Cell Membrane Functions of Cell Membrane communication via

Cell Membrane

Functions of Cell Membrane § communication via cell receptors § transport, controls what enters and leaves the cell § encloses all other organelles § CANNOT keep harmful substances out of cell

Cell Receptors § Notes from background reading of cell receptor activity

Cell Receptors § § § are in cell membrane attach to specific chemicals receives message from those chemicals specific, like enzymes are proteins

Examples of messengers § from background reading of cell receptor activity

Examples of messengers § § § hormones bee venom pollen viruses like HIV steroids fertility drugs

Cell Receptors § Receptor must fit with hormone or other chemical § Receptor receives message from messenger like hormone § Receptors are specific because of their shape.

Perform activity

Target cells § Hormones are produced in one area of the body and are transported by the bloodstream to the target cell.

Cell Receptors Cell A is the target cell for the circular messenger. Cell B is the target cell for the triangular messenger. receptor messenger

Structure of Cell Membrane Fluid Mosaic Model lipids proteins Pearsonsuccessnet Activity 6. 2

Cell Membrane - Cheek Cell cell membrane lipid bilayer

Cell Membrane - micrograph § lipid bilayer seen through electron microscope

Types of Membrane Transport § Passive transport § molecules move from high concentration to low concentration § occurs because of a concentration gradient, no energy required

Types of Membrane Transport § Active transport § molecules move from low concentration to high concentration § requires energy in the form of ATP

Examples of passive transport § diffusion, osmosis § Where occurs diffusion animation gas exchange animation Lungs, oxygen diffuses from lungs to blood Lungs, carbon dioxide diffuses from blood to lungs Small intestine, nutrients diffuse into blood

Diffusion in the Digestive System high concentration low concentration equilbrium

Diffusion in the Respiratory System § oxygen diffuses from lungs into bloodstream § carbon dioxide diffuses from blood into lungs

Diffusion into body cells § oxygen diffuses from blood into cells § carbon dioxide diffuses from cells into blood

Diffusion dotted line represents cell membrane

Diffusion permeable to small molecules, not permeable to large molecules

Diffusion § Size of the molecule determines if it can cross the membrane § Cell membrane is semi-permeable § Net result of diffusion is equilibrium

Size of molecules big molecules Pearson. Successnet Activity 6. 3 small molecules § sugars, ex. glucose § carbs, ex. starch § amino acids § proteins § fatty acids § lipids § nucleotides § nucleic acids § oxygen, water, carbon dioxide

Osmosis § diffusion of water

Osmosis in a red blood cell in blood plasma in distilled water (100% water) H L equal concentration inside and outside of cell water diffuses into cell

Transport in and out of cells § Water diffusing in cell § Water diffusing out of cell § http: //www. linkpublishing. com/videotransport. htm#OSMOSIS

Water concentrations § Tap water around 95% water § Distilled water is 100% water (always considered high concentration) § Cytoplasm is around 75% water § Salt water is from 85%-94% water (always considered low concentration)

Osmosis in a Paramecium 75% water in cytoplasm 99% water paramecium video Water is pumped out of the paramecium. Active transport: low to high conc. , using ATP Water moves into the cell by osmosis.

Plasmolysis § Shrinkage of the cell membrane and cytoplasm due to water loss § Water leaves the cell by osmosis

Elodea cell in distilled water 99% water 100% water moves into cell by osmosis

Elodea cell in salt water 95% water 99% water moves out of cell by osmosis

Elodea cell wall cell membrane chloroplasts 400 x cytoplasm

Plasmolyzed elodea cell wall cell membrane chloroplasts 400 x cytoplasm elodea video

Types of Transport § Passive movement of molecules from high concentration to low concentration no energy used molecules move because of a difference in concentration - a concentration gradient

Examples § Diffusion and osmosis

Types of Transport § Active Transport movement of molecules from low concentration to high concentration energy is needed § Examples paramecium pumping water out of cell