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17 Cards in this Set

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Key facts about membranes (3)

- Bilaminar


- Partially permeable


- Double membranes in mitochondria and chloroplasts: envelope

Key components (3)

- Amphipathic phospholipids


- Proteins and glycoproteins


- Cholesterol (animal cells only)

Draw and label fluid mosaic model

Effect of cholesterol in membrane

- Can compose up to 50% of membrane


- Reduces fluidity by reducing movement of phospholipid tails


- Reduces permeability to some solutes

Difference in between saturated and unsaturated acids in membrane

Saturated acid: less fluid, unsaturated: more fluid

Membrane protein types

- Peripheral


- Integral

Membrane protein functions (7)

- Receptors (hormones, neurotransmitters)


- Active transport


- Facilitated diffusion


- Electron carriers


- Immobilized enzymes


- Cell adhesion


- Cell to cell communication

Davson-Danielli model

- "Sandwich Model"


- Based on observations of electron micrographs that showed two dark lines with a pale line in between


- Stipulated that proteins coated both layers around phospholipids


- Many problems: proteins exposed to hydrophilic surfaces on both sides, lipid soluble substances could not pass through

Singer-Nicholson model

- Proposed much later: fluid-mosaic model


- Supported by observations with a more powerful electron microscope


- Proteins on surface but not as a continuous layer


- Some went through the membrane

Simple diffusion

- Substances move freely along the concentration gradient through membrane


- Usually smaller molecules no ATP needed

Facilitated diffusion

- Molecules that are too large to diffuse through membrane are able to pass through channel proteins that have a hydrophilic core.


- Can be gated in order to control substance flow


- Also passive transport does not require ATP

Osmosis

Diffusion of water across a membrane, against the concentration gradient. Passive transport, does not use ATP.

Determining osmolarity

- Cells placed in hypertonic solution will lose water and shrink


- Cells placed in hypotonic solution will gain water and swell


- Cells placed in an isotonic solution will remain the same

Kidney dialysis

Uses partially permeable membrane to filter substances and replace functioning of Kidneys

Active transport

- Uses ATP that is hydrolyzed into ADP + Pi


- Transport against concentration gradient


- Requires integral protein, such as K/Na pump


- Has specific binding sites for certain substrates

Endocytosis

- Taking substances into cell


- Phagocytosis takes in particles


- Pinocytosis takes in solutions


- ATP required


- Plasma membrane folds inward to form vesicle with substance

Exocytosis

- Removes substances from cell


- Includes secretion of useful substances and excretion of waste


- Vesicle in cytoplasm joins membrane and bursts