SB8a-e Flashcards
Where does gas exchange in the lungs occur?
Inside the alveoli.
What are the adaptations of alveoli?
- Tiny air sacs inside the lungs
- Have extra walls within them so they increase surface area for gas exchange, causing faster diffusion
- Walls of the alveoli are very thin (one cell thick) to decrease diffusion distance
- Each alveolus has its own network of capillaries to maintain a concentration gradient, causing faster diffusion
How does gas exchange take place?
- During ventilation and blood circulation a high concentration of gradient of gases is maintained in the alveoli and capillaries
- There is high concentration of oxygen in the alveoli and high concentration of carbon dioxide in the blood
- This causes oxygen to diffuse into the blood down a concentration gradient and carbon dioxide to diffuse into the alveoli
- Large surface area allows for a more rapid gas exchange
- When we breathe in alveoli fill with oxygen
- Capillaries bring deoxygenated blood to the alveoli
- By breathing continuously (ventilation) a concentration gradient is maintained and gas exchange occurs very quickly
Why do alveoli have a large surface area to volume ratio?
For gas exchange to be efficient, the organism needs to have a large SA:V ratio. The bigger the surface area in comparison to volume, the more area the molecules have to enter. This is why alveoli provide a large surface area in order for animals to get as much oxygen as possible to satisfy their needs.
How does the human surface area to volume ratio affect us?
Humans have small surface area to volume ratio so they need an efficient transport system so that all cells in the body get oxygen and glucose for all metabolic activities in the body. Efficient transport systems such as the breathing system and the circulatory system.
What do the lungs consist of?
- Trachea
- Bronchus
- Bronchioles
- Alveolus
What is the structure of the alveoli?
Check book page 163 diagram and teacher notes “Efficient transport and exchange”.
What are the 4 factors affecting diffusion?
- Temperature
- Concentration of molecules
- Surface area
- Diffusion distance
What is Fick’s Law?
Diffusion rate ∝ concentration gradient * surface area / diffusion distance
How does temperature affect diffusion?
- The higher the temperature, the higher the rate of diffusion
- Molecules gain more kinetic energy and move faster
- This causes the diffusion to happen a lot faster
How does concentration of molecules affect diffusion?
- By increasing the concentration of one of the reactants, the rate of diffusion increases
- The more molecules you have on one side, the bigger the concentration gradient and thus the faster the diffusion
- The rate of diffusion is directly proportional to the concentration gradient
How does surface area affect diffusion?
- The larger the surface area, the faster the rate of the fusion
- Particles have more area to move on so more of them will pass in the same amount of time, increasing the rate of diffusion.
- Surface area is proportional to the rate of diffusion
How does diffusion distance affect diffusion?
- The smaller diffusion distance, the higher the rate of diffusion
- Particles have less distance to move across so diffusion will happen faster
- Therefore, if a membrane is thick, it will take a lot more time for the particles to move and so the rate will be lower
- The rate of diffusion is inversely proportional to the diffusion distance
What is the structure of the heart?
Four chambers:
2 upper atria
2 upper ventricles
Four valves:
2 atrioventricular valves (between atria and ventricles)
2 semilunar valves (base of aorta and pulmonary arteries)
Four blood vessels:
Aorta
Pulmonary artery
Vena cava
Pulmonary vein
Describe the pathway of the blood.
- Deoxygenated blood returns to the heart from the body through the vena cava
- Blood enters the right atrium which contracts and pushes the blood into the right ventricle
- Right ventricle (thinner wall because it contracts with little force and pressure) sends the blood to the lungs to get oxygenated through the pulmonary artery
- When ventricle contracts, the atrioventricular valve closes to stop the backflow of blood to the atrium
- At the same time the semilunar valve in the pulmonary artery will open so blood enters the artery and then closes so blood does not fall back into the ventricle
- Oxygenated blood returns to the heart through the pulmonary veins
- Blood enters the left atrium which contracts and pushes the blood to the left ventricle
- Left ventricle (thicker wall because it contracts with a lot of force and pressure) sends the blood to the whole body
- When ventricle contracts the atrioventricular valve closes to stop the backflow of blood to the atrium
- At the same time the semilunar valve in aorta will open so blood enters the artery and then closes so blood does not fall back into the ventricle
- Blood enters the aorta and goes to the whole body
Check teacher notes “The heart” for heart diagram + blood pathway.
What is the circulatory system made up of?
