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Cell Structure and Function

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Cell Structure and Function

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  1. Cell Structure and Function Chapter 4 Biology Concepts and Applications, Eight Edition, by Starr, Evers, Starr. Brooks/Cole, Cengage Learning 2011. Biology, Ninth Edition, by Solomon, Berg, Martin. Brooks/Cole, Cengage Learning 2011.

  2. Cells and Organisms • The cell is the smallest unit that can carry out all activities associated with life • Most prokaryotes and many protists and fungi consist of a single cell • Most plants and animals have millions of cells • In multicellular organisms, cells are modified in a variety of ways to carry out specialized functions • Cells exchange materials and energy with the environment; and convert energy to chemical energy stored in ATP

  3. 4.1 What is a Cell? • Each cell has a plasma membrane, cytoplasm, and a nucleus (in eukaryotic cells) or a nucleoid (in prokaryotic cells)

  4. Components of Cell Membranes • Lipid bilayer

  5. extracellular environment one layer of lipids one layer of lipids membrane protein cytoplasm Fig. 4.4, p. 53

  6. Organization of Cells • The organization and small size of cells allow them to maintain an appropriate internal environment (homeostasis) • To maintain homeostasis, the plasma membraneacts as a selective barrier between cell contents and the environment • Most cells have internal structures (organelles)specialized to carry out metabolic activities • Each cell has genetic instructions coded in DNA, which is concentrated in a limited region of the cell

  7. Cell Size and Shape • Cell sizes and shapes are adapted to their functions: • Amoebas and white blood cells change shape as they move • Sperm cells have long, whiplike tails (flagella) for locomotion • Nerve cells have long, thin extensions that enable them to transmit messages over great distances • Rectangular epithelial cells and stack like building blocks to form sheetlike tissues

  8. Surface Area–To-Volume Ratio Fig. 4-2, p. 77

  9. Key Concepts: WHAT ALL CELLS HAVE IN COMMON • Each cell has a plasma membrane, a boundary between its interior and the outside environment • The interior consists of cytoplasm and an innermost region of DNA

  10. 4.2 Cell Theory: A Unifying Concept • Cell theory is a unifying concept: • All organisms consist of one or more cells • The cell is the smallest unit that retains the capacity for life • A cell arises from the growth and division of another cell • Evidence that all living cells have a common origin is provided by basic similarities in their structures and molecules of which they are made

  11. Relative Sizes

  12. Fig. 4.6, p. 54

  13. Microscopes • Different microscopes use light or electrons to reveal details of cell shapes or structures

  14. path of light rays (bottom to top) to eye Ocular lens enlarges primary image formed by objective lenses. prism that directs rays to ocular lens Objective lenses (those closest to specimen) form the primary image. Most compound light microscopes have several. stage supports microscope slide Condenser lenses focus light rays through specimen. illuminator light source (in base) Fig. 4.7, p. 55

  15. Light microscope Light beam Ocular lens Objective lens Specimen Condenser lens Light source (a) A phase contrast light microscope can be used to view stained or living cells, but at relatively low resolution. Fig. 4-4a, p. 80

  16. Five Different Views

  17. Key Concepts: MICROSCOPES • Microscopic analysis supports three generalizations of the cell theory: • Each organism consists of one or more cells and their products • A cell has a capacity for independent life • Each new cell is descended from a living cell

  18. 4.3 Membrane Structure and Function • Each cell membrane is a boundary (lipid bilayer) that controls the flow of substances across it • Fluid mosaic model • Membrane is composed of phospholipids, sterols, proteins, and other components • Phospholipids drift within the bilayer

  19. Membrane Proteins • Many proteins are embedded in or attached to cell membrane surfaces • Receptors (insulin receptors), transporters (active and passive), recognition adhesion proteins, and enzymes. **Table 4.1 in text** • Plasma (outer) membrane also incorporates recognition proteins (self vs. non-self),

  20. Common Membrane Proteins Passive Active

  21. Membrane Structure Studies

  22. human cell mouse cell fusion into hybrid cell proteins from both cells in fused membrane Fig. 4.10, p. 57

  23. Key Concepts:COMPONENTS OF CELL MEMBRANES • All cell membranes are mostly a lipid bilayer (two layers of lipids) and a variety of proteins • The proteins have diverse tasks, including control over which water-soluble substances cross the membrane at any given time

  24. Prokaryotic Cells

  25. 4.4 Introducing Prokaryotic Cells • Bacteria and archaeans • The simplest cells • The groups with greatest metabolic diversity • Biofilms • Shared living arrangements of prokaryotes

