Chapter 3 Cell Anatomy Cell = Chamber/Compartment 4/22/2017 Chapter 3 Cell Anatomy Cell = Chamber/Compartment

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Basic Structure of the Cell 4/22/2017 Basic Structure of the Cell Plasma membrane Cytoplasm containing organelles (little organs) Nucleus Functions of the Cell Basic unit of life Protection and support through production and secretion of various kinds of molecules Movement. Various kinds occur because of specialized proteins produced in the cell (Flagella and Cilla) Communication. Cells produce and receive electrical and chemical signals Cell metabolism and energy release Inheritance. Each cell contains DNA. Some cells are specialized to gametes for exchange during sexual intercourse

Plasma Membrane (phospholipid bilayer) 4/22/2017

Plasma Membranes Fluid-mosaic model 4/22/2017 Plasma Membranes Fluid-mosaic model theory explaining how cell membranes are constructed Molecules of the cell membrane are arranged in a sheet The mosaic of molecules is fluid; that is, the molecules are able to float around slowly Chemical attraction is the force that holds membranes together

Membrane Lipids 4/22/2017 Primary structure of a cell membrane is a double layer of phospholipid molecules Heads are hydrophilic (water-loving) Tails are hydrophobic (water-fearing) Molecules arrange themselves in bilayers in water Cholesterol molecules are scattered among the phospholipids to allow the membrane to function properly at body temperature Most of the bilayer is hydrophobic; therefore water or water-soluble molecules do not pass through easily

Membrane Lipids (cont) 4/22/2017 Membrane Lipids (cont) What is it composed of? Phospholipids and cholesterol predominate Phospholipids: bilayer. Polar heads facing water in the interior and exterior of the cell (hydrophilic); nonpolar tails facing each other on the interior of the membrane (hydrophobic) Cholesterol: interspersed among phospholipids. Amount determines fluid nature of the membrane

Membrane Proteins TYPES of Membrane Proteins Integral / intrinsic 4/22/2017 Membrane Proteins TYPES of Membrane Proteins Integral / intrinsic Extend deeply into membrane, often extending from one surface to the other Can form channels through the membrane Peripheral / extrinsic Attached to integral proteins at either the inner or outer surfaces of the lipid bilayer Functioning depends on 3-D shape and chemical characteristics. Markers, attachment sites, channels, receptors, enzymes, or carriers.

1) Marker Molecules: Glycoproteins 4/22/2017 1) Marker Molecules: Glycoproteins Carbohydrates attach to proteins Allow cells to identify one another or other molecules Immunity Intercellular communication

4/22/2017 2) Attachment Sites Attachment sites to other cells or to extra/intracellular molecules.

4/22/2017 3) Channel Proteins (Integral): hydrophilic region faces inward; charge determines molecules that can pass through Nongated ion channels: always open Responsible for the permeability of the plasma membrane to ions when the plasma membrane is at rest Gated ion channels can be open or closed Ligand gated ion channel: open in response to small molecules that bind to proteins or glycoproteins Voltage-gated ion channel: open when there is a change in charge across the plasma membrane

4/22/2017 4) Receptor Molecules Proteins in membranes with an exposed receptor site Can attach to specific ligand molecules and act as an intercellular communication system Ligand can attach only to cells with that specific receptor

5) Enzymes and Carrier Protein 4/22/2017 5) Enzymes and Carrier Protein Enzymes: some act to catalyze reactions at outer/inner surface of plasma membrane. Carrier proteins: integral proteins move ions from one side of membrane to the other Have specific binding sites Protein change shape to transport ions or molecules

4/22/2017 Cytoplasm Cytoplasm: gel-like internal substance of cells that includes many organelles suspended in watery intracellular fluid called cytosol Cellular material outside nucleus but inside plasma membrane Two major groups of organelles (Table 3-3) Membranous organelles are sacs or canals made of cell membranes Nonmembranous organelles are made of microscopic filaments or other nonmembranous materials

Endoplasmic Reticulum 4/22/2017 Endoplasmic Reticulum 2 Types Smooth ER Rough ER

Endoplasmic Reticulum 4/22/2017 Endoplasmic Reticulum Smooth (SER): No ribosomes attached Synthesizes lipids and carbohydrates: phospholipids and cholesterol (membranes) steroid hormones (reproductive system) glycerides (storage in liver and fat cells) Storage of Ca++ Fat metabolism and drug detoxification (liver) Rough (RER) Has attached ribosomes - Proteins produced and modified here

