Topic 3B - More Exchange and Transport Systems Flashcards
Why can’t large biological molecules (e.g. starch proteins) be absorbed from the gut into the blood?
They are too big to cross cell membranes
How does digestion aid these large biological molecules?
During digestion these large molecules are broken into smaller molecules (e.g. glucose amino acids) which can move across cell membranes
- This means they can easily be absorbed from the gut into the blood, to be transported around the body for use by the body cells
- Most large biological molecules are ………….., which can be broken down into smaller molecules, (………..), using …… reactions. …………… reactions break bonds by ………. water
- During hydrolysis, Carbohydrates are broken down into …………. and …………… .
- Fats are broken down into ………. and ……………….. .
- Proteins are broken down into …………….
- During hydrolysis, Carbohydrates are broken down into …………. and …………… .
1 - polymers, monomers, hydrolysis, adding
2- monosaccharides, disaccharides
-fatty acids, monoglycerides
- amino acids
How are digestive enzymes produced and where do they end up ?
They are produced by specialised cells in the digestive systems of mammals
- these enzymes are then released into the gut to mix with food
Why are different enzymes required to catalyse the breakdown of different food molecules?
Enzymes only work with specific substrates
What is amylase?
Amylase is a digestive enzyme that catalyses the conversion of starch (a polysaccharide) into the small sugar maltose (a disaccharide). This involves the hydroysis of the glycosidic bonds in starch
How is amylase produced?
Amylase is produced by the salivary glands (which release amylase into the mouth) and also by the pancreas (which releases amylase into the small intestine)
What are membrane-bound disaccharidases?
They are enzymes that are attached to the cell membranes of epithelial cells lining the ileum (the final part of the small intestine)
- They help to break down disaccharides (e.g. maltose sucrose and lactose) into monosaccharides (glucose fructose and galactose). This also involves the hydrolysis of glycosidic bonds
What are the disaccharidases for maltose, sucrose and lactose?
Maltase, sucrase, and lactase
starch is broken down by 1………… and 2…………..
Where is 2, produced?
Amylase and maltase
Maltase is produced in the epithelium of small intestine.
Lipids are broken down by …………
Lipases (with the help of bile salts)
What do lipase enzymes do?
They catalyse the breakdown of lipids into monoglycerides and fatty acids. This involves the hydrolysis of the ester bonds in lipids
Where are lipases produced?
They are produced in the pancreas. They work in the small intestine
How are bile salts produced and what do they do?
They are produced by the liver and emulsify lipids - this means they cause the lipids to form small droplets
Why are bile salts important in the process of lipid digestion?
Several small lipid droplets have a bigger surface area than a single large droplet (for the same volume of lipid ). So the formation of small droplets greatly increases the surface area availabe for lipases to work on
What happens once a lipid has been broken down? (DIAGRAM)
Once the lipid has been broken down , the monoglycerides and fatty acids stick with the bile salts to form tiny structures called micelles
Proteins are broken down by…
Endopeptidases and exopeptidases (different proteases/peptidases)
What are proteases/peptidases?
They are enzymes that catalyse the conversion of proteins into amino acids by hydrolysing the peptise bonds between amino acids
What do endopeptidases do and give 3 examples of them?
- They act to hydrolyse peptide bonds within a protein
- Trypsin and chymotrypsin are endopeptidases that are synthesised in the pancreas and secreted in the small intestine
- Pepsin is another endopeptidase that is released in the stomach by cells in the stomach lining. It only works in acidic conditions - these are provided by HCL in the stomach
- Trypsin and chymotrypsin are endopeptidases that are synthesised in the pancreas and secreted in the small intestine
What do exopeptidases do and give an example of a type of exopeptidase?
- They act to hydrolyse peptide bonds at the ends of protein molecules. They remove single amino acids from proteins
- Dipeptidases are exopeptidases that work specifically on dipeptides. They act to separate the 2 amino acids that make up a dipeptide by hydrolysing the peptide bond between them
- Dipeptidases are often locates in the cell-surface membrane of epithelial cels in the small intestine
- Dipeptidases are exopeptidases that work specifically on dipeptides. They act to separate the 2 amino acids that make up a dipeptide by hydrolysing the peptide bond between them
Where are the products of digestion absorbed across?
ileum epithelium of the bloodstream
How are monosaccharides absorbed into the bloodstream?
- Glucose is absorbed by active transport with sodium ions via a co-transporter protein. Galactose is absorbed the same way using the same co-transporter protein
- Fructose is absorbed via facilitated diffusion through a different transporter protein
How are monoglycerides and fatty acids absorbed into the blood stream?
Micelles help to move monoglycerides and fatty acids towards the epithelium
- Because 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 the epithelium
- Monoglycerides and fatty acids are lipid-soluble, so can diffuse directly across the epitheial cell membrane
How are amino acids absorbed into the bloodstream?
