Lecture 4

• Two ways of defining life:

  • Structure (what a thing is made of)
  • Function (what a thing does)
• 7 functions of living things (Mrs. Nerg)

  • Movement: changing place or position
  • Respiration; converting energy in food to a biologically useful form
  • Sensitivity; respond to the external environment:
  • Nutrition: require a source of energy (food/fuel)
  • Excretion: getting rid of waste
  • Reproduction: generating offspring
  • Growth: increasing in physical size
• Cell Theory (a structural definition of life)

  1. All living things are composed of cells (single celled organisms up to large organisms like whales)
  2. The cell is the fundamental structural unit of living organisms
  3. Cells come from other cells, they do not arise spontaneously
  4. Hereditary information is passed from cell to cell
  5. Energy flow occurs within cells
  6. All cells have the same basic chemical composition
• Structure and function complement one another—the ability to perform a given function depends on having the structures (the physical characteristics) necessary to perform those functions.
• All cells possess an outer layer, made of lipids and proteins, that regulates what enters and leaves a cell: cell membrane
• Prokaryotic Cell

  • Examples: E. coli
  • No membrane-bound nucleus
  • Usually smaller (~1 µm)
  • Usually single-celled
  • Membrane-bound organelles are rare
  • Think of as a simple bag
• Eukaryotic Cell

  • Examples: Animals (YOU), plants, fungi (e.g. yeast), amoeba
  • Has membrane-bound nucleus
  • Usually bigger (~ > 10 µm)
  • Many (but not all) are multicellular
  • Membrane-bound organelles are common
  • Think of as a bigger bag full of smaller bags!
• Cells: fundamental units of life
• Prokaryotes and eukaryotes

  • Plasma membrane
  • Cytoplasm
  • DNA and RNA
  • Ribosomes
• Eukaryotes

  • Membrane-bound organelles
  • Nucleus
• Prokaryotes and eukaryotes

  A) Bacteria

  B) Archaea

  C) Eukaryotes

  D) Prokaryotes

  
• Animal Cell

  
• Plant Cell

  
• The plasma membrane is composed of a phospholipid bilayer that acts a a selective barrier

  
• The eukaryotic cell’s genetic instructions are housed in the nucleus

  
• In the nucleus, DNA is organized into discrete units called chromosomes
• Each chromosome contains one DNA molecule associated with proteins called chromatin
• Ribosomes are protein factories

  
• Ribosomes are complexes made of ribosomal RNA and proteins
• Ribosomes build proteins in two locations:

  • In the cytosol (free ribosomes)
  • On the outside of the endoplasmic reticulum or the nuclearenvelope (bound ribosomes)
• The endomembrane system regulates protein traffic and performs metabolic functions
• Endomembrane system consist of:

  • Nuclear Envelope
  • Endoplasmic Reticulum
  • Golgi Apparatus
  • Lysosomes
  • Vacuoles
  • Plasma Membrane
• The endoplasmic reticulum is the largest internal membrane and have two distinct regions:

  A) Ribosomes

  B) Rough ER

  C) Smooth ER

  
• The Rough ER contains ribosomes, which secrete glycoproteins (proteins covalently attached to carbohydrates)
• Proteins synthesized on surface of rough ER are destined to be exported from the cell, sent to lysosomes or vacuoles, or embedded in the plasma membrane
• The Smooth ER stores calcium ions, synthesizes lipids, and detoxifies drugs and poisons
• Proteins and lipids manufactured on the rough and smooth ER membranes are transported into the golgi apparatus and modified as they pass through it

  
• The most common modification is the addition or modification of short sugar chains, forming glycoproteins and glycolipids
• A vacuole is a large membrane-bound vesicle that is importantfor digestion, storage, and waste disposal

  A) Food vacuole

  
• A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules

  A) Lysosome

  
• The central vacuole in plants contains sap, the plant’s repository of inorganic ions

  
• Central Vacuole

  • contains channels for water that are used to help the cell maintain its tonicity
  • plays a major role in the growth of plant cells, which enlarge as the vacuole absorbs water
• Endomembrane System

  
• Peroxisomes are specialized metabolic compartments that contain oxidation enzymes

  
• Peroxisomes contain enzymes that remove hydrogen atoms from various substrates and transfers them to oxygen, making hydrogen peroxide (H2O2)

  • Contains enzymes to convert H2O2 to water
• Mitochondria are the sites of cellular respiration, the metabolic process that uses oxygen to generate ATP

  
• Chloroplast contains the green pigment chlorophyll, and uses light to generate ATP and sugars

  
• Tay-Sachs diseases is a human genetic disorder that results in cellular accumulation of large, complex, undigested lipids. Which of the following organelles is most likely defective in Tay-Sachs disease?

  • the golgi apparatus
  • the lysosome
  • the smooth ER
  • the rough ER
• Roles of the cytoskeleton: support and motility
• The cytoskeleton helps to support the cell and maintain its shape. It interacts with motor proteins to produce cell motility. Inside the cell, vesicles and other organelles can use motor protein “feet” to travel along tracks provided by the cytoskeleton.