Topic 3 — B: More Exchange and Transport Systems Flashcards
What is digestion, and why is it essential?
breaks down large biological molecules (e.g., starch, proteins) into smaller molecules that can cross cell membranes, allowing nutrients to be absorbed from the gut into the bloodstream and transported around the body for cellular use.
What is a hydrolysis reaction?
break down polymers into monomers by adding water. For example, carbohydrates are broken into monosaccharides, fats into fatty acids and monoglycerides, and proteins into amino acids.
Which enzymes are involved in carbohydrate digestion, and where are they produced?
Amylase, produced by the salivary glands and pancreas, catalyzes starch breakdown into maltose. Membrane-bound disaccharidases, located on the ileum’s epithelial cells, break down disaccharides into monosaccharides
Describe the role of amylase in carbohydrate digestion.
Amylase catalyzes the hydrolysis of glycosidic bonds in starch, producing maltose. It’s secreted into the mouth (by salivary glands) and the small intestine (by the pancreas).
What are membrane-bound disaccharidases? Give an example.
These enzymes, attached to the cell membranes of ileum epithelial cells, break down disaccharides into monosaccharides. For example, sucrase breaks down sucrose into glucose and fructose.
Explain the digestion process of lipids
Lipase enzymes break down lipids into monoglycerides and fatty acids by hydrolyzing ester bonds. Lipases are mainly made in the pancreas and secreted into the small intestine
What role do bile salts play in lipid digestion?
Bile salts, produced by the liver, emulsify lipids, increasing the surface area for lipases to act by breaking lipids into smaller droplets, facilitating their breakdown.
What are micelles, and what is their function in lipid absorption?
Micelles are tiny lipid-bile salt structures that help deliver monoglycerides and fatty acids to the ileum epithelium for absorption. Micelles break up and reform, releasing their contents for absorption.
Describe the process of protein digestion.
Proteins are broken down by peptidases, which hydrolyze peptide bonds. Endopeptidases act within proteins, exopeptidases remove amino acids from protein ends, and dipeptidases work specifically on dipeptides.
Provide examples of endopeptidases and their locations.
Trypsin and chymotrypsin (from the pancreas, active in the small intestine) and pepsin (from the stomach lining, active in acidic stomach conditions).
What are dipeptidases, and where are they located?
membrane-bound exopeptidases that hydrolyze dipeptides into amino acids. They are located in the cell-surface membrane of the small intestine’s epithelial cells.
How is glucose absorbed in the ileum?
Glucose is absorbed by active transport with sodium ions via a co-transporter protein in the ileum epithelial cells.
How are monoglycerides and fatty acids absorbed?
they are lipid-soluble and diffuse directly across the epithelial cell membrane after being transported to the epithelium by micelles.
Explain amino acid absorption in the ileum.
Sodium ions are actively transported out of epithelial cells into the ileum and then diffuse back in, carrying amino acids with them through sodium-dependent transporter proteins.
What is the main role of haemoglobin in the circulatory system?
Haemoglobin in red blood cells carries oxygen throughout the body. It binds oxygen in the lungs and releases it to respiring tissues where oxygen concentration is low
Describe haemoglobin’s quaternary structure and its oxygen-binding capacity.
has four polypeptide chains, each with a haem group that contains an iron ion, which allows each haemoglobin molecule to carry up to four oxygen molecules.
What is the relationship between pO₂ and haemoglobin’s affinity for oxygen?
Haemoglobin’s affinity for oxygen increases with higher pO₂ (e.g., in the lungs) and decreases with lower pO₂ (e.g., in respiring tissues).
Explain the terms “loading” and “unloading” in relation to haemoglobin and oxygen.
Loading” (association) occurs when oxygen binds to haemoglobin, forming oxyhaemoglobin, typically in the lungs. “Unloading” (dissociation) occurs when oxygen is released to tissues.
