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Chapter 3

Chapter 3. Cell Structure and Function. Cell structure and function Outline. Cellular Organization Plasma Membrane Functions Nucleus Cell division and protein synthesis (ch. 19 and 18) Endomembrane System Cytoskeleton Cilia and Flagella Cellular Respiration Fermentation.

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Chapter 3

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  1. Chapter 3 Cell Structure and Function

  2. Cell structure and function Outline • Cellular Organization • Plasma Membrane • Functions • Nucleus • Cell division and protein synthesis (ch. 19 and 18) • Endomembrane System • Cytoskeleton • Cilia and Flagella • Cellular Respiration • Fermentation

  3. Cellular Organization • Plasma membrane surrounds the cell and regulates entrance and exit of substances. • Nucleus is the centrally located structure containing chromosomes and is the control center of the cell. • Cytoplasm is the portion of the cell between the nucleus and plasma membrane.

  4. Cellular Organization • Organelles are small membranous structures, each with a specific function. • Cytoskeleton is a network of interconnected filaments and microtubules in the cytoplasm that maintain cell shape.

  5. Plasma Membrane • Plasma membrane is a phospholipid bilayer with attached or embedded proteins. • Polar head and non-polar tails. • Form spherical bilayer when placed in water. • Plasma membrane proteins form receptors, conductors, or enzymes in metabolic reactions.

  6. Plasma Membrane Model

  7. Plasma Membrane Functions • Plasma membrane is selectively permeable, and regulates movement of molecules and ions across the cell membrane. • Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration until they are equally distributed.

  8. Plasma Membrane Functions • Osmosis is the diffusion of water across a plasma membrane. • Tonicity is the degree to which a solution’s solute concentration causes water to move into or out of cells. • Cells gain water in hypotonic solutions, and lose water in hypertonic solutions. • Osmotic pressure is the force exerted on a selectively permeable membrane due to the osmotic movement of water.

  9. Tonicity= # of solute particles dissolved per set volume For diagram b. # of solute particles outside is lower than inside Thus solvent outside is higher/lower (circle one) than Solvent inside For diagram c Solvent outside is hiher/lower (circle one) than Solvent inside # solutes particles outside equals inside

  10. Plasma Membrane Functions • Transport by Carriers. • Maintains cellular homeostasis (membrane proteins create selective permeability) • Facilitated transport occurs when a molecule is transported across the plasma membrane down a concentration gradient. • Active transport occurs when a molecule is moving against a concentration gradient with the input of energy.

  11. Active Transport- things that normally do not get across the cell membrane

  12. Plasma Membrane Functions • Transport by Carriers. • Endocytosis occurs when a portion of the plasma membrane invaginates to envelop a substance and then pinches off to form an intracellular vesicle. • Exocytosis occurs when a vesicle fuses with the plasma membrane as secretion occurs.

  13. The Nucleus • The nucleus stores genetic information that determines body cell characteristics and metabolic functioning. • Nucleus is separated from the cytoplasm by a nuclear envelope. • Contains nuclear pores to permit passage of proteins and ribosomal subunits.

  14. Ch. 19 DNA and RNA Structure and Function • DNA is the genetic material found principally in chromosomes. • In between cell divisions, chromosomes exist in long fine threads of chromatin. • When a cell is about to divide, chromosomes coil and condense.

  15. DNA Location and Structure

  16. DNA Structure and Replication • DNA is a sequential series of joined nucleotides. • Sugar (deoxyribose), phosphate, and base. • Adenine (A). • Thymine (T). • Cytosine (C). • Guanine (G). nucleotides

  17. DNA Structure and Replication • DNA is a double helix with a sugar-phosphate backbone and bases projecting between the backbones. • Exhibits complementary base pairing. • A-T. • G-C.

  18. DNA Replication- for cell reproduction/division • Replication Steps. • Hydrogen bonds between strands break and the molecule unzips. • New nucleotides fit beside parental strand. • DNA polymerase joins new nucleotides. • Two complete molecules present, each with one old strand and one new strand. • Semi-conservative replication.

  19. DNA Replication/ cell division Mitosis and Meiosis (replacing cells or making babies)

  20. Structure and Function of RNA- protein synthesis (the way we look) • RNA is made up of nucleotides containing the sugar ribose and the base uracil in place of thymine. • Single stranded. • RNA is a helper to DNA allowing protein synthesis.

