TRANSPORT ACROSS THE CELL MEMBRANE Name I. Structure of the Cell Membrane 2 layers (bi-layer) of with imbedded known as the (molecules are in motion) II. The Functions of the Cell Membrane 1. between the cell s external and internal environment (like a gatekeeper) o some molecules can cross it; others cannot o small molecules (H 2 O, CO 2, O 2 ) cross o large molecules (, ) cannot Why is it important that the cell membrane be semi-permeable? o Helps the cell molecules they want to let in: molecules they want to let out: molecules they DO NOT want to let in: 3. Cell-to-cell communication Receives, recognizes and responds to signals from other cells The attached to the surface of the cell membrane act as for molecules like hormones or neurotransmitters (chemical produced by nerve cells). The SHAPE of the cell receptor matches the SHAPE of the chemical signal, like a lock and key or puzzle pieces. Example of a Cell Receptor The target cell has receptors that match the hormone. The binding of the hormone or neurotransmitter to the receptor results in a change in the cell s Molecules that stop the signal from binding to the receptors prevent the cell from responding to the signal. These molecules are called SPECIFICITY In biology, specificity refers to molecules that have a particular affinity for, or attachment to, each other. In other words, they must in order to function 1
Example of a Cell Receptor Has receptors that match the hormone. The binding of the hormone or neurotransmitter to the receptor results in a change in the cell s Molecules that stop the signal from binding to the receptors prevent the cell from responding to the signal. These molecules are called Specificity - In biology, specificity refers to molecules that have a particular affinity for, or attachment to, each other In other words, they must in order to function YOUR TURN: Match the hormone to its target cell Cell A Cell B Cell C Hormone # 1 Hormone # 2 Hormone # 3 1) What is the target cell for hormone #1? 2) What is the target cell for hormone #2? 3) What is the target cell for hormone #3? 2
III. TYPES OF TRANSPORT ACROSS THE MEMBRANE 1. PASSIVE TRANSPORT Requires ENERGY A. DIFFUSION Molecules move from an area of concentration to an area of concentration Molecules move the concentration - like going down a slide. DYNAMIC EQUILIBRIUM when molecules evenly throughout a space and stay in motion. The of diffusion depends on temperature, /surface area of the molecules, & type of molecules diffusing o Substances that may diffuse: B. OSMOSIS - of water molecules CELLS IN DIFFERENT OSMOTIC SOLUTIONS (TONICITY) Cells behave differently when placed in different solutions! This is due to OSMOSIS - Most cells are ~ 98% water! Basic Rule for Determining types of Osmotic conditions.. Sucks If the area outside the cell has salt then water will be pulled out of the cell 1. Isotonic- "ISO" means the 2. Hypotonic (Hypo = ) moves of cell Cell may, or organelles called vacuoles remove water 3. Hypertonic (Hyper = ) moves of cell Cell will (Plasmolysis) or die, plants 3
Water relations and Cell shape in blood cells Water relations in a plant cell. C. Facilitated Diffusion form of passive transport Facilitate- to guide or. channels help guide some molecules through the cell membrane. D. Active Transport Movement of molecules from areas of concentration to areas of high concentration. (energy). the molecules move the concentration gradient like climbing a mountain. Examples of Active Transport 1. - bring the cell Phagocytosis = extends out and material to be brought into the cell. Ex. cells and. 2. - move of the cell 4
Everyday Examples of Diffusion in the Human Body 1) What: nutrients (, amino acids) From: To: Where: -------------------------------------------------------------------------------------- 2) What : From : lungs blood To : blood lungs Where : --------------------------------------------------------------------------------------- 3 What :, carbon dioxide, wastes From : mom baby To : baby mom Where : 5