Surface Area to Volume Ratio and Gas Exchange Flashcards
What is the need for specialised exchange surfaces?
As the size or an organism and it’s surface area to volume ratio increases.
What are the main features of an efficient exchange surface?
- Large surface area
- Short diffusion distance
- Good blood supply/ventilation
What are the main features of Fish exchange system?
- Four pairs of gills, each supported by an arch
- Along each arch are gill filaments
- Gill filaments lined with lamellae
- Projections held apart by water flow = stick together out of water = fish can’t breathe
What is meant by counter current flow?
- Blood and water flow in opposite directions
- Ensures a steep diffusion gradient maintained
- Maximum amount of oxygen is diffusing into deoxygenated blood from the water
How does ventilation occur in fish?
- Continuous unidirectional flow
- Fish opens mouth = lowering the floor of buccal cavity
- Allows water to flow in
- Fish closes mouth = raising buccal cavity floor, increasing the pressure.
- Water is forced over gill filaments by the difference in pressure.
- Operculum acts as a valve and pump.
What are the main features of terrestrial insects gas exchange systems?
- Spiracles = small openings covering insects body
- Trachea and Tracheoles
- Cellular fluid
How does the terrestrial insect gas exchange system work?
- Gases move in and out through diffusion, mass transport as a result of muscle contraction and as a result of volume changes in the trachea.
What is the plant gas exchange system?
- Leaves have many small holes called stomata
- Large number of stomata of these = no cell is far from the stomata, reducing the diffusion distance.
What is the structure of mammalian lungs?
- Pair of lobed structures with large surface are located in the chest cavity, that are able to inflate.
- Surrounded by a ribcage to protect them.
- External and internal intercostal muscles between ribs contract and relax to raise and lower the ribcage.
- Diaphragm.
- Trachea, bronchi, and bronchioles.
- Alveoli = gas exchange occurs.
How is the airway held open?
- Rings of cartilage, incomplete in the trachea to allow passage of for food down the oesophagus behind the trachea.
What is loose tissue?
The inside surface of cartilage is a layer of glandular and connective tissue, elastic fibres, smooth muscle and blood vessels.
How are alveoli adapted for gas exchange?
- Very thin (one cell thick), surrounded by one cell thick capillaries = short diffusion pathway
- Constant blood supply by capillaries = step concentration gradient maintained
- Large number of alveoli = large collective surface area
What is the function of the Goblet cells?
- Present in the trachea, bronchi and bronchioles involved in mucus secretion, to trap bacteria and dust = reduces risk of infection.
What is the function of the Ciliated Epithelium?
- Present in bronchi, bronchioles and trachea, involved in moving mucus along to prevent lung infection, by moving it toward the throat to be swallowed.
What is the function of smooth muscle?
- Ability to contract enables them to play a role in constricting the airway, controlling the flow of air to and from the alveoli.
What is the function of Elastic fibres?
- Stretch when we exhale and recoil when we inhale thus controlling the flow of air.
What is the process of inspiration?
- External intercostal muscles contract
- Internal intercostal muscles relax
- Diaphragm contracts and flatterns
- Increases the volume inside the thorax, lowering the pressure
- Difference in pressure creates a gradient and causes air to be forced into the lungs.
What is the process of expiration?
- Internal intercostal muscles contract
- External intercostal muscles relax
- Diaphragm relaxes and returns to domes shape
- Decreasing the volume inside the thorax, increasing pressure forcing air out of the lungs.
What is a Spirometer?
- A device used to measure lung volume
- A person breathe in and out of the air tight chamber, causing it to move up and down, leaving a trace on a graph
What is vital capacity?
The maximum volume of air that can be inhaled or exhaled in a single breath
- depends on gender, age, size and height
What is tidal volume?
The volume of air we breathe in and out at each breath at rest
What is breathing rate?
The number of breaths per minute, can be calculated from the spirometer trace by counting the number of peaks or troughs per minute
What is digestion?
The hydrolysis of large biological molecules into smaller molecules which can be absorbed across cell membranes
How are carbohydrates broken down?
