More Exhange And Transport Flashcards
How is Food Broken Down into Smaller Molecules During Digestion
The whole point of digestion is breaking down the food into small molecules that your cells can absorb.
- involves loads of different chemical reactions and our enzymes.
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1) The large biological molecules (e.g. starch, proteins) in food are too big to cross cell membranes.
»_space; means can’t be absorbed from the gut into blood.
2) In digestion, large molecules are broken into smaller molecules (e.g. glucose, amino acids)
- wch can move across cell membranes.
- means can be easily absorbed from gut into blood,
- to be transported round body for use by the body cells.
3) most large biological molecules are polymers, which can be broken into monomers in hydrolysis reactions.
»_space;Hydrolysis reactions break bonds by adding water.
4) During hydrolysis, carbohydrates are broken into disaccharides then monosaccharides.
- Fats are broken into fatty acids and monoglycerides.
- Proteins are broken down into amino acids.
What enzyme type are carbohydrates broken down by
Lots of diff digestive enzymes are produced by specialised cells in the digestive systems of mammals.
- These enzymes are then released into gut to mix with food
- Since enzymes work with specific substrates, diff enzymes are needed to catalyse breakdown of diff food molecules.
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Carbohydrates are Broken Down by Amylase
and Membrane-Bound Disaccharidases
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- Amylase is a digestive enzyme that catalyses conversion of starch (a polysaccharide)
into the sugar maltose (a disaccharide).
- involves hydrolysis of glycosidic bonds in starch.
-
-Amylase is produced by salivary glands (release amylase into mouth)
-and also by the pancreas (wch releases amylase into small intestine).
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Membrane-bound disaccharidases are enzymes attached to cell membranes of epithelial cells
» lining the ileum (final part of small intestine).
>
They help break down disaccharides
(e.g. maltose, sucrose and lactose) into monosaccharides
(e.g. glucose, fructose and galactose).
- Also involves hydrolysis of glycosidic bonds.
Monosaccharides can be transported across cell membranes of ileum epithelial cells
via specific transporter proteins
How are lipids broken down in digestion by enzymes
Lipids are Broken Down by Lipase (with the Help of Bile Salts)
- Lipase enzymes catalyse breakdown of lipids into monoglycerides and fatty acids.
> involves hydrolysis of lipids’ ester bonds
> a monoglyceride is a glycerol with one fatty acid
>
>Lipases are made in the pancreas; and work in the small intestine.
..
Bile salts are produced by liver and emulsify lipids
> cause lipids to form small droplets.
-
- Bile salts are important in lipid digestion.
Several small lipid droplets have a bigger SA than a single large droplet (for same volume).
- So formation of small droplets greatly increases the SA of lipid
that’s available for lipases to work on.
- once lipid has been broken down monoglycerides and fatty acids
- stick with bile salts (forming tiny micelles)
What two enzyme types are Proteins are broken down by
Proteins are Broken Down by Endopeptidases and Exopeptidases
- Proteins are broken down by a combo of diff proteases (or peptidases)
> These enzymes catalyse conversion of proteins into aas,
hydrolysing peptide bonds between aas.
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You need to know abt endopeptidases and exopeptidases (including dipeptidases):
Endopeptidases
- act to hydrolyse peptide bonds INSIDE a protein. (Trypsin, chymotrypsin)
- synthesised in pancreas, secreted into small intestine
•
• Pepsin is another endopeptidase.
released into stomach by cells in its lining.
• Pepsin only works in acidic conditions — provided by stomach hydrochloric acid
Exopeptidases
- act to hydrolyse peptide bonds at ENDS of protein molecules.
- remove single aas from proteins.
•
•Dipeptidases are exopeptidases that work specifically on dipeptides.
•act to separate the two aas by hydrolysing their peptide bond.
• Dipeptidases are often located in cell-surface membrane of epithelial cells in small intestine.
How are diff Products of Digestion are Absorbed Across Cell Membranes
products of digestion are absorbed across
ileum epithelium into the bloodstream.
.
Monosaccharides
• Glucose is absorbed by active transport with Na+
via a co-transporter protein.
• Galactose is absorbed same way using same co-transporter protein.
• Fructose is absorbed via facilitated diffusion through a diff transporter protein.
