Exchanging substances Flashcards
What are the adaptations for gas exchange?
- steep concentration gradient
- good blood supply
- large surface area
- thin diffusion distance
Why do fish require a special gas exchange system?
- have a small surface area to volume ratio
- impermeable membrane
What are the lamellae?
found on gill filaments- the main site of gas exchange
What is meant by a counter-current flow and why is it an advantage?
blood and oxygen flow in opposite directions- it maintains a steep concentration gradient
what are the adaptations of fish?
- countercurrent flow of water and blood maintains a steep concentration gradient
- there is a large number of gills, filaments, lamellae and capillaries, which increase the surface area for diffusion
Describe the process of gas exchange in fish
- fish opens its mouth to enable water to flow in, then closes to increase pressure
- water passes through the lamellae, and the oxygen diffuses into the bloodstream (capillaries)
- waste carbon dioxide diffuses into the water and flows back out of the gills
State the internal network of tubs inside insects
spiracles, trachea, tracheoles
What is the function of spiracles?
spiracles can be opened and closed by a valve to control gas exchange and water loss
What are the ways gases move in and out of the tracheal system?
mass transport and tracheal water
Describe the process of mass transport
contraction of muscles in insects squeezes the trachea, speeding up the movement of gases
Describe the process of tracheal water
- lactic acid lowers the water potential of cells
- water osmoses into the cells from the tracheole
- less volume in the tracheole, drawing more oxygen in
What are the limitations of the tracheal system?
-relies on diffusion
-pathway must be short
-size of the organism is limited
What is the function of air spaces in a leaf?
create a high surface area to volume ratio
What is the function of guard cells?
open and close to regulate gas exchange and control water loss
What is the function of the waxy cuticle?
prevents water loss
Why do humans need to absorb large volumes of oxygen from the lungs?
- humans are large
- humans have a high metabolic rate
- higher number of respiring cells
- higher demand for gas exchange
Why are lungs internal?
- air is not dense enough to support the delicate structures of the lungs
- the high surface area would result in lots of water loss
What is the function of the rib cage?
supports and protects the lungs
What is the function of the lungs?
lobed structures made up of highly branched tubes
what is the trachea?
a muscular airway strenghtened with cartilage and lined with epithelial cells
What is the bronchi?
two divisions leading to its own lung
What are the bronchioles?
branching subdivisions made of muscle that constrict and relax to regulate airflow into the alveoli.
What is the alveoli?
100-300 um air sacs lined with elastic collagen fibres. the membrane is our gas exchange surface.
How is a diffusion gradient maintained at the alveolar surface?
- a constant supply of oxygen due to the movement of the external medium (air) and the internal medium (blood)
Why will diffusion occur rapidly?
-breathing movements constantly ventilate the lungs and the heart constantly circulates blood
-alveoli and pulmonary capillaries have a very large surface area
- the walls of alveoli and capillaries are thin
- distance between alveolar air and red blood cells is reduced when cells are flattened
- red blood cells are slowed to allow more time for diffusion
What is the function of the oesophagus?
carries food from the mouth to the stomach
What is the function of the stomach?
a muscular sac with an inner layer that produces enzymes. It’s role is to store and digest food
What is the function of the ileum?
a long muscular tube which absorbs the products of digestion into the bloodstream.
What is the function of the rectum?
faeces are stored here before being removed via the anus in a process called egestion
What is the function of the salivary glands?
pass their secretions via a duct into the mouth
What is the function of the pancreas?
produces a secretion called pancreatic juice. This contains proteases to hydrolyse proteins, lipases to hydrolyse lipids and amylase to hydrolyse starch
What is the structure of the ileum?
its wall is folded and has villi
What are the adaptations of the villi?
