6a. EXCHANGE Flashcards
Name some substances that are exchanged
Oxygen, carbon dioxide, nutrients, excretory products
Describe the surface area to volume ratio of smaller organisms
Smaller organisms have higher surface area:volume ratio
Describe the surface area to volume ratio of larger organisms
Larger organisms have smaller surface area:volume ratio
How does surface area : volume ratio affect rate of heat exchange?
As surface area : volume ratio decreases, rate of heat exchange also decreases
State why smaller animals have high metabolic rate
Smaller animals lose heat at a faster rate so therefore they need a high metabolic rate in order to generate enough heat to stay warm.
List the four features gas exchange surfaces that increase the rate of gas exchange
Large surface area, thin walls, a transport system, and ventilated
Why do exchange surfaces have a large surface area?
To increase the rate of gas exchange
Why do exchange surfaces have a thin epithelium? (one cell thick)
To minimise the diffusion distance
Why are exchange surfaces surrounded by lots of capillaries?
To maintain the concentration gradients
Why are exchange surfaces ventilated?
To maintain the diffusion gradients
State the equation that links diffusion, surface area, length of diffusion pathway and difference in concentration
Diffusion ∞ surface area x difference in concentration / length of diffusion path
State the formula to calculate volume of a sphere
V = 4/3πr3
State the formula to calculate volume of a cylinder
V = πr2h
Describe how single-celled organisms exchange gases
Single-celled organisms exchange gases by diffusion through their outer surface which is covered by a cell surface membrane.
Name the different parts of an insect’s gas exchange system
Spiracles, trachae, trachioles
Describe the function of spiracles
The pores on the insect’s surface which allow air to diffuse in and out of the trachaea
Describe how air is moved in and out of the spiracles
Abdominal pumping
Why do smaller insects not need to abdominal pump?
As their small surface area : volume allows a shorter diffusion distance to tissues.
Describe the structure of the trachaea and tracheoles
Trachaea are tubes that divide into smaller tubes called tracheoles, which are highly branched with thin walls
Why are tracheoles highly branched with thin walls?
To provide a short diffusion distance to any body cell
Why is respiration important in the gas exchange system of insects?
It maintains the diffusion gradients between the inside of the tracheoles and the air
What are the end of the tracheoles filled with?
Tracheal fluid.
When insects respire anaerobically, what is produced?
Lactate (lactic acid).
What effect does the presence of lactate have on insect muscle cells?
Lactate is soluble in water so lowers the water potential of muscle cells.
What is the effect of the reduction of the water potential of the muscle cells?
Fluid moves into the muscle cells from the tracheoles by osmosis.
What happens as the tracheal fluid is drawn into the muscle cells?
This draws more air into the tracheoles, increasing the rate of diffusion
How is water lost from an insect’s exchange system?
Evaporation
What is the purpose of the tiny hairs around the spiracles?
They reduce evaporation.
How does an insect control water loss from it’s exchange system?
It opens and closes its spiracles
Describe the structure of fish gills.
Each gill has many gill filaments extending from a gill arch. Along the gill filaments, at right angles to them, are gill lamellae.
Why does each gill have many gill filaments?
To increase the surface area.
What is the function of the lamellae?
To increase the surface area.
Describe the features of fish gills that increase the rate of exchange
Large surface area, thin walls, a transport system, and ventilated
How do fish ventilate their gills?
Buccal pumping
During buccal pumping, the fish will lower the floor of their mouths. Why does this draw water into the mouth?
It increases the volume and decreases the pressure inside the mouth.
During buccal pumping, the fish will raise the floor of their mouths. Why does this force water over the gills?
It decreases the volume and increases the pressure inside the mouth.
Why are a fish’s gill filament and lamellae surrounded by many capillaries?
The circulation maintains the concentration gradients
What is the counter-current system?
Blood flows in the opposite direction to water
Explain why the counter-current system increases gas exchange
Blood is always passing water with a higher oxygen concentration, so a diffusion gradient is maintained throughout the length of the gill filaments.
Name the different parts of the human gaseous exchange system
Trachea, bronchi, bronchioles, ribcage, right and left lungs, alveoli
What is the function of the rings of cartilage around the trachea?
They prevent it collapsing under low pressure
What is the trachea divided into?
Two bronchi
What do the bronchi divide into?
Bronchioles
What are found at the end of brionchioles?
Alveoli
What is the function of the alveoli?
They are the site of gas exchange
Why do alveoli contain elastic and collagen fibres?
To allow them to stretch and recoil
Why do the lungs contain many alveoli?
To produce a large surface area
Why is the alveolar epithelium one cell thick?
To provide a short diffusion pathway
Why are the alveoli surrounded by many capillaries?
Circulation maintains the diffusion gradients
Why are the capillary epithelium one cell thick?
To provide a short diffusion pathway
List in the correct sequence all the structures that air passes through a human respiratory system
Nostril, nasal cavity, trachea, bronchi, lungs, bronchioles, alveoli.
What is the purpose of ventilation of the lungs?
To maintain the diffusion gradients
Name the two types of muscle involved in human ventilation
Diaphragm and intercostal muscles
What is inspiration?
When air is drawn into the lungs down a pressure gradient
Why is inspiration an active process?
It involves muscle contraction
What happens to the intercostal muscles during inspiration?
External intercostal muscles contract and internal intercostal muscles relax. They are antagonistic.
What happens to the ribs during inspiration?
They are pulled upwards and outwards
What happens to the diaphragm during inspiration?
It contracts and flattens
Describe what happens to the volume and pressure inside the thorax during inspiration that causes air to be drawn into the lungs?
Volume increases and pressure decreases
What is expiration?
Expiration is when air is forced out of the lungs down a pressure gradient.
Why is expiration a passive process?
It does not involves muscle contraction
What happens to the intercostal muscles during expiration?
Internal intercostal muscles contract and external intercostal muscles relax. They are antagonistic.
What happens to the ribs during expiration?
They move downwards and inwards.
What happens to the diaphragm during expiration?
It relaxes (and moves up).
Describe what happens to the volume and pressure inside the thorax during expiration that causes air to be pushed out of the lungs
Volume decreases and pressure increases
Define tidal volume.
The volume of air in each breath.
Define breathing / ventilation rate.
The number of breaths per minute.
Define forced expiratory volume.
This is the maximum volume of air that can be breathed out in one second.
Define forced vital capacity.
This is the maximum volume of air it is possible to breathe forcefully.
Define PVR
Pulmonary Ventilation Rate: volume of air moved into lungs per minute.
Recall the equation used to calculate PVR
PVR (dm3 min-1) = tidal volume dm3) × breathing rate (min-1)
State what a spirometer is.
An equipment used to measure the volume of air breathed in and out.
Name some lung diseases.
Asthma, Emphysema, Pulmonary Tuberculosis, fibrosis.
Describe some risk factors for lung diseases.
Smoking, air pollution, genetic makeup, infections, occupation
Describe how breathing in dust and harmful gases can decrease the rate of gas exchange
It can cause the epithelium to become thicker, increasing the diffusion distance
Describe what happens during an asthma attack
The muscle walls of the bronchi contract and the walls of the bronchi secrete more mucus, which reduces the diameter of the airways, reducing the air flow.
How does smoking reduce air flow to the lungs?
Smoking causes the airways to become inflamed and produce excess mucus. This narrows the airways.
Smoking can cause scar tissue to form on the alveoli. What effect does this have?
It reduces the elasticity of the lungs, and reduces the surface area available for gas exchange.
