Exchange ( Year 12 content ) Flashcards
How does an organims size relate to their surface area to volume ratio?
The larger the organism, the lower their surface area to volume ratio
How does an organism surface area to volume ratio relate to their metabolic rate?
The smaller the surface area to volume ratio, the higher the metabolic rate
How might a large organism adapt to compensate for it small surface area to volume ratio?
Changes that increase surface area such as folding and body parts become larger, e.g., elephant ears; elongating shape
Why do multicellular organisms require specialised gas exchange surfaces?
Their smaller surface area to volume ratio Means the distance that needs to be crossed is larger, as substances can not easily enter the cells as in single-celled organism
Name three features of an efficient gas exchange surface
1) Large surface area
2) thin/ short diffusion distance
3) steep concentration gradient
Why can’t insects use their bodies as an exchange surface?
They have a waterproof chitin
Exoskeleton and a small surface area to volume ratio in order to conserve water
Name and describe the three main features of an insect gas transport system
●spiracles= holes on the body’s surface which may be opened or closed by a valve for gas or water exchange
● Tracheae= large tubes extending through all body tissues, supported by rings to prevent collapse
● Tracheoles= smaller branches dividing off the tracheae
Explain the process of gas exchange in insects
●Gases move in and out of the trachea through the spiracales
● A diffusion gradient allows oxygen to diffuse into the body tissue while waste CO2 diffuses out
● contraction of muscles in the trachea allows mass movement of air in and out
Why can’t fish use their bodies as an exchange surface?
They have a waterproof, impermeable outer membrane and a small surface area to volume ratio.
Name and describe the two main features of a fish’s gas transport system
Gills= located within the body, supported by arches, along which are multiple projections of Gill filaments, which are stacked up in piles
Lamellae= at right angles to the Gill filaments, gives an increased surface area. Blood and water flow across in opposite directions(counter current flow)
Explain the process of gas exchange in fish
● The fish opens its mouth to enable water to flow in, then closes its mouth to increase pressure
● The water passes over the lamellae, and the oxygen diffuses into the bloodstream
● Waste carbon carbon dioxide diffuses into the water and flows back out of the gills
How does the counter current exchange system maximise oxygen absorbed by the fish?
Maintains a steep concentration gradient along the gills, as water is always next to blood of a lower oxygen concentration. Keeps the rate of diffusion constant along the whole length of the Gill, enabling 80% of available oxygen to be absorbed
Name and describe three adaptations of a leaf that allow efficient gas exchange
1) Thin and flat to provide short diffuses pathway and large surface area to volume ratio
2) Many stomata in the underside of the leaf allow gases to easily enter
3) Air spaces in the mesophyll allow gases to move around the leaf, facilitating photosynthesis
How do plants limit their water loss while still allowing gases to be exchanged?
Guard cells control the opening and closing of the stomata. Most stay closed to prevent water loss while some open to let oxygen in
Explain the process of inspiration
●External intercostal muscles contract
●Internal intercostal muscles relax
●The ribs are pulled upwards and outwards
●the diaphragm muscles contracts, causing it to flatten
●increases the volume of the thorax
●reduces pressure
●atmospheric pressure is greater than pulmonary pressure, so air is forced into the lungs
Explain the process of expiration and the changes that occur throughout the thorax
●external intercostal muscles relax
●internal intercostal muscles contract
●the ribs are pulled downwards and inwards
●the diaphragm muscles relax, causing it to become dome shaped
●decreases the volume in the thorax
●increases pressure
●atmospheric pressure is less than pulmonary pressure, so air is forced out of the lungs
Whats tidal volume?
The volume of air we breathe in and out during each breath at rest
What is breathing rate?
The number of breaths we take per minute
How do you calculate the pulmonary ventilation rate?
Tidal volume X breathing rate
Define digestion
The hydrolysis of large insoluble molecules into smaller molecules that can be absorbed across cell membranes
Which enzymes are involved in carbohydrate digestion? Where are they found?
●amylase in mouth
● maltase,sucrase, lactase in small intestine
What are the substrates and products of carbohydrates digestive enzymes?
●Amylase—> starch into smaller polysaccharides
● Maltase—> maltose into 2 alpha glucose
● sucrase—> sucrose into glucose and fructose
● Lactase—> lactose into glucose and galactose
Where are lipids digested?
Small intestine
What needs to happen before lipids can be digested?
They must be emulsified by bile salts produced by the liver. This breaks down large fat molecules Into smaller,soluble molecules called micelles, increasing surface area
How are lipids digested?
Lipase hydrates the ester bond between monoglycerides and fatty acids
Which enzymes are involved in protein digestion?
●Endopeptidases= break between specific amino acids in the middle of the polypeptide
●Exopeptidases=break between specific amino acids at the end of a polypeptide
●Dipeptidases= break dipeptides into amino acids
How are certain molecules absorbed into the ileum despite a negative concentration gradient?
Through Co-transport
Which molecules require co-transport?
Amino acids and glucose
Explain how sodium ions are involved in co-transport
Sodium ions(Na+) are actively transported out of the cell into the lumen, creating a diffusion gradient. Nutrients are then taken up into the cells along with Na+ ions
Why do fatty acids and monoglycerides not require co-transport?
