Anatomy of the Human Cell- PDF

Anatomy of the Human Cell Dr. James GN.,Ph.D. © 2012 Pearson Education, Inc. An Introduction to Cells Learning Outcomes 3-1 List the functions of the plasma membrane and the structural features that enable...

Anatomy of the Human Cell Dr. James GN.,Ph.D. © 2012 Pearson Education, Inc. An Introduction to Cells Learning Outcomes 3-1 List the functions of the plasma membrane and the structural features that enable it to perform those functions. 3-2 Describe the organelles of a typical cell, and indicate the specific functions of each. 3-3 Explain the functions of the cell nucleus and discuss the nature and importance of the genetic code. 3-4 Summarize the role of DNA in protein synthesis, cell structure, and cell function. © 2012 Pearson Education, Inc. An Introduction to Cells Learning Outcomes 3-5 Describe the processes of cellular diffusion and osmosis, and explain their role in physiological systems. 3-6 Describe carrier-mediated transport and vesicular transport mechanisms used by cells to facilitate the absorption or removal of specific substances. 3-7 Explain the origin and significance of the transmembrane potential. © 2012 Pearson Education, Inc. An Introduction to Cells Learning Outcomes 3-8 Describe the stages of the cell life cycle, including mitosis, interphase, and cytokinesis, and explain their significance. 3-9 Discuss the regulation of the cell life cycle. 3-10 Discuss the relationship between cell division and cancer. 3-11 Define differentiation, and explain its importance. © 2012 Pearson Education, Inc. An Introduction to Cells Cell Theory Developed from Robert Hooke’s research Cells are the building blocks of all plants and animals All cells come from the division of preexisting cells Cells are the smallest units that perform all vital physiological functions Each cell maintains homeostasis at the cellular level © 2012 Pearson Education, Inc. An Introduction to Cells Sex Cells (Germ Cells) Reproductive cells Male sperm Female oocyte (a cell that develops into an egg) Somatic Cells Soma = body All body cells except sex cells © 2012 Pearson Education, Inc. Figure 3-1 Anatomy of a Model Cell  Plasma membrane  Nonmembranous organelles  Membranous organelles Secretory vesicles Centrosome and Centrioles Cytoplasm contains two centrioles CYTOSOL at right angles; each centriole is composed of 9 microtubule triplets in a 9  0 array Functions Essential for Centrosome movement of chromosomes during cell division; organization of Centrioles microtubules in cytoskeleton © 2012 Pearson Education, Inc. Figure 3-1 Anatomy of a Model Cell  Plasma membrane  Nonmembranous organelles Cytoskeleton Proteins organized  Membranous organelles Microfilament in fine filaments or slender tubes Functions Strength and support; movement of cellular structures Microtubule and materials Plasma Membrane Lipid bilayer containing phospholipids, steroids, proteins, Free ribosomes and carbohydrates Functions Isolation; protection; sensitivity; support; Cytosol (distributes controls entry materials and exit of by diffusion) materials © 2012 Pearson Education, Inc. Figure 3-1 Anatomy of a Model Cell Microvilli Membrane extensions containing microfilaments Function Increase surface area to facilitate absorption of extra-cellular materials  Plasma membrane  Nonmembranous organelles  Membranous organelles © 2012 Pearson Education, Inc. Figure 3-1 Anatomy of a Model Cell Cilia Cilia are long extensions containing microtubule doublets in a 9  2 array (not  Plasma membrane shown in the model cell)  Nonmembranous organelles Function Movement of material over  Membranous organelles cell surface Proteasomes Hollow cylinders of proteolytic enzymes with regulatory proteins at their ends Functions Breakdown and recycling of damaged or abnormal intracellular proteins Ribosomes RNA  proteins; fixed ribosomes bound to rough endoplasmic reticulum, free ribosomes scattered in cytoplasm Function Protein synthesis © 2012 Pearson Education, Inc. Figure 3-1 Anatomy of a Model Cell Golgi apparatus Stacks of flattened membranes (cisternae) containing chambers Functions Storage, alteration, and packaging of secretory products and lysosomal enzymes Mitochondria Double membrane, with inner membrane folds (cristae) enclosing important metabolic enzymes Functions Produce 95% of the ATP required by the cell Endoplasmic reticulum (ER) Network of membranous Rough ER NUCLEUS channels extending modifies and throughout the packages newly cytoplasm synthesized proteins Functions Synthesis of secretory Smooth ER products; intracellular synthesizes storage and transport lipids and carbohydrates Peroxisomes Vesicles containing degradative enzymes Functions Catabolism of fats and other organic compounds,  Plasma membrane neutralization of toxic compounds generated in  Nonmembranous organelles the process  Membranous organelles © 2012 Pearson Education, Inc. Figure 3-1 Anatomy of a Model Cell  Plasma membrane  Nonmembranous organelles  Membranous organelles Peroxisomes Vesicles containing degradative enzymes Functions Catabolism of fats and other organic compounds, neutralization of toxic compounds Free ribosomes generated in the process Lysosomes Vesicles containing digestive enzymes Functions Intracellular removal of damaged organelles or pathogens © 2012 Pearson Education, Inc. Figure 3-1 Anatomy of a Model Cell Chromatin Nuclear NUCLEUS envelope Nucleoplasm containing NUCLEOPLASM Nucleolus nucleotides, (site of rRNA enzymes, synthesis and nucleoproteins, and assembly of chromatin; ribosomal surrounded by a subunits) double membrane, the