after it has passed through the lungs, so...
Define the heart
The heart is a muscular pump that creates pressure to propel blood through the arteries and...
What does the right side of the heart do?
Pumps deoxygenated blood to the lungs to be oxygenated.
What does the left side of the heart do?
Pumps oxygenated blood to the rest of the body.
What forces blood along the arteries?
The heart squeezes the blood, putting it under pressure. The pressure forces the blood along...
Look at diagram of heart
What do the coronary arteries do?
They carry oxygenated blood to the heart muscle itself.
What do the atria do?
These recoeve blood from the major veins.
Where does deoxygenated blood from the body flow?
From the vena cava into the atrium.
Where does oxygenated blood from the lungs flow?
From the pulmonary vein into the left atrium.
Where does blood flow from the atria?
Blood flows down through the atrioventricular valves into the ventricles.
What happens when the ventricles contract?
The valves fill with blood and remain closed. This ensures that the blood flows upwards into...
What is the septum and what does it do?
A wall of muscle that seperates the ventricles from each other. This ensures that the oxygenated...
What do the semilunar valves do?
They are at the base of the major arteries and prevent blood returning to the heart as the...
Why is the muscle of the atria very thin?
Because these chambers do not need to create much pressure. Their function is to push the blood...
Why are the walls of the right venticle thicker than the walls of the atria?
This enables the right ventricle to pump blood out of the heart.
Why are the walls of the right ventricle thinner than those of the left?
The right ventricle pumps deoxygenated blood to the lungs. The lungs are in the chest cavity...
Why are the walls of the left venrticle much thicker than the right?
The blood from the left ventricle is pumped out through the aorta and needs sufficient...
Define cardiac cycle
The cardiac cycle is the sequence of events in one heartbeat.
Describe the filling phase (1)
While both the atria and the ventricles are relaxing, the internal volume increases and blood...
Describe atrial contraction (2)
The heart beat starts when the atria contract. Both right and left atria contract together....
Describe ventricular contraction (3)
Now there is a short period when all four heart valves are closed. The walls of the ventricles...
How do the atrioventricular valves work?
When the venticle walls relax and recoil after contracting, the pressure in the ventricles...
How do the semilunar valves work?
When the ventricles start to contract, the pressure in the major arteries is higher than the...
What is the sound of the heart?
The sound of the heart is made by the valves closing. - the first sound (lub) is made by the...
Define sionatrial node
The SAN is the heart's pacemaker. It is a small patch of tissue that sends out waves of electrical...
Define Purkyne tissue
Purkyne tissue is specially adapted muscle fibres that conduct the wave of excitation from...
Why is heart muscle described as myogenic?
Because it can initiate its own contraction.
How does the heartbeat start? (1)
At the top of the right atrium, near the point where the vena cava empties blood into the atrium,...
Desctibe how contaction of the atria works (2)
The wave of excitation quickly spreads over the walls of both atria. It travels along...
Descirbe how contraction of the ventricles works (3)
After this delay, the wave of excitation is carried away from the AVN and down specialised...
What are electrocardiograms and how do they work?
ECG's are used to measure the activity heart. Sensors are attached to the skin. Some of the...
What is this?
A normal ECG - P shows excitation of the atria - QRS indicates excitation of the ventricles -...
Define open circulatory system.
In an open circulatory system the blood is not always in vessels.
Define closed circulatory system.
In a closed circulatory system the blood always remains within vessels.
Why don't all animals have an open system?
Open systems work for insects as they are small and they don't rely on the blood to transport...
What happens in closed circulatory systems?
The blood stays entirely inside vessels. Tissue fluid bathes cells and tissues. This means...
Describe arteries.
Arteries carry blood away from the heart. The blood is at high pressure so the wll must be...
Describe veins.
Veins carry blood back to the heart. The blood is at low pressure and the walls do not need...
Describe capillaries.
Capillaries have very thin walls. They allow exchange of materials between the blood and cells...
Define blood
Blood is held in the heart and blood vessels.
Define tissue fluid
Tissue fluid bathes the cells of induvidual tissues.
Define lymph
Lymph is help within the lymphatic system.
Describe blood.
Blood consists of blood cells in a watery liquid called plasma. The plasma contains many dissolved...
Describe tissue fluid and its role
Tissue fluid is similar to blood but does not contain plasma proteins or as many cells. The...
Explain how tissue fluid is formed
The fluid that leaves the capillary is known as tissue fluid. This fluid surrounds the body...
