BIOL 2401 Biol 2401 Fundamentals of Anatomy and

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. 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. 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 (17 th century) 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 Sex Cells (Germ Cells) Reproductive cells: Male (sperm); Female (oocyte) Somatic Cells (Soma—body) © 2012 Pearson Education, Inc.

An Introduction To Cells In our model cell, a _______separates the cell contents, called the______, from its surroundings. The cytoplasm can be subdivided into the ______a liquid, and intracellular structures collectively known as_______. Organelles are structures suspended within the cytosol that perform specific functions within the cell and can be further subdivided into membranous and nonmembranous organelles. Cells are surrounded by a watery medium known as the_______. The extracellular fluid in most tissues is called________. The _______ is usually the largest and most conspicuous structure in a cell. © 2012 Pearson Education, Inc.

Organelles Cytosol Cytoplasm Nucleus Plasma Membrane 1 List the three principle parts of a

Plasma Membrane © 2012 Pearson Education, Inc. Non-membranous (no membrane) Membranous (membrane) Nucleus

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 Sensitivity to the Environment Extracellular fluid composition Chemical signals Structural Support Anchors cells and tissues © 2012 Pearson Education, Inc.

3 -1 Plasma 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 Proteins Integral Proteins—within the membrane Peripheral Proteins—bound to inner or outer surface of membrane Anchoring Proteins (stabilizers)—attach to inside or outside structures Recognition Proteins (identifiers)—label cells as normal or abnormal Enzymes—catalyze reactions Receptor Proteins—bind and respond to ligands (ions, hormones) Carrier Proteins--transport specific solutes through membrane Channels--forms pathway across plasma membrane and regulate water flow and solutes through membrane) © 2012 Pearson Education, Inc.

3 -1 Plasma Membrane Carbohydrates Proteoglycans, glycoproteins, and glycolipids Extend outside cell membrane Form sticky “sugar coat” layer (glycocalyx) Functions of the glycocalyx Lubrication and Protection Anchoring and Locomotion Specificity in Binding (receptors) Recognition (immune response) © 2012 Pearson Education, Inc.

The Plasma Membrane 2 What is the glycocalyx? © 2012 Pearson Education, Inc.

3 -2 Organelles and the 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 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 The Cytoskeleton Microfilaments — thin filaments composed of the protein actin Provide additional mechanical strength; pair with thick filaments of myosin in muscle movement Intermediate filaments — mid-sized between microfilaments and thick filaments; strengthen cell; maintain shape; stabilize organelles; stabilize cell position; durable collagen Microtubules — large, hollow tubes of tubulin protein Attach to centrosome (cytoplasm surrounding centrioles) Strengthen cell and anchor organelles; change cell shape; move vesicles within cell; form spindle apparatus © 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 3 Which cytoskeleton component helps form the structure of centrioles, cilia, and flagella? © 2012 Pearson Education, Inc.

3 -2 Organelles and the Cytoplasm Ribosomes Build polypeptides in protein synthesis Two types Free ribosomes (polysomes) in cytoplasm Manufacture proteins for cell 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 Endoplasmic Reticulum (ER) Endo- = within, plasm = cytoplasm, reticulum = network Cisternae are storage chambers within membranes Functions Synthesis of proteins, carbohydrates, and lipids Storage of synthesized molecules and materials Transport of materials within the ER 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) 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 -5 a The Endoplasmic Reticulum Nucleus Rough endoplasmic reticulum with fixed (attached) ribosomes Ribosomes The three-dimensional relationships between the rough and smooth endoplasmic reticula are shown here. Cisternae 4 What are the structural and functional differences between rough and smooth endoplasmic reticulum? © 2012 Pearson Education, Inc. Smooth endoplasmic reticulum

3 -2 Organelles and the Cytoplasm Golgi Apparatus Vesicles enter forming face and exit maturing face. Vesicles contain flattened membranous discs called cisternae. Functions Modifies and packages secretions Hormones or enzymes Released through exocytosis Renews or modifies the plasma membrane Packages special enzymes within vesicles for use in the cytoplasm © 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 Functions Clean up inside cells (Break down large molecules, Attack bacteria, Recycle damaged organelles, and Eject wastes by exocytosis). Autolysis (Auto—self; Lysis—breakdown) (Self destruction of damaged cells—lysosome membranes breakdown, digestive enzymes released, cell decomposes, cellular materials recycled) © 2012 Pearson Education, Inc.

Figure 3 -8 Lysosome Functions Activation of lysosomes occurs when: Golgi apparatus Damaged organelle Autolysis liberates digestive enzymes Secondary lysosome Primary lysosome Reabsorption Endosome Secondary lysosome Extracellular solid or fluid A primary lysosome fuses with the membrane of another organelle, such as a mitochondrion A primary lysosome fuses with an endosome containing fluid or solid materials from outside the cell The lysosomal membrane breaks down during autolysis following injury to, or death of, the cell Endocytosis Exocytosis ejects residue 5 What are three general destinations for proteins that leave the Golgi complex? © 2012 Pearson Education, Inc.

