Chapter 6 - Gas Exchange Flashcards
How does a large surface area affect the rate if diffusion
organisms that have a large surface area relative to their volume so the diffusion of substances is fast
How does a small SA:V affect rate of diffusion
organisms that have a small surface area relative to their volume so the diffusion of substances is slower.
How to calculate the surface area of a cube
Length x width x 6
How to calculate the volume (V) of a cube:
V = length x width x depth
Why can’t substances diffuse directly across the cell membrane in multicellular organisms
- Cells are not in direct contact with the external environment.
- Diffusion distances between cells and their environment are large.
- Larger organisms have higher metabolic rates, so they need more oxygen and glucose.
How are exchange surfaces specialised to allow materials to be transferred between cells and an organisms environment
- large surface area to provide a larger area across which substances can be exchanged
- thin walls to minimise diffuse distance
- an extensive blood supply or ventilation to maintain a steep concentration gradient
- being surrounded by selectively partially permeable membranes to control what substances are exchanged
Why do insects need efficient systems for gas exchange
- To deliver oxygen to cells - This allows aerobic respiration to occur to release energy for cellular processes.
- To remove carbon dioxide from cells - The build up of carbon dioxide produced as a waste product of respiration reduces pH, which can denature enzymes.
Main structures of an insects gas exchange system
Tracheae - These are air-filled tubes branching throughout the body.
Tracheoles - These are fine branches of tracheae that deliver gases to cells.
Spiracles - These are external openings of the tracheal system on the exoskeleton along the abdomen and thorax.
How is the tracheae adapted for gas exchange
Reinforced with spirals of chitin - This prevents collapsing.
Multiple tracheae - This increases surface area.
How are the tracheoles adapted for gas exchange
Penetrate directly into tissues - This reduces the gas diffusion distance.
Thin walls - These reduce the gas diffusion distance.
Highly branched - This maximises the surface area.
Not reinforced with chitin - This allows gas exchange to occur.
Fluid at the ends of the tracheoles (tracheal fluid) - This allows oxygen to dissolve to aid diffusion and reduces water loss and
moves out (into tissues) during exercise
so faster diffusion through the air to the
gas exchange surface;
How are the spiracles adapted for gas exchange
Open and close - This allows them to control gas exchange with the atmosphere and minimise water loss.
How does gas exchange occur in an insect
1)Air enters the tracheal system through open spiracles.
2)Air moves into larger tracheae and diffuses into smaller tracheoles.
3)Tracheoles branch throughout the body, transporting air directly to cells.
4)Oxygen dissolves in water in tracheal fluid and diffuses down its concentration gradient from tracheoles into body cells.
5)Carbon dioxide diffuses down its concentration gradient out of body cells into the tracheoles.
6)Air is then carried back to the spiracles via the tracheae and released from the body.
How is the concentration gradient maintained in insects
Cells using up oxygen for respiration - This keeps oxygen concentration low in cells.
Cells producing carbon dioxide in respiration - This keeps carbon dioxide concentration high in cells.
Continuous ventilation - Fresh air is supplied to the tracheal system via spiracles.
Other ventilation mechanism insects use for gas exchange
- Mechanical active ventilation - This is when muscles around the tracheae contract and relax, changing the volume and pressure in the abdomen and squeezing the tracheae to pump air in and out of the spiracles.
- Wing muscles connected to sacs - These pump air to ventilate the tracheal system.
- Vibration of thoracic muscles - This pumps air to ventilate the tracheal system.
Structure of gills
Gills are covered by an operculum flap.
Gills consist of stacked filaments containing gill lamellae.
Gill lamellae are surrounded by extensive blood vessels.
Adaptation of the gills for efficient gas exchange
- The lamellae provide a large surface area.
- The lamellae membranes are thin to minimise diffusion distance.
- The gills have a rich blood supply to maintain steep diffusion gradients.
- The countercurrent flow of blood and water creates even steeper concentration gradients.
- Overlapping filament tips increase resistance, slowing water flow over gills and allowing more time for gas exchange.
What happens in a countercurrent flow system
1) the blood and water flow over the lamellae in opposite directions
2) the blood constantly has less oxygen than the water
3) so when the oxygen rich blood meets water that is at is highest percentage of oxygen the oxygen will move down its concentration gradient into the blood as the blood will have less oxygen than the water
4) the oxygen poor blood returning from t body tissue will also meet oxygen poor water which had had most of its oxygen removed but the water will still have a higher concentration of oxygen so the oxygen will move down it’s concentration gradient
5) this countercurrent happens along the whole fish which maintains a steep concentration gradient across the entire gill
Why can’t fish use parallel flow/ con counter current
As this oxygen in the blood and in the water will eventually reach equilibrium this reduces the concentration gradient so less oxygen is absorbed
How do plants limit water loss in general
They have a waterproof waxy cuticle on their leaves.
