Summary Notes designed for the International Baccalaureate Diploma Programme. These notes are detailed yet concise, with all the information to achieve a 7 in IB Biology HL or SL. These notes were made using information from the IB syllabus, Oxford IB Diploma HL Biology Textbook, Bioninja and the B...
Class notes Biology Oxford IB Diploma Programme: Biology Course Companion
IBDP HL Biology - 2.2 Water Notes
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La Côte International School
IB Biology Unit 6- Human Physiology
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Unit 6.1
• In the mouth, mechanical digestion is used to increase the surface area. Saliva contains salivary
amylase.
• HCl in the stomach lowers the pH to 2 which
kills bacteria and pepsin breaks down
proteins.
• The walls of the stomach are adapted to
expand when food enters.
• The duodenum is the first section of the
small intestine.
• Bile from the gall bladder is secreted into the
duodenum to emulsify fats.
• Amylase, lipase and endopeptidase are also
secreted by the pancreas.
• The contraction of circular and longitudinal muscle helps move the bolus in the small intestine
and the oesophagus, known as peristalsis.
• Enzymes digest most macromolecules in food into monomers in the small intestine:
• Starch→Maltose →Glucose using amylase and maltase
• Lipids →Fatty Acids+Glycerol using lipase
• Proteins→Peptides →Amino Acids using protease and pepsin
• Nucleic Acids→Nucleotides using nucleases
• All of these reactions are catabolic and require water.
• Most enzymes work at pH 7, with pepsin being an exception.
• The small intestine is made up of 4 tissue layers:
• Serosa • Submucosa
• Muscle Layer • Mucosa
• Absorption is the uptake of digested molecules into the blood.
• The inner epithelial lining of the small intestine is folded into finger-like projections called villi and
microvilli.
• The villi are highly adapted to absorption:
• Microvilli further increase surface area
• Rich blood supply created by network of
capillaries
• Short diffusion pathway (one cell thick
epithelium)
• Lacteals absorb lipids into the lymphatic system
• Intestinal crypts release digestive juices
• Membrane proteins facilitate transport of
digested materials into epithelial cells
• Membrane transport in the epithelial cells:
• Lipids are non polar and pass via simple diffusion
• Water soluble molecules such as fructose and vitamins pass via facilitated diffusion
• Amino acids and charged ions pass via active transport using ATP
• Glucose passes by actively transporting Na+ to create a concentration gradient (cotransport)
, Unit 6.2
• The blood consists of the plasma, buffy coat and erythrocytes.
• Red blood cells have many adaptations, including a biconcave shape,
no nucleus and haemoglobin.
• haemoglobin + oxygen ⇌ oxyhaemoglobin
• Platelets help the clotting of blood, which helps:
• Stop pathogens from entering the body
• Stop you from losing too much blood
• A pathogen is defined as a disease-causing
organism.
• Plasma acts as a solvent and dissolves or
carriers other components if the blood, such as
hormones, waste, iron, minerals, amino acids,
glucose, salts etc.
• Coronary arteries supply the cardiac muscles
with blood.
• Cardiac muscle cells are myogenic, meaning
they can beat independently.
• The heart is double circulatory which helps
contain pressure:
• Pulmonary circulation: blood moves from the
heart to lungs to heart.
• Systemic circulation: blood moves from the heart to body to heart.
• Arterioles and venules are used to join capillaries from the arteries and veins.
• There are three main blood vessels, the veins, arteries and capillaries.
• The arteries bring oxygenated blood away from the heart under high pressure (excluding
pulmonary artery):
• The inner layer (endothelium) is smooth to prevent clotting.
• The middle layer contains elastic fibres and muscle to maintain high pressures.
• The outer layer is made out of collagen/elastic fibres for protection.
• The veins bring deoxygenated blood to the heart under low pressure (excluding pulmonary
vein):
• The inner layer consists of endothelium cells.
• The middle layer has few elastic fibres and muscle as it operates under low pressure.
• The outer layer is the thickest and is made out of collagen/elastic fibres for protection.
• Veins have valves to prevent back flow, and a larger lumen.
• Capillaries surround tissue and organs to allow the exchange of substances:
• Only consist of endothelium cells, and are one cell thick for fast diffusion.
• They are very small to create a steeper concentration gradient and operate under low
pressure.
• The basement membrane is permeable to many substances.
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