3 -2 Organelles and the Cytoplasm Peroxisomes Are enzyme-containing vesicles. The enzymes differ from those of the lysosomes. Break down fatty acids, organic compounds Produce hydrogen peroxide (H 2 O 2) Replicate by division Membrane Flow A continuous exchange of membrane parts by vesicles All membranous organelles (except mitochondria) Allows adaptation and change © 2012 Pearson Education, Inc.

Proetin Synthesis 6 How do the entry and exit faces of protein synthesis differ?

3 -2 Organelles and the Cytoplasm Mitochondria Have smooth outer membrane and inner membrane with numerous folds cristae. These cisternae increase the surface area available for chemical reactions and contain some of the enzymes needed for ATP production) Matrix Fluid around cristae Mitochondrion takes chemical energy from food (glucose) and produces energy molecule ATP © 2012 Pearson Education, Inc.

3 -2 Organelles and the Cytoplasm Mitochondrial Energy Production Glycolysis (takes place in the cytoplasm) 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 CO 2 (in matrix) Electron transport chain Inner mitochondrial membrane Mitochondrial Energy Production Called aerobic metabolism (cellular respiration) Produces 95% of ATP needed to keep cell alive Mitochondria use oxygen to break down food and produce ATP Glucose + oxygen + ADP carbon dioxide + water + ATP © 2012 Pearson Education, Inc.

Figure 3 -9 a Mitochondria Inner membrane Organic molecules and O 2 Outer membrane Matrix Cristae Cytoplasm of cell Cristae Enzymes 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 -9 b Mitochondria CYTOPLASM Glucose Glycolysis Pyruvate Citric Acid Cycle Enzymes and ADP phosphate coenzymes of cristae 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 Largest organelle. It is the cell’s control center. Nuclear envelope (double membrane around the nucleus) Perinuclear space (between the two layaers of the nuclear membrane) Nuclear pores (communication passages) How the Nucleus Controls Cell Structure and Function Direct control through synthesis of: structural proteins and secretions Indirect control over metabolism through enzymes © 2012 Pearson Education, Inc.

3 -3 Cell Nucleus Contents of the Nucleus DNA (all information to build and run organism) Nucleoplasm (fluid containing ions, enzymes, nucleotides, anad some RNA) Nuclear matrix (support filaments) Nucleoli (related to protein production; made of RNA, enzymes and histones (proteins); synthesize r. RNA and ribosomal subunits) Nucleosomes (DNA coiled around histones) Chromatin (loosely coiled DNA (cells not dividing) Chromosomes (tightly coilded DNA (cells dividing) © 2012 Pearson Education, Inc.

3 -3 Cell Nucleus Information Storage in the Nucleus (“genetic code”) 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 Gene—functional unit of heredity © 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. Gene activation – uncoiling DNA to use it Promoter (control segment) at “start” of gene → Terminator “stop” Transcription Copies instructions from DNA to m. RNA (in nucleus) RNA polymerase produces messenger RNA (m. RNA) Translation Ribosome reads code from m. RNA (in cytoplasm) and assembles amino acids into polypeptide chain Processing (RER and Golgi apparatus produceg protein) Gene Activation Transcription Translation © 2012 Pearson Education, Inc. Processing

3 -4 Protein Synthesis The Transcription of m. RNA Step 1: Gene activation (DNA strands separate and RNA polymerase binds to the promoter of the gene). Step 2: DNA to m. RNA (RNA polymerase moves from one nucleotide to another along length of the template strand. At each site, complementary RNA nucleotides for hydrogen bonds with the DNA nucleotides of the template stand. RNA polymerase strings the arriving nucleotides together into a strand of m. RNA). Step 3: RNA processing (On reaching the stop signal at the end of the gene, the RNA polymerase and the m. RNA strand detach, and the two DNA strands reassociate). © 2012 Pearson Education, Inc.

Figure 3 -12 m. RNA Transcription DNA Template strand Coding strand RNA polymerase Codon 1 Codon 2 Promoter 1 Gene Triplet 2 2 Triplet 3 3 Triplet 4 4 Complementary triplets Triplet 1 m. RNA strand Codon 3 Codon 1 1 Codon 4 (stop codon) 2 3 RNA nucleotide 4 KEY After transcription, the two DNA strands reassociate Adenine Uracil (RNA) Guanine Thymine (DNA) Cytosine 7 Where does transcription occur? Where does translation occur? © 2012 Pearson Education, Inc.

http: //www. youtube. com/watch? v=AGzsg. TMg. Sog © 2012 Pearson Education, Inc.

3 -4 Protein Synthesis Translation m. RNA moves from the nucleus through a nuclear pore → to a ribosome in the cytoplasm surrounded by amino acids → binds to ribosomal subunits → t. RNA delivers amino acids to m. RNA. t. RNA anticodon binds to m. RNA codon Enzymes join amino acids with peptide bonds Polypeptide chain has specific sequence of amino acids At stop codon, components separate © 2012 Pearson Education, Inc.