..
Monoglycerides and fatty acids
• Micelles help move monoglycerides and fatty acids towards epithelium.
• as micelles constantly break up and reform they can ‘release’ monoglycerides and fatty acids,
• allowing them to be absorbed — whole micelles are not taken up across epithelium.
> Monoglycerides and fatty acids are lipid-soluble, so can diffuse directly across epithelial cell membrane.
…
Amino acids
• absorbed via co-transport, like glucose and galactose.
>
> Na+ are actively transported out the ileum epithelial cells into blood.
> creates a sodium ion conc gradient.
> Na+ can then diffuse from lumen of ileum into epithelial cells
> through sodium-dependent transporter proteins, carrying aas with them.
What is haemoglobin and what does it carry round
Are proteins that carry oxygen round the body
- Red blood cells contain haemoglobin (Hb).
- Haemoglobin is a large protein with a quaternary structure — made up of more than four polypeptide chains.
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- Each chain has a haem group, wch contains an Fe2+, makes haemoglobin red.
- Haemoglobin has a high affinity (tendency to combine with) for oxygen -
- each molecule can carry four oxygen molecules.
- In lungs, oxygen joins to haemoglobin in red blood cells; forms oxyhaemoglobin.
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Hb + 4O2 = HbO8 (oxyhaemo)
> reversible reaction; when oxygen leaves/dissociates from it near body cells
> turns back to Hb/haemoglobin
There are many chemically similar types of Hb found in diff organisms,
all wch carry out same function.
> As well as found in all vertebrates,
haemoglobin is found
in earthworms, starfish, some insects, some plants and even in some bacteria.
How does haemoglobin saturation depend on partial pressure of oxygen
The partial pressure of oxygen (pO2) is a measure of oxygen conc.
- The greater the conc of dissolved oxygen in cells, the higher the partial pressure.
- Similarly, the partial pressure of carbon dioxide (pCO2) is a measure of the conc of CO2 in a cell.
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Haemoglobin’s affinity for oxygen varies depending on partial pressure of oxygen:
- Oxygen loads onto haemoglobin to form oxyhemoglobin where there’s high pO2;
- Oxyhemoglobin unloads its oxygen where there’s lower pO2
- Oxygen enters blood capillaries at alveoli, wch have a high pO2; oxygen loads onto haemoglobin forming oxyhemoglobin.
When cells respire, they use up oxygen (lowers the pO2)
- Red blood cells deliver oxyhemoglobin to respiring tissues, where it unloads its oxygen.
- The haemoglobin then returns to the lungs to pick up more oxygen.
How do dissociation curves show how affinity for oxygen varies
Where pO2 is high (e.g. lungs), haemoglobin has a high affinity for oxygen
>readily combines with oxygen, so has high saturation of oxygen.
Where pO2 is low (e.g. respiring tissues),
haemoglobin has low affinity for oxygen,
> releases oxygen not combining so has a low saturation of oxygen.
..
Graph is ‘S-shaped’ as when Hb combines with first O2 molecule,
its shape alters to make it easier for other molecules to join too.
> But as Hb starts to become saturated, it gets harder for more O2 to join.
> so curve is steep in middle where it’s easy for O2 to join,
> shallow bits at each end where it’s harder.
When the curve is steep, a small change in pO2 causes big change in amount of oxygen carried by Hb.
graph diagram no1
How does carbon Dioxide Concentration Affects Oxygen Unloading in Hb
haemoglobin gives up oxygen more readily at higher partial pressures of carbon dioxide (pCO2).
- A way of getting more oxygen to cells during activity.
1) When cells respire they produce CO2, which raises the pCO2.
- The saturation of blood with oxygen is lower for a given pO2
meaning that more oxygen is being released.
3) This is called the Bohr effect.
graph no2
How is Hb Different in Different Organisms
Diff organisms have diff types of Hb with diff oxygen transporting capacities.
- Having a particular type of Hb is an adaptation; helps the organism to survive in a particular environment.
1) Organisms that live in environments with a low conc of oxygen
have Hb with higher affinity for oxygen than human Hb
— the dissociation curve is to the left of ours.