nuclear envelope Nuclear Functions: pore Control of metabolism; storage and processing of genetic information; control of protein synthesis © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Extracellular Fluid (Interstitial Fluid) A watery medium that surrounds a cell Plasma membrane (cell membrane) separates cytoplasm from the extracellular fluid Cytoplasm Cytosol = liquid Intracellular structures collectively known as organelles © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Functions of the Plasma Membrane Physical Isolation Barrier Regulation of Exchange with the Environment Ions and nutrients enter Wastes eliminated and cellular products released © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Functions of the Plasma Membrane Sensitivity to the Environment Extracellular fluid composition Chemical signals Structural Support Anchors cells and tissues © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Membrane Lipids Phospholipid bilayer Hydrophilic heads — toward watery environment, both sides Hydrophobic fatty-acid tails — inside membrane Barrier to ions and water — soluble compounds © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Membrane Proteins Integral Proteins Within the membrane Peripheral Proteins Bound to inner or outer surface of the membrane © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Membrane Proteins Anchoring Proteins (stabilizers) Attach to inside or outside structures Recognition Proteins (identifiers) Label cells as normal or abnormal Enzymes Catalyze reactions © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Membrane Proteins Receptor Proteins Bind and respond to ligands (ions, hormones) Carrier Proteins Transport specific solutes through membrane Channels Regulate water flow and solutes through membrane © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Membrane Carbohydrates Proteoglycans, glycoproteins, and glycolipids Extend outside cell membrane Form sticky “sugar coat” (glycocalyx) Functions of the glycocalyx Lubrication and Protection Anchoring and Locomotion Specificity in Binding (receptors) Recognition (immune response) © 2012 Pearson Education, Inc. Figure 3-2 The Plasma Membrane EXTRACELLULAR FLUID Glycolipids Phospholipid Integral protein Integral of glycocalyx bilayer with channel glycoproteins Hydrophobic tails Plasma membrane Cholesterol Peripheral Hydrophilic proteins heads Gated channel Cytoskeleton  2 nm (Microfilaments) CYTOPLASM © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Cytoplasm All materials inside the cell and outside the nucleus Cytosol (intracellular fluid) Dissolved materials Nutrients, ions, proteins, and waste products High potassium/low sodium High protein High carbohydrate/low amino acid and fat Organelles Structures with specific functions © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm The Organelles Nonmembranous organelles No membrane Direct contact with cytosol Include the cytoskeleton, microvilli, centrioles, cilia, ribosomes, and proteasomes Membranous organelles Covered with plasma membrane Isolated from cytosol Include the endoplasmic reticulum (ER), the Golgi apparatus, lysosomes, peroxisomes, and mitochondria © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Nonmembranous Organelles Six types of nonmembranous organelles 1. Cytoskeleton 2. Microvilli 3. Centrioles 4. Cilia 5. Ribosomes 6. Proteasomes © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm The Cytoskeleton Structural proteins for shape and strength Microfilaments Intermediate filaments Microtubules © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm The Cytoskeleton Microfilaments — thin filaments composed of the protein actin Provide additional mechanical strength Interact with proteins for consistency Pair with thick filaments of myosin for muscle movement © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm The Cytoskeleton Intermediate filaments — mid-sized between microfilaments and thick filaments Durable (collagen) Strengthen cell and maintain shape Stabilize organelles Stabilize cell position © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm The Cytoskeleton Microtubules — large, hollow tubes of tubulin protein Attach to centrosome Strengthen cell and anchor organelles Change cell shape Move vesicles within cell (kinesin and dynein) Form spindle apparatus © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm The Cytoskeleton Thick filaments Myosin protein in muscle cells © 2012 Pearson Education, Inc. Figure 3-3a The Cytoskeleton Microvillus Microfilaments Plasma membrane Terminal web Mitochondrion Intermediate filaments Endoplasmic reticulum Microtubule Secretory vesicle The cytoskeleton provides strength and structural support for the cell and its organelles. Interactions between cytoskeletal components are also important in moving organelles and in changing the shape of the cell. © 2012 Pearson Education, Inc. Figure 3-3b The Cytoskeleton Microvillus Microfilaments Terminal web The microfilaments and microvilli of an intestinal cell. Such an image, produced by a scanning electron microscope, is called a scanning electron micrograph (SEM) (SEM  30,000). © 2012 Pearson Education, Inc. Figure 3-3c The Cytoskeleton Microtubules (yellow) in a living cell, as seen after special fluorescent labeling (LM  3200). © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Microvilli Increase surface area for absorption Attach to cytoskeleton Centrioles in the Centrosome Centrioles form spindle apparatus during cell division Centrosome cytoplasm surrounding centriole Cilia Small hair-like extensions Cilia