Cell Structure & Function Chapter 3

The Diversity of Cells in the Human Body There are over 200 different kinds of cells in the body Figure 3-1

Anatomy of a representative cell

Parts of a “representative” cell Plasma (Cell) Membrane barrier between outside environment (extracellular fluid (ECF) and inside environment Cytoplasm Cytosol (intracellular fluid (ICF)) Organelles

Plasma (cell) membrane Comprised primarily of: Phospholipids Proteins Carbohydrates Cholesterol

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)

Plasma (cell) membrane Proteins

Plasma (cell) membrane Functions of Membrane Proteins include: Receptors Channels Carriers Enzymes Anchors Identifiers

Plasma (cell) membrane Carbohydrates act as receptors & identity markers

Plasma (cell) membrane Cholesterol helps keeps membrane fluid (flexible) Blood type based on glycoproteins (CHO) on RBC membrane

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

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

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

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

Transport Processes between/within fluid compartments Two types of processes of transport (movement): Passive – Active –

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

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

Diffusion Across Cell Membranes (simple diffusion) (channel mediated diffusion)

Facilitated Diffusion (passive carrier-mediated transport) No ATP required but requires a carrier protein (transporter) (GLUT-1)

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

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

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

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

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

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

Receptor-Mediated Endocytosis

Pinocytosis Cell membrane folds inward “engulfing” ECF “_____________” Cell membrane folds inward “engulfing” ECF No receptor proteins involved

Phagocytosis

Exocytosis Secretory vesicles Exocytosis

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

The Nucleus

DNA/Chromosomes/Chromatin/Genes DNA = deoxyribonucleic acid Gene Adenine Guanine Cytosine Uracil (RNA only) Thymine

Nucleoli Nucleoli are non membranous organelles within the nucleus Synthesize ribosomal RNA (rRNA) – building block that creates ________________ RNA = ribonucleic acid

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)

Protein Synthesis Two step process: Transcription – Translation –

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

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

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 ________ & ______

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

Overview of Protein Synthesis, Processing, and Packaging

Lysosomes Produced by golgi apparatus Vesicles containing digestive enzymes Clean-up cellular debris & recycle worn out organelles Defend against bacteria

Mitochondria Site of ___________________ production Double layered membrane with inner folds (cristae) enclosing metabolic enzymes for cellular respiration (aerobic metabolism) Figure 3-15

The Cytoskeleton Internal protein framework to provide strength & structural support, movement of cellular structures & materials Includes: Microfilaments Microtubules

The Cytoskeleton Microfilaments microvilli – increase cell surface area

The Cytoskeleton Microtubules centrioles - move chromosomes during mitosis cilia - move substances across cell surface flagella - moves cell through fluid (sperm)

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

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

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