Sodium ions are actively transported out of the epithelial cells in the ileum itself. They can diffuse back into the cells through sodium-dependent transporter proteins in the epithelial cell membranes, carrying the amino acids with them (similar to glucose and galactose)
What is haemoglobin?
It is a large protein with a quaternary structure
Where is haemoglobin found?
In red blood cells
What makes haemoglobin red in colour?
Each chain has a haem group, which contains an iron ion (which gives a red colour)
Haemoglobin has a high …….. for oxygen. What does this mean?
affinity
-it means it has a tendency to combine with oxygen (can carry four O2 molecules)
What do you call the product when oxygen joins to haemoglobin?
Give the formula for oxygen joining to haemoglobin
Oxyhaemoglobin
Hb + 4O2 ———– HbO8
Is the formation of oxyheamoglobin reversible or irreversible?
reversible
Haemoglobin is chemically (similar/dissimilar)? in different organisms and carries (same/different) function in different organisms
- Similar
2. Same
Give examples of organisms that contain haemoglobin
All vertebrates, earthworms, starfish, Some insects/plants/bacteria
Define partial pressure of 02 and CO2.
It is a measure of O2/CO2 conc. The greater the conc of dissolved O2/CO2, the higher the partial pressure
How does Haemoglobins affinity for O2 depend on the partial pressure of O2?
- O2 will load onto Hb to form oxyhaemoglobin where theres a high p02
- Oxyhaemoglobin unloads its O2 where theres a lower pO2
Apply your last answer (about how haemoglobins affinity for O2 depending on partial pressure of 02) to cells
- O2 enters blood capillaries at alveoli in lungs, giving alveoli a high pO2. so O2 loads onto haemoglobin to form oxyheamoglobin
- When cells respire, they use up O2 - this lowers pO2 so red blood cells will unload oxygen to respiring tissue
- Haemoglobin then returns to lungs to collect O2
What does 100% saturated mean on a haemoglobin dissociation curve?
It means ever Hb molecule is carrying the max of 4 molecules of O2
What shape would a haemoglobin dissociation curve form?
An S-curve
Explain the S-curve of a haemoglobin dissociation curve
- When haemoglobin combines with first O2 molecule, it shape changes to make it easier to collect more O2
- As Hb starts to become more saturated, it gets harder for O2 molecules to join
- This is why the curve will be steep in the middle, but shallow at each end, where its harder to collect O2
Describe the Bohr effect dissociation curve
- When cells respire,they produce CO2, which raises pCO2
- This increases rate of O2 unloading- so the dissociation curve shifts right .
- The saturation of blood with O2 is lower for a given pO2, meaning that more oxygen is being released
Draw the ‘bohr effect’ dissociation curve
DIAGRAM IN BOOK
DRAWN
Describe the O2 affinity of heamoglobin in organisms that live in environments with little O2
The O2 affinity is high
Describe the O2 affinity of heamoglobin in organisms that are very active and have a high oxygen demand
The O2 affinity is low
Draw the curve for:
A- animal living in depleted oxygen environment
B- Animal living in high altitudes, with little O2
C- Human dissociation curve
D - active animal in environment with lots of O2
DIAGRAM IN BOOK
Drawn`
What is the circulatory system made up of?
The heart and blood vessels
Why do multicellular organisms need a circulatory system?
multicellular organisms have a low SA:V ratio, so they need a specialised transport system to carry raw materials from specialised exchange organs to their body cells
What are the functions of the 2 different blood circuits
- 1st circuit: pumps blood from heart to lungs, and back to heart again
- 2nd circuit: pumps blood around rest of the body
Where does the heart get its blood supply from?
From the left and right coronory arteries
Draw a diagram of the heart and circulatory system
DIAGRAM IN BOOK
drawn
Name the 4 different blood vessels
- Arteries
- Arterioles
- Veins
- Capillaries
Describe the function and properties/adaptations of arteries
DIAGRAM
Function
- Carry blood from heart to rest of body
- All arteries carry oxygenated blood except for pulmonary arteries (deoxygenated blood to lungs)
Properties:
- To help maintain high pressure:
1. Walls are thick and muscular and have elastic tissue to stretch and recoil as heart beats
2. Inner lining is folded, allowing artery to stretch
Describe the function and properties/adaptations of arterioles
Function
- Blood is directed to areas of demand in body by muscles in arterioles
Properties (same as arteries)
- small vessels
- Form a network throughout body and are formed by division of arteries
Describe the function and properties/adaptations of veins
DIAGRAM
Function
- Take blood back o heart under low pressure
- All veins carry deoxygenated blood, except for pulmonary veins, which carry oxygenated blood from lungs to heart
Properties/Adaptations
1- Have a wider lumen than arteries, with little elastic or muscle tissue
2- Contain valves to stop blood flowing backwards
3- Contraction of body muscles surrounding veins helps blood flow
Descrie the function and properties/adaptations of capillaries
DIAGRAM
Function:
- Substances are exchanged between blood and body tissues at capillaries
Properties/Adaptations
- Always found near cells in exchange tissues (e.g. alveoli in lungs), giving a short diffusion pathway
- Walls are only 1 cell thick, shortening diffusion pathway
- A large number of capillaries to increase SA for exchange (networks of capillaries in tissue are capillary beds)
What is tissue fluid?