move fluids across the cell surface © 2012 Pearson Education, Inc. Figure 3-4a Centrioles and Cilia Microtubules Centriole. A centriole consists of nine microtubule triplets (known as a 9  0 array). A pair of centrioles orientated at right angles to one another occupies the centrosome. This micrograph, produced by a transmission electron microscope, is called a TEM. © 2012 Pearson Education, Inc. Figure 3-4b Centrioles and Cilia Plasma membrane Microtubules Basal body Cilium. A cilium contains nine pairs of microtubules surrounding a central pair (9  2 array). The basal body to which the cilium is anchored has a structure similar to that of a centriole. © 2012 Pearson Education, Inc. Figure 3-4c Centrioles and Cilia Power stroke Return stroke Ciliary movement. Action of a single cilium. During the power stroke, the cilium is relatively stiff; during the return stroke, it bends and returns to its original position. © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Ribosomes Build polypeptides in protein synthesis Two types 1. Free ribosomes in cytoplasm Manufacture proteins for cell 2. Fixed ribosomes attached to ER Manufacture proteins for secretion Proteasomes Contain enzymes (proteases) Disassemble damaged proteins for recycling © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Membranous Organelles Five types of membranous organelles 1. Endoplasmic reticulum (ER) 2. Golgi apparatus 3. Lysosomes 4. Peroxisomes 5. Mitochondria © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Endoplasmic Reticulum (ER) Endo- = within, plasm = cytoplasm, reticulum = network Cisternae are storage chambers within membranes Functions 1. Synthesis of proteins, carbohydrates, and lipids 2. Storage of synthesized molecules and materials 3. Transport of materials within the ER 4. Detoxification of drugs or toxins © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Endoplasmic Reticulum (ER) Smooth endoplasmic reticulum (SER) No ribosomes attached Synthesizes lipids and carbohydrates Phospholipids and cholesterol (membranes) Steroid hormones (reproductive system) Glycerides (storage in liver and fat cells) Glycogen (storage in muscles) © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Endoplasmic Reticulum (ER) Rough endoplasmic reticulum (RER) Surface covered with ribosomes Active in protein and glycoprotein synthesis Folds polypeptide protein structures Encloses products in transport vesicles © 2012 Pearson Education, Inc. Figure 3-5a The Endoplasmic Reticulum Nucleus Rough endoplasmic reticulum with fixed (attached) ribosomes Smooth endoplasmic Ribosomes reticulum The three-dimensional relationships between the rough and smooth endoplasmic reticula are shown here. Cisternae © 2012 Pearson Education, Inc. Figure 3-5b The Endoplasmic Reticulum Rough endoplasmic reticulum with fixed (attached) ribosomes Free ribosomes Smooth endoplasmic reticulum Endoplasmic TEM  111,000 Reticulum Rough endoplasmic reticulum and free ribosomes in the cytoplasm of a cell. © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Golgi Apparatus Vesicles enter forming face and exit maturing face Functions 1. Modifies and packages secretions Hormones or enzymes Released through exocytosis 2. Renews or modifies the plasma membrane 3. Packages special enzymes within vesicles for use in the cytoplasm © 2012 Pearson Education, Inc. Figure 3-6a The Golgi Apparatus Secretory vesicles Secretory product Transport vesicles Here is a three-dimensional view of the Golgi apparatus with a cut edge. © 2012 Pearson Education, Inc. Figure 3-6b The Golgi Apparatus Golgi apparatus TEM  42,000 This is a sectional view of the Golgi apparatus of an active secretory cell. © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Protein released into cytoplasm Smooth ER Ribosome DNA Rough ER mRNA Cytoplasm Nucleus Transport vesicle Nuclear pore © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Cisternae Lysosome Exocytosis at Secreting cell surface vesicle Cis face of Golgi complex Trans face of Golgi complex Membrane renewal vesicle Membrane renewal © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis DNA mRNA Cytoplasm Nucleus © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Ribosome Rough ER mRNA Cytoplasm © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Protein released into cytoplasm Ribosome © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Rough ER Cytoplasm © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Smooth ER Transport vesicle © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Cisternae Cis face of Golgi complex © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Cisternae Cis face of Golgi complex Trans face of Golgi complex © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Lysosome Trans face of Golgi complex © 2012 Pearson Education, Inc. Figure 3-7 Protein Synthesis Exocytosis at Secreting cell surface vesicle Trans face of Golgi complex Membrane renewal vesicle Membrane renewal © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Lysosomes Powerful enzyme-containing vesicles Lyso- = dissolve, soma = body Primary lysosome Formed by Golgi apparatus and inactive enzymes Secondary lysosome Lysosome fused with damaged organelle Digestive enzymes activated Toxic chemicals isolated © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Lysosomes Functions 1. Clean up inside cells 2. Autolysis © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Clean Up inside Cells Break down large molecules Attack bacteria Recycle damaged organelles Eject wastes by exocytosis © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Autolysis