1. Cells: The Living Units
Chapter 3 – Part 1
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2. Cell Theory
Cells are the basic structural and functional units of life.
Activity of an organism depends on the activities of its cells.
Biochemical activities of a cell are dictated by their organelles.
Continuity of life has a cellular basis.
Characteristics of Cells
Vary greatly in their size, shape, and function.
All are composed primarily of CHONS
All have the same basic parts and some common functions.
A generalized human cell contains the plasma membrane, the cytoplasm, and the nucleus

3. The Plasma Membrane: Structure
Inward-facing and outward-facing surfaces of the plasma membrane differ in the kinds and amounts of lipids they contain.
Glycolipids are found only in the outer membrane.
Lipid rafts only in outer membrane, assumed to function in cell signaling.
Integral proteins are firmly inserted into plasma membrane.
Most integral proteins are transmembrane proteins that span the entire width of the membrane and are involved with transport as channels or carriers.
Fluid Mosaic Model
Plasma membrane is composed of a double layer of phospholipids embedded with small amounts of cholesterol and proteins.
Peripheral proteins are not embedded in plasma membrane, but attach to integral proteins or to phospolipids.
Peripheral proteins may function as enzymes or mechanical functions of cell.
The glycocalyx is the fuzzy, sticky, carbohydrate-rich area surrounding the cell.
Phospholipid bilayer is composed of two layers of phospholipids lying tail to tail, with their polar heads exposed to water inside and outside the cell.
animation

5. Specializations of the Plasma Membrane
Most body cells are bound together using glycolipids, specialized interlocking regions, or specialized membrane junctions.
Gap junctions are a communication junction between cells that allows substances to pass between adjacent cells.
Tight junctions are a type of membrane junction in which integral proteins on adjacent cells fuse together to form an impermeable junction in order to prevent molecules from passing through the extracellular space between cells.
Desmosomes are mechanical couplings that are scattered along the sides of adjoining cells that prevent their separation and reduce the chance of tearing when a tissue is stressed.
Microvilli – increase surface area for absorption (intestines, kidneys)
Layers of the skin
Cardiac
Conduction
System
Blood Brain Barrier

6. Plasma Membrane: Functions
Separates intracellular fluids from extracellular fluids
Membrane Transport – selectively permeable
CAM’s
Generating & Maintaining a Resting Membrane Potential – nerve and muscle cells
Functions of Membrane Proteins
Transport
Enzymatic activity
Receptors for signal transduction
Intercellular adhesion
Cell-cell recognition
Attachment to cytoskeleton and extracellular matrix

7. Cytoplasm Compostion
The cytoplasm is the cellular material between the cell membrane and the nucleus, and is the site of most cellular activity.
Contents of Cytoplasm
Cytosol – largely water with dissolved protein, salts, sugars, and other solutes
Inclusions – chemical substances such as glycosomes, glycogen granules, and pigment
Cytoplasmic organelles – metabolic machinery of the cell
Membranous - mitochondria, peroxisomes, lysosomes, endoplasmic reticulum, and Golgi apparatus
Nonmembranous - cytoskeleton, centrioles, and ribosomes.

8. Organelles: Mitochondria
Double membrane structure with shelflike cristae (internal matrix)
Provide most of the cell’s ATP via aerobic cellular respiration
Contain their own DNA and RNA
Self replicating
Protein synthesis of respiratory proteins
Passed to offspring by female parent

9. Organelles: Ribosomes and Endoplamic Reticulum
Granules containing protein and rRNA
Smooth Endoplasmic Reticulum
Tubules arranged in a looping network
Catalyzes the following reactions in various organs of the body
In the liver – lipid/cholesterol metabolism, detoxification of drugs
In the testes – synthesis of steroid-based hormones
In the intestinal cells – absorption, synthesis, and transport of fats
Rough Endoplasmic Reticulum
External surface studded with ribosomes
Manufactures all secreted proteins
Site of protein synthesis
Free ribosomes synthesize soluble proteins
Responsible for the synthesis of integral membrane proteins and phospholipids for cell membranes
Membrane-bound ribosomes synthesize proteins to be incorporated into membranes
Synthesized by the nucleolus in the nucleus
In muscle – storage and release of calcium

10. Golgi Apparatus and Endomembrane System
Stacked, flattened membranous sacs
Functions in modification, concentration, and packaging of proteins
Transport vessels from the ER fuse with the cis face of the Golgi apparatus
Proteins then pass through the Golgi apparatus to the trans face
Secretory vesicles Golgi stack and move to designated parts of the cell
Vesicle Pathways
Secretion vesicles
New membrane vesicles
Lysosome vesicle

11. Lysosomes Peroxisomes Abundant in liver and kidney cells
Spherical membranous bags containing digestive enzymes
Digest ingested bacteria, viruses, and toxins
Degrade nonfunctional organelles
Breakdown glycogen and release thyroid hormone
Breakdown bone to release Ca2+
Secretory lysosomes are found in white blood cells, immune cells, & melanocytes
Peroxisomes
Abundant in liver and kidney cells
Membranous sacs containing oxidases and catalases
Catalase breaks down H2O2 --->H2O + O2
Detoxify harmful or toxic substances
Neutralize dangerous free radicals
Free radicals – highly reactive chemicals with unpaired electrons (O2–)
Lack of enzyme causes ALD

12. Cytoskeleton structure and movement
Microfilaments – Dynamic strands of protein actin
Attached to the cytoplasmic side of plasma membrane
Braces and strengthens cell surface
Intermediate filaments
Scaffolding of the cell
Tough, insoluble protein fibers with high tensile strength (keratin)
Microtubules -Determines overall shape of cell & distribution of organelles
Make up centrioles which function in mitosis
Makes up cilia and flagella

13. Motor Molecules Kinesin Dynein
Attach to receptors on organelles and transport organelles
Motion accomplished by Motor Molecules and cytoskeleton
Protein complexes that function in motility
Powered by ATP
Cause Cilia and Flagellum Action

14. Centrioles
Small barrel-shaped organelles located in the centrosome near the nucleus
Pinwheel array of nine triplets of microtubules
Form the bases of cilia and flagella
Organize mitotic spindle during mitosis
kinetochore

15. Nucleus
Contains the genetic library with blueprints for nearly all cellular proteins
Dictates the kinds and amounts of proteins to be synthesized
Nuclear Envelope –double membrane
Chromatin - Threadlike strands of DNA and histones
Arranged in fundamental units called nucleosomes
Form condensed, barlike chromosomes when nucleus starts to divide
Outer membrane is continuous with the rough ER and is studded with ribosomes
Pore complex regulates transport of large molecules into and out of the nucleus
Nucleoli - Dark-staining spherical bodies within the nucleus
Site of ribosome production

16. Rafts return Composed of sphingolipids and cholesterol
Are concentrating platforms for cell-signaling molecules
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