ap biology chapter 6 and 7 tour of the cell membrane transport
TRANSCRIPT
AP Biology Chapter 6 and 7
Tour of the Cell Membrane Transport
Eukaryotic cell’s genetic instructions Nucleus Nuclear envelope Nuclear lamina Chromosomes Nucleolus
Eukaryotic cell ribosomes Ribosomes
Free ribosomes Bound ribosomes
Endomembrane system Nuclear envelope ER Golgi apparatus Lysosomes Plasma membrane Vesicles Vacuoles
Endosymbiosis Theory
Mitochondria Mitochondria Cristae Mitochondrial matrix
Chloroplasts Thylakoids Granum Stroma plastids
Peroxisomes
Cytoskeleton Network of fibers extending throughout
the cytoplasm Roles of cytoskeleton
Mechanical support to cell shape Cell motility (movement) using motor
proteins
Cell junctions Tight junctions-
plasma membrane of other cells form a seal which prevents leakage
Cell Junction Desmosomes
(anchoring) Fasten cells together into strong sheets
Cell Junction Gap Junction-
provide cannels so cells can communicate with each other, and molecules can pass to and from
AP Biology- Quiz today Finishing extracellular components
Cell wall parts of plant Cell wall- protects and maintains shape Primary cell wall- thin flexible wall (young
plant) Secondary cell wall- hardened structure
between the plasma membrane and primary wall
Middle lamella- Thin layer with sticky polysaccharides (pectins) glues cells together
Plasmodesmata- communicating channel between plant cells
Chapter 7- Membranes The plasma membrane separates the
living cell from its surroundings Selectively permeable: some substances
cross more easily than others Membrane encloses a solution different
from the surrounding solution
Phospholipid bilayer Contains: lipids,
proteins, and carbohydrates
Most abundant lipid: phospholipid
Amphipathic molecule: hydrophilic and hydrophobic regions
Phospholipid Bilayer Fluid mosaic model: the membrane is a
fluid structure with various proteins embedded in or attached to the double layer
Phospholipid bilayer1. Not all membranes are like
Membranes with different functions differ in chemical composition and structure
2. Measurements showed that membrane proteins are not very soluble in water
Phospholipid bilayer Freeze fracture technique
Splits a membrane along the middle of the phospholipid bilayer
Found that: membranes are more mosaic than fluid, lipids appear to form defined regions
Phospholipid Bilayer Membrane molecules are held in place
by relatively weak interactions Most lipids and some proteins drift
laterally in the plane of the membrane but rarely flip-flop from one phospholipid layer to the other
Phospholipid bilayer Membrane fluidity is influenced by
temperature: As temperature cools, membranes switch
from a fluid state to a solid state Phospholipids pack together more closely
Phospholipid bilayer Steroid cholesterol is wedged between
phospholipid molecules in the plasma membrane of animal cells Warm temp: restrains movement (reduces
fluidity) Cold temp: maintains fluidity by
preventing tight packing Fluidity buffer
Proteins determine membrane’s function
Two major populations of membrane proteins: integral and peripheral
Membrane Proteins Integral-
Embedded in the bilayer
Penetrate hydrophobic interior of bilayer
Peripheral- Not embedded in
the bilayer Loosely bound to
surface of membrane
Major functions of membrane proteins1. Transport2. Enzymatic activity3. Signal transduction (relaying
messages)4. Cell-cell recognition5. Intercellular joining6. Attachment to cytoskeleton
Cell to cell recognition- