BIO-180 Ch-5 Student-Homeostasis & Transport PDF

BIO-180 Chapter -5 Homeostasis & Transport  Homeostasis p.95 All organisms maintain stable internal conditions E.g. in humans, the body temperature is maintained around 370C (980F) pH: All other organs and fluids will fluctuate in their range in order to keep...

BIO-180 Chapter -5 Homeostasis & Transport  Homeostasis p.95 All organisms maintain stable internal conditions E.g. in humans, the body temperature is maintained around 370C (980F) pH: All other organs and fluids will fluctuate in their range in order to keep the blood a strict pH between 7.35 and 7.45 (slightly alkaline). The body makes constant adjustments in tissue and fluid pH to maintain this very narrow pH range in the blood This process is called homeostasis.  Passive transport p. 95 Passive transport is a movement of biochemical and other atomic or molecular substances across cell membranes without energy input by the cells  Diffusion p.95 Is the movement of molecules from an area of higher concentration to an area of lower concentration This is a passive transport  Equilibrium Diffusion causes the concentration of the molecules to become same throughout a space This state is equilibrium  Diffusion across membrane p. 96 The incoming molecules can enter the cell if they can dissolve in the lipids of the membrane through diffusion – E.g. CO2, O2 (The lipids act as the solvents for these solute molecules)  Osmosis p.96 Osmosis is a passive transport as cells do not need energy to be spent as water molecules move down their concentration gradient  Direction of Osmosis p.96 1) If the medium is hypertonic — with a lower water concentration outside the cell — the cell will lose water by osmosis. 2) If the medium is isotonic — a solution outside with exactly the same water concentration as within the cell — there will be no net movement of water across the cell membrane. 3) If the medium is hypotonic — a diluted solution, with a higher water concentration outside the cell than within the cell — the cell will gain water through osmosis. Refer fig. 5-1/97 Direction of Osmosis p.97 Direction of Osmosis p.96 Direction of Osmosis p.96  Direction of Osmosis p.96 Water will diffuse from hypotonic to hypertonic solutions  How cells deal with Osmosis In unicellular organisms such as paramecia, water diffuses into them constantly. However, the contractile vacuoles present in the cytosol removes excess water from the cell Refer fig 5-2/p.97  Diagrammatic – Assignment: Direction of Osmosis Draw and explain the net movement of water in different conditions:- 1) Hypotonic, 2) Hypertonic, 3) Isotonic Facilitated diffusion p.99 Facilitated diffusion For larger molecules that cannot diffuse through cell membrane, they can be assisted by Carrier proteins to diffuse from higher to lower concentration It’s a passive transport Refer fig 5-5 / p.99 Facilitated diffusion p. 99  Diffusion through ion channels p.100 Ion channels provide small passageways for ions like Na+, K+, Ca2+, Cl- These cannot diffuse through cells membrane as they are not soluble in lipids Ion channels are specific to certain ions  Assignment Do section review 5-1 / p.100 Active Transport Sec 5-2: p. 101 Transport of materials from lower to higher area of concentrations Cells need to spend energy Cell membrane ‘pump’ p.101 Carrier protein involved in active transport is termed cell membrane ‘pump’, which transports against the concentration gradient Energy will be spent by cells Sodium-Potassium Pump p. 101 It is an active transport carried out by carrier proteins in animal cells Cells need higher concentration of Na+ outside and K+ inside of the cell 3 Na+ ions pumped from inside to outside 2 K+ ions are pumped from outside to inside `  Sodium-Potassium Pump p. 102 The exchange of 3 Na+ outside and K+ inside creates an electrical gradient across the cell membrane Outside becomes +vely charged and inside –ve This electrical gradient conducts electrical impulses along nerve cells  Endocytosis p. 103 Macromolecules and food particles are brought into the cells by membranous organelle vesicle Two types: pinocytosis and phagocytosis Refer 5-7 / p. 103 Endocytosis  Endocytosis Pinocytosis Phagocytosi s Solutes Large particles Fluids Whole cells  Exocytosis p. 104 Reverse of Endocytosis Exocytosis is expulsion of waste materials, secretion of cellular products such as digestive enzymes, hormones and proteins  Do Section-5-2 review