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 Lungs, oxygen diffuses from lungs to blood Lungs, carbon dioxide diffuses from blood to lungs Small intestine, nutrients diffuse into blood diffusion animation gas exchange animation

Diffusion in the Digestive System equilbrium high concentration low concentration

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

represents cell membrane 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 PearsonSuccessnet Activity 6.3 big molecules small molecules sugars, ex. glucose amino acids fatty acids nucleotides oxygen, water, carbon dioxide carbs, ex. starch proteins lipids nucleic acids

Osmosis diffusion of water

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

Transport in and out of cells Water diffusing in cell Water diffusing out of cell http://www.linkpublishing.com/video-transport.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 Water is pumped out of the paramecium. Active transport: low to high conc., using ATP 75% water in cytoplasm 99% water Water moves into the cell by osmosis. paramecium video

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

Elodea cell in distilled water water moves into cell by osmosis

Elodea cell in salt water water moves out of cell by osmosis

Elodea cell cell wall cell membrane chloroplasts 400x cytoplasm

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

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