Chapter 3 Cell Diversity

Learning Objectives Cell Diversity Cell Physiology

Cell Diversity: Connective Fibroblasts: Elongated cell that secretes cable-like protein fibers. Large rough ER and Golgi apparatus Erythrocyte (RBC): carries O2 throughout the body. No organelles, lots of hemogolbin

Cell Diversity

Cell Diversity: Covers and Lines Epithelial Cell: intermediate filaments resist tearing Hexagonal shape, pack together in sheets

Cell Diversity

Cell Diversity: Movement Skeletal and Smooth Muscle cells Elongated Lots of contractile filaments

Cell Diversity

Cell Diversity: Store nutrients Fat cells (adipose): Spherical shape holds large lipid droplet

Cell Diversity

Cell Diversity: Fights disease Macrophages, T-cells, B-cells (WBC’s): Some have pseudopods (fake feet) Lots of lysosomes

Cell Diversity

Cell Diversity: Gathers information and controls body functions Nerve cell (neuron): Axon: sends info Dendrites: receives info Lots of ER to synthesize membrane components.

Cell Diversity

Cell Diversity: Reproduction Oocyte: Female Largest cell in the body Lots of organelles Sperm: Male Long and streamline flagellum

Cell Diversity

Cell Physiology: Membrane Transport Membrane transport—movement of substances into and out of the cell Two basic methods of transport Passive transport No energy is required Active transport Cell must provide metabolic energy (ATP)

Solutions and Transport Solution—homogeneous mixture of two or more components Solvent—dissolving medium; typically water in the body Solutes—components in smaller quantities within a solution Intracellular fluid—nucleoplasm and cytosol Interstitial fluid—fluid on the exterior of the cell

Selective Permeability The plasma membrane allows some materials to pass while excluding others This permeability influences movement both into and out of the cell

Passive Transport Processes Diffusion: Movement of a substance from a high concentration to a low concentration Usually lipid-soluble or small enough to pass through membrane pores Osmosis Water diffusion Assisted by aquaporins Facilitated diffusion: substances require a protein carrier Usually lipid insoluble or large

Active Transport Processes ATP is used for transport because the substance may be too big Not able to pass the lipid interior of the membrane Have to move against a concentration gradient

Active Transport Processes Two common forms of active transport Active transport (solute pumping) Vesicular transport Exocytosis – substances leave the cell through a vesicle Endocytosis – substances enter the cell through a vesicle Phagocytosis – “Cell eating” Pinocytosis – “cell drinking”

Exocytosis

Endocytosis Extracellular fluid Cytoplasm Pit Recycling of membrane and receptors (if present) to plasma membrane Cytoplasm Extracellular fluid Plasma membrane Detachment of vesicle Vesicle containing ingested material Vesicle Vesicle fusing with lysosome for digestion Release of contents to cytoplasm Lysosome Transport to plasma membrane and exocytosis of vesicle contents Ingested substance Pit (a)