The molecules are non-polar, meaning they can easily digguse across the membrane of the epithelial cells
Describe the structure of haemoglobin
Protein consisting of 4 polypeptide chains, each carrying a haem group(quaternary structure)
Describe the role of haemoglobin
Present on red blood cells, oxygen molecules bind to the haem groups and are carried around the body where they are needed in respiring tissues
Name three factors affecting oxygen-haemoglobin binding
1) concentration of oxygen
2) concentration of carbon dioxide
3) saturation of haemoglobin with oxygen
How does the concentration of oxygen affect oxygen-haemoglobin binding?
As the concentration of oxygen increases, the affinity of haemoglobin for oxygen increases, so oxygen binds tightly to haemoglobin. When oxygen concentration is low, oxygen is released from haemoglobin
How does concentration of carbon dioxide affect oxygen-haemoglobin binding?
As the concentration of carbon dioxide increases, the conditions become acidic, causing haemoglobin to change shape. The affinity of haemoglobin for oxygen decreases, so oxygen is released from haemoglobin
How does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding?
It is hard for the first oxygen molecule to bind. Once it does, it changes the shape to make it easier for the second and third molecule to bind, known as positive cooperativity.
Explain why oxygen binds to haemoglobin in the lungs?
● concentration of oxygen is high
● low concentration of carbon dioxide in the lungs, so affinity is high
● positive cooperativity
Explain why oxygen is released from haemoglobin in respiring tissues
● concentration of oxygen is low
● High concentration of carbon dioxide In respiring tissues, affinity decreases
How does carbon dioxide affect the position of an oxhaemogloboin dissociation curve?
Curve shifts to the right because haemoglobins affinity for oxygen has decreased
Relate the structures of the Chambers to their functions
●atria: thin-walled and elastic, so they can stretch when filled with blood
●Ventricles: thick muscular walls pump blood under high pressure. The left ventricle is thicker than right because it has to pump blood all the way around the body
Relate the structure of the vessels to their functions
●Arteries have thick walls to handle high pressure without tearing, and are muscular and elastic to control blood flow
● Veins have thin walls due to lower pressure, therefore requiring valves to ensure blood doesn’t flow backwards. Have less muscular and elastic layer
Why are there two pumps(left and right) needed instead of one?
To maintain blood pressure around the whole body. When blood passes through the narrow capillaries of the lungs, the pressure drops sharply and, therefore, would not be flowing strongly enough to continue around the whole body. Therefore, it is returned to the heart to increase the pressure
Describe what happens during cardiac diastole
The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atrioventricular valves. This allows blood to flow into the ventricles.
What happens during atrial systole
The atria contract, pushing any remaining blood into the ventricles
What happens during ventricular systole
The ventricles contract. The pressure increases, closing the AV valves to prevent the back flow of blood. And opening the semi-lunar valves. Blood flows into the arteries
How is the structure of capillaries suited to their function?
●walls are only one cell thick; short diffusion pathway
●very narrow, so can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues
●Numerous and highly branched,providing a large surface area
What is tissue fluid?
A watery substance containing glucose, amino acids, oxygen, and other nutrients. It supplies these to the cells while also removing any waste material
How is tissue fluid formed?
As blood is pumped through increasingly small vessels, this creates hydrostatic pressure, which forces fluid out of the capillaries
How is water transported in plants?
Through the xylem vessels; long, continuous columns that also provide structural support to the stem
Explain the cohesion-tension theory
Water molecules form hydrogen bonds with each other, causing them to ‘stick’ together(cohesion). Additionally, water molecules form hydrogen bond between the xylem, which causes it to be pulled in increasing surface tension. Therefore, as water is lost through transpiration, more can be drawn up the stem.
What are the three components of phloem vessels?
●Sieve tube elements = from a tube to transport sucrose in the dissolved form of sap
●Companion cells= involved in ATP production for active loading of sucrose into sieve tubes
Name the process whereby organic materials are transported around the plant
Translocation
How do phloem vessels transport sucrose around the plant?
●sucrose is made in the leaf and is transported into the phloem via companion cells through Co-transport
●This lowers the water potential in the phloem
●This causes water to enter from the xylem via osmosis
●This increases the hydrostatic pressure
●mass flow of sucrose to the sink end
Give evidence for the mass flow hypothesis of translocation
●Sap is released when a stem is cut. Therefore, there must be pressure in the phloem
●There is a higher sucrose concentration in the leaves than the roots
●Increasing sucrose levels in the leaves results in increased sucrose in the phloem
Give evidence against the mass flow hypothesis of translocation
●The structure sieve tubes seem to hinder mass flow
●Not all solutes move at the same speed, as they would in mass flow
●Sucrose is delivered at the same rate throughout the plant, rather than to areas with lowest sucrose concentration first
How can ringing experiments be used to investigate transport in plants?
The bark and phloem of a tree are removed in a ring, leaving behind the xylem. Eventually, the tissues above the missing ring swell due to accumulation of sucrose as the tissue below begins to die. Therefore, sucrose must be transported in the phloem
How can tracing experiments be used to investigate transport in plants?
Plants are grown in the presence of radioactive CO2, which will be incorporated into the plants’ sugars. Using autoradiography,we can see that areas exposed to radiation correspond to where the phloem is