They have guard cells that can close stomata when needed.
What are xerophytes
plants adapted to living in dry environments with limited water availability.
How are xerophytes adapted to minimise water loss
- Thick waxy cuticle - This reduces water loss through evaporation.
- Rolling or folding of leaves - This encloses the stomata on the lower surface to reduce air flow and the evaporation of water.
- Hairs on leaves - These trap moist air against the leaf surface to reduce the diffusion gradient of water vapour.
- Sunken stomata in pits - These reduce air flow and the evaporation of water.
- Small, needle-like leaves - These reduce the surface area across which water can be lost.
- Water storage organs - These conserve water for when it is in low supply.
Structure and functions of a leaf
- Upper epidermis with waxy cuticle - This reduces water loss from the leaf surface.
Air spaces - Mesophyll cells - These are cells within the mesophyll tissue, located between the upper and lower epidermis.
- Stomata - These are small pores surrounded by guard cells on the underside of leaves that can open and close.
- Lower epidermis - This is the bottom layer of cells in a leaf that contains the stomata and guard cells.
- Vascular tissue (xylem and phloem) - This transports water and nutrients.
Adaptions of structure of the leaf for gas exchange
Air spaces - These provide a network for gases to quickly diffuse in and out of the leaf and access photosynthesising cells.
Mesophyll cells - These are dispersed throughout the leaf, providing a large surface area across which gases can diffuse.
Stomata - These open when conditions are suitable for photosynthesis, allowing inward diffusion of carbon dioxide and outward diffusion of oxygen, and close to minimise water loss.
How does air travel through a humans respiratory system
1) Air first enters the trachea.
2) Air travels into the bronchi, with each bronchus going to each lung.
3) Air travels into smaller airways called bronchioles.
4) Air travels into clusters of air sacs called alveoli at the end of the bronchioles.
How does the ciliated epithelium protect our airways against microbes
contains mainly goblet cells and ciliated epithelial cells:
- Goblet cells - These produce and secrete mucus that traps dust and microbes.
- Cilia on ciliated epithelial cells - These waft the mucus upward to the mouth so it can be swallowed.
What is the trachea
A large tube that carries air from the throat down to the lungs.
Adaptions of the trachea
1) Rings of cartilage keep the airway open.
2) Smooth muscle can contract or relax to constrict or dilate the airway and change airflow.
3) Elastic tissue contains elastic fibres with elastin that allows stretching and recoiling.
4) Lined with ciliated epithelial cells and goblet cells.
What is the bronchi
two main branches extending from the trachea that carry air into each lung
Adaptations of the bronchus
1) Reinforced with cartilage to keep the airway open.
2) Smooth muscle can contract or relax to constrict or dilate the airway and change airflow.
3) Elastic tissue contains elastic fibres with elastin that allows stretching and recoiling.
4) Lined with ciliated epithelial cells and goblet cells.
What are the bronchioles
smaller airways branching from the bronchi that carry air to the alveoli.
Adaptions of bronchioles
1) No cartilage, can change shape.
2) Smooth muscle can contract or relax to constrict or dilate the airway and change airflow.
3) Elastic tissue contains elastic fibres with elastin that allows stretching and recoiling.
4) Simple squamous epithelium (only larger bronchioles have a ciliated epithelium).
How does the alveoli carry out gas exchange
1) Oxygen diffuses across the alveolar epithelium and across the epithelium of a capillary into the blood
2) Carbon dioxide dissociates from haemoglobin and diffuses from the across the
epithelium of a capillary and then across the alveolar epithelium into the alveoli
Adaptations of the alveoli
1) Large surface area - This increases rate of gas exchange.
2) Partially permeable - This means that only certain gases can move across the wall.
3) Surrounded by dense network of capillaries - This maintains steep diffusion gradient and rapid rate of diffusion
4) Ventilation of air and is one cell thick (as its wall consists of one layer of squamous epithelial cells) - reduces diffusion distance for gas exchange
5) Elastic fibres - These allow stretching and recoiling.
(6) Collagen fibres - These contain strong collagen that prevents alveoli from bursting and limits overstretching.) - good for essays
7) Moist inner surface - This allows gases to dissolve, and lung surfactant helps alveoli remain inflated.
What are the pulmonary blood vessels that are involved in the circulation of blood in the lungs
- The pulmonary artery - This delivers deoxygenated blood from heart to pulmonary capillaries.
- The pulmonary vein - This delivers oxygenated blood from capillaries to heart.
- The pulmonary capillaries - These are the site of gas exchange between blood and alveoli.
Adaptions of the pulmonary capillaries for gas exchange
- Thin walls (one endothelial cell thick) - This maintains a short diffusion distance.
- Red blood cells pressed against capillary walls - This reduces diffusion distance.
- Large surface area - This increases diffusion speed.
- Movement of blood - This maintains steep diffusion gradient.
- Slow blood movement - This allows more time for diffusion.
