Bota: cell membrane real

cell membrane

• separates the living cell from non living surroundings 
• controls traffic in and out of the cell 
• selectively permeable
• allow some substances to cross more easily than others 
• made of phospholipids, proteins and other macromolecules

phospholipids

• fatty acids tails - hydrophobic
• phosphate group head - hydrophilic 
• arranged as a bilayer 

fluid mosaic model by

singer and g nicolson 

membrane fat composition

• membrane must be fluid and flexible - cell surface must stay soft and flexible
• unsaturated fatty acid- keep the membrane loose and fluid
• cholesterol- balances membane softness and stiffness

membrane proteins 

• peripheral proteins - loosly bound to surface of membrane, cell surface identity or marker(antigens)
• integral proteins- penetrate lipid bilayer, usually across the whole membrane, also called as transmembrane protein, transport protein. since gina penetrate na ang bilog nga membrane. 

protein domain anchor molecule 

• within membrane - non polar, hydrophobic, anchors protein into the membrane 
• outer surfaces of membrane- polar, hydrophilic, extend into extra cellular fluid and into cytosol

non polar (hydrophobic) amino acid

• anchors protein into the membrane

polar amino acid (hydrophilic)

• extend into extracellular fluid and into cytosol

function of membrane proteins 

• transport
• enzyme activity
• cell surface receptor
• cell surface identity marker 
• cell adhesion
• attachment to cytoskeleton

membrane carbohydrates

• ability of a cell to distinguish one cell from another (antigen)
• important in organ and tissue development 
• basis for recognition of foreign cells by immune system

diffusion

• movement from high- low concentration

passive transport

no energy needed

osmosis 

diffusion in water 

diffusion across cell membrane 

• let some molecules in and out, since cells need materials in and products/ waste out
• import: carbs, sugar, protein, amino acids, lipids, salts.
• export: waste, ammonia, salts, CO2, h20 products 

diffusion through phospholipid bilayer

• fats n lipids can get through directly 
• what can not get through: polar molecules like h20, ions, large molecules

facillitated diffusion

• diffusion through protein channels 
• with help 

active transport

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• high to low concentration or vice versa 
• the doorman
• costs energy= ATP 
• protein""pump""

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active transport mode and mechanism

• antiport -moves opposite direction of the gradient
• symport- same direction of the concentration gradient

antiport

• moves opposite direction of concentration gradient

symport 

• same direction of concentration gradient

passive transport 

• simple diffusion- diffusion of nonpolar, hydrophobic molecules. (lipids, high - low concentration gradient)
• faciltated transport- diffusion of polar, hydrophilic molecules, through a protein channel (high to low concentration gradient)

moving of large molecules, in and out of the cell

• through vesicles and vacoules
• endocytosis (phagocytosis, pinocystosis, receptor mediated endocytosis)
• exocytosis - exit of materials out of the cell

phagocytosis

• cell eating
• fuse with lysosome for digestion

pinocytosis

• cell drinking
• non specific process

receptor mediated endocytosis

triggered by molecular signal

different concentration of water

• hypertonic- more solute, less water 
• hypotonic- less solute, more water
• isotonic- equal

plasmolysis

• shrinking of protoplasm away from the cell wall of a plant or bacterium due to water loss
• affect of osmosis

hypotonic solution

• less solute, more water
• animal cell- lysed or lusbot 
• plant cell- turgid or normal

hypertonic solution

• more solute, less water
• animal cell- shriveled 
• plant cell- plasmolysed