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SA:V ratio and the digestive system - Coggle Diagram
SA:V ratio and the digestive system
surface area to volume ratio
-unicellular organisms:
-eg, an amoeba
-an organism like amoeba obtains what it needs through:
-H2O and O2 by diffusion across cell surface membrane
-food particles by phagocytosis
-CO2 leaves by diffusion
-diffusion rate quick as distance is small
-large surface area to volume ratio
-can exchange gasses and nutrients by diffusion across cell surface membrane
-SA of a cube: length x width x num of sides
-volume of a cube: length x width x height
-as the size of an object increases:
-volume increases
-SA increases (not as much)
-therefore as the size increases the SA:V decreases
-what materials are exchanged in an environment and how:
-respiratory gasses (CO2, O2)
-nutrients (glucose, fatty acids, amino acids)
-heat
-exchanged through diffusion, facilitated diffusion, and active transport
-features of exchange surfaces:
-thin: short diffusion distance
-large SA: high rate of diffusion
-selectively permeable: allow selected material through
-maintenance of conc gradient: through ventilation and transport system
-some multicellular organisms cope by becoming thin and flat:
-reduces distance for gas diffusion and increases SA:V
-no specialised exchange surfaces / systems
-eg, jellyfish and flatworm
-why are specialised exchange surfaces / systems needed:
-some cells are deep in the body
-have a low SA:V ratio
-high metabolic rate so high respiration and glucose / O2 needed
-skin / surface tissue impermeable
digestive enzymes and the role of bile
-proteases:
-digestive enzymes are hydrolases
-proteases catalyses the hydrolysis of proteins
-proteases may be categorised as endopeptidases that break peptide bonds whithin the polypeptide chain (pepsin and trypsin) and exopeptidases that break the terminal peptide bonds releasing dipeptides or AA (carboxypeptidase)
-dipeptidases:
-dipeptidases hydrolyse the bond between 2 amino acids
-dipeptidases are membrane bound, being part of the cell surface membrane or epithelial cells lining the ileum
-carbohydrases:
-carbohydrases hydrolyse carbohydrates, breaking glyosidic bonds
-amylase breaks polysaccharides; maltase, sucrase and lactase break disaccharides
-lipases:
-lipases hydrolyse lipids breaking ester bonds
-bile salts emulsify lipids increasing the SA of lipids enabling lipases to hydrolyse lipids
-digestion of fats:
1) dietary fats are emulsified into tiny droplets called micelles through the action of bile salts in the intestinal lumen
2) pancreatic lipase hydrolyses fats in the micelles to produce fatty acids and monoglycerides
the digestive system
-digestion:
-digestion is the breakdown of large insoluble food molecules into smaller soluble ones, the breakdown of polymers to monomers to enter body cells
-components of the digestive system:
-salivary glands:
-saliva moistens food
-bicarbonate maintains PH
-amylase digests starch
-lysozyme inhibits bacteria
-gall bladder:
-stores and concentrates bile
-liver:
-produces bile
-performs functions to store and process nutrients
-pancreas:
-secretes digestive enzymes into small intestine
-secretes bicarbonate into small intestine to neutralise stomach acid
-mouth:
-teeth chew food
-tongue positions and chews food
pharynx:
-passageway for food and air
-participates in swallowing
-esophagus:
-moves food from pharynx into stomach
-stomach:
-stores and mixes food
-begins chemical digestion of protein by enzymes and acid
-regulates delivery to the small intestine
-large intestine:
-absorbs nutrients and stores waste material
-small intestine:
-digests proteins, fats and carbohydrates
-absorbs most of the nutrients
-secretes digestive hormones and enzymes
-rectum:
-passageway for feces
-anus:
-expels undigested material