4. Gas exchange Flashcards
Why does the volume of an organism affect the rate of gas production/use
Bigger volume = more cells
Increase use of oxygen and production of carbon dioxide
Why do some animals need a higher metabolic rate than others
Smaller mammals and birds have a larger SA:V so lose heat faster. They need a higher metabolic rate so respire faster
What is aerobic respiration
Glucose + Oxygen -> Carbon dioxide + water + ATP
How do gases exchange over surfaces for aerobic respiration
Diffusion
How do single celled organisms gas exchange
Simple diffusion of gases across their outer surface membrane.
Large SA:V and short diffusion pathway so rates can be achived.
Continuous aerobic respiration will maintain concentration gradients for O2 and CO2
What stuructures do fish use to gas exchange
The gills
Between the buccal cavity and the operculum
How is the surface area of the gill alow for effiecient gas exchange
Each gill contains many filaments each covered in many lamellae. Give a large SA for diffusion
How are a fishs gill diffusion pathway structured for efficient gas exchange
Gills have rich blood supply
Many capillaries in a single layer of thin epithelium
Close to thin-walled lamellae
Many cappilaries increase SA
Thin epithelium ensures short diffusion pathway between blood and water
How is a concentration gradient maintained in a fish’s gill
- Continous flow of blood through capillaries ensures frsh oxygenated blood is quickly removed from gills and replaced with deoxygenated blood
- Water flows over the gill plates in the opposite direction to the flow of blood in capillaires. = Counter current mechanis
Why is the counter current mechanism an improvment over parallel flow
Gas exchange takes place across the entire gill
Oxygen never reaches equilibrium
Blood always meets with water with higher concentration of O2 so conc gradient is maintained along whole length of lamellae
Constant diffusion can occur
What does a ventilation mechanism do in a fish
Ensures water enters the fishs mouth and flows over the gills, leaving via operculum
Constant flow of water over the gills
What is the fructure of an insects body
Protected by an exoskeleton made of chitin - prevents insects using their bodies surface for diffusion
Outermost layer is waxy and waterproof which minimises water loss
Tracheal system constists of air-filled tubes (tracheae) that open to the outside through small holes in exoskelenton called spiricales
What is the trachea system
Larger tracheal tubes subdivide into smaller tubes that penetrate into and between cells.
Finer tubes are tracheoles - site of gas exchange
Large number of them gives large SA for diffusion and short diffusion pathway
How do insects repire at resting
Rely on diffusion down a concentration gradient taht is maintained int the tracheal system due to cellular repsiration in the insects tissues
How does an insects respiration change during flight
Require more ATP to fly
Increase in O2 needed
Ventillation by contraction of the abb muscles force air in and out of spiricles and tracheae to maintain greater airfoe
Maintain steeper conc gradients for fast diffusion
Abdominal pumping
How are insects adapted to minimise water loss
-Waterproof waxy cuticle
-Spiricles guraded by valves which can close spiricles
-Spiricles surrounded by hairs which trap a layer of moist air
Where does gas excange occur in a plant
Spongy mesophyll layer of leaf
Large air spaces and thin-walled cells -Large SA and short diff pathway
In close contact with numerous stomata which gases enter and leave via diffusion down a steep concentration gradient
Why will there be a steep concentration gradient for gases in a plant
CO2 will be low in the day as its used in photosynthesis.
The reverse for oxygen
O2 conc low at night as its used in repsiration
Reverse for CO2
How is a short diffusion pathway maintained in a plant
The spongy mesophyl cells have thin cell walls and being in direct contact with air.
Leaf is a thin structure
How does a leaf minimise water loss while still maintaining effective diffusion
Stomata mainly on underside of leaf
Thicker waxy cuticle on upper eppidermis
Guard cells can close stomata
Why do humans need gas exchange
Need a constant supply of oxygen to release energy in the form of ATP duiring respiration.
We need to remove CO2 or it would lower the pH
Why is the volume of gases needed to exchange larger in mammals
High rate of respiration as they need to maintain a constant body tempertaure
What is the structure of the gas exchange system in humans
Lungs situated on either side of the heart in the thorax.
Surrounded by ribs and with the diaphragm at the base
Allows gaseous exchange between air in lungs and blood in cappilaries
Where does air move through in humans
Nose/mouth -> trachea -> bronchi -> bronchioles -> alveoli
What do airways contain
Mucus membranes containing goblet cells which secrete mucus and are lined with a ciliated epithelium.
mucus- traps micro-organisms and debris
-Cilia - move micro-organisms and dust particles allong with the mucus
Where does gas exchange take place in humans
Alveoli and capillaries.
O2 diffuses through epithelium of alveoli and the endothelium of the capillairies into the blood
Combines with heamoglobin
How do alveoli enable a maximum rate of diffusion
Provide a large SA - there are millions of alveoli
Have thin exchange surface - only 2 layers of cell to diffuse across
Large conc gradient -Blood continously circulated and ventilation ensures the right molecules are being taken in and out
What does breathing invlove
Inspiration
Expiration
Both require movements to alter volume of thorax
Creates air pressure difference between thorax and atmosphere
Thorax is airtight so air is drawn in when thorax pressure is lower than atmospheric. Vise versa
How does air move
from an area of higher pressure to one of lower pressure down a pressure gradient.
How do pressure and volume relate in the lungs
Inversely proportional
What is the ventillation mechanism in the lungs
Movements of the ribcage, the diaphragm and the internal and external intercostal muscles. The muscles are anatgonistic - one contracts whilsts one stretch
how does the intercostal muscles and diaphragm muscles bring about inspiration
- External intercostal muscles contract
-Ribcage moves up and out - Diaphragm muscles contract and diapraghm flattens
-Elastic tissue stretches
-Thorax volume increase
-Pressure decreases below atmospheric
-Air enters down a pressure gradient
how does the intercostal muscles and diaphragm muscles bring about expiration at rest
- External intercostal muscles relax
-Ribcage moves down and in
-Diaphragm muscles relax and returns to dome shape
-Elastic tissue recoils
Vol of thorax decreases
-pressure increases above atmospheric
-Air forced out down a pressure gradient
What happens in forced expiration
Same as normal expiration except external intercostal muscles realx and the internal intercostal muscles contract
This pulls the ribcage futher down and in
What is the role of elastic tissue in breathing
Walls of alveoli contain elastin
During inspiration the elastic tissue in the the lungs stretches to allow the lungs to inflate
During expiration the elastic tissue recoils
What is tidal volume
The volume of air breathed in or out of the lungs in a normal resting breath
What is ventilation rate
The number of breathes in and out per min
What is pulomonary ventillation
The total volume of air that is moved into the lungs in one min
PV = TV x VR
How do correlation and causation link
a correlation between two variables does not mean the variables are linked. Any correlation observed between two variables could just be a coincidence, and an extraneous factor may be responsible for causing the changes
