Gas Exchange, Digestion & Absorption Flashcards
Why did elephants have large ears
An adaption to increase surface area for heat loss
What is the difference in a mouse and elephants surface area to volume ratio
mice - large
elephant - small
How much heat do mice lose?
The mice loses large amount of heat relative to its mass
Why do mice respire at a high rate?
Thes loose a large amount of heat so respire at a high rate to maintain a constant body temp thus high uptake if oxygen
What is in the gas exchange system ?
• trachea
• bronchi
• bronchioles
Describe the gas exchange system
trachea supported by rings if cartilage to prevent it collapsing during pressure changes in ventilation
• trachea divides into 2 bronchi that repeatedly divide into bronchioles
• alveoli at end bronchioles provide large surface area for gaseous exchange
How are the alveoli adapted for gaseous exchange?
• shape and large number provide large surface area
• fluid lining alveolus allows gases to dissolve and diffuse across
• two cell layers= short diffusion pathway
• blood capillaries = large SA
Whats the function of the circulatory system?
maintain high concentration gradient for gas exchange by transporting deoxygenated blood to lungs and removing oxygenated blood from lungs
What is the function of the ventilation mechanism?
continuously provides air with high oxygen concentration and removes air with high carbon dioxide conc
- maintains high concentration gradient for gaseous exchange
What is the function of the fluid lining the epithelium of the alveolus?
oxygen in the alveolar air space dissolves in the fluid
What are the two cells separating blood and air in the alveoli?
flattened epithelial cells (alveolar wall)
endothelial cells (capillary wall)
What is inspiration
breathing in (INspiritation>
Describe inspiration.
- external intercostal muscles contact
- rib cage pulled up and out
- diaphragm muscles contract
- diaphragm flattens
- thorax volume increases and pressure decreases
- air enters area of low pressure IN LUNGS
Describe Expiration
- external intercostal muscles relax
- rib cage pulled down and in
- diaphragm muscles relax
- diaphragm moves up to dome shape
- thorax volume decreases and pressure increases
- air enters area of low pressure OUT LUNGS
What is the equation for pulmonary ventilation
pulmonary ventilation = tidal volume(dm3) x ventilation rate(min-1)
What is the ventilation rate?
number if breaths per minute (usually 12-20)
What is the tidal volume?
Volume if air normally taken in with each breath ( usually 0.5)
What are spiracles?
- tiny holes on opening of tracheae
- have valves that can close ti reduce water loss
What are tracheoles?
- branches from the trachea
- thin thus providing short diffusion distance for oxygen
- many = large surface area
How dies oxygen enter the insects cell?
- diffuses from air into spiracles along trachea and tracheoles into cells
- CO2 leaves in the reverse path way
What happenens during increased activity in insects?
anaerobic respiration creates lactic acid
- lowers WP of cells and water ends in tracheoles move into cells by osmosis
- more air moves along tracheoles
How are gills adapted for gas exchange?
-
large surface area
provided by gill filaments which posesss lamellae -
short diffusion pathway
bc blood and water is separated by two cell layers
• epithelial layer if lamellae
• endothelial layer of capillaries
Describe the countercurrent system?
blood and water flow in opposite directions
- blood continuously meets water with a higher oxygen conversion
- this maintains a high diffusion gradient along the length of the lamellae
How does the ventilation system help gas exchange in fish?
provides continual flow of water over gills
- this brings more oxygen and removes CO2 thus maintaining high diffusion gradient
How does the circulatory system help gas exchange im fish?
Provides continual flow of blood through respiratory surface to absorb oxygen and remove CO2
- maintaining high diffusion gradient
Which structures are involved in gas exchange in plants?
stomata and mesophyll cells and air spaces between them
What are stomata?
pores in the epidermis of leaves that surrounded by guard cells
- gases diffuse in and out the stomata
- leaves are thin = short diffusion pathway
whats the function of mesophyll cells?
provide large surface area for gas exchange
Whats the function of amylase?
hydrolyses starch into maltose
How is food broken down during chewing?
saliva contains salivary amylase which breaks down starch
- only a small amount is broken down as chewing is a short process
How dies chewing speed up hydrolysis if starch?
breaks down food to smaller pieces which increases the surface area
How dies the pancreas aid in breaking down the remainder if the starch?
- releases pancreatic juice into small intestine which contains enzymes pancreatic amylase
this hydrolyses the remaining starch
Where does the complete hydrolsis of starch occur?
In the ileum
What do membrane bound disaccharides do ?
Maltase and other disaccharides
form the cell membrane of epithelial cells that line the ileum
Which enzyme hydrolyses lipids?
lipase (hydrolyse the ester bonds in lipids)
Where is lipase secreted from?
The pancreas into the small intestine
How do bile salts increase the rate of hydrolysis of lipids?
- they emulsify lipids causing them to form droplets
- this increases surface area for hydrolysis
What hydrolyses proteins?
endopeptides
exopeptides
dipeptidases
How do Endopeptidases work?
They hydrolyse the INTERNAL peptide bonds between amino acids to form short amino acid chains
How do exopeptidase work?
- they hydrolyse peptide bonds at either end if a polypeptide so individual amino acids are removed
What is the final stage of protein digestion
Breaking down dipeptides to single amino acids
- enzyme dipeptidase found in epithelial cells of the ileum
- hydrolyse dipeptide
How is the ileum adapted for absorption?
- large surface area due to long length villi and microvilli
-
villi contain blood capillaries that absorb
monosaccharides and aminos, this maintains high diffusion gradient - lacteals in villi absorb digested lipids that also maintain high diffusion gradient for absorption
- many mitochondria to provide ATP for active transport
How do villi increase absorption?
Villus wall contain a single layer of epithelia cells providing short diffusion pathway
Outline the absorption digested of lipids?
- bile salts emulsify lipids droplets
- bile salts combine with monoglycerides and fatty acids to firm micelles
- micelles transport MG and FA to surface of epithelial cell
- micelles break down and release FA and MG and they diffuse thru epithelial cell
- FA and MG recombine in smooth ER
- packaged in protein and phospholipid by golgi and form CHYLOMICRONS
- Chylomicrons absorbed into lacteals which drain into blood
How are monosaccharides and aminos absorbed?
*they’re at a high concentration in lumen of ileum
so they will be absorbed down a concentration gradient by facilitated diffusion
How are monosaccharides and aminos transported?
by co-transport against a concentration gradient
How is glucose taken up by co-transport?
- Na+ actively transported out epithelial cells into blood to ensure low conc of sodium in epithelial cell
- high conc of sodium will be in lumen
- so there will be a conc gradient for sodium ions to diffuse into cell
- Na+ diffuse into epithelial cell from lumen with glucose via a co transport protein by facillitated diffusion
- glucose enters blood by facillitated diffusion
Define digestion
process where large molecules are hydrolysed by enzymes to produce small molecules that can be absorbed
Where is the endopeptidase Pepsin secreted from?
cells lining the stomach
Where are exopeptidases secreted from?
pancreas