What is the oxygen dissociation curve, and why is it S-shaped?
shows the percentage saturation of haemoglobin at different pO₂ levels. Its S-shape reflects cooperative binding, where binding the first O₂ molecule makes it easier for additional molecules to bind
Describe the Bohr effect and its importance in oxygen unloading.
occurs when high pCO₂ (from active respiration) shifts the dissociation curve to the right, lowering haemoglobin’s oxygen affinity and promoting oxygen release to tissues.
How does haemoglobin adaptation help animals in different environments?
Animals in low-oxygen environments (e.g., underground or high altitudes) have haemoglobin with a higher oxygen affinity, while highly active animals have haemoglobin with lower affinity for efficient oxygen unloading.
What is haemoglobin and its primary role?
Haemoglobin is a protein in red blood cells that binds to oxygen in the lungs and releases it at tissues for respiration.
How does haemoglobin’s affinity for oxygen change?
Its affinity changes based on oxygen concentration (partial pressure of oxygen), CO₂ concentration, and pH (Bohr effect).
Define partial pressure of oxygen (pO₂).
Partial pressure of oxygen is a measure of oxygen concentration; high in the lungs and low in respiring tissues.
Explain the oxygen dissociation curve.
It shows haemoglobin saturation with oxygen at different pO₂. The curve is sigmoidal due to cooperative binding.
What is cooperative binding in haemoglobin?
When one oxygen molecule binds to haemoglobin, it increases the affinity for more oxygen molecules to bind.
Describe the Bohr effect
At high levels of CO₂, haemoglobin’s affinity for oxygen decreases, facilitating oxygen release in tissues.
How do fetal haemoglobin and adult haemoglobin differ?
Fetal haemoglobin has a higher oxygen affinity to extract oxygen from the mother’s blood across the placenta.
What adaptations do animals in low oxygen environments have in their haemoglobin?
They have haemoglobin with higher oxygen affinity for efficient oxygen uptake in environments with low pO₂.
What is myoglobin and how does it differ from haemoglobin?
Myoglobin is a muscle protein with a higher oxygen affinity than haemoglobin, storing oxygen for muscle use.
What is the cardiac cycle?
The cardiac cycle consists of systole (contraction of the heart) and diastole (relaxation), which pump blood through the circulatory system.
Differentiate between arteries, veins, and capillaries.
Arteries: Thick walls, high pressure, carry blood away from the heart.
Veins: Thin walls, lower pressure, have valves to prevent backflow, carry blood to the heart.
Capillaries: Thin, one-cell-thick walls for efficient exchange of substances.
What is tissue fluid, and how is it formed?
Tissue fluid is formed from blood plasma at the capillary bed, carrying nutrients and oxygen to cells while removing waste products.
What causes the movement of tissue fluid in and out of capillaries?
Hydrostatic pressure and osmotic pressure gradients between blood plasma and tissue fluid
Explain the lymphatic system’s role in the circulatory system
The lymphatic system collects excess tissue fluid (lymph), filters it, and returns it to the bloodstream, helping maintain fluid balance.
Describe the structure of haemoglobin.
Haemoglobin is a quaternary protein made of four polypeptide chains, each containing a haem group that binds oxygen.
What are coronary arteries, and why are they important?
Coronary arteries supply oxygen-rich blood to the heart muscle itself. Blockage can lead to heart attacks.
What factors affect the oxygen dissociation curve of haemoglobin?
Factors include pO₂, pCO₂, pH, temperature, and 2,3-bisphosphoglycerate (BPG) levels.
How does oxygen transport differ in high-altitude animals?
Their haemoglobin has higher oxygen affinity to maximize oxygen uptake in low-pO₂ environments.
What is cardiovascular disease (CVD)?
CVD refers to diseases affecting the heart and blood vessels, such as coronary heart disease (CHD) and stroke.
What causes atherosclerosis?
Atherosclerosis is caused by the buildup of fatty deposits (atheroma) in arterial walls, reducing blood flow and increasing blood pressure.
