Exchange Surfaces Flashcards
How do insects draw oxygen further into the muscles during intense activity?
1) Leak a bit of water across muscle membrane
2) Anaerobic respiration produces lactate, which is soluble and lowers water potential
3) Previously leaked water returns into the muscles, drawing air in with it too
What occurs during inspiration?
1) External intercostal muscle contract while intercostal muscles relax and ribs are moved up and out, increasing volume of thoracic cavity
2) Diaphragm muscles contract and flatten
3) Increased volume in thoracic cavity decreases pressure in the lungs, forcing air down the pressure gradient into the trachea
What is the flow of air in the human respiratory system?
Pharynx - Larynx - Trachea - Bronchi - Bronchioles - Alveoli
What are the advantages and disadvantages of retrospective studies?
+ cheap and easy to perform
- people may have forgotten information or deliberately deceive or exaggerate information, making it fairly unreliable
What are the key features/adaptations of the trachea?
- rings of cartilage to keep the walls open
- walls made of muscle and elastic tissue
- lined with ciliated epithelium, which help to move mucus along, and goblet cells, which trap excess mucus
- epiglottis closes entrance to trachea when swallowing
What is counter current flow?
In the gill filaments, the blood and water flow in opposite directions, maintaining the diffusion gradient along the entire lamellae
What is an example of a single-celled organism?
Chlamydomonas
What is the digestion pathway?
1) begins in mouth with mechanical (chewing) and chemical (enzymes) digestion
2) food travels to stomach where mechanical (churning) and chemical (enzymes and acid) digestion continues
3) food moves to small intestine where chemical digestion continues as it gets mixed with enzymes from the pancreas and bile
What two organelles maintain diffusion gradients in a leaf?
Mitochondria and chloroplasts
What are the two ways insects reduce water loss?
Spiracles can open and close and tiny hairs round edge of spiracles
What are the four different substances that need to be exchanged with the environment?
- respiratory gases
- nutrients
- excretory products
- heat
What are the enzymes involved in the digestion of proteins?
Endopeptidases - hydrolyse bonds within the central regions to form peptides
Exopeptidase - hydrolyse bonds on the terminal amino acids of a peptide to release dipeptides and single amino acids
Membrane-bound Dipeptidases - exopeptidase that specifically work on dipeptides
What ensures tracheae stay open?
Rings of chitin
What is the structure of the gills?
- each gill has two stacks of filaments
- a row of lamellae is positioned perpendicular to each filament
- each lamellae is a single layer of cells covering a vast network of capillaries
- all the gills are attached to a primary gill arch
What are the key features/adaptations of the alveolar epithelium?
- network of capillaries to ensure continuous blood flow and movement of oxygen
- walls consist of flattened singular cells, reducing diffusion distance
- capillary walls are very thin and narrow, further reducing diffusion distance
- inner surface of the alveolus wall is covered in a thin film of water, as cell-surface membranes are permeable to water, which reduces diffusion rate and increases distance, so other mechanisms need to try to overcome this
What adaptations do cacti have?
- leaves can roll up so only one side is exposed to wind
- exposed surface has no stomata
- inner surface has many hairs to trap water
How are gills adapted to increase the rate of diffusion?
- lots of lamellae, increasing SA:V ratio
- lamellae are only covered with a very thin layer of cells, reducing diffusion pathway
- rich supply of capillaries, so diffusion pathway is maintained
- counter-current flow maintains diffusion gradient along the whole length of the lamellae
What are some of the main risk factors of COPD?
- smoking (around 90% of COPd patients have been heavy smokers)
- air pollution
- genetics
- infections
What are the key features/adaptations of the bronchi and bronchioles?
- bronchi have sections of cartilage in their walls to maintain their structure
- bronchioles repeatedly branch into smaller and smaller tubes
- bronchioles can contract and relax during ventilation
What are the 5 key features of exchange surfaces?
- Large SA:V ratio
- Very thin walls
- Selectively permeable membranes
- Movement of environmental medium
- Moderation of internal medium
What occurs during expiration?