The heart and 3 types of blood vessels:
1. Arteries
2. Veins
3. Capillaries
What is the job and characteristics of the arteries?
- Carry blood away from the heart
- Small lumen to maintain high blood pressure
- Thick muscular wall to contract with enough force to push the blood forward
- Thick wall to withstand high blood pressure so it won’t burst
- Elastic fibres to allow the arteries to expand and recoil to push the blood forward
Check teacher notes “The circulatory system” for diagram.
What is the job and characteristics of the veins?
- Carry blood into the heart
- Large lumen causing low blood pressure
- Thin muscular layer because they don’t contract as much as the arteries
- Have valves to keep the blood flowing in one direction
Check teacher notes “The circulatory system” for diagram.
What is the job and characteristics of the capillaries?
- Site for gas exchange and other substances between cells and blood
- Very small lumen so that red blood cells move one behind the other
- One cell thick wall for fast diffusion of gases
Check teacher notes “The circulatory system” for diagram.
What is the blood made up of?
- Red blood cells / Erythrocytes
- White blood cells / Leukocytes
- Platelets
- Plasma
What does plasma contain?
Contains amino acids, hormones, glucose, carbon dioxide, urea and water.
What are the 2 types of white blood cells and what is their job?
- Lymphocytes (produce antibodies that destroy pathogens)
- Phagocytes (digest pathogens)
What are platelets and what is their job?
Fragments of cells that have no nuclei which cause the blood to clot when there is injury.
What is the structure of red blood cells?
- Biconcave disc shape which increases SA:V of the cell for more efficient diffusion of oxygen
- Contains red pigment haemoglobin (substance that binds with oxygen to carry it around the body)
- No nucleus to allow more space for more haemoglobin
What is respiration?
The release of energy in the form of ATP.
What are the differences between aerobic and anaerobic respiration?
Aerobic respiration:
1. Uses oxygen
2. Releases lots of energy (32 ATP)
3. Takes place in the mitochondria
Anaerobic respiration:
1. Does not use oxygen
2. Releases little energy (2 ATP)
3. Takes place in the cytoplasm
What is the equation for aerobic respiration?
Glucose + oxygen –> Carbon dioxide + water + (energy)
What is the equation for anaerobic respiration?
Glucose –> Lactic acid + (energy)
What occurs with respiration during exercise?
- When you exercise your muscles need to contract faster and with more force
- The heart rate increases to increase blood flow to the muscles and supply them with more oxygen and glucose
- Breathing rate increases to supply the blood with more oxygen
- Muscle get the oxygen and glucose in order to respire aerobically and release lots of energy in the form of ATP
How does intense exercise affect the concentration of oxygen in blood inside the arteries and veins?
- As intensity of exercise increases, the muscles work harder so they need to respire a lot more, thus more oxygen is needed
- Artery provides the muscles with oxygen
- Muscles use a lot more oxygen during intense exercise, so the oxygen left in the vein is a lot less in comparison with resting time or during less intense exercise
What happens during intense exercise?
- During intense exercise, anaerobic respiration occurs which produces lactic acid
- Too much lactic acid can create cramps and muscle fatigue
- Oxygen breaks down lactic acid
What is oxygen debt?
When you stop exercising, your heart rate and breathing rate remain high since you get the extra oxygen needed from the air to break down the lactic acid.
Why is soda lime used while measuring rates or respiration?
To absorb carbon dioxide.
Describe the steps to measure rates of respiration.
- Add soda lime to a test tube
- Add your organisms on a cotton wool in the test tube
- Close the test tube airtight with a bung using a capillary tube
- Add a drop of coloured liquid in the capillary tube at the point where the scale reads 0
- Observe how far the liquid drop has moved in a set amount of time
- Scale will read the volume of oxygen used during the set time
- Return the coloured liquid back to 0 to repeat the experiment
- Repeat the experiment 3 times and take a mean for the given temperature
- Repeat the experiment in different temperatures
Why does the coloured liquid drop move?
- Once soda lime absorbs the carbon dioxide, only oxygen is left in the test tube
- When oxygen is being absorbed, there is a change in pressure in the test tube
- Pressure decreases which causes the coloured liquid drop to move towards the test tube, giving you a measurement
How does temperature affect the rate of respiration?
- The higher the temperature, the more the kinetic energy
- Enzymes have more successful collisions with the substrate
- Rate of reaction increases therefore oxygen is being used to carry out respiration
