3.3.4 Mass transport Flashcards
What is haemoglobin?
A large protein with quaternary stricture
What is haemoglobin made up of?
4 polypeptide chains - 2 alpha and 2 beta
Each chain has a haem unit (total of 4) which contains Fe2+
How do haemoglobin differ in crustaceans
In the form of haemocyanin which is made up of copper units
Where are haemogoblin found in?
All vertebrates
What is association or loading?
When oxygen molecule joins to haemoglobin
What is dissociation or unloading?
When oxygen molecule leaves oxyhaemoglobin
What is the affinity for oxyegn?
The tendency a molecule has to bind with oxygen
How is haemoglobin’s affinity for oxygen varied and in what way?
By partial pressure (concentration of dissolved oxygen in cells) of oxygen - pO2
Higher PP, affinity for oxygen increases, more association of oxygen - load onto haemoglobin
Lower PP, affinity for oxygen decreases, more dissociation of oxygen - unload from oxyhaemoglobin
Where in the body is pO2 high or low?
High in alveoli in lungs
Low in respiring tissues
What is the Bohr effect?
When oxygen dissociation curve ‘shifts’ to the right due to an increase of pCO2
Why does an increase in CO2 decrease affinity for oxygen
- CO2 and H2O released from aerobic respiration is joined together by carbonic anhydrase (catalyst) to form carbonic acid (H2CO3)
- H2CO3 then dissociates into H+ and HCO3-
- H+ is acidic which causes a conformational change (change in shape of macromolecule due to environmental factors) of haemoglobin
- Quaternary structure changes -affinity for oxygen decreases
- Oxygen is unloaded from oxyhaemoglobin and will then enters cell
How would oxygen dissociation curve look at different conditions?
High activity level / metabolism:
Graph shifts to the right- lower affinity for oxygen (more unloading of oxygen) at lower pO2
High altitude:
Graph shifts to the left - higher affinity for oxygen (more loading of oxygen) at lower pO2
What does oxygen dissociation graph show?
A sigmoid curve - S shaped
At lower pO2, affinity of oxygen is lower - less oxygen bound to haem unit (shallower)
As haemoglobin combine with the first O2 (more partial pressure needed), its shape alters which makes it easier for other O2 to join afterwards (steeper curve in the middle)
Curve gets shallower towards the end as it is now harder for more oxygen molecules to join
What valves separate the atria and ventricle
atrioventricular valves
Tricuspid on the right
Bicuspid on the left
Which are the only arteries that contains valves (semi-lunar)?
Pulmonary artery contains semi-lunar pulmonary valve
Aorta contains semi-lunar aortic valve
What is the septum and its function?
A wall of tissue that separates the left and right ventricle - keeping oxygenated and deoxygenated blood separate
What is the general structure of a blood vessel (artery/vein)?
Outside to inside:
Three tunica layers:
Tunica intima (thin layer of elastic tissues)
Tunica media (thick layer of smooth muscle)
Tunica externa (thick layer of fibrous protein, collogen - withstand pressure and elastic tissue)
A single layer of endothelial cells
Lumen
How does structure of artery and vein differ?
Lumen:
A: small/narrow
V: large/wider
Thickness of layers in walls:
A: thicker
V: thinner
Valves in lumen:
A: absent
V: present
How are structure of artery and vein similar?
Both have a single layer of endothelial cells surrounding the lumen
Both have elastic tissue, smooth muscle and collogen in their walls
What are tissue fluids?
Fluid that surrounds cells in tissue
What causes tissue fluid to move in and out of capillary?
Tissue fluid move out of capillary at the arteriole end and re-enters at the venule end
Hydrostatic pressure causes soluble substances to move out of vessel
Osmotic pressure causes soluble substances to move inside vessel
Higher hydrostatic kPa at arteriole end - net movement of tissue fluid moving out of arteriole
Higher osmotic kPa at venule end - net movement of tissue fluid moving into venule
What is cardiac output?
stroke volume x heart rate
What are the four stages of cardiac cycle?
Atrial systole
Isovolumetric contraction
Ejection phase
Isovolumetric relaxation
What happens in the first stage of cardiac cycle?
Atria contracts – systole
(Ventricle is relaxed)
Pressure inside atria increases, this forces atrioventricular valves to open
Blood now flows from atria to ventricle through opened valve
What happens in the second stage of cardiac cycle?
Volume of ventricles decreases as blood flows into them, pressure increases
Ventricle contracts - systole - pressure increases, this forces atrioventricular valves to shut to prevent back-flow
(Atria is relaxed)
What happens in the third stage of cardiac cycle?
Ventricle’s high pressure forces semi-lunar valves to open
Blood is ejected from the heart into arteries
Volume of blood in ventricle decreases
What happens in the last stage of cardiac cycle?
Atria and Ventricle both relaxes
High pressure in arteries forces semi-lunar valves to shut
When blood returns to heart again, atria will be filled and pressure increases, forcing atrioventricular valves to open, allowing blood to flow passively from atria into ventricle
When atria contracts, process starts again
How has the structure of arteries adapted to its function?
Contains a thick layer of elastic fibre to stretch to accommodate high blood pressure from heart
Contains thick outer wall to withstand high blood pressure
Narrow lumen to keep blood under high pressure
How has the structure of veins adapted to its function?
Contains thinner muscular and elastic outer walls due to a decrease in blood pressure - does not have to withstand as high pressure
Contains valves to prevent blood from flowing backwards due to lower blood pressure
Wider lumen as blood pressure is lower
How has the structure of capillaries adapted to its function?
Contain walls that are one cell thick, allowing a shorter diffusion pathway as they are exchange surfaces
Very narrow lumen (slightly larger than a RBC) to ensure slow blood flow - efficient exchange
What does the xylem tissue transport in plants?
Water and mineral ions in solution
What direction are substances transported in the xylem?
Move up from roots to leaves - unidirectional
What are the features of the xylem tissue?
Long and hollow
Formed from dead cells
No end walls - continuous tube
Cell wall made of cellulose
How does water move up the xylem against the force of gravity?
Through water adhesion and cohesion:
- Transpiration occurs at the top of the xylem in the leaves
- Water cohesion meant water molecules will be pulled into leaf as previous water molecules leaf through their ‘stickiness’
- Whole column of water in the xylem will be pulled upwards from the roots
- Water adhesion meant water molecules will bind to cellulose found in the cell wall - this pull on the cell wall creates tension
What is the process of transpiration?
Evaporation of water from plant’s surface, especially leaves
Water move out of xylem into spongy mesophyll layer via osmosis
Water is evaporated from the moisture cell walls into the air space
Water molecule moves out of leaf via diffusion through the stomata down the water potential gradient
What factors affect transpiration rate?
- Light intensity - positive correlation
High: Stomata open to allow CO2 in for photosynthesis (more)
Low: Stomata close (less) - Temperature - positive correlation
High: molecules have more energy - rate of evaporation increases - concentration gradient between inside and outside increases (more) - Humidity - negative correlation
Low: Dry air around leaves give a larger water potential gradient between inside of leaf and air (more) - Wind speed - positive correlation
High: Lots of air movement blows away water molecules around the stomata - increase in water potential gradient (more)