4/22/2017 Ribosomes - Tiny round bodies in the cytoplasm made of a large and small subunit - Build polypeptides in protein synthesis Two types: Free ribosomes in cytoplasm: manufacture proteins for cell Fixed ribosomes attached to ER membranes: manufacture proteins for secretion

4/22/2017 Golgi Apparatus Flattened membrane sacs stacked on each other (cisternae) Modification, packaging, distribution of proteins and lipids for secretion or internal use

Function of Golgi Apparatus 4/22/2017 Function of Golgi Apparatus Proteins made in the ER are packaged into tiny vesicles, which pinch off and move towards the golgi apparatus. Vesicles fuse with the golgi membrane and release the proteins. Enzymes within the golgi modify the proteins The processed molecules eventually pinch off and move towards the plasma membrane where they are secreted.

Function of Golgi Apparatus 4/22/2017 Function of Golgi Apparatus

Lysosomes Powerful enzyme containing vesicles Functions of Lysosomes 4/22/2017 Lysosomes Powerful enzyme containing vesicles Functions of Lysosomes Clean up inside cells: Break down large molecules Attack bacteria Recycle damaged organelles Eject wastes by exocytosis

Proteasomes Hollow protein cylinders found throughout the cytoplasm 4/22/2017 Proteasomes Hollow protein cylinders found throughout the cytoplasm Break down abnormal or misfolded proteins and normal proteins no longer needed by the cell (and that may cause disease) Break down protein molecules one at a time by tagging each one with a chain of ubiquitin molecules, unfolding the protein as it enters the proteasome, and then breaking apart peptide bonds

4/22/2017 Proteasomes

Peroxisomes Peroxisomes Smaller than lysosomes 4/22/2017 Peroxisomes Peroxisomes Smaller than lysosomes Detoxify harmful substances in cell Contain enzymes to break down fatty acids and amino acids Contain peroxidase and catalase Hydrogen peroxide is a by-product of breakdown

Mitochondria Major site of ATP synthesis Membranes 4/22/2017 Mitochondria Major site of ATP synthesis Membranes Cristae: Infoldings of inner membrane Matrix: Substance located in space formed by inner membrane Mitochondria increase in number when cell energy requirements increase. Mitochondria contain DNA that codes for some of the proteins needed for mitochondria production.

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Nucleus - The cell’s control center Contains genetic material (DNA) 4/22/2017 Nucleus - The cell’s control center Contains genetic material (DNA) Three distinct regions: 1. Nuclear Membrane 2. Nucleoli 3. Chromatin

Nuclear Structure and Content 4/22/2017 Nuclear Structure and Content Nuclear Membrane - double membrane connected by nuclear pores -encloses nucleoplasm Nucleoli - site of ribosome formation Chromatin -carries cells DNA -condenses into Chromosomes during cell division

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4/22/2017 Cytoskeleton Supports the cell but has to allow for movements like changes in cell shape and movements of cilia Cell fibers: Microfilaments: “cellular mm” Made of thin, twisted strands of protein molecules that lie parallel to the long axis of the cell Can slide past each other and cause shortening of the cell Actin and myosin are subcategories Microtubules: hollow, made of tubulin. Internal scaffold, transport, cell division, move things around cell Intermediate filaments: mechanical strength

4/22/2017 Cell Fibers

4/22/2017 Centrosome An area of the cytoplasm near the nucleus that coordinates the building and breaking apart of microtubules in the cell Nonmembranous structure also called the microtubule organizing center Center of microtubule formation Before cell division, centrioles divide, move to ends of cell and organize spindle fibers General location of the centrosome is identified by the centrioles

Cell Extensions Cilia Appendages projecting from cell surfaces 4/22/2017 Cell Extensions Cilia Appendages projecting from cell surfaces Capable of movement Moves materials over the cell surface Shorter and more numerous than flagella Coordinated oar like movements Respiratory tract

Flagella Similar to cilia but longer Usually only one per cell 4/22/2017 Flagella Similar to cilia but longer Usually only one per cell Move the cell itself in wave-like fashion Human Example: sperm cell

Microvilli Extension of plasma membrane Line intestines 4/22/2017 Microvilli Extension of plasma membrane Line intestines Increase the cell surface area for absorption Normally many on each cell One tenth to one twentieth size of cilia Do not move

Cell Connections Membrane junctions 4/22/2017 Cell Connections Membrane junctions 1. Tight junctions – Adjacent plasma membranes fused together tightly 2. Desmosomes – Anchoring junctions that prevent cells subjected to mechanical stress from being pulled apart 3. Gap junctions - Allow communication between cells