Auto- = self, lysis = break Self-destruction of damaged cells Lysosome membranes break down Digestive enzymes released Cell decomposes Cellular materials recycle © 2012 Pearson Education, Inc. Figure 3-8 Lysosome Functions Activation of lysosomes occurs when: Golgi apparatus A primary lysosome fuses with the membrane of another Damaged organelle organelle, such as a mitochondrion Autolysis liberates Secondary digestive enzymes Primary lysosome lysosome A primary lysosome fuses with an endosome containing fluid Reabsorption or solid materials from outside the cell Reabsorption Endosome The lysosomal membrane Secondary breaks down during autolysis lysosome following injury to, or death of, the cell Extracellular solid or fluid Endocytosis Exocytosis Exocytosis ejects residue ejects residue © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Peroxisomes Are enzyme-containing vesicles Break down fatty acids, organic compounds Produce hydrogen peroxide (H2O2) Replicate by division © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Membrane Flow A continuous exchange of membrane parts by vesicles All membranous organelles (except mitochondria) Allows adaptation and change © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Mitochondria Have smooth outer membrane and inner membrane with numerous folds (cristae) Matrix Fluid around cristae Mitochondrion takes chemical energy from food (glucose) Produces energy molecule ATP © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Mitochondrial Energy Production Glycolysis Glucose to pyruvic acid (in cytosol) Citric acid cycle (also known as the Krebs cycle and the tricarboxylic acid cycle or TCA cycle) Pyruvic acid to CO2 (in matrix) Electron transport chain Inner mitochondrial membrane © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Mitochondrial Energy Production Called aerobic metabolism (cellular respiration) Mitochondria use oxygen to break down food and produce ATP Glucose + oxygen + ADP carbon dioxide + water + ATP © 2012 Pearson Education, Inc. Figure 3-9a Mitochondria Inner membrane Organic molecules and O2 Outer membrane Matrix Cristae Enzymes Cytoplasm of cell Cristae Matrix Outer membrane Mitochondrion TEM  46,332 Shown here is the three-dimensional organization and a color-enhanced TEM of a typical mitochondrion in section. © 2012 Pearson Education, Inc. Figure 3-9b Mitochondria CYTOPLASM Glucose Glycolysis Pyruvate Enzymes ADP  and phosphate coenzymes of cristae Citric Acid Cycle MATRIX MITOCHONDRION This is an overview of the role of mitochondria in energy production. Mitochondria absorb short carbon chains (such as pyruvate) and oxygen and generate carbon dioxide and ATP. © 2012 Pearson Education, Inc. 3-3 Cell Nucleus Nucleus Largest organelle The cell’s control center Nuclear envelope Double membrane around the nucleus Perinuclear space Between the two layers of the nuclear envelope Nuclear pores Communication passages © 2012 Pearson Education, Inc. Figure 3-10a The Nucleus Nucleoplasm Chromatin Nucleolus Nuclear envelope Nuclear pore Nucleus TEM  4800 Important nuclear structures are shown here. © 2012 Pearson Education, Inc. Figure 3-10b The Nucleus Nuclear pore Perinuclear space Nuclear envelope A nuclear pore is a large protein complex that spans the nuclear envelope. © 2012 Pearson Education, Inc. Figure 3-10c The Nucleus Nuclear pores Inner membrane of nuclear envelope Broken edge of outer membrane Outer membrane of nuclear envelope Nucleus Freeze fracture SEM  9240 This cell was frozen and then broken apart to make its internal structures visible. The technique, called freeze fracture or freeze-etching, provides a unique perspective on the internal organization of cells. The nuclear envelope and nuclear pores are visible. The fracturing process broke away part of the outer membrane of the nuclear envelope, and the cut edge of the nucleus can be seen. © 2012 Pearson Education, Inc. 3-3 Cell Nucleus Contents of the Nucleus DNA All information to build and run organisms Nucleoplasm Fluid containing ions, enzymes, nucleotides, and some RNA Nuclear matrix Support filaments © 2012 Pearson Education, Inc. 3-3 Cell Nucleus Contents of the Nucleus Nucleoli Are related to protein production Are made of RNA, enzymes, and histones Synthesize rRNA and ribosomal subunits Nucleosomes DNA coiled around histones © 2012 Pearson Education, Inc. 3-3 Cell Nucleus Contents of the Nucleus Chromatin Loosely coiled DNA (cells not dividing) Chromosomes Tightly coiled DNA (cells dividing) © 2012 Pearson Education, Inc. Figure 3-11 The Organization of DNA within the Nucleus Nucleus Telomeres of sister chromatids Centromere Kinetochore Supercoiled region Cell prepared for division Visible chromosome Nondividing cell Chromatin in nucleus DNA double helix Nucleosome Histones © 2012 Pearson Education, Inc. 3-3 Cell Nucleus Information Storage in the Nucleus DNA Instructions for every protein in the body Gene DNA instructions for one protein Genetic code The chemical language of DNA instructions Sequence of bases (A, T, C, G) Triplet code 3 bases = 1 amino acid © 2012 Pearson Education, Inc. 3-4 Protein Synthesis The Role of Gene Activation in Protein Synthesis The nucleus contains chromosomes Chromosomes contain DNA DNA stores genetic instructions for proteins Proteins determine cell structure and function © 2012 Pearson Education, Inc. 3-4 Protein Synthesis The Role of Gene Activation in Protein Synthesis Gene activation – uncoiling DNA to use it Promoter Terminator Transcription Copies instructions from DNA to mRNA (in nucleus) RNA polymerase produces messenger