LECTURE 6 THE CELL – CH. 3 PART 1

A Cell has 3 Major Parts Plasma membrane – Selectively permeable – Intercellular communication Nucleus - the largest organelle -contains genetic material - has nucleoli Cytoplasm – Contains organelles specific to the cell type See figure 3.1 textbook

Plasma Membrane Properties Selectively permeable – allows some substances to pass through, but not others Nonpolar molecules get through easily. Why? It’s a lipid bilayer: outside/inside is polar Interior of membrane is nonpolar Integral and peripheral proteins – may be glycoproteins or lipoproteins Cholesterol makes up membranes Fluid mosaic model See fig. 3.2

Phagocytosis cell eating Receptor-mediated endocytosis – requires the substance to bind to a membrane- bound receptor Pinocytosis cell drinking 3 TYPES OF ENDOCYTOSIS Click here

Exocytosis reverse of endocytosis substances in a vesicle fuse with cell membrane contents released outside the cell

Cilia and Flagella Cilia - tiny hair-like structures that project from the surface of a cell. -Found on epithelium -Composed of microtubules (thin cylinders formed from proteins) -Non-motile: arrangement -Motile: arrangement Flagellum – a single whip-like structure which propels a cell

Microvilli (a brush border) Folds in the plasma membrane that increase the surface area for chemical reactions and rapid diffusion Examples: intestines and kidney tubules

Cytoplasm Material within a cell a.Includes organelles, a fluid called cytosol, the cytoskeleton, inclusions. b.Inclusions – stored chemical aggregates such as glycogen, melanin, and triglycerides

Cytoskeleton a.Organized system of microtubules and microfilaments b.Proteins of the cytoskeleton are mobile. c.They organize the intracellular environment and allow movement of muscle cells and phagocytic cells. d.They form the spindle apparatus that pulls chromosomes apart in mitosis. e.They also serve as a “railway” system for vesicles and organelles to move along using molecular motors of myosin, kinesins, and dyneins.

Lysosomes Organelles filled with digestive enzymes

Student Activity Read Clinical Application, p. 58. What is a lysosomal storage disease? How is it caused? Name at least one. Turn to your neighbor and report.

Peroxisomes 1.Contain enzymes specific to certain oxidative reactions 2.Found in most cells but most numerous in the liver; often oxidize toxic molecules (such as alcohol) 3.Enzymes used to remove hydrogen from a molecule and transfer it to O 2, forming hydrogen peroxide 4.Also contain the enzyme catalase, which converts hydrogen peroxide into water and O 2

Mitochondria Sites of ATP production (aerobic respiration) They migrate around the cell and can make copies of themselves. Have their own DNA. Come from mom. Mutations of mitochondrial DNA may contribute to aging and disease

Ribosomes 1.mRNA takes genetic information to the ribosome proteins can be assembled. 2.Very small; made of 2 subunits of ribosomal RNA and protein 3.Found free in the cytoplasm or associated with the granular endoplasmic reticulum 4.Serves as enzymes called ribozymes that are needed for protein synthesis

Endoplasmic Reticulum 1.System of membranous passageways from the nuclear membrane to the the plasma membrane 2.Granular ER is also called rough ER. -Has ribosomes on surface -Functions in protein modification 3.Agranular ER OR smooth ER. -many functions, depends on the cell

Student activity Go to p. 61 of the text. Read the Clinical application. How might the agranular endoplasmic reticulum play a role in a person’s tolerance to alcohol? Turn to your neighbor and discuss this.

Vesicles headed for exocytosis are called endosomes Proteins can be modified within the cisternae Retrograde transport- extracellular proteins brought in by endocytosis and then through the Golgi complex to the ER Golgi Complex hollow, flattened sacs; cavities called cisternae