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More Exchange and Transport
Systems
Created
Class

@February 13, 2025 4:50 PM
Cells to Systems

Digestion
Large molecules like protein can’t cross cell membrane
Molecules are broken down for absorption and transported around the
body
Polymers are the biggest biological molecules, broken down using
hydrolysis
Hydrolysis
Breaks carbs down into disaccharides and monosaccharides
Breaks fats into fatty acids
Breaks proteins into amino acids

Digestive Enzymes
Breaks down biological molecules
Produced by specialised cells in digestive system
Enzyme works with substrate to catalyse processes that break down food

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Breakdown of Carbs
Amylase
Digestive enzyme
Produced by salivary glands and pancreas
Uses hydrolysis as catalyst when converting starch into maltose
Membrane- Bound Disaccharidases
Enzyme attached to epithelial cell cell membrane
Breaks down disaccharides into monosaccharides
Transporter proteins take monosaccharides across cell membrane in
epithelial cells

Breakdown of Lipids
Enzyme lipase catalyses breakdown of lipids
Lipase is made in pancreas
Liver produces bile salts and forces lipids to form droplets
Droplets contain big surface area, ideal for lipase
Broken down lipids means monoglycerides and fatty acids stick to bile
salts forming micelles

Breakdown of Proteins
Endopeptidases
Hydrolyses peptide bonds
Trypsin and Chymotrypsin
Made in pancreas and secreted into small intestine

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Pepsin
Secreted into stomach
Works in acidic conditions
Exopeptidases
Hydrolyses peptide bonds on protein ends
Dipeptidases
Works on dipeptides
Separates amino acids using hydrolysis
Found in cell- surface membrane of epithelial cells

Products of Digestion Absorption
Monosaccharides
Active transport absorbs glucose using sodium ions with co-transport
protein
Facilitated diffusion absorbs fructose using another transport protein
Monoglycerides and Fatty Acids
Micelles move monoglycerides and fatty acids to epithelium
Micelles not absorbed by epithelium
Monoglycerides and fatty acids diffuse across epithelial cell membrane
because they’re lipid soluble
Amino Acids
Absorbed using co-transport
Sodium ions actively transported outside epithelial cells
Creates sodium ion concentration gradient

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The ions diffuse from ileum lumen into epithelial cells through sodiumdependent transporter proteins

Oxygen and Haemoglobin (Hb)
Red blood cells contain haemoglobin
Hb
Protein with quaternary structure
Each peptide chain contains iron ion
Ion contains high o2 affinity, hb molecule carries 4 o2 molecules
Oxygen+hb= oxyhaemoglobin
Reversible reaction leading to dissociation

Hb Saturation Depends on O2 Partial Pressure
Partial Pressure
Measures o2 concentration
Higher dissolved o2 cell concentration creates higher partial pressure
CO2 partial pressure measures CO2 concentration
Hb affinity for o2 is dependent on partial pressure
O2 enters alveoli blood capillaries , lungs has high o2 partial pressure
creating oxyhaemoglobin
Cell respiration uses o2 lowering partial pressure

CO2 Concentration Affects O2 Unloading

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CO2 is produced during respiration increasing CO2 partial pressure
Dissociation of oxyhaemoglobin forms haemoglobin and o2 increases
Blood saturation lowered for specific O2 partial pressure, releases more
O2
Described as Bohr Effect

Haemoglobin Difference
Organisms in low O2 areas have higher O2 affinity than human haemo
Active organisms have high O2 demand and contain lower affinity haemo

Circulatory System
Require special transport system carrying materials from organs to cells
Made of heart and blood vessels
Heart pumps blood through blood vessels
Substances transported include gases, digestion products, waste and
hormones
One circuit takes only blood from heart to lungs, other circuit is global
Coronary arteries are the blood supply of the heart

Different Blood Vessels
Arteries
Carries blood from heart to body parts
Contains thick, muscular walls

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Tissue can stretch and recoil retaining high pressure
Inner lining also helps to retain high pressure
Carries oxygenated blood except pulmonary arteries
Arterioles
Creates vessel networks
Directs blood to different muscles
Able to restrict or allow blood flow
Veins
Takes low pressured blood to heart
Has wider lumen with minimum elasticity or muscle tissue
Muscle contraction helps blood flow in veins
Carries deoxygenated blood except pulmonary veins

Capillaries
Short diffusion pathway
Thin walls
Lots of capillaries increasing surface area
Capillary Beds
Network of capillaries

Tissue Fluid Formation
Hydrostatic pressure inside capillaries is higher than inside fluid (start of
capillary bed)

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Difference in pressure leads to pressure forcing fluid out of capillaries into
cell spaces creating tissue fluid
Hydrostatic pressure reduces in capillaries after fluid leaves
Fluid loss+ increased concentration of plasma proteins= Low water
potential at venule end of capillary
Water re-enters capillaries via osmosis

Heart Pumps
Right side pumps deoxygenated blood into lungs
Left side pumps oxygenated blood to whole body

Parts of the Heart
Ventricle
Left ventricle is thicker and more muscular than right ventricle
More contraction needed to pump blood to whole body
Right side pumps blood to lungs
Thicker walls than atria
Atrioventricular valve (AV)
Links atria to ventricles and prevents backflow of blood during
contraction
Semi-lunar valve
Links ventricles to pulmonary artery and aorta
Prevents backflow of blood after ventricular contraction
Cords

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Attaches AV to ventricles preventing AV access into atria during
ventricular contraction

Higher pressure behind valve forces entry but pressure in front of valve closes
it
...
v disease
Atheromas lead to increased blood pressure and blood clots
Blocks blood flow to coronary arteries
Can cause myocardial infarction
High saturated fats relate to high cholesterol
High salt diets increase risk of high blood pressure and c

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