How does a blood clot (thrombosis) form in an artery?
Atheroma ruptures the arterial wall, triggering clotting factors that form a thrombus (blood clot), potentially blocking blood flow.
What is an aneurysm, and how is it related to atherosclerosis?
An aneurysm is a weakened arterial wall that balloons out due to increased pressure from atherosclerosis, which may rupture.
List risk factors for cardiovascular disease.
high blood pressure, smoking, high cholesterol, poor diet, lack of exercise, obesity, and genetics.
How does smoking increase the risk of cardiovascular disease?
Smoking damages arterial walls, increases blood pressure, reduces oxygen transport due to carbon monoxide, and promotes clot formation.
What role does high cholesterol play in CVD?
High levels of low-density lipoproteins (LDLs) contribute to atheroma formation, narrowing arteries and increasing blood pressure
Describe how diet can influence cardiovascular health.
Diets high in saturated fats and salt increase LDL levels and blood pressure, while diets rich in fiber, fruit, and omega-3 reduce risk.
What is the function of high-density lipoproteins (HDLs)?
HDLs help transport cholesterol from tissues to the liver for excretion, reducing the risk of atherosclerosis.
How can regular exercise reduce the risk of CVD?
Exercise improves heart efficiency, reduces LDL cholesterol, raises HDL cholesterol, and helps manage weight and blood pressure.
How does hypertension contribute to cardiovascular disease?
Hypertension (high blood pressure) damages arterial walls, promoting atheroma formation and increasing the risk of heart attacks and strokes.
What is angina, and how is it related to coronary heart disease?
Angina is chest pain caused by reduced blood flow to the heart muscle, often due to narrowed coronary arteries in CHD.
How can a myocardial infarction (heart attack) occur?
A heart attack occurs when a coronary artery is completely blocked, cutting off oxygen supply to part of the heart muscle, leading to damage or death of the tissue.
Explain the difference between LDLs and HDLs in terms of cardiovascular health.
LDLs (Low-Density Lipoproteins): Deliver cholesterol to tissues, can lead to atheroma buildup, and increase CVD risk.
HDLs (High-Density Lipoproteins): Remove excess cholesterol to the liver for disposal, reducing CVD risk.
What are some lifestyle changes to prevent or manage cardiovascular disease?
Stop smoking, maintain a healthy diet, engage in regular physical activity, manage stress, and monitor blood pressure and cholesterol levels.
What medications are commonly used to treat or prevent cardiovascular disease?
Statins (lower cholesterol), beta-blockers (reduce blood pressure), and anticoagulants (prevent blood clots).
How does obesity increase the risk of cardiovascular disease?
Obesity leads to high cholesterol levels, hypertension, and increased strain on the heart, all of which elevate CVD risk.
What is the role of antioxidants in cardiovascular health?
Antioxidants reduce oxidative stress and prevent damage to blood vessel walls, which may help lower the risk of atherosclerosis.
How does diabetes influence the risk of developing cardiovascular disease?
Diabetes causes high blood glucose levels, which can damage blood vessels and accelerate atherosclerosis.
Why is it important to reduce salt intake for cardiovascular health?
High salt intake raises blood pressure, increasing the risk of hypertension and subsequent cardiovascular complications.
What is tissue fluid, and how is it formed?
Tissue fluid surrounds cells and is formed from small molecules (e.g., oxygen, water, nutrients) filtered out of blood plasma under high hydrostatic pressure in the capillaries.
What prevents large molecules like proteins from entering the tissue fluid?
Large molecules such as proteins cannot pass through capillary walls due to their size.
Describe the pressure filtration process in tissue fluid formation.
At the arteriole end of a capillary bed, hydrostatic pressure inside capillaries exceeds that in the tissue fluid, forcing plasma out.
At the venule end, lower hydrostatic pressure and higher plasma protein concentration lead to water reentering capillaries via osmosis
What happens to excess tissue fluid?
