BCMB 230 1st Edition Lecture 3 Outline of Last Lecture I Chemical Bonds II Macromolecules III Protein Structure and Function Outline of Current Lecture I Cells II Plasma Membrane III Membrane Proteins IV Characteristics of Membranes V Membrane Junctions VI Cytoplasm VII Organelles Current Lecture Cell Structure and Function Cells Divide into plasma membrane and cytoplasm Plasma membrane limiting barrier surrounding a cell also called a cell membrane responsible for a lot of physiological processes Cytoplasm collectively everything inside the cell membrane cytosol organelles membranous and nonmembranous Cells are specialized have different shapes and functions not all cells are small or microscopic ex nerve cells muscle cells length of arm nucleus shape size and location varies depending on cell type can tell the difference between white blood cells and red blood cells by the nucleus shape of nucleus in white blood cells red blood cells lack a nucleus Plasma Membrane Plasma membrane consists of a phospholipids bilayer These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute phospholipids have polar and non polar ends arranged this way because of interaction with water cytosol on the inside interstitial fluid extracellular on the outside anything lipid soluble goes into the cell most chemicals in our body are water soluble so the plasma membrane is a good boundary If you need to get something water soluble into the cell use proteins Membrane proteins Two main types of membrane proteins Integral proteins embedded in bilayer many but not all integral proteins may be transmembrane completely cross the membrane can also be stuck on one side embedded into the membrane Peripheral proteins on the inside of the cell and lie next to or on the surface of the plasma membrane have a nonpolar tail that anchors it to the membrane not embedded not as firmly attached Transmembrane protein can provide for transport of water soluble material through the membrane one way or another spans the plasma membrane Transporters can move slightly bigger materials polyatomic ions actually have to have a shape change to get the material moved across the membrane Channels have a protein structure so that there is a passageway through the middle of the protein big tube which water or a small ion can go through channels can be very specific can have sodium channels calcium channels etc channels can also be gated can open and close mechanical gating ligand gated voltage gated Different functions of membrane proteins Channels have to be integral Transporters have to be integral Receptors can be either Enzymes can be either Structural can be either Characteristics of Membranes Glycocalyx fuzzy coating on extracellular surface of plasma membrane consists of short branched carbohydrate chains carbohydrate component only on the outside of the cell that can attach to proteins or lipids can attach to a protein to form a glycoprotein or a lipid to form a glycolipid Difference in blood types is the difference between something with the glycocalyx Cholesterol found in the plasma membrane lipid soluble found in nonpolar middle portion of membrane helps maintain fluidity of plasma membrane helps to stabilize cell membrane over temperature changes creates steroids in excess can be bad Membrane Junctions Special Junction ways that cells are attached to each other epithelial layer basement membrane or basal lamina that helps to hold the cells in place can influence what gets down between the cells movement across the epithelium paracellular transport material slips down in between the cells goes between cells we have less control over this one depends on the space between cells and the nature chemical composition transcellular transport material goes all the way through a cell centers one side leaves through the other side cross the membrane twice through the cell then the epithelial layer Desmosome hold cells together giving them support but not controlling transport have spaces where things can get around cells connected by shared overlapping proteins but there is still room for paracellular transport Tight junction seals up gaps between the cells give lots of control of what moves through the epithelial cells connected by shared overlapping portiens but there is no room between cells which forces transcellular transport look at this mostly in epithelial cells Gap junction provides passage way between adjacent cells without going outside the cell helps to coordinate cell activity not usually in epithelial cells but muscle cells and others Cytoplasm Cytosol water and proteins salts sugars and various waste products dissolved in water generally kind of syrupy proteins give it a little more viscosity fills up the inside of the cell Organelles Nonmembranous organelles Cytoskeleton provides shape and structure made with proteins that come in long strands called filaments microtubule filament made from protein called tubulin has the biggest diameter can provide for movement as well as structure produce cilia and flagella on outside movement of chromosomes during mitosis is controlled by microtubules Cilia and Flagella have microtubles inside of them allows them to bend movement of cilia is important for movement of materials Ribosome site of making proteins in the cell may be free scattered throughout cytosol may be associated with membranous organelles site of making proteins in the cell free floating proteins created are used inside the cell attached to organelle proteins created are transported outside cell or to cell membrane Membranous Organelles membranes are similar to plasma membrane except with no glycocalyx Nucleus has a double membrane membrane has holes in it called nuclear pores which is the only place where you can easily get large molecules across the membrane this cannot be seen in any other membrane Chromatin inside nucleus combination of DNA and proteins DNA has coding telling what amino acids sequence is for every protein in every cell Mitochondrion also has double membrane site of ATP energy synthesis number present depends on how much energy cell needs Endoplasmic reticulum can form flattened sacs or more tubular structures in the cell Rough Endoplasmic Reticulum more flattened reticulums usually have ribosomes attached used for protein synthesis and processing for proteins used in cell membrane or outside of cell