1 Cytoplasm The contents of a cell, consisting of the cellular organelles, (except the nucleus and cell membrane), suspended in a liquid called the cytosol. The cytoplasm surrounds the nucleus and is contained within the cell membrane.

2 Organelles Endoplasmic Reticulum (ER): composed of interconnected membrane-bound sacs, canals, and vesicles. Provides for a transport system throughout the cell. Rough ER – has ribosomes Protein synthesis Smooth ER Lipid synthesis – lipids added to proteins arriving from rough ER Break down of drugs Ribosomes – tiny spheres composed of rRNA and protein: Free floating or connected to ER Provide the structure and the enzymes needed to link amino acids to form protein Membranes Ribosomes Membranes (b)(c) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

3 Organelles Golgi apparatus – “Post office”: Stack of flattened, membranous sacs Modifies, packages and delivers proteins Vesicles: Membranous sacs Storage of materials Inner membrane Outer membrane Cristae (a)(b) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a: © Bill Longcore/Photo Researchers, Inc. Mitochondrion: Membranous sacs with inner partitions – highly folded membrane forms cristae Generate energy in the form of ATP

4 Organelles Lysosomes “Garbage disposal” digestive enzymes for digesting worn out cell parts and other cellular debris Peroxisomes over 40 different enzymes for catalyzing reactions Enzyme catalase – breaks down hydrogen peroxide (toxic to cell) Centrosome Two rod-like centrioles Used to produce cilia and flagella Forms mitotic spindle to distributes chromosomes during mitosis (a)(b) Centriole (cross-section) Centriole (longitudinal section) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a: © Don W. Fawcett/Visuals Unlimited

5 Organelles Cilia Short hair-like projections Propel substances on cell surface Flagellum Long tail-like projection Provides motility to sperm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a: © Oliver Meckes/Photo Researchers, Inc. © Colin Anderson/Brand X/CORBIS

6 Microfilaments and microtubules (Cytoskeleton) Thin rods and tubules Support cytoplasm Allows for movement of organelles Organelles Inclusions Temporary nutrients and pigments Microtubules Microfilaments Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © M. Schliwa/Visuals Unlimited

7 Cell Nucleus Control center of the cell Nuclear envelope Porous double membrane Separates nucleoplasm from cytoplasm Nucleolus Dense collection of RNA and proteins Site of ribosome production Chromatin (loosely coiled chromo- somes) strands of DNA and proteins called histones. Stores information in the form of genes for synthesis of proteins Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleus Nucleolus Chromatin Nuclear pores Nuclear envelope

8 Active Transport Carrier proteins, (often called “pumps”) move particles across the cell membrane from a region of lower concentration to higher concentration (ie. movement against the concentration gradient) Requires energy in the form of ATP Sugars, amino acids, sodium ions, potassium ions, etc. Almost half of a cell’s energy supply may be used for active transport

9 ACTIVE TRANSPORT Endocytosis Cell engulfs a substance by forming a vesicle around the substance Three types: Pinocytosis – substance is liquid - mostly water Phagocytosis – substance is a solid Receptor-mediated endocytosis – requires the substance to bind to a membrane-bound receptor NucleusNucleolus Vesicle Cell membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10 ACTIVE TRANSPORT Endocytosis Cytoplasm Vesicle (a)(b)(c)(d) Receptor protein Cell membrane Molecules outside cell Cell membrane indenting Receptor-ligand combination NucleusNucleolus Particle Vesicle Phagocytized particle Cell membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11 ACTIVE TRANSPORT Exocytosis Reverse of endocytosis Substances in a vesicle fuse with cell membrane Contents released outside the cell Release of neurotransmitters from nerve cells Nucleus Endoplasmic reticulum Golgi apparatus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

12 ACTIVE TRANSPORT Transcytosis Endocytosis followed by exocytosis Substance is moved quickly from one side of the cell to the other Example: HIV crossing a cell layer Viruses bud HIV Exocytosis Receptor-mediated endocytosis HIV-infected white blood cells Anal or vaginal canal Lining of anus or vagina (epithelial cells) Virus infects white blood cells on other side of lining Receptor-mediated endocytosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell membrane