Main component is the PHOSPHOLIPID

Fatty acids

Hydrophilic head-polar

Hydrophobic tail-nonpolar

Phosphate group

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Simplified Cell Membrane

Cell-cell recognition

Glycoproteins may serve as ID tags that are recognized by other cells

Attachment to the cytoskeleton and the extracellular matrix

Protein and carbo mix located outside the cells

Enzymatic Activity

Examples: disaccharides in small intestine

many enzymes involved in photosynthesis and cellular respiration

Signal Transduction

Protein may have binding site for a hormone which relays a message to the inside of the cell.

Intercellular joining

Examples in animal cells-tight junctions-gap junctions-anchoring junctions

Tight JunctionsProteins hold cells together and don’t allow passage of material between cell. Important in epithelial cells lining intestine. Nutrients inside intestine must pass THROUGH cells. Not between.

Tight junctions

Anchoring junction-keeps cells from being pulled apart

Gap junctions

Plasma membranesof adjacent cells

Extracellular matrix

Gap Junctions -molecules can pass directly from cytoplasm of

one cell to the next. Found in cardiac muscle and some neurons. Speeds communication between cells

• Found in plant cells• Connection between

plasma membrane and cell wall.

• Allow molecules to move from one plant cell to another

This means it allows some things to pass but keeps some things out

What can pass and what cannot? Where do things pass through?

Some through lipids

Some need the proteins

The Plasma Membrane is

Lipid portion of the plasma membrane

Small nonpolar molecules can pass throughO2, CO2

Charged ions or polar molecules cannot pass through

Lipids can pass-ex: steroids

Na+

How can they get in or out??????

Diffusion • Depends on concentration gradients

• Goes from high concentration to lowlow concentration

•Diffusion stops when there is no more concentration gradient

Individual molecules still are moving however

The system is then said to be in equilibrium

Passive Transport

Facilitated DiffusionSTILL DIFFUSION

Direction of movement of molecules????

Needs help (facilitation) of a protein.

DIFFUSION OF WATER ACROSS A SELECTIVELY PERMEABLE MEMBRANE

STILL DIFFUSION PASSIVE NO ENERGY REQUIRED

Uses channel proteins called aquaporins

The direction that WATER goes during osmosis depends on the amount of dissolved solutes on either side of the membrane

If there are more solutes, there is less available water

they refer to the concentration of solutes in that solution

IsotonicHypertonicHypotonic

terms used to compare solutions.

ACTIVE TRANSPORTMoves molecules AGAINST their concentration gradient-”uphill”-requires a membrane protein -source of energy

-usually ATP

Large molecules may cross the membrane by exocytosis and endocytosis

• Exocytosis -substances move out of the cell by packaging them in vesicles which fuse with the plasma membrane

Movement of large materials across the membrane

Phagocytosis (cell eating) -large particles

Pinocytosis (cell drinking) -dissolved solutes

Endocytosis bringing into the cell by way of vesicle (vacuole) formation

Pincytosis is indiscriminate. Cells use receptor-mediated endocytosis to take up specific substance

4.6% solution

5.2% solution

An outer membrane (the plasma membrane)

Genetic material (DNA)Something to build proteins

(ribosomes)

Cells can be categorized into one of the following two groups PROKARYOTIC EUKARYOTIC

Literally means “NO nucleus”Earliest fossils are prokaryotesHave DNA (but not organized into a

nucleus)Have ribosomes (to build proteins)Are “simple” cellsHave no membrane bound

organelles Include the bacteria and archaea

A B

CD

Contain a nucleus and membrane bound organelles

Includes us, plants, fungi, protists