Excess tissue fluid is drained into lymph vessels, which transport it back into the circulatory system.
How are capillaries adapted for efficient exchange of substances?
Walls are one cell thick for short diffusion paths.
Capillaries are numerous, increasing surface area.
Located near cells to reduce diffusion distance.
What are capillary beds?
Capillary beds are networks of capillaries that facilitate the exchange of substances between blood and tissues
How does high blood pressure affect tissue fluid formation?
High blood pressure increases hydrostatic pressure, leading to more fluid being pushed out, potentially causing tissue swelling (edema).
formula for oxyhemoglobin:
haemoglobin (Hb) + oxygen (4O2) →← HbO8 (oxyhaemoglobin)
affinity for oxygen meaning:
the tendency a molecule has to bind with oxygen.
what does haemoglobin’s affinity for oxygen varies depend on?
one of the conditions that affects it is the partial pressure of oxygen (pO2).
what is pO2
measure of oxygen concentration.
The greater the concentration of dissolved oxygen in cells, the higher the partial pressure.
As pO2 increases….
haemoglobin’s affinity for oxygen also increases
where does oxygen load onto?
haemoglobin to form oxyhaemoglobin where
there’s a high pO2.
where does Oxyhaemoglobin unload its oxygen?
where there’s a lower pO2
where does oxygen enter the blood capillaries?
at the alveoli in the lungs
why does Alveoli have a high pO2?
so oxygen loads onto haemoglobin to form oxyhaemoglobin.
what is used when cells respire?
oxygen — this lowers the pO2.
what do Red blood cells do?
deliver oxyhaemoglobin to respiring tissues, where it unloads its oxygen.
The haemoglobin then returns to the lungs to pick up more oxygen.
alveoli in lungs:
- high oxygen concentration
- high pO2
- high affinity
- oxygen loads
respiring tissue:
- low oxygen concentration
- low pO2
- low affinity
- oxygen unloads
what does the oxygen dissociation curve show?
shows how saturated the haemoglobin is with oxygen at any given partial pressure.
The affinity of haemoglobin for oxygen affects how saturated the haemoglobin is
pO2 in oxygen dissociation curve:
Where pO2 is high (e.g. in the lungs), haemoglobin
has a high affinity for oxygen, so it has a high
saturation of oxygen.
Where pO2 is low (e.g. in respiring tissues), haemoglobin has a low affinity for oxygen, so it has a low saturation of oxygen.
saturation affecting affinity:
saturation of haemoglobin can also affect the affinity
this is why the graph is ‘S-shaped’ and not a straight line.
The S-shaped dissociation curve for haemoglobin:
When haemoglobin combines with
the first O2 molecule, its shape alters
in a way that makes it easier for other
O2 molecules to join too. But as the
haemoglobin starts to become saturated,
it gets harder for more oxygen molecules
to join. As a result, the curve has a
steep bit in the middle where it’s really
easy for oxygen molecules to join,
and shallow bits at each end where it’s
harder — see Figure 5. When the curve
is steep, a small change in pO2 causes
a big change in the amount of oxygen
carried by the haemoglobin.
what is partial pressure of carbon dioxide (pCO2)?
a measure of the concentration of CO2 in a cell.
how does pCO2 affect oxygen unloading?
Haemoglobin gives up its oxygen more readily at a
higher pCO2 to get way more O2 to cells during activity.
what do cells produce when they respire?
carbon dioxide, which raises the pCO2. This increases the rate of oxygen unloading (i.e. the rate at which oxyhaemoglobin dissociates to form haemoglobin and oxygen)
what is the Bohr effect?
shape). The saturation of blood with oxygen is lower for a given pO2, meaning that more oxygen is
being released
haemoglobin in different organisms:
Different organisms have different types of haemoglobin with different oxygen transporting capacities — it depends on things like where they live, how active they are and their size.