RNA (mRNA) © 2012 Pearson Education, Inc. 3-4 Protein Synthesis The Role of Gene Activation in Protein Synthesis Translation Ribosome reads code from mRNA (in cytoplasm) Assembles amino acids into polypeptide chain Processing RER and Golgi apparatus produce protein © 2012 Pearson Education, Inc. 3-4 Protein Synthesis The Transcription of mRNA A gene is transcribed to mRNA in three steps 1. Gene activation 2. DNA to mRNA 3. RNA processing © 2012 Pearson Education, Inc. 3-4 Protein Synthesis Step 1: Gene activation Uncoils DNA, removes histones Start (promoter) and stop codes on DNA mark location of gene Coding strand is code for protein Template strand is used by RNA polymerase molecule © 2012 Pearson Education, Inc. 3-4 Protein Synthesis Step 2: DNA to mRNA Enzyme RNA polymerase transcribes DNA Binds to promoter (start) sequence Reads DNA code for gene Binds nucleotides to form messenger RNA (mRNA) mRNA duplicates DNA coding strand, uracil replaces thymine © 2012 Pearson Education, Inc. 3-4 Protein Synthesis Step 3: RNA processing At stop signal, mRNA detaches from DNA molecule Code is edited (RNA processing) Unnecessary codes (introns) removed Good codes (exons) spliced together Triplet of three nucleotides (codon) represents one amino acid © 2012 Pearson Education, Inc. Figure 3-12 mRNA Transcription DNA Template Coding strand strand Codon mRNA RNA 1 strand polymerase Promoter Codon 2 Codon Triplet 1 1 Codon 3 1 Gene 1 Complementary Codon 4 (stop codon) triplets Triplet 2 2 2 3 RNA Triplet 3 3 nucleotide 4 Triplet 4 4 KEY Adenine Uracil (RNA) After transcription, the two DNA strands reassociate Guanine Thymine (DNA) Cytosine © 2012 Pearson Education, Inc. 3-4 Protein Synthesis Translation mRNA moves: From the nucleus through a nuclear pore mRNA moves: To a ribosome in cytoplasm surrounded by amino acids mRNA binds to ribosomal subunits tRNA delivers amino acids to mRNA © 2012 Pearson Education, Inc. 3-4 Protein Synthesis Translation tRNA anticodon binds to mRNA codon 1 mRNA codon translates to 1 amino acid Enzymes join amino acids with peptide bonds Polypeptide chain has specific sequence of amino acids At stop codon, components separate © 2012 Pearson Education, Inc. Figure 3-13 The Process of Translation The mRNA strand binds to the NUCLEUS small ribosomal subunit and is joined at the start codon by the first tRNA, which carries the mRNA amino acid methionine. Binding occurs between complementary base pairs of the codon and anticodon. Amino acid Small KEY ribosomal tRNA Adenine subunit Anticodon tRNA binding sites Guanine Cytosine Uracil Start codon mRNA strand © 2012 Pearson Education, Inc. Figure 3-13 The Process of Translation The small and large ribosomal subunits interlock around the mRNA strand. Large ribosomal subunit © 2012 Pearson Education, Inc. Figure 3-13 The Process of Translation A second tRNA arrives at the adjacent binding site of the ribosome. The anticodon of the second tRNA binds to the next mRNA codon. Stop codon © 2012 Pearson Education, Inc. Figure 3-13 The Process of Translation 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 © 2012 Pearson Education, Inc. Figure 3-13 The Process of Translation The chain elongates until the stop codon is reached; the components then separate. Small ribosomal subunit Completed polypeptide Large ribosomal subunit © 2012 Pearson Education, Inc. Table 3-1 Examples of the Triplet Code © 2012 Pearson Education, Inc. 3-4 Protein Synthesis How the Nucleus Controls Cell Structure and Function 1. Direct control through synthesis of: Structural proteins Secretions (environmental response) 2. Indirect control over metabolism through enzymes © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Membrane Transport The plasma (cell) membrane is a barrier, but: Nutrients must get in Products and wastes must get out Permeability determines what moves in and out of a cell, and a membrane that: Lets nothing in or out is impermeable Lets anything pass is freely permeable Restricts movement is selectively permeable © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Membrane Transport Plasma membrane is selectively permeable Allows some materials to move freely Restricts other materials Selective permeability restricts materials based on: Size Electrical charge Molecular shape Lipid solubility © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Membrane Transport Transport through a plasma membrane can be: Active (requiring energy and ATP) Passive (no energy required) Diffusion (passive) Carrier-mediated transport (passive or active) Vesicular transport (active) © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Diffusion All molecules are constantly in motion Molecules in solution move randomly Random motion causes mixing Concentration is the amount of solute in a solvent Concentration gradient More solute in one part of a solvent than another ANIMATION Membrane Transport: Diffusion © 2012 Pearson Education, Inc. Figure 3-14 Diffusion © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Factors Influencing Diffusion Distance the particle has to move Molecule Size Smaller is faster Temperature More heat, faster motion Concentration Gradient The difference between high and low concentrations Electrical Forces Opposites attract, like charges repel © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Diffusion across Plasma Membranes Can be simple or channel mediated Materials that diffuse through plasma membrane by simple diffusion Lipid-soluble compounds (alcohols, fatty acids, and steroids) Dissolved gases (oxygen and carbon