  26. Prokaryote Structure • Cell wall • Surrounds plasma membrane • Flagella • Used for motion • Pili • Protein filaments used for attachment • “Sex” pilus transfers genetic material

  27. Structure of a Prokaryotic Cell • Bacteria and archaea are prokaryotic cells • ~1/10 the diameter of the average eukaryotic cell • DNA is located in a nuclear area, or nucleoid • Nuclear area is not enclosed by a membrane • No membrane-enclosed internal organelles • Most have cell wallsoutsidethe plasma membrane • Many have prokaryotic flagellawhich operate like propellers • Some have hairlikefimbriaethat increase adherence • Interior contains ribosomes and storage granules

  28. Prokaryote Structure

  29. Prokaryote Structure

  30. 4.5 Microbial Mobs • Biofilm formation  community of microorganisms living within a shared mass of slime (polysaccharides and proteins) • Can include bacteria, algae, fungi, protists, and archaeans • Benefit  prevents being washed away by fluid currents

  31. Key Concepts:PROKARYOTIC CELLS • Archaeans and bacteria are prokaryotic cells which have few, if any, internal membrane-enclosed compartments • In general, they are the smallest and structurally the simplest cells

  32. Eukaryotic Cells

  33. 4.6 Introducing Eukaryotic Cells • Start with a nucleus and other organelles • Carry out specialized functions inside a cell

  34. plasma membrane nucleus mitochondria Fig. 4.14, p. 60

  35. cell wall plasma membrane central vacuole nucleus chloroplast Fig. 4.14, p. 60

  36. Components of Eukaryotic Cells

  37. Structure of a Eukaryotic Cell • Eukaryotic cells are characterized by highly organized membrane-enclosed organelles • A nucleuscontains DNA • The part of the cell outside the nucleus is cytoplasm • Cytoplasm  semifluid substance enclosed by a cell’s plasma membrane • The part of the cell within the nucleus isnucleoplasm • The fluid component of cytoplasm is cytosol • Many specialized organelles and a supporting framework (cytoskeleton) allow a larger size than prokaryotes • Some organelles are present only in specific cells

  38. 4.7 Components of The Nucleus • Nucleus separates DNA from cytoplasm • Chromatin (all chromosomal DNA with proteins) • Chromosomes (condensed) • Nucleolus assembles ribosomal subunits • Nuclear envelope encloses nucleoplasm • The envelop is a double membrane that constitutes the outer boundary of the nucleus • Pores, receptors, transport proteins • Nucleoplasm • Viscous fluid enclosed by the nuclear envelop

  39. Nucleus and Nuclear Envelope

  40. Nucleus and Nuclear Envelope

  41. Nucleus and Nuclear Envelope

  42. 4.8 The Endomembrane System • System that includes interacting organelles between the nucleus and plasma membrane 1. Endoplasmic reticulum (ER) • An extension of the nuclear envelope • Rough ER modifies new polypeptide chains, studded with ribosomes • Smooth ER makes lipids; other metabolic functions 2. Golgi bodies • Further modify polypeptides and assemble lipids • Sort and package finished products into vesicles

  43. The Endomembrane System 3. Vesicles membrane included saclike organelle that can store, transport, or degrade contents • Endocytic and exocytic: Transport or store polypeptides and lipids • Peroxisomes: Digest fatty acids and amino acids; break down toxins and metabolic by-products • Enzyme-filled • Lysosomes: Intracellular digestion (animal cells) • Enzyme-filled • Central vacuole: Storage in many plant cells • fluid-filled vesicles that produce fluid pressure • Fluid pressure keeps plant cells plump and firm

  44. Endomembrane System

  45. Endomembrane System

  46. Endomembrane System

  47. Golgi Complex TheGolgi complex (Golgi body or Golgi apparatus) consists of stacks of flattened membranous sacs (cisternae) Each Golgi stack has three areas: Entry surface (cis face) Exit surface (trans face) Medial region in between

  48. Golgi Complex and Proteins Transport vesicles carrying proteins from the ER move along microtubules to the cis face of the Golgi complex The Golgi complex processes, sorts, and modifies proteins Carbohydrate of a glycoprotein may be modified to route the protein to a specific organelle Proteins are packaged in transport vesicles in the trans face

  49. Protein Transport Within the Cell

  50. Mitochondria and Chloroplasts Mitochondria and chloroplasts are organelles specialized to facilitate conversion of energy from one form to another Chemical energy (in food molecules such as glucose) or light energy must be converted into more convenient forms – usually the chemical energy of ATP Mitochondria and chloroplasts have their own ribosomes and DNA molecules