- increase surface area for diffusion
- thin walls to decrease diffusion distance
- contain muscle to maintain a diffusion gradient
- have blood vessels so can carry away absorbed molecules
- the epithelial cells surrounding the villi have microvilli to increase surface area
How is glucose absorbed?
active transport with sodium ions via a co-transporter protein
How is galactose absorbed?
active transport with sodium ions via a co-transporter protein
How is fructose absorbed?
facilitated diffusion via a different transporter protein
What is haemoglobin?
globular proteins with a quaternary structure evolved for loading and unloading of oxygen
What does the term associating mean?
the process by which haemoglobin binds with oxygen
What does the term dissociating mean?
the process by which haemoglobin releases oxygen
What does affinity mean?
the strength of attraction between two molecules
What does high affinity mean?
it readily associates, unreadily dissociates
What does low affinity mean?
it readily dissociates, unreadily associates
Where does haemoglobin have a high affinity for oxygen?
at the gas exchange surfaces
Where does haemoglobin have a low affinity for oxygen?
at tissues repairing it
What happens to haemoglobin in the presence of CO2
it changes shape. when the co2 concentration is high- it will bind to oxygen easily and oxygen is released
Explain the bohr effect
The greater the concentration of carbon dioxide, the more readily the haemoglobin releases its oxygen. This is because dissolved carbon dioxide is acidic and the low ph causes haemoglobin to change shape.
How are arteries adapted?
Thick muscular layer which constrict and relax to control pressure
Thick elastic layer is stretched following systole and recoils during diastole to maintain a high pressure
Thick collagen wall resists bursting under high pressure
How are veins adapted
Thin muscular layer as constriction and relaxing would not achieve anything
Thin elastic layer due to the pressure being low to cause only stretching
Thin walls due to the pressure being low to risk bursting. This allows then to be flattened
How are capillaries adapted
Walls consist mostly of the thin lining (endothelium) to reduce a diffusion distances
Highly branched and form networks
Being narrow means they can permeate tissues so that no cell is even far from a capillary
Narrow lumen causing red blood cells to squeeze against the walls
Endothelial cells have spaces to allow white blood cells out to deal with tissue infections
What is the role of the tissue fluid
Supply glucose, oxygen, amino acids to tissue cells
Remove carbon dioxide and waste materials from cells
Controlled by various homeostatic environment
What are the 2 pathways for water
Cell wall pathway (apoplast)
Cytoplasmic pathway (symplast)
How are xylem vessels adapted
Thick walled hollow tubes
What factors affect the rate of transpiration
Temperature, humidity, wind, light intensity
Define translocation
The process by which organic molecules are moved around a plant in the phloem tissue
What is the structure of a phloem cell
Consists of sieve tube elements arranged end to end. The walls are perforated to form sieve plates . Companion cells
Define ventilation
To maintain diffusion gradients across the alveolar epithelium, air must constantly be moved into and out of the lungs
Define inspiration
When air pressure of the atmosphere is greater than inside the lungs, air is forced into the lungs
Define expiration
When air pressure of the lungs is greater than atmosphere, air is forced out of the lungs
What muscles control pressure changes
Diaphragm, intercostal muscles
What is the diaphragm
Sheet of muscle separating the thorax from the abdomen
What are the internal intercostal muscles
In between the ribs, the contraction leads to expiration
What are the external intercostal muscles
In between ribs, the contraction leads to inspiration
Describe the process of inspiration
External intercostal muscles contract, internal relax
Ribs are pulled upwards and outwards increased volume of thorax
Diaphragm contracts,tending, further increasing thorax volume
Increased thorax volume reduces the air pressure within the lungs
Atmospheric pressure is now greater than lunch and pulmonary pressure
Describe the process of exhalation
Internal intercostal muscles contract, external relax.
The ribs move downwards and inwards. Decreasing volume of the thorax.
Diaphragm relaxes and is pushed up by the abdomen. Volume of thorax decreased.
Decreased thorax volume increases air pressure within the lungs
Pulmonary pressure is now greater than the lungs and the atmosphere.