dioxide) © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Diffusion across Plasma Membranes Channel-mediated diffusion Water-soluble compounds and ions Factors in channel-mediated diffusion Size Charge Interaction with the channel – leak channels © 2012 Pearson Education, Inc. Figure 3-15 Diffusion across the Plasma Membrane EXTRACELLULAR FLUID Lipid-soluble molecules diffuse through the plasma membrane Plasma membrane Channel protein Small water-soluble molecules and ions diffuse through Large molecules that cannot membrane channels diffuse through lipids cannot cross the plasma membrane unless they are transported CYTOPLASM by a carrier mechanism © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Osmosis: A Special Case of Diffusion Osmosis is the diffusion of water across the cell membrane More solute molecules, lower concentration of water molecules Membrane must be freely permeable to water, selectively permeable to solutes Water molecules diffuse across membrane toward solution with more solutes Volume increases on the side with more solutes © 2012 Pearson Education, Inc. Figure 3-16 Osmosis Volume Applied increased force Volume Original Volumes decreased level equal Water molecules Solute molecules Selectively permeable membrane © 2012 Pearson Education, Inc. Figure 3-16 Osmosis Two solutions containing different solute concentrations are separated by a selectively permeable membrane. Water molecules (small blue dots) begin to cross the membrane toward solution B, the solution with the higher concentration of solutes (large pink dots) Water molecules Solute molecules Selectively permeable membrane © 2012 Pearson Education, Inc. Figure 3-16 Osmosis At equilibrium, the solute concentrations on the two sides of the membrane are equal. The volume of solution B has increased at the expense of that of solution A. Volume increased Volume Original decreased level © 2012 Pearson Education, Inc. Figure 3-16 Osmosis Osmosis can be prevented by resisting the change in volume. The osmotic pressure of solution B is equal to the amount of hydrostatic pressure required to stop the osmotic flow. Applied force Volumes equal © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Osmosis: A Special Case of Diffusion Osmotic pressure Is the force of a concentration gradient of water Equals the force (hydrostatic pressure) needed to block osmosis © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Osmolarity and Tonicity The osmotic effect of a solute on a cell Two fluids may have equal osmolarity, but different tonicity Isotonic (iso- = same, tonos = tension) A solution that does not cause osmotic flow of water in or out of a cell Hypotonic (hypo- = below) Has less solutes and loses water through osmosis Hypertonic (hyper- = above) Has more solutes and gains water by osmosis © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Osmolarity and Tonicity A cell in a hypotonic solution: Gains water Ruptures (hemolysis of red blood cells) A cell in a hypertonic solution: Loses water Shrinks (crenation of red blood cells) © 2012 Pearson Education, Inc. Figure 3-17 Osmotic Flow across a Plasma Membrane Water molecules Solute molecules SEM of normal RBC SEM of RBC in a SEM of crenated RBCs in an isotonic solution hypotonic solution in a hypertonic solution © 2012 Pearson Education, Inc. Figure 3-17a Osmotic Flow across a Plasma Membrane Water molecules Solute molecules SEM of normal RBC in an isotonic solution In an isotonic saline solution, no osmotic flow occurs, and these red blood cells appear normal. © 2012 Pearson Education, Inc. Figure 3-17b Osmotic Flow across a Plasma Membrane SEM of RBC in a hypotonic solution Immersion in a hypotonic saline solution results in the osmotic flow of water into the cells. The swelling may continue until the plasma membrane ruptures, or lyses. © 2012 Pearson Education, Inc. Figure 3-17c Osmotic Flow across a Plasma Membrane SEM of crenated RBCs in a hypertonic solution Exposure to a hypertonic solution results in the movement of water out of the cell. The red blood cells © 2012 Pearson Education, Inc. shrivel and become crenated. 3-6 Carriers and Vesicles Carrier-Mediated Transport Of ions and organic substrates Characteristics Specificity One transport protein, one set of substrates Saturation Limits Rate depends on transport proteins, not substrate Regulation Cofactors such as hormones © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Carrier-Mediated Transport Cotransport Two substances move in the same direction at the same time Countertransport One substance moves in while another moves out © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Carrier-Mediated Transport Facilitated Diffusion Passive Carrier proteins transport molecules too large to fit through channel proteins (glucose, amino acids) Molecule binds to receptor site on carrier protein Protein changes shape, molecules pass through Receptor site is specific to certain molecules © 2012 Pearson Education, Inc. Figure 3-18 Facilitated Diffusion EXTRACELLULAR Glucose FLUID molecule Receptor site Carrier protein Glucose released into cytoplasm CYTOPLASM © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Carrier-Mediated Transport Active Transport (Primary or Secondary) Active transport proteins Move substrates against concentration gradient Require energy, such as ATP Ion pumps move ions (Na+, K+, Ca2+, Mg2+) Exchange pump countertransports two ions at the same time © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Carrier-Mediated Transport Primary Active Transport Sodium–potassium exchange pump Active transport, carrier mediated Sodium ions (Na+) out, potassium ions (K+) in 1 ATP moves 3 Na+ and 2 K+ © 2012 Pearson Education, Inc. Figure 3-19 The Sodium-Potassium Exchange Pump EXTRACELLULAR FLUID Sodium potassium exchange pump CYTOPLASM © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Carrier-Mediated Transport Secondary Active Transport Na+ concentration gradient drives glucose transport ATP energy pumps Na+ back out © 2012 Pearson Education, Inc. Figure 3-20 Secondary Active Transport Glucose Sodium molecule ion (Na) pump CYTOPLASM © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Vesicular Transport (Bulk Transport) Materials move into or out of cell in vesicles Endocytosis (endo- = inside) is active transport using ATP Receptor mediated Pinocytosis Phagocytosis © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Endocytosis Receptor-mediated endocytosis Receptors (glycoproteins) bind target molecules (ligands) Coated vesicle (endosome) carries ligands and receptors into the cell © 2012 Pearson Education, Inc. Figure 3-21 Receptor-Mediated Endocytosis Ligands Receptor-Mediated Endocytosis EXTRACELLULAR FLUID Ligands binding to receptors Target molecules (ligands) bind to receptors in plasma membrane. Exocytosis Endocytosis Ligand Areas coated with ligands form receptors deep pockets in plasma membrane surface. Coated Pockets pinch off, forming vesicle endosomes known as coated vesicles. Coated vesicles fuse with primary lysosomes to form secondary chment Fusion lysosomes. eta D Primary Ligands are removed and lysosome absorbed into the cytoplasm. Ligands Secondary removed lysosome The lysosomal and endosomal CYTOPLASM membranes separate. The endosome fuses with the plasma membrane, and the receptors are again available for ligand binding. © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Endocytosis Pinocytosis Endosomes “drink” extracellular fluid Phagocytosis Pseudopodia (pseudo- = false, pod- = foot) Engulf large objects in phagosomes Exocytosis (exo- = outside) Granules or droplets are released from the cell © 2012 Pearson Education, Inc. Figure 3-22a Pinocytosis and Phagocytosis Bloodstream Plasma membrane Pinosome formation Cytoplasm Pinosome fusion Surrounding tissues and exocytosis Pinocytosis Color enhanced TEM  20,000 © 2012 Pearson Education, Inc. Figure 3-22b Pinocytosis and Phagocytosis Bacterium Pseudopodium PHAGOCYTOSIS Phagosome Lysosome Phagosome fuses with a lysosome Secondary lysosome Golgi apparatus EXOCYTOSIS © 2012 Pearson Education, Inc. Table 3-2 Mechanisms Involved in Movement across Plasma Membranes © 2012 Pearson Education, Inc. 3-7 Transmembrane Potential Transmembrane Potential Charges are separated creating a potential difference Unequal charge across the plasma membrane is transmembrane potential Resting potential ranges from –10 mV to –100 mV, depending on cell type © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle Cell Life Cycle Most of a cell’s life is spent in a nondividing state (interphase) Body (somatic) cells divide in three stages DNA replication duplicates genetic material exactly Mitosis divides genetic material equally Cytokinesis divides cytoplasm and organelles into two daughter cells © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle DNA Replication Helicases unwind the DNA strands DNA polymerase 1. Promotes bonding between the nitrogenous bases of the DNA strand and complementary DNA nucleotides dissolved in the nucleoplasm 2. Links the nucleotides by covalent bonds DNA polymerase works in one direction Ligases piece together sections of DNA A&P FLIX: DNA Replication © 2012 Pearson Education, Inc. Figure 3-23 DNA Replication DNA polymerase Segment 2 DNA nucleotide KEY Segment 1 Adenine DNA Guanine polymerase Cytosine Thymine © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle Interphase The nondividing period G-zero (G0) phase — specialized cell functions only G1 phase — cell growth, organelle duplication, protein synthesis S phase — DNA replication and histone synthesis G2 phase — finishes protein synthesis and centriole replication © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Interphase INTERPHASE Most cells spend only a small part of their time actively engaged in cell division. Somatic cells spend the majority of their When the activities of G1 have been completed, functional lives in a state known as the cell enters the S phase. Over the next 68 interphase. During interphase, a cell hours, the cell duplicates its chromosomes. perfoms all its normal functions and, if This involves DNA replication and necessary, prepares for cell division. the synthesis of histones and other proteins in the nucleus. A cell that is ready to divide first enters the G1 6 to 8 hou phase. In this phase, the cell rs Once DNA makes enough mitochondria, replication has cytoskeletal elements, endo- S DNA ended, there is a brief plasmic reticula, ribosomes, (25-hour) G2 phase Golgi membranes, and replication, synthesis devoted to last-minute protein cytosol for two functional of synthesis and to the comple- cells. Centriole replica- histones 2t tion of centriole replication. tion begins in G1 and o5 commonly continues G1 G2 hou until G2. In cells Normal Protein dividing at top cell functions rs 8 or more hours speed, G1 may last synthesis plus cell growth, just 812 hours. duplication of Such cells pour organelles, THE all their energy protein CELL Centrioles in centrosome into mitosis, and synthesis CYCLE Proph all other activities ase cease. If G1 lasts for days, weeks, or Me months, preparation MITOSIS ta ph for mitosis occurs as as the cells perform their e An normal