1) Internal intercostal muscles contract while external intercostal muscles relax and ribs are moved down and in, decreasing thoracic cavity volume
2) Diaphragm muscles relax
3) Decreased volume of thoracic cavity increases pressure in lungs, forcing air out
What adaptations do xerophytes have?
- thick cuticle
- rolled up leaves that form spines
- stomata in pits or grooves to trap moist air
- reduced SA:V ratio of the leaf
- few stomata
- hairs around the stomata to trap any water
Why do insects require a high rate of oxygen?
Very high metabolism due to their small size
What adaptations do cacti have?
- leaves reduced to spines to reduce water loss
- stem with chloroplasts and water storing sacs
- shallow and deep roots to penetrate as much of the water table as possible
What are xerophytes?
Xerophytes are plants that have adaptations to reduce water loss, as they live in deserts
What makes it harder for gases to diffuse into the insect?
Waxy, waterproof exoskeleton
What are the key features/adaptations of the lungs?
- each lung contains over 350 million alveoli to provide large surface area
- lungs are ventilated to ensure constant movement of air
What are four main adaptations of leaves to ensure rapid division?
- lots of stomata, so short diffusion pathway
- numerous interconnecting air spaces, creating large SA to volume ratio
- large surface area of mesophyll cells
- thin tissue covering the leaves
How do fish ventilate their gills?
1) Opens its mouth while closing the opercula and lowering the buccal floor
2) Draws in water due to a decreased pressure
3) Closes its mouth while opening the opercula and raising the buccal floor
4) Pushes water over the gills and out the opercula due to increased pressure
What is the process of the digestion of lipids? (enzymes)
1) Bile salts emulsify lipids into smaller droplets, providing a large surface area for the hydrolysis of lipase to occur
2) Lipases hydrolyse lipids into fatty acids and monoglycerides
How are carbohydrates and proteins absorbed?
1) Potassium is moved along concentration gradient into epithelial cells while sodium is actively transported using co-transport out of the EC into the capillary
2) Sodium can then move along the conc. gradient into EC and co-transports glucose or amino acids against the conc. gradient
3) Glucose or amino acids can move into the capillary through simple diffusion as blood movement maintains the conc. gradient
How to plants manage the conflicting needs of gas exchange and water loss?
Guard cells that open and close the stomata, depending on the conditions and what is needed
What are the three main ways that respiratory gases move into the insect?
- along the diffusion gradient, as the respiring cells use oxygen, so a steel concentration gradient is created
- mass transport, when the abdominal plates are squeezed, a mass rush of air floods in
- ends of tracheoles filling with water, and as diffusion happens quicker in liquids, the diffusion pathway gets reduced
How are lipids absorbed?
1) Emulsified by bile salts
2) Lipase hydrolyses them into fatty acids and monoglycerides
3) Micelles form due to the amphipathic nature of the bile salts
4) Micelles constantly break down and reform, allowing the freely dissolved monoglycerides and fatty acids to travel across phospholipid bilayer
5) Recombined to form triglycerides in the endoplasmic reticulum
6) Packaged with cholesterol and phospholipids in the Golgi apparatus to form chylomicrons
7) Chylomicrons are transferred to lymph vessel by exocytosis
What is the process of the digestion of carbohydrates?
1) Salivary amylase hydrolyses alternate glycosidic bonds, producing maltose
2) Pancreatic amylase continues to break down the bonds, with the help of alkaline salts maintaining a neutral pH
3) Disaccharides are hydrolysed into monosaccharides by membrane-bound disaccharides in the small intestine
What is a spiracle?
An opening in the exoskeleton of an insect that connects to the tracheal system
How do insects get extra oxygen deep into their air sacs when required?
1) Spiracles close
2) Muscles pull abdominal plates together
3) Squeezes tracheal system, forcing more oxygen deeper into the tracheoles
4) Atmospheric pressure in insect decreases, so when spiracles open, air rushes in
What is the diaphragm?
Tough membrane attached by muscles to the inner wall of the chest at the bottom of the ribcage
Why can’t insects become giant?
Their respiration relies mainly on diffusion, so a short diffusion pathway is needed
Why is counter-current flow such an advantageous adaptation for fish?
Enables fish to get far more oxygen into their blood stream, around 80% gets extracted from the water compared to only around 50% without it
