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Cell Structure & Function
Chapter 3
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The Diversity of Cells in the Human Body
There are over 200 different kinds of cells in the body Figure 3-1
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Anatomy of a representative cell
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Parts of a “representative” cell
Plasma (Cell) Membrane barrier between outside environment (extracellular fluid (ECF) and inside environment Cytoplasm Cytosol (intracellular fluid (ICF)) Organelles
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Plasma (cell) membrane
Comprised primarily of: Phospholipids Proteins Carbohydrates Cholesterol
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Plasma (cell) membrane
Phospholipids Arranged as bilayer Hydrophilic phosphate “heads” Hydrophobic fatty acid “tails” acts as a selective physical barrier between extracellular fluid (interstitial fluid) and intracellular fluid (cytosol)
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Plasma (cell) membrane
Proteins
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Plasma (cell) membrane
Functions of Membrane Proteins include: Receptors Channels Carriers Enzymes Anchors Identifiers
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Plasma (cell) membrane
Carbohydrates act as receptors & identity markers
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Plasma (cell) membrane
Cholesterol helps keeps membrane fluid (flexible) Blood type based on glycoproteins (CHO) on RBC membrane
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Functions of The Cell Membrane
Functions of the plasma membrane include: Physical isolation Regulation of exchange with the environment (“selective permeability”) Sensitivity to surrounding environment Help maintain shape and structural support between cells Cell identification Communication (signaling) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Cytoplasm Cytoplasm All the “stuff” inside a cell The “stuff”:
Cytosol (a.k.a. intracellular fluid ICF) Organelles Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Cytosol Cytosol Intracellular fluid that usually has a __________ consistency Contains water, dissolved nutrients (including amino acids, sugars (glucose/glycogen) & lipids), ions, proteins (enzymes), and wastes Surrounds and suspends organelles; site of some chemical reactions; transportation medium ICF not the only place we have fluids in body Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Fluid compartments of the body
Intracellular fluid (ICF) – a.k.a. cytosol Extracellular fluid (ECF) interstitial fluid plasma lymph ISF Blood vessel (plasma) Cell (ICF) Cell ISF Lymphatic vessel (lymph) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Transport Processes between/within fluid compartments
Two types of processes of transport (movement): Passive – Active –
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Passive processes of transport
No energy required for movement Movement occurs with (“down”) the concentration gradient Includes: Diffusion (simple & channel-mediated) Facilitated diffusion (carrier-mediated transport) Osmosis Filtration Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Movement continues until “equilibrium” is reached
Diffusion Random movement down a concentration gradient (from higher to lower concentration) Simple diffusion: Random movement of molecules from high to low concentration; occurs within interstitial fluid and within/though cytosol Movement continues until “equilibrium” is reached
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Diffusion Across Cell Membranes
(simple diffusion) (channel mediated diffusion)
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Facilitated Diffusion (passive carrier-mediated transport)
No ATP required but requires a carrier protein (transporter) (GLUT-1)
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Osmosis Movement of water across a selectively permeable membrane, down a water concentration gradient (from higher H2O concentration to lower), due to osmotic pressure Osmotic pressure – relates to the concentration of solutes. The higher the concentration of solutes, the higher the osmotic pressure. Water will always move from _______ to _______ osmotic pressure
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Osmotic Effects of Solutions on cells
Isotonic solution- same concentration solutes (equal osmotic pressure) Cells maintain normal size and shape Hypertonic solution- more solutes in surrounding solution (higher osmotic pressure) therefore less H2O Cells lose water osmotically and shrink and shrivel Hypotonic solution- less solutes in surrounding solution (lower osmotic pressure) therefore more H2O Cells gain water osmotically and swell and may burst. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Filtration Hydrostatic pressure ( _____ pressure in the body) pushes on water Water crosses membrane (across capillary endothelium in the body) If membrane is permeable to solutes, solutes follow water movement Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Active processes of transport
- Cell must generate energy (ATP – adenosine triphosphate) for movement - Movement can occur against (“up”) the concentration gradient - Larger substances can move in/out of the cell Includes: Active transport Vesicular transport endocytosis exocytosis
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Active transport Carrier-Mediated
