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17 Cards in this Set

  • Front
  • Back

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


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


- Taking substances into cell

- Phagocytosis takes in particles

- Pinocytosis takes in solutions

- ATP required

- Plasma membrane folds inward to form vesicle with substance


- Removes substances from cell

- Includes secretion of useful substances and excretion of waste

- Vesicle in cytoplasm joins membrane and bursts