2) Organisms that are very active and have a high oxygen demand
have Hb with a lower affinity for oxygen than human Hb
— the curve is to the right of the human one.
graph no.3
How is the circulatory system described as a mass transportation system
the circulatory system is responsible for circulating stuff around the body - blood, to be specific.
Most multicellular organisms (mammals, insects, fish) have a circulatory system of some type.
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1) Multicellular organisms, eg mammals, have a low SA:V, so need a specialised transport system
> to carry raw materials from specialised exchange organs to their body cells
— this is the circulatory system.
2) The circulatory system is made up of the heart and blood vessels.
- The heart pumps blood through blood vessels (arteries, arterioles, veins and capillaries)
»_space; to reach diff parts of the body.
(need to know the blood vessels entering/ leaving heart, lungs and kidneys.)
diagram 4
3) Blood transports
respiratory gases, products of digestion, metabolic wastes and hormones round the body.
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There are two circuits.
»_space;One circuit takes blood from heart to lungs, then back to heart.
> other loop takes blood around rest of the body.
The heart has its own blood supply — the left and right coronary arteries.
diagram 5
How are Different Blood Vessels are Adapted for Different Functions (arteries)
Arteries, arterioles and veins have different characteristics…
1) Arteries carry blood from heart to the rest of the body.
- walls are thick and muscular
- have elastic tissue to stretch and recoil as heart beats; helps maintain the high pressure.
- The inner lining (endothelium) is folded, allowing artery to stretch — helps maintain high pressure.
- All arteries carry oxygenated blood except pulmonary arteries, take deoxygenated to lungs.
2) Arteries divide into smaller vessels called arterioles.
- form a network throughout body. Blood is directed to diff areas of demand in body
- by muscles inside arterioles, contract to restrict blood flow or relax to allow full blood flow.
diagram 6
How are Different Blood Vessels are Adapted for Different Functions (vein)
Veins take blood back to the heart under low pressure.
- have a wider lumen than arteries,
- very little elastic or muscle tissue.
- contain valves to stop blood flow backwards.
> Blood flow through veins is helped by contraction of surrounding body muscles
diagram 7
All veins carry deoxygenated blood (as oxygen has been used up by body cells),
>except for pulmonary veins; carry oxygenated blood to heart from lungs.
How are Substances are Exchanged between Blood and Body Tissues at Capillaries (third blood vessel)
Arterioles branch into capillaries, smallest of the blood vessels.
> Substances (e.g. glucose and oxygen)
are exchanged between cells and capillaries,
> adapted for efficient diffusion.
always found very near cells in exchange tissues (e.g. alveoli), so short diffusion pathway.
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- walls/endothelium are only one cell thick, which also shortens the diffusion pathway.
> large number of capillaries, to increase SA for exchange.
> Networks of capillaries in tissue are called capillary beds.
Whats Tissue Fluid
Tissue fluid is the fluid surrounding cells in tissues.
- made from small molecules that leave the blood plasma, (e.g. oxygen, water and nutrients)
- Unlike blood, tissue fluid doesn’t contain red blood cells/big proteins, as too large to be pushed out through capillary walls.
Cells take in oxygen and nutrients from the tissue fluid,
and release metabolic waste into it.
> In a capillary bed, substances move out of capillaries, into the tissue fluid, by pressure filtration
What are the Two Muscular Pumps the heart consists of
The heart is the ‘pump’ that gets oxygenated blood to your cells.
2) The right side of heart pumps deoxygenated blood to lungs
2) The left side pumps oxygenated blood to whole body.
diagram inside heart 9
— the left and right sides are reversed on diagram,; the left and right of the person
What do the Different Parts of the Heart Do
Each bit of the heart is adapted to do its job effectively.
1) The left ventricle of the heart
- has thicker, more muscular walls than right, as needs to contract powerfully
»_space; to pump blood all the way round body.
-
- right side only needs to get blood to lungs, nearby.
- ventricles have thicker walls than atria, as have to push blood out of heart
2) the atria
- need to push blood a short distance into the ventricles.
- atrioventricular (AV) valves link the atria to ventricles
» stop blood flowing back into atria when ventricles contract.
3) The semi-lunar (SL) valves link ventricles to pulmonary artery or aorta,
- and stop blood flowing back into heart after ventricles contract.
4) The cords attach atrioventricular valves to ventricles
> to stop them being forced up into atria when ventricles contract.
