BIO 11

• All cells share certain basic features:

  • Bounded by the plasma membrane
  • Contains cytosol where organelles are suspended
  • Contain chromosomes which carry the genes in the form of DNA
  • Have ribosomes that makes protein
• Prokaryotic cells:

  • Bacteria, Archaea
  • DNA concentrated in the nucleoid
  • Circular strand of DNA
  • Few organelles
• Eukaryotic cells:

  • Protists, Fungi, Plant, Animals
  • DNA in the nucleus
  • DNA in several linear chromosomes
  • Many specialized membrane-bound organelles
• Eukaryotic cells have internal membranes that compartmentalize their functions
• Nucleus:

  • Contains most of the genes in the eukaryotic cell
  • Directs protein synthesis and other cellular processes
• Nucleolus:

  • Mass of densely stained fibers and granules where ribosomal RNA (rRNA) is synthesized
• Protein synthesis:

  • Synthesize mRNA (messenger RNA) according to instructions provided by the DNA (transcription)
  • Transport synthesized mRNA to the cytoplasm via the nuclear pores
  • Ribosomes translate the mRNA's genetic message into the primary structure of a specific polypeptide (translation)
• Ribosomes:

  • Made of ribosomal RNAs (rRNAs) and proteins
  • Carry out protein synthesis
  • Types: Free ribosomes and Bound ribosomes
• Endomembrane system:

  • Regulates protein traffic and performs metabolic functions
  • Includes: Nuclear envelope, endoplasmic reticulum, Golgi apparatus, Lysosomes, Vacuoles/vesicles, Plasma membrane
  • Carries out a variety of tasks in the cell, including synthesis of proteins, transport of proteins, metabolism, movement of lipids, and detoxification of poisons
• Endoplasmic Reticulum:

  • "Biosynthetic factory"
  • Consists of a network of membranous tubules and fluid-filled sacs called cisternae
  • Has 2 regions: Smooth ER and Rough ER
• Golgi Apparatus:

  • Warehouse for receiving, sorting, shipping, and sometimes manufacturing
  • Transport vesicles goes here for modifications (from ER)
  • Consists of flattened membranous sacs (cisternae)
  • A golgi stack has 2 sides: cis (receives) and trans (ships) side
• Lysosomes:

  • Membrane-bound sac of hydrolytic enzymes that digest macromolecules
  • Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids
  • Massive leakage from lysosomes can destroy an entire cell by autodigestion
  • Can fuse with other organelles or parts of the cytosol (Autophagy)
  • Can fuse with food vacuoles, when a food item is brought into the cell by phagocytosis
• Vacuoles:

  • Large vesicles derived from the endoplasmic reticulum and Golgi apparatus
  • The vacuolar membrane is selective in transporting solutes
  • Vesicles & vacuoles are membrane bound sacs with varied functions
• Food vacuoles:

  • Formed by phagocytosis
  • Fused with lysosomes
• Contractile vacuole:

  • Pumps out excess water out of the cell
  • Usually found in freshwater protists
• Central vacuole:

  • Found in many mature plant cells
• Tonoplast:

  • Membrane that surrounds the central vacuole
  • Transport solutes to central vacuole
  • Contains glycolipids (instead of phospholipids)
• Central vacuole:

  • Stockpiling proteins or inorganic ions (K, Cl)
  • Depositing metabolic byproducts
  • Storing pigments (not chlorophyll)
  • Storing defensive compounds against herbivores
  • Major role in growth of plant cells: cells enlarge as their vacuoles absorb water with minimal investment in new cytoplasm (cell elongation or expansion)
• Mitochondria & Chloroplasts:

  • Main energy transformers of cells
  • Convert energy to forms that cells can use for work
• Mitochondria:

  • Found in nearly all eukaryotic cells
  • The mitochondrion is enclosed in a phospholipid bilayer with unique collections of embedded proteins
  • Smooth outer membrane and highly folded inner membrane (cristae)
• Chloroplast:

  • Capture of light energy
  • Contain the green pigment chlorophyll, along with enzymes and other molecules that function in the photosynthetic production of sugar
  • Parts: Stroma (contains DNA), Thylakoids (critical for converting light to chemical energy), Grana (stacks of thylakoids)
• Peroxisomes:

  • Oxidation
  • Generate and degrade hydrogen peroxide in performing various metabolic functions
  • Bound by a single membrane
  • Contain enzymes that transfer hydrogen from various substrates to oxygen (oxidation reactions)
  • Intermediate product is hydrogen peroxide but the peroxisome has another enzyme (catalase) that converts peroxide to water
  • Some peroxisomes break fatty acids down to smaller molecules that are transported to mitochondria for fuel
  • Others detoxify alcohol and other harmful compounds
• Cytoskeleton:

  • Support and motility
  • Network of fibers that organizes structures and activities in the cell
  • Gives mechanical support and maintains cell shape
  • Provides anchorage for organelles and cytosolic enzymes
• Microtubules:

  • Hollow rods constructed from globular proteins called tubulins
  • Move chromosomes during cell division
  • Central structural support in cilia and flagella
• Centrosomes and Centrioles:

  • Region often located near the nucleus
  • In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring
  • During cell division, the centrioles replicate
• Cilia and Flagella:

  • Microtubule-containing extensions that project from some cells
• Microfilaments:

  • Thinnest part of the cytoskeleton
  • Solid rods of the globular protein actin (actin filaments)
  • Resist tension
  • Form structural 3D networks with other proteins just inside the plasma membrane to support cell shape
• Intermediate Filaments:

  • Keratin
  • Found only in some animal cells
  • For bearing tension
  • More permanent fixtures than microfilaments and microtubules
  • Reinforce cell shape and fix organelle locations
• Cell Wall:

  • Found in prokaryotes, fungi, some protists & plants
  • Protects, maintains the shape and prevents excessive uptake of water
  • Microfibrils of cellulose embedded in a matrix of proteins and other polysaccharides
• Extracellular Matrix:

  • For animal cells
  • Made of glycoproteins (collagen fibers) embedded in a network of proteoglycans
  • Fibronectins in ECM connect to integrins, intrinsic membrane proteins
  • Integrins connect ECM to the cytoskeleton
• Intercellular Junctions:

  • Help integrate cells into higher levels of structure and function
  • Neighboring cells in tissues adhere, interact and communicate through direct physical contact
  • Plant cells are perforated with plasmodesmata, channels allowing cytosol to pass between cells
• Plant Crystals:

  • Waste or excretory products of the protoplast
  • Calcium carbonate or Calcium oxalate
• What is the difference between the nucleus and nucleoid?

  Nucleus is a membrane-bound organelle while the nucleoid is not
• Nuclear Envelope:

  • Double membrane that encloses the nucleus, separating its contents from the cytoplasm
  • Perforated with pore structure (nuclear pore)
  • The inside is lined by the nuclear lamina
  • Contains the nuclear matrix
• Nuclear Pore

  • Regulates the entry and exit of proteins, RNAs, and macromolecules
  • Located on the surface of the nuclear envelope
• Nuclear Lamina

  • Network of intermediate filaments
  • Maintain the shape of the nucleus by mechanically supporting the nuclear envelope
• Nuclear Matrix

  • Framework of protein fibers extending throughout the nuclear interior
• What helps organize genetic material?

  Nuclear lamina & matrix
• Chromatin

  • The complex of DNA and proteins that makes up the chromosome
  • DNA + HISTONES(protein) = CHROMATIN
• What is the difference between the smooth and rough ER?

  The presences of bound ribosomes on its surface