functions. Telopha Nucleus ap ha se rs u ho se to 3 1 G0 E SIS OKIN CYT MITOSIS AND Interphase An interphase cell in the G0 phase is During CYTOKINESIS not preparing for division, but is performing interphase, all of the other functions appropriate for that the DNA strands particular cell type. Some mature cells, such as are loosely coiled and skeletal muscle cells and most neurons, remain in chromosomes G0 indefinitely and never divide. In contrast, stem cells, cannot be seen. which divide repeatedly with very brief interphase periods, never enter G0. © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Interphase THE CELL CYCLE G0 An interphase cell in the G0 phase is not preparing for division, but is performing all of the other functions appropriate for that particular cell type. Some mature cells, such as skeletal muscle cells and most neurons, remain in G0 indefinitely and never divide. In contrast, stem cells, which divide repeatedly with very brief interphase periods, never enter G0. © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Interphase INTERPHASE G1 Normal cell functions 8 or more hours plus cell growth, duplication of THE organelles, CELL protein CYCLE synthesis © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Interphase When the activities of G1 have been completed, the cell enters the S phase. Over the next 68 hours, the cell duplicates its chromosomes. This involves DNA replication and the synthesis of histones and other proteins in the nucleus. 6 to 8 hou rs S DNA replication, synthesis of histones THE CELL CYCLE © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Interphase Once DNA replication has ended, there is a brief (25-hour) G2 phase devoted to last-minute protein 2t synthesis and to the o5 completion of centriole G2 hou replication. Protein rs synthesis THE CELL CYCLE © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle Mitosis Divides duplicated DNA into two sets of chromosomes DNA coils tightly into chromatids Chromatids connect at a centromere Protein complex around centromere is kinetochore © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Interphase THE CELL Centrioles in centrosome CYCLE Proph ase Me MITOSIS ta ph as e An Nucleus ap Telopha ha s ur se ho 3 to e s 1 ES IS TOKIN CY MITOSIS AND Interphase CYTOKINESIS During interphase, the DNA strands are loosely coiled and chromosomes cannot be seen. © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle Mitosis Prophase Nucleoli disappear Centriole pairs move to cell poles Microtubules (spindle fibers) extend between centriole pairs Nuclear envelope disappears Spindle fibers attach to kinetochore Metaphase Chromosomes align in a central plane (metaphase plate) © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Mitosis and Cytokinesis Chromosome Centrioles Astral rays and Chromosomal Metaphase with two sister (two pairs) spindle fibers microtubules plate chromatids Early prophase Late prophase Metaphase © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle Mitosis Anaphase Microtubules pull chromosomes apart Daughter chromosomes group near centrioles Telophase Nuclear membranes re-form Chromosomes uncoil Nucleoli reappear Cell has two complete nuclei A&P FLIX: Mitosis © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Mitosis and Cytokinesis Daughter Cleavage chromosomes furrow Daughter cells Anaphase Telophase Cytokinesis © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle Cytokinesis Division of the cytoplasm Cleavage furrow around metaphase plate Membrane closes, producing daughter cells © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Mitosis and Cytokinesis A dividing cell shown held in place by a sucker pipe to the left and being injected with a needle from the right. © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle The Mitotic Rate and Energy Use Rate of cell division Slower mitotic rate means longer cell life Cell division requires energy (ATP) Muscle cells, neurons rarely divide Exposed cells (skin and digestive tract) live only days or hours – replenished by stem cells © 2012 Pearson Education, Inc. 3-9 Regulation of the Cell Life Cycle Cell Division Normally, cell division balances cell loss Increased cell division Internal factors (M-phase promoting factor, MPF) Extracellular chemical factors (growth factors) Decreased cell division Repressor genes (faulty repressors cause cancers) Worn out telomeres (terminal DNA segments) © 2012 Pearson Education, Inc. Table 3-3 Chemical Factors Affecting Cell Division © 2012 Pearson Education, Inc. 3-10 Cell Division and Cancer Cancer Develops in Steps Abnormal cell Primary tumor Metastasis Secondary tumor © 2012 Pearson Education, Inc. 3-10 Cell Division and Cancer Tumor (Neoplasm) Enlarged mass of cells Abnormal cell growth and division Benign tumor Contained, not life threatening unless large Malignant tumor Spreads into surrounding tissues (invasion) Starts new tumors (metastasis) © 2012 Pearson Education, Inc. Figure 3-25 The Development of Cancer Abnormal cell Primary tumor cells Secondary tumor cells Growth of blood vessels into tumor Cell Cell divisions Invasion divisions Penetration Escape Circulation © 2012 Pearson Education, Inc. 3-11 Differentiation Differentiation All cells carry complete DNA instructions for all body functions Cells specialize or differentiate To form tissues (liver cells, fat cells, and neurons) By turning off all genes not needed by that cell All body cells, except sex cells, contain the same 46 chromosomes Differentiation depends on which genes are active and which are inactive © 2012 Pearson Education, Inc.