What happens during inspiration
- Diaphragm (muscles) contract and diaphragm flattens/pulled down;
- External intercostal muscles contract and ribcage pulled up and out
- Internal Intercostal muscles relax
- Lung volume increase and lung pressure decrease in thoracic cavity
- Air is then forced into the lungs
What happens during expiration
- Diaphragm (muscles) relaxes and diaphragm unflattens and are pulled up
- internal intercostal muscles contract and ribcage pulled in and down
- External Intercostal muscles relax
- Lung volume decreases and lung pressure increases in thoracic cavity
- Air is then forced out of the lungs down the pressure gradient
What are the two main ways the digestive system breaks down food and how does both processes work
- Physical digestion - The break down of large food pieces into smaller ones to increase the surface area for chemical digestion.
- Chemical digestion - Enzymes catalyse hydrolysis reactions that break bonds in large insoluble molecules to form smaller soluble molecules.
Key components involved in digestion
- Salivary glands - These secrete saliva containing amylase.
- Oesophagus - This transports food to the stomach.
- Stomach - This digests food (especially proteins) and produces acid to destroy pathogens.
- Liver - This produces bile salts to aid lipid digestion.
- Pancreas - This secretes pancreatic juice containing enzymes (proteases, lipases, and amylases).
- Small intestine - This consists of three parts (you only need to know the final part, the ileum) that are the site of further digestion and absorption.
- Large intestine - This absorbs water and stores waste.
- Rectum - This stores faeces before removal via egestion through the anus.
What is the order that food travels down your alimentary canal (the pathway food takes through the body)
Mouth ➔ oesophagus ➔ stomach ➔ small intestine ➔ large intestine ➔ rectum ➔ anus
What do carbohydrases do
They break down large carbohydrates into smaller polysaccharides, disaccharides and monosaccharides
Where are carbohydrases produced
salivary glands, the pancreas, and the epithelial cells lining the ileum.
How does starch digestion occur
1) Salivary amylase breaks down starch into the disaccharide maltose in the mouth.
2) Acid in stomach denatures salivary amylase.
3) Pancreatic amylase continues starch digestion in small intestine.
4) The epithelial cells in the ileum lining produce maltase to break down maltose into α-glucose monomers.
What does the lipases do
breaks down lipids into fatty acids and monoglycerides.
What are lipase produced by
the pancreas and act in the small intestine.
How does the digestion of lipids occur
1) Bile salts emulsify lipids into tiny droplets called micelles, increasing the surface area of the lipids.
2) Pancreatic lipase breaks down micelles into fatty acids and monoglycerides.
What do protease do
break down proteins, polypeptides, or dipeptides into smaller units and eventually into amino acids
What are the three types of protease and what do they do
-Endopeptidases - These hydrolyse internal peptide bonds in the middle of proteins to form shorter polypeptides, increasing the number of ends for other proteases to work on.
- Exopeptidases - These hydrolyse peptide bonds at the ends of polypeptides to remove terminal amino acids or dipeptides.
- Dipeptidase - These break down any remaining dipeptides into amino acids.
What are the adaptions of the ileum (small intestine)
1) The walls are folded into villi to increase surface area.
2) Epithelial cells have microvilli to further increase surface area.
3) It has thin walls reduce diffusion distance.
4) It has an extensive capillary network and a good blood supply to maintain steep diffusion gradients.
5)Muscles in the ileum wall contract to mix content and bring new material into contact with villi.
How are triglycerides absorbed into the bloodstream
1) Bile salts emulsify triglycerides into micelles (tiny droplets of fat)
2) Micelles are broken down to release fatty acids and monoglycerides.
3) As they are both non-polar, fatty acids and monoglycerides can diffuse into the epithelial cells that line the ileum.
4) Triglycerides reform inside the cells’ endoplasmic reticulum.
5) Triglycerides are packaged into chylomicrons for transport.
6) Chylomicrons are released from the epithelial cells by exocytosis into lacteals, which are lymphatic vessels in the villi.
7) Chylomicrons are transported via lymph vessels in the lymphatic system to the blood.
Suggest and explain ways the cell-surface membranes of the cells lining the
uterus may be adapted to allow rapid transport of nutrients.
- Membrane folded so increased/large surface
area; - Large number of protein channels/carriers (in
membrane) for facilitated diffusion; - Large number of protein carriers (in membrane)
for active transport; - Large number of protein (channels/carriers in
membrane) for co-transport;
The adult damselfly uses a tracheal system for gas exchange.
Explain three ways in which an insect’s tracheal system is adapted for efficient gas
exchange.
- Tracheoles have thin walls so short
diffusion distance to cells; - Highly branched/large number of
tracheoles so large surface area (for gas
exchange); - Fluid in the end of the tracheoles that
moves out (into tissues) during exercise
so faster diffusion through the air to the
gas exchange surface;