Explain how the fluid returns to the blood.
The tissue fluid itself has some hydrostatic pressure and this pushes the fluid back into the...
Describe the formation of lymph.
Lymph is similar to tissue fluid and contians the same solutes.
What is haemoglobin?
Haemoglobin is a complex protein with 4 subunits. Each subunit consists of a polypeptide chain...
How does haemoglobin take up oxygen?
Oxygen molecules diffuse into the blood plasma and enter the red blood cells. Here they are...
How is oxygen released by heamoglobin?
Cells need oxygen for aerobic respiration. Oxyhaemoglobin must be able to release the oxygen....
Describe and explain haemoglobin and oxygen transport
The ability of haemoglobin to take up and release oxygen depends on the amount of oxygen in...
What is fetal heamoglobin?
Has a higher affinity for oxygen than adult haemoglobin. It must be able to absorb oxygen from...
How is carbon dioxide transported?
5% dissolved directly into plasma10% combined with haemoglobin to form carbaminohaemoglobin85%...
How are hydrogencarbonate ions formed?
CO2 enters the red blood cell and is combined with water to form carbonic acid. The enxyme...
Describe the Bohr effect
The Bohr effect results in oxygen being more readily released where more carbon dioxide is...
Define xylem
Xylem transports water up the plant
Define phloem
Phloem transports sugars and other assimilates up and down the plant
Why do plants need transport systems?
So that all of the cells can recieve enough water and nutrients in order to survive.
What substances do plants need to move?
- water and soluble minerals (these travel upwards in xylem tissue) - sugars (these travel...
What are the vascular tissues?
xylem and phloem
What is the vascular bundle?
The xylem and phloem are found together in vascular bundles. These bundles often contain other...
Describe xylem and phloem in the stem.
The vascular bundles are found near the outer edge of the stem. The xylem is found towards...
Describe xylem and phloem in the leaf
The vascular bundles form the midrib and veins of a leaf. A dicotyledon leaf has a branching...
Describe the structure of xylem
Xylem tissue consitsts of tubes to carry the water and dissolved minerals, fibres, to help...
What are xylem vessels?
These are long cells with thick walls that have been inpregnated by lignin. - The lignin waterproofs...
How is xylem adapted to its function?
- It is made from dead cells aligned end-to-end to form a continuous column - The tubes are...
Describe the structure of phloem
Phloem tissue consists of two types of cell: - sieve tube elements - companion cells
What are sieve tubes?
Sieve tubes are not true cells as they contain little cytoplasm and no nucleus. They are lined...
What are companion cells?
In between the sieve tubes are small cells which have a large nucleus and dense cytoplasm....
Define water potential
Water potential is the total potential energy of the water molecules in a system. It is a measure...
How does water move between cells?
When plant cells are touching each other, water molecules can pass from one cell to another....
Describe the apoplast pathway
The cellulose cell walls have many water-filled spaces between the cellulose molecules. Water...
Describe the symplast pathway
Water enters the cell cytoplasm through the plasma membrane. It can then pass through the plasmodesmata...
Describe the vacuolar pathway
This is similar to the symplast pathway, but the water is not confined to the cytoplasm of...
Define plasmodesma
A plasmodesma is a fine strand of cytoplasm that links the contents of adjacent cells.
How is water taken up from the soil?
How does water move across a root?
What is the role of the Casparian strip?
What three processes help to move water up the stem?
Describe and explain root pressure
Describe and explain transpiration pull.
Describe and explain capillary action
Describe and explain how water leave the leaf
Define transpiration
What three processes does transpiration involve?
What is the transpiration stream?
In what ways is movement of water up the stem useful to the plant?
How can we measure the rate of transpiration?
What features affect th rate of water loss and how do they affect water loss?
What happens if the plant loses too much water?
Define xerophyte
Why is the loss of water via transpiration unavoidable?
Most plants can reduce water loss by strucutal and behavioural adaptations. List 4 examples.
List adaptations of xerophytes.
Define translocation.
Define source.
Define sink.
How does sucrose enter the phloem?
How does sucrose move along the phloem at the source?
Sucrose is used in all cells surrounding the phloem. The sucrose may be converted to starch...
How does sucrose move along the phloem at the sink?
Water entering the phloem at the source, moving down the hydrostatic pressure gradient and...
Where are the sources and sinks?
Sources: leaf, roots,
What is meant by active loading?
Active loading means using ATP (energy) to transport sugars in the phloem.

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