Energy from ATP consumed by carrier protein Molecular movement is independent of concentration gradients (low high concentration) Ion pumps (e.g. Na-K exchange pump) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Vesicular Transport Membranous vesicles requiring energy for movement
Transport in both directions Endocytosis - movement into cell Receptor-mediated endocytosis Pinocytosis Phagocytosis Exocytosis - movement out of cell Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Receptor-Mediated Endocytosis
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Pinocytosis Cell membrane folds inward “engulfing” ECF
“_____________” Cell membrane folds inward “engulfing” ECF No receptor proteins involved
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Phagocytosis
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Exocytosis Secretory vesicles Exocytosis
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The Organelles Membranous organelles Nonmembranous organelles
- Isolated compartments Nucleus Mitochondria Endoplasmic reticulum (smooth & rough ER) Golgi apparatus Lysosomes Nonmembranous organelles - In direct contact with cytosol Cytoskeleton (including microvilli, centrioles, cilia, flagella) Ribosomes Nucleolus
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The Nucleus
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DNA/Chromosomes/Chromatin/Genes
DNA = deoxyribonucleic acid Gene Adenine Guanine Cytosine Uracil (RNA only) Thymine
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Nucleoli Nucleoli are non membranous organelles within the nucleus
Synthesize ribosomal RNA (rRNA) – building block that creates ________________ RNA = ribonucleic acid
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Ribosomes Made of ribsosomal RNA & protein subunits
Found free in cytoplasm (free ribosomes) or attached to rough endoplasmic reticulum (ER) (fixed ribosomes) Participates in protein synthesis by manufacturing of polypeptides (translation)
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Protein Synthesis Two step process: Transcription – Translation –
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Protein Synthesis Transcription — the production of RNA from a single strand of DNA Occurs within nucleus with production of messenger RNA (mRNA) mRNA exits through nuclear pore to go to ribosome
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Protein Synthesis Translation — the assembling of a polypeptide (“potential” protein) on ribosomes Transfer RNAs (tRNA) bring specific amino acids based on transcribed “message” of mRNA Occurs within cytoplasm
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The Endoplasmic Reticulum
Network of intracellular membranes primarily for molecular synthesis, storage & intracellular transport Rough ER (RER) Contains ribosomes on surface of membrane Stores, modifies (folds) & transports newly made ________________ Smooth ER (SER) Lacks ribosomes Synthesizes, stores & transports ________ & ______
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Golgi apparatus Receives new proteins from RER & lipids from SER
Modifies proteins by adding carbohydrates and lipids Packages proteins & lipids in vesicles Secretory vesicles (for exocytosis) Membrane renewal vesicle Synthesizes Lysosomes
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Overview of Protein Synthesis, Processing, and Packaging
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Lysosomes Produced by golgi apparatus
Vesicles containing digestive enzymes Clean-up cellular debris & recycle worn out organelles Defend against bacteria
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Mitochondria Site of ___________________ production
Double layered membrane with inner folds (cristae) enclosing metabolic enzymes for cellular respiration (aerobic metabolism) Figure 3-15
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The Cytoskeleton Internal protein framework to provide strength & structural support, movement of cellular structures & materials Includes: Microfilaments Microtubules
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The Cytoskeleton Microfilaments
microvilli – increase cell surface area
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The Cytoskeleton Microtubules
centrioles - move chromosomes during mitosis cilia - move substances across cell surface flagella - moves cell through fluid (sperm)
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Cell division Somatic Cell division - The reproduction of body cells; necessary for growth & repair. Results in the formation of 2 genetically identical “daughter” cells Mitosis - nuclear (chromosomal) division of somatic cells (after chromosomal replication has occurred). Cytokinesis - division of cytoplasmic contents Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Nucleus Spindle fibers Mitosis begins Chromosome with two
Interphase Early prophase Late prophase Nucleus Spindle fibers Mitosis begins Chromosome with two sister chromatids Centrioles (two pairs) Centromeres Metaphase Anaphase Telophase Separation Daughter chromosomes Cytokinesis Metaphase plate Cleavage furrow Daughter cells Figure 3-22 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
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Cell Diversity and Differentiation
Somatic (Body) Cells All have same genes Some genes inactivate during development Cells thus become structurally and functionally specialized. This specialization is known as “differentiation” of cells Specialized (differentiated) cells form distinct tissues in the body
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