BIOL 1190: Human anatomy and physiology ILecture 3 (15-Sept-2021)Chapter 3: The cellular level of organizationHuman lung fibroblast,Zeiss Microscopy
This lecture•Parts of a cell (3.1)•The plasma membrane (3.2)•Transport across the plasma membrane (3.3)•Cytoplasm (3.4)
Cells are diverse•There are many different types of cells in the human body•Each cell has astructurethat reflects isfunction
Cells are diverse•Cells are the basic unit of life•Three major parts:•Plasma membrane•Flexible barrier that separates thecell’s internal environment fromthe external environment•Regulates exchange of materialswith environment•Cytoplasm•Includes the cytosol (fluidand solutes) and organelles(subcellular structures withspecific functions)•Nucleus•Contains the nucleolus andDNANucleusPlasma MembraneCytoplasm
Plasma membrane•Flexible, sturdy barrier that surrounds and contains thecytoplasm of the cell•Regulates bidirectional transport of molecules•Facilitates communication between cells
The plasma membrane is a fluid mosaic•The fluid mosaic model describes how lipids and proteinsare arranged within the plasma membrane•Mosaic–membrane contains many different components•Fluid–lipids and some proteins flow freely
Lipids of the cell membrane•The plasma membrane is formed by a phospholipid bilayer•75% of membrane lipids are phospholipids•20% is cholesterol (fluidity buffer)•5% is glycolipids (carbohydrate + lipid)•Why do phospholipids form a stable bilayer in aqueoussolutions?
Proteins of the cell membrane•Integral membrane proteinsare anchored to thehydrophobic core of the lipid bilayer•Transmembrane proteinsare a subtype of integral membraneproteins that span the entire membrane•Peripheral membrane proteinsare bound to the surfaceof the membrane by electrostatic interactions
Proteins of the cell membrane•Glycoproteinsare membrane proteins bound tosaccharides•Exclusively found on extracellular face of the membrane•The saccharides on glycoproteins and glycolipids together formtheglycocalyx; important for cell-cell interactions
Proteins of the cell membrane•Proteins determine most ofthe membrane’s specificfunctions•Ion channels and carriers•Transport substances acrossthe membrane•E.g. Na+, glucose•Receptors•Bind specific molecules andsend a signal to the inside ofthe cell to change cellbehaviour•E.g. insulin receptor
Proteins of the cell membrane•Enzymes•Catalyze chemical reactions•E.g. lactase splits lactose intoglucose and galactose•Linker proteins•Connect cells and facilitatelocomotion•E.g. integrins•Cell identity markers•Usually glycoproteins that helpbody distinguish between cells•E.g. MHC proteins
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