unit 3. a&b - bio

• Cells


  The basic unit of life
• Prokaryotic cell


  • Smaller in size than eukaryotic cell
  • Lack much of the internal compartmentalization and complexity of eukaryotic cells
  • Genetic material is concentrated in a region that is not membrane-enclosed (nucleoid)
• Eukaryotic cell


  • Larger than prokaryotic cell
  • Have a great variety of complex organelles and structures
  • Genetic material is located in the nucleus, which is bounded by a double membrane
• Most cells are relatively small because as size increases, volume increases much more rapidly
• As a cell increases in size, its surface area-to-volume ratio decreases
• Cell sizes

  • Escherichia coli (E.coli) bacteria: 1 µm by 3 µm
  • Human red blood cell: 8 µm in diameter
  • Largest cell on the human body: ovum, 1000 µm in diameter (1 mm)
  • Smallest cell in the human body: sperm cell, 50 µm
  • Largest cell with a metabolism: Chaos chaos, 1-5 mm in length (Giant Amoeba)
  • Largest cell: yolk of an ostrich egg
• Nucleus


  • Contains most genes
  • Enclosed by a nuclear envelope (double membrane)
  • Contains chromosomes (made of DNA)
  • Contains chromatin (DNA and proteins)
  • Contains nucleolus (produces and assembles ribosomes)
• Ribosomes


  • Made of rRNA and protein
  • Synthesized in the nucleolus, exit through nuclear pores, and are located in the cytoplasm
  • Site of protein synthesis (two subunits)
  • Read mRNA and translate the genetic code into amino acids
  • Cytoplasmic locales: cytosol (free ribosomes) and ER (bound ribosomes)
• Endoplasmic reticulum (ER)


  • Synthesis of membranes for other organelles and modification of proteins
  • Smooth ER: lacks ribosomes, lipid synthesis
  • Rough ER: numerous ribosomes attached, synthesis, secretion or storage of proteins
• Golgi apparatus


  • Consist of flattened membranous sacs or cisternae
  • Proteins are modified and stored, then sent to other destinations
  • Two sides: cis face (receiving) and trans face (shipping)
  • Transport vesicles move material from ER to Golgi, products are modified during transit, sorted, and dispatched by budding vesicles
• Lysosomes


  • Membranous sac of hydrolytic enzymes
  • Digest macromolecules
  • Made by ER and Golgi apparatus
  • Involved in phagocytosis (engulfment of smaller organisms or food particles) and autophagy (reusing old and damaged cell parts)
• Vacuoles


  • In a plant cell, 90% volume may be taken up by one or two large central vacuoles
  • Bounded by vacuolar membranes (tonoplasts)
  • Filled with a watery fluid called cell sap
  • Play major roles in storing water and maintaining turgor pressure against the cell wall
• Mitochondria


  • Sites of cellular respiration, the powerhouse of the cell
  • Enclosed by two membranes: outer membrane (smooth) and inner membrane (folds into cristae generating ATP)
  • Mitochondrial matrix contains many different enzymes as well as DNA and ribosomes
• Chloroplasts


  • Contain the green pigment chlorophyll
  • Site of photosynthesis
  • Thylakoids: flattened interconnected sacs containing chlorophyll molecules
  • Granum: stacked thylakoids
  • Stroma: fluid that contains the chloroplast DNA and ribosomes
• Peroxisomes


  • Bounded by a single membrane
  • Contain enzymes needed by some plants to survive during hot conditions in a process called photorespiration
  • Enzymes remove hydrogen atoms, oxygen (O2), and produce hydrogen peroxide (H2O2), which is then converted to water
• Cytoskeleton


  • Maintains cell shape
  • Involved in cell motility (changes in cell location)
  • Microtubules: thickest, control the addition of cellulose to the cell wall, involved in cell division
  • Microfilaments (actin filaments): thinnest, involved in contraction and movement of substances within the cell
  • Intermediate filaments: provide structural support
• Plasma membrane (cell membrane)


  • Controls traffic into and out of the cell
  • Exhibit permeability
  • Integral proteins: penetrate the hydrophobic interior of the lipid bilayer, including transmembrane proteins that span the membrane
  • Peripheral proteins: not embedded in the lipid bilayer, loosely bound to the surface of the membrane
• Transport across cell membrane

  1. Passive transport: no energy required, substances move due to gradient (high to low)

  2. Facilitated diffusion: polar molecules and ions diffuse passively with the help of transport proteins

  3. Active transport: uses energy (ATP) to move solutes against their gradients (low to high concentration)

  4. Endocytosis: movement of large material into the cell (phagocytosis, pinocytosis, receptor-mediated endocytosis)

  5. Exocytosis: cell discharges material
• Cell membranes are permeable to specific ions and a variety of polar molecules (water)
• Transport proteins can avoid contact with the lipid bilayer by passing through them
• Channel proteins simply provide corridors that allow specific molecules or ions to cross the membrane
• Carrier proteins undergo subtle changes in shape that translocate the solute-binding site across the membrane
• The sodium-potassium pump uses energy (ATP) to maintain internal concentrations of small solutes that differ from concentrations in the environment
• Cellular Metabolism


  The sum of all the chemical and energy transformations taking place in cells that are essential for the growth, maintenance, and repair of cells, and other activities of the body
• Catabolic

  (Animals)
• Anabolic


  (Plants)
• ATP

  The energy molecule produced in cellular respiration which is usable by cells and living organisms

  
• Cellular Respiration


  The process where energy in food molecules is released and converted to a form that can be used by the cell which is ATP (adenosine triphosphate)

  
• Chemical Structure of ATP

  • Consist of three phosphate group attached to adenosine
• Reproduction


  Making copies, biologically it is producing offspring that may or may not be exact copies of parents
• Life cycle

  1. Grow

  2. Develop

  3. Reproduce
• All cells come from pre-existing cells
• Cellular reproduction

  Cell Division
• Cell Division/Reproduction

  Ensures the continuity of life from one generation to the next
• Importance of cell division

  • Reproduction for one-celled organisms
  • Replacement/repair of worn-out tissues
  • Formation of gametes
• Asexual Reproduction

  Organisms make exact copies of themselves (BINARY FISSION and MITOSIS)
• Sexual Reproduction

  Organisms make unique copies of themselves (MEIOSIS)
• Prokaryotic binary fission

  Cell division in prokaryotes
• Cytokinesis

  Division of the cytoplasm
• Extracting the Energy from ATP

  1. Breaking the high-energy bonds between phosphates

  2. Energy is released from ATP when the terminal phosphate bond is broken

  3. ATP becomes adenosine diphosphate (ADP)