Post on 17-Jan-2018
description
Main component is the PHOSPHOLIPID
Fatty acids
Hydrophilic head-polar
Hydrophobic tail-nonpolar
Phosphate group
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