Tissue fluid is the fluid that surrounds cells in tissues
What is tissue fluid made from?
It is made from small molecules that leave blood plasma (e.g. O2, H20 and nutrients)
Why doesnt tissue fluid contain red blood cells or big proteins?
They’re too large to be pushed out of the capillary walls
What is the importance of the tissue fluid for normal body cells?
Cells take in O2 and nutrients from the tissue fluid, and release metabolic waste into it
What is the process that moves substances from the the blood plasma (in the capillary bed), into the tissue fluid?
Pressure filtration
Describe how pressure filtration causes substances to move into tissue fluid space
DIAGRAM
1- At start of capillary bed, near arteries, the hydrostatic (liquid) pressure in capillaries is greater than hydrostatic pressure in tissue fluid
2- Difference in hydrostatic pressure means overall outward pressure forces fluid into spaces around cells (tissue fluid)
Describe how pressure filtration causes substances to move from tissue fluid, back to the capillaries
DIAGRAM
- As fluid leaves capillaries, hydrostatic pressure reduces in capillaries and is much lower at venule end of capillary bed (end that is nearest to veins)
- Due to fluid loss, and an increasing conc of plasma cells that dont leave the capillaries, water potential at venule end is lower than water potential in tissue fluid
- This causes water to re-enter the venule end of the capillaries by osmosis
What happens to excess tissue fluid?
It is drained into the lymphatic system (network of tubes), which transports the excess tissue fluid and dumps it back into the circulatory system
What does high blood pressure mean?
It means there is a high hydrostatic pressure in the capillaries, which can lead to an accumulation of tissue fluid in the tissues
What are the functions of the right and left side of the heart?
Left side - pumps oxygenated blood to the whole body
Right side - pumps deoxygenated blood to the lungs
Why is the left ventricle of the heart thicker than the right one?
It has thicker, more muscular walls as it must contract powerfully to pump blood all around body, and not just lungs
Why are the walls of the ventricles thicker than the ATRIA?
Because the ventricles have to pish blood out of the heart whilst the atria only need to push blood a short distance into the ventricles
What are the functions of:
- The atrioventricular valves
- The semi-lunar ventricles
1- Atrioventricular valves: Link atria to ventricles and stop blood flowing back into atria when ventricles contract
2- Semi-lunar ventricles: Links ventricles to pulmonary artery and aorta, and stop blood flowing back into heart after ventricles contract
What is the function of the cords? (in the heart)
They attach the atrioventricular valves to the ventricles to stop them being forced up into the atria when the ventricles contract
What does the opening of the valves depend on?
The valves opening depends on the relative pressure of the heart chamber. If theres a higher pressure behind a valve, its forced open, but if pressure is higher in front of the valve, its forced shut
- This means that blood only flows in 1 direction through the heart
Describe the 1st step of the cardiac cycle
DIAGRAM
- Ventricles relax, atria contract:
- decreasing volume of atria chambers and hence, increasing pressure of atria chambers
- This pushed blood into ventricles
- There is a slight increase in ventricular pressure and atria chamber volume as the ventricles receive the ejected blood from the contracting atria
Describe the 2nd step of the cardiac cycle
DIAGRAM
- Ventricles contract, atria relax:
- decreasing volume of ventricles, and hence, increasing pressure of ventricles
- Pressure becomes higher in ventricles than atria, forcing AV valves shut to prevent back flow
- Pressure in ventricles is also higher than aorta and pulmonary artery, forcing open SL valves, and forcing blood out into arteries
Describe the 3rd step of the cardiac cycle
DIAGRAM
- Ventricles relax, atria relax:
- Higher pressure in aorta and pulmonary artery closes SL valves to prevent back-flow into ventricles
- Blood returns to heart and atria fills up again due to higher pressure in vena cava and pulmonary vein
- pressure of Atria starts to increase
- As ventricles continue to relax, pressure falls below pressure of atria, causing AV valves to open, allowing blood to flow into ventricles
- Atria contract, and whole process begins again *
Whats another word for cardiac contraction and relaxation?
Contraction - Systole
Relaxation - Diastole
What is exocytosis
Process in which large molecules are transported across membranes through vesicles
What is the role of the muscle layer in arteries?
To make the artery more narrow when it contracts
