* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Cells
Survey
Document related concepts
SNARE (protein) wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cell culture wikipedia , lookup
Cell encapsulation wikipedia , lookup
Extracellular matrix wikipedia , lookup
Cell growth wikipedia , lookup
Cytoplasmic streaming wikipedia , lookup
Cell nucleus wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Signal transduction wikipedia , lookup
Cytokinesis wikipedia , lookup
Cell membrane wikipedia , lookup
Transcript
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 Cytoplasm Plasma (cell) membrane Comprised primarily of: Phospholipids Proteins Carbohydrates 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 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 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 Cell (ICF) ISF Cell 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 Diffusion Random movement down a concentration gradient (from higher to lower concentration) Movement continues until “equilibrium” is reached Diffusion Across Cell Membranes (simple diffusion) (channel mediated diffusion) Facilitated Diffusion (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 solution (higher osmotic pressure) therefore less H2O Cells lose water osmotically and shrink and shrivel Hypotonic solution- less solutes in 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 Osmotic Flow across a RBC Cell Membrane Hemolysis Crenation 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 Receptor-Mediated Endocytosis EXTRACELLULAR FLUID Exocytosis Molecules bind to receptors Target molecules bind to receptors in cell membrane. Endocytosis receptors Coated vesicle Areas coated with bound molecules form deep pockets in membrane surface. Pockets pinch off, forming vesicles. Vesicles fuse with lysosomes. CYTOPLASM Molecules are removed and absorbed into the cytoplasm. Lysosome Molecules removed Fused vesicle and lysosome The membrane containing the receptor molecules separates from the lysosome. The vesicle returns to the surface (Exocytosis). Figure 3-10 Pinocytosis “_____________” Cell membrane folds inward “engulfing” ECF No receptor proteins involved Phagocytosis Phagocytosis Cell membrane of phagocytic cell Lysosomes A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. The pseudopodia approach one another and fuse to trap the material within the vesicle. Vesicle The vesicle moves into the cytoplasm. Lysosomes fuse with the vesicle. Foreign object CYTOPLASM This fusion activates digestive enzymes. Pseudopodia (cytoplasmic extension) EXTRACELLULAR FLUID Exocytosis The enzymes break down the structure of the phagocytized material. Residue is then ejected from the cell by exocytosis. Figure 3-11 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Exocytosis Exocytosis The Organelles Membranous organelles - Isolated compartments Nucleus Mitochondria Endoplasmic reticulum (smooth & rough ER) Golgi apparatus Lysosomes Peroxisomes Nonmembranous organelles - In direct contact with cytosol Cytoskeleton (including microvilli, centrioles, cilia, flagella) Ribosomes The Nucleus Figure 3-16 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 DNA RNA polymerase Complementary triplets Gene 4 mRNA strand RNA nucleotide KEY Adenine Guanine Cytosine Uracil (RNA) Protein Synthesis Translation — the NUCLEUS mRNA The mRNA strand binds to the small ribosomal subunit and is joined at the start codon by the first tRNA, which carries the amino acid methionine. Binding occurs between complementary base pairs of the codon and anticodon. The small and large ribosomal subunits interlock around the mRNA strand. Amino acid KEY Adenine Small ribosomal subunit tRNA Anticodon tRNA binding sites Guanine Cytosine Uracil (RNA) Thymine Start codon A second tRNA arrives at the adjacent binding site of the ribosome. The anticodon of the second tRNA binds to the next mRNA codon. mRNA strand The first amino acid is detached from its tRNA and is joined to the second amino acid by a peptide bond. The ribosome moves one codon farther along the mRNA strand; the first tRNA detaches as another tRNA arrives. Peptide bond Large ribosomal subunit The chain elongates until the stop codon is reached; the components then separate. Small ribosomal subunit Completed polypeptide Stop codon Large ribosomal subunit 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 Golgi apparatus Endoplasmic reticulum EXTRACELLULAR CYTOSOL FLUID Lysosomes Cell membrane Secretory vesicles Transport vesicle Golgi apparatus (a) Membrane renewal vesicles (b) Exocytosis Vesicle Incorporation in cell membrane Figure 3-14 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Lysosomes and Peroxisomes Lysosomes: Produced by golgi apparatus Vesicles containing digestive enzymes Clean-up cellular debris & recycle worn out organelles Defend against bacteria Peroxisomes: contain digestive enzymes to break down fatty acids & other organic compounds 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 (actin) Microtubules (tubulin) The Cytoskeleton Microfilaments myofilaments of muscle cells – muscle contraction 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 Interphase Nucleus Early prophase Mitosis begins Spindle fibers Centrioles (two pairs) Metaphase Late prophase Centromeres Anaphase Chromosome with two sister chromatids 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 functionally specialized. This specialization is known as “differentiation” of cells Specialized (differentiated) cells form distinct tissues in the body