  21. Types of RNA • Ribosomal RNA. • Joins with proteins made in the cytoplasm to form the subunits of ribosomes. • Messenger RNA. • Carries genetic information from DNA to the ribosomes in the cytoplasm where protein synthesis occurs. • Transfer RNA. • Transfers amino acids to the ribosomes where amino acids are joined.

  22. Gene Expression • Structure and Function of Proteins. • Proteins are composed of amino acids. • Proteins differ because the number and order of their amino acids differ.

  23. DNA Code • Genetic code is essentially universal. • Contains a triplet code. • Every three bases represents one amino acid. • Transcription. • Strand of mRNA forms that is complementary to a portion of DNA. • Triplet of mRNA is termed a codon.

  24. Processing of mRNA • Most human genes are interrupted by introns. • Intragene segments interrupt gene segments, exons. • During processing, introns are removed and exons are joined to form an mRNA molecule.

  25. Function of Introns

  26. Translation • Translation is the synthesis of a polypeptide under the direction of an mRNA molecule. • Transfer RNA molecules bring amino acids to the ribosomes. • Anticodon is triplet complementary to an mRNA codon. • Polypeptide synthesis requires three steps. • Initiation. • Elongation. • Termination.

  27. Anticodon-Codon Base Pairing this occurs in cytoplasm or an endoplasmic reticulum

  28. Regulation of Gene Expression • Gene Regulation Mechanisms. • Transcriptional control. • Posttranscriptional control. • Translational control. • Posttranslational control.

  29. Ch. 18 Genotype and Phenotype • Genotype refers to an individual’s genes. • Alleles are alternate forms of a gene. • Dominant alleles are assigned uppercase letters, while recessive alleles are assigned lowercase letters. • Homozygous Dominant = EE. • Homozygous Recessive = ee. • Heterozygous = Ee. • Phenotype refers to an individual’s physical appearance.

  30. Genetic Inheritance

  31. Dominant/Recessive Traits • Forming the Genes. • Reduction of chromosome number occurs when pairs of chromosomes separate as meiosis occurs.

  32. Gametogenesis

  33. Nucleus and Nuclear Membrane

  34. Ribosomes • Ribosomes are found singly or in groups (polyribosomes) in the cytoplasm. • Function in protein synthesis.

  35. The Endomembrane System- also function in protein synthesis • Endoplasmic Reticulum. • System of membranous channels and saccules. • Rough ER is studded with ribosomes and synthesizes proteins. • Smooth ER synthesizes phospholipids, as well as various other functions.

  36. The Endomembrane System- process final products and monitor incoming vesicles • The Golgi Apparatus. • Consists of a stack of three to twenty curved saccules, along with vesicles. • Receives protein and or lipid vesicles that bud from the ER. • Lysosomes. • Membranous sacs produced by the Golgi apparatus that contain hydrolytic digestive enzymes.

  37. Endomembrane System

  38. Mitochondria- The “powerhouse” • Mitochondria are double-membrane organelles involved in cellular respiration. • Site of ATP production.

  39. The Cytoskeleton • The cytoskeleton is formed of several types of filamentous structures that give the cell its shape and organelles the ability to move about the cell. • Microtubules. • Actin Filaments.

  40. Centrioles • Centrioles are short cylinders composed of microtubules that are involved in spindle formation during cell division

  41. Cilia and Flagella • Cilia and flagella (cilium, flagellum) are projections that move in an undulating or whipping fashion. • Cilia tend to be shorter while flagella tend to be longer.

  42. Cellular Metabolism • Cellular metabolism includes all the chemical reactions that occur in a cell. • Often organized into metabolic pathways. • Most regulated by feedback inhibition.

  43. Enzymes and Coenzymes • When an enzyme speeds up a reaction, the participating reactants are called the enzyme’s substrates. • Many enzymes require cofactors for assistance. • Some cofactors may accept or donate atoms to the reaction.

  44. Enzymatic Action

  45. Cellular Respiration • Glucose breakdown requires three sub-pathways. • Glycolysis. • Citric Acid Cycle. • Electron Transport System. • Altogether, the breakdown of one glucose molecule results in 36 ATP molecules.

  46. Cellular Respiration

  47. Fermentation • Fermentation is an anaerobic process that results in the buildup of lactate. • Lactate is toxic to cells and causes muscle cramps and fatigue. • Only produces two ATP per glucose molecule.

  48. Lecture Review • Describe the function and structure of the cell membrane. • Define isotonic, hypotonic and hypertonic solutions. • Describe the nucleus and its contents including the process of protein sysnthesis and cell reproduction (cell division- mitosis and meiosis). • Describe cell metabolism (cell respiration) anaerobic and aerobic

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