> The valves open one way
— whether they’re open or closed depends on relative pressure of heart chambers.
— If higher pressure behind valve, it’s forced open,
— if pressure is higher in front of valve it’s forced shut.
Means blood only flows one direction through heart.
Whats The Cardiac Cycle and how does it Pump Blood Round the Body (stage 1)
The cardiac cycle is an ongoing sequence of contraction and relaxation
- of atria and ventricles that keeps blood continuously circulating round the body.
» (Cardiac contraction is also called systole and relaxation is called diastole.)
-
- The volume of atria and ventricles changes as they contract and relax.
- Pressure changes also occur, due to changes in chamber volume
> (e.g. decreasing vol of a chamber by contraction increases pressure in a Chamber).
. .
The cardiac cycle can be simplified into three stages:
1) Ventricles relax, atria contract
- The ventricles are relaxed, atria contract, decreasing vol of chambers
- increasing pressure inside chambers, pushing blood into ventricles.
-
- There’s a slight increase in ventricular
pressure and chamber vol
- as ventricles receive ejected blood from contracting atria.
diagram 10
Whats The Cardiac Cycle and how does it Pump Blood Round the Body (stage 2)
2)Ventricles contract, atria relax
- atria relax; ventricles contract decreasing vol, so increasing pressure.
- pressure becomes higher in ventricles than atria, wch forces AV valves to shut, preventing back-flow.
-
- The pressure in ventricles is also higher than in aorta and pulmonary artery
> wch forces open SL valves and blood is forced out into these arteries.
diagram 11
Whats The Cardiac Cycle and how does it Pump Blood Round the Body (stage 3)
3)Ventricles relax, atria relax
- ventricles and atria both relax.
- The higher pressure in pulmonary artery and/or aorta closes SL valves to prevent back-flow into ventricles.
- Blood returns to heart and atria fill again due to higher pressure in vena cava and pulmonary vein.
- so increases pressure of atria. As the ventricles continue to relax, their pressure falls below pressure of atria
»_space; so AV valves open; allows blood to flow passively
»_space; (without being pushed by atrial contraction) into ventricles from atria.
The atria contract, and the whole process begins again.
diagram 12
How do you interpret graphs on the cardiac cycle ?? 🚨
**diagram 13*
How to draw diagrams to explain pressure and volume changes 🚨🚨
diagram 14
Most Cardiovascular Disease Starts with Atheroma Formation
Disease associated with heart and blood vessels are cardiovascular disease
- there are diff factors that increase risk of developing it
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1) The wall of an artery is made up of several layers.
> The endothelium (inner lining) is usually smooth and unbroken.
2) If damage occurs to the endothelium (e.g. high blood pressure)
- white blood cells (mostly phagocytes) and lipids (fat) from blood
> clump together under lining to form fatty streaks.
3) Over time, more white blood cells, lipids and connective tissue build up
- harden to form a fibrous plaque called an atheroma.
4) This plaque partially blocks the lumen of the artery
> restricts blood flow; causes blood pressure to increase.
diagram 15
Coronary heart disease (CHD) is a type of cardiovascular disease.
> occurs when coronary arteries have lots of atheromas in them,
> which restricts blood flow to heart muscle; leads to myocardial infarction
How do Atheromas Increase the Risk of Aneurysm and Thrombosis
Two types of disease that affect the arteries are:
• Aneurysm — a balloon-like swelling of the artery.
1) Atheroma plaques damage and weaken arteries.
> They also narrow arteries, increasing blood pressure.
2) When blood travels through a weakened artery at high pressure,
- may push inner layers of artery through outer elastic layer to form balloon-like swelling
— an aneurysm.
3) This aneurysm may burst, causing a haemorrhage (bleeding).
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•Thrombosis - formation of a blood clot.
1) An atheroma plaque can rupture/burst the endothelium (inner lining) of an artery.
> damages the artery wall and leaves a rough surface.
2) Platelets and fibrin (a protein) accumulate at site of damage
> form a blood clot (a thrombus).
3) This blood clot can cause a complete blockage of the artery,
- or it can become dislodged and block a blood vessel elsewhere in the body.
4) Debris from rupture can cause another blood clot to form further down artery.