- Amylase in the mouth = large polymers
- Maltase in the ileum break down monosaccharides
- Sucrase and lactase break down the disaccharides sucrose and lactose
How are lipids broken down?
- Lipases hydrolyse ester bonds between the monoglycerides and fatty acids
- Emulsified into micelles by bile salts released by the liver
- Increases the surface area for enzymes to act on
How are proteins broken down?
(Three types of enzyme?)
- Endopeptidases = hydrolyse peptide bonds between amino acids in the middle of a polypeptide
- Exopeptidases = hydrolyse bonds at the end of polypeptides
- Dipeptidases = hydrolyse dipeptides into individual amino acids.
How are amino acids absorbed in mammals?
- Absorbed in the ileum
- Amino acids by facilitated diffusion, in epithelial cells
- With each amino acid a Na+ is also taken up through co-transport.
- Diffusion gradient for Na+ is maintained by active transport through the epithelial cells.
How are monoglycerides and fatty acids absorbed in mammals?
- They are polar so they can easily diffuse across the cell membrane into the epithelial cells.
- They are then transported to the endoplasmic reticulum, where they are made into triglycerides again.
- Then they move out of the cells by vesicles into the lymph system.
What is Haemoglobin?
- A water soluble globular protein, which consists of two beta polypeptide chains and two alpha helices.
- Each molecule contains a haem group.
- Carries oxygen in the blood, oxygen binds to the haem group.
Each molecule can carry four oxygen molecules.
What is affinity of oxygen and how does it vary?
- Varies depending on the partial pressure of oxygen which is a measure of the oxygen concentration.
- The greater the concentration of dissolved oxygen in cells the greater the partial pressure.
- As partial pressure increases, the affinity of haemoglobin for oxygen increases.
What happens to affinity for oxygen during repatriation?
- Oxygen is used up and the partial pressure decreases so = affinity of oxygen decreases.
- Oxygen is released in respiring tissues where needed.
- The haemoglobin returns to the lungs to be loaded again.
What do oxygen dissociation curves tell us?
- The change in haemoglobin saturation as partial pressure changes.
- The saturation of haemoglobin is affected by its affinity for oxygen, therefore when partial pressure is high, haemoglobin has a high affinity for oxygen, so it is highly saturated.
How does saturation affect oxygen affinity?
- After bing to the first oxygen, the affinity of haemoglobin for oxygen increases due to a change in shape, making it easier for the other oxygen molecules to bind.
How is fetal haemoglobin different to adult?
- It needs to be better at absorbing oxygen because by the time oxygen reaches the placenta, oxygen saturation of the blood has decreased.
- So fetal haemoglobin has a higher affinity for oxygen.
How does the partial pressure of carbon dioxide affect the affinity of haemoglobin?
- Presence of carbon dioxide, the affinity of haemoglobin for oxygen decreases, causing it to be released.
- This is BOHR EFFECT
What is the circulatory system in mammals?
- Closed double circulatory system.
- One pumps bloods to the lungs to be oxygenated whilst the other is large and string and pumps oxygenated blood around the body.
What’s is the atrium?
Thin walled and elastic, the atrium can stretch when filled with blood
What is a ventricle?
Thick muscular wall to pump blood around the body or to the lungs
What is the name of the valves between the atria and ventricles?
Atrioventricular valves
(Bicuspid and Tricuspid valves)
what is the name of the values between the ventricles and the aorta or pulmonary artery?
Semi-lunar valves
What is the aorta?
Connected to the left ventricular and carries oxygenated blood to the body
What is the pulmonary artery?
Connected to the right ventricle and carries deoxygenated blood to the lungs where it is oxygenated and the carbon dioxide is removed
What is the pulmonary vein?
Connected to the left atrium and brings oxygenated blood back from the lungs
What is the vena cava?
Connected to the right atrium sand brings deoxygenated blood back from the tissues except the lungs
What is the term for when a heart can initiate its own contraction?
Myogenic
What is the sinoatrial node and what does it do?
- Region of specialised fibres which are the pacemaker of the heart.
- They initiate a wave of electrical stimulation which causes the atria to contract at roughly the same time.
