Chapter 3 Cells PDF

Chapter 3 Cells  Introduction Cells – The basic, living, structural and functional units of the body Cell biology – the study of cellular structure and function Cells perform chemical reactions to create life processes  metabolism  A Generalized Cell...

Chapter 3 Cells  Introduction Cells – The basic, living, structural and functional units of the body Cell biology – the study of cellular structure and function Cells perform chemical reactions to create life processes  metabolism  A Generalized Cell Plasma membrane – Encloses the cell – forms outer boundary – separates the cell’s internal (living) environment from the external (non-living) environment – Bilayer is a selective barrier of phospholipids – plays a role in cellular communication  A Generalized Cell Cytoplasm – Fills interior of cell – Semifluid – Contains macromolecules necessary for cellular activity – Contains organelles – Cytosol Part of cytoplasm that contains water, organic molecules, and ions Cytoplasm is the collective term for cytosol plus organelles  A Generalized Cell Nucleus – centrally located – contains chromosomes consists of a single molecule of DNA and associated proteins – a chromosome contains thousands of hereditary units called genes  The Plasma Membrane Integral proteins – extend through the lipid bilayer Peripheral proteins – attached to the inner or outer surface of the membrane, do not extend through it  The Plasma Membrane Some integral proteins are ion channels Transporters - selectively move substances through the membrane Receptors - for cellular recognition; a ligand is a molecule that binds with a receptor Enzymes - catalyze chemical reactions Others act as cell-identity markers  The Plasma Membrane Selectively permeable – oxygen, carbon dioxide, water and steroids – Not glucose, proteins, and ions How do they enter the cell? – Integral proteins can be channels Na/K pump G protein Tyrosine Kinase Pathway  The Plasma Membrane Intracellular fluid (ICF) – fluid within the cells – also called cytosol  The Plasma Membrane Extracellular fluid (ECF) – fluid outside cells – Interstitial fluid ECF filling the spaces between cells (intercellular fluid) – Plasma the ECF in blood vessels – Lymph the ECF in lymphatic vessels The Plasma Membrane  Membrane Transport Passive transport – High to low (with conc. gradient) – No ATP Active transport – Low to high (against conc. gradient) – ATP needed  Membrane Transport Diffusion – the net movement of a substance from a region of high concentration to a region of lower concentration Osmosis – the net movement of water through a selectively permeable membrane from an area of high concentration to a lower concentration  Membrane Transport Facilitated diffusion – the net movement of a substance through an integral protein from a region of high concentration to a region of lower concentration  Membrane Transport Na/K pump – Ions are transported across plasma membranes via integral protein (antiporter) – ATP is needed – Movement is from a region of lower concentration to a region of higher concentration  Membrane Transport Vesicle – a small spherical sac formed by budding off from a membrane Golgi apparatus membrane Plasma membrane Lysosome membrane Exocytosis – vesicles fuse with the plasma membrane, releasing their contents into the ECF  Membrane Transport Endocytosis – materials move into a cell in a vesicle formed from the plasma membrane – Receptor-mediated endocytosis – Phagocytosis – Pinocytosis  Cytoplasm Ribosomes – Site of protein synthesis – Composed of rRNA and proteins – Attach to internal membranes of endomembrane system – Float freely in cytoplasm  Cytoplasm Ribosomes – Composed of 2 subunits Join to form functional unit when synthesizing protein  Cytoplasm The Endomembrane system – Endoplasmic Reticulum – Golgi Apparatus – Lysosomes – Microbodies Peroxisome – Vacoules  Cytoplasm Endoplasmic Reticulum (ER) – Membrane-bound – Embedded proteins – Cisternal space (lumen) Internal compartment of ER – Two types Smooth Rough Cytoplasm  Cytoplasm Rough ER – Embedded ribosomal proteins Protein synthesis – Glycoproteins » Carbohydrate added to the protein chain – Membrane proteins » Cellular transport  Cytoplasm Smooth ER – Contains enzymes Catalyze synthesis of carbohydrates and lipids – Phospholipis for the membrane – Steroids for secretion – Stores ions Ca++ – Used as a signaling molecule » When released pathways are activated  Cytoplasm Golgi apparatus – Collect, sort, package, and distribute proteins – Modifies proteins and lipids from ER Creates glycolipids or glycoproteins – Addition of short sugar chains – Most abundant in glandular cells Secretion is high  Cytoplasm Golgi apparatus – Cis face is receiving end Located near ER – Trans face is distribution end faces the plasma membrane – Packages products in cisternae Terminal ends that pinch off – Diffuse through cytoplasm – Deliver products to appropriate destination Fig. 4.12 Fig. 4.13 Cell structure overview Fig. 4.13 Cell structure overview  Cytoplasm Lysosomes – Digestive vesicles Arise from the Golgi – Bud from trans face Contain hydrolytic enzymes Phagocytosis of… – Macromolecules – Particles – Cells – Worn out organelles  Cytoplasm Microbodies – Peroxisome Contain digestive enzymes – Produce hydrogen peroxide as byproduct Contains detoxifying enzymes – Break down hydrogen peroxide into water and oxygen Catalyze the removal of electrons and H+ – Isolate oxidative enzymes to decrease disruptions to metabolic rxns in the cytoplasm  Cytoplasm Vacuoles – Storage depot Water sugars Ions Waste products  Cytoplasm Centrioles – Microtubule organizing centers – Occur in pairs Move to opposite poles of the cell during cell division – Cylindrical Composed of 9 triplet rows of microtubules Cytoplasm  Cytoplasm Mitochondria – Contain their own DNA Genes translate into proteins essential for function – Can duplicate themselves during cell replication – Contain oxidative metabolic enzymes for transferring energy within macromolecules to ATP  Cytoplasm Mitochondria – Surrounded by two membranes Outer Inner – Cristae » Increases surface area of inner membrane – Matrix » “cytoplasm” of the mitochondria Cytoplasm  Cytoplasm Cytoskeleton – network of protein fibers found in all eukaryotic cells – supports the shape of the cell – keeps organelles in fixed locations – helps move materials within the cell  Cytoplasm Cytoskeleton – Microtubules Attach to chromosomes and move them to opposite poles during anaphase – Actin Slide relative to myosin to create contraction in muscles  Cytoplasm Cytoskeleton – Intermediate filaments provide structural stability Ex. – Keratin – support in epithelial cells – Neurofilaments – support in nerve cells 42  Cilia and Flagella Cilia – short, hair-like projections from the cell surface – move fluids along a cell surface Flagella – longer than cilia – move an entire cell Cilia and Flagella  Nucleus Largest organelle – Usually just one per cell Centrally located Stores genetic information Contains nucleolus – Synthesis of rRNA Fig. 4.8  Nucleus Surround by nuclear envelope – Outer and inner membrane – Pores Allow proteins in Allow RNA and RNA-protein complexes out  Interphase 50 Interphase is composed of: G1 (gap phase 1) – time of cell growth S phase – synthesis of DNA (DNA replication) - 2 sister chromatids are produced G2 (gap phase 2) – chromosomes condense, proteins synthesis  Mitosis 51 Mitosis is divided into 5 phases: 1. prophase 2. prometaphase 3. metaphase 4. anaphase 5. telophase  Cellular Diversity The average adult has nearly 100 trillion cells There are about 200 different types of cells Cells come in a variety of shapes and sizes Cellular diversity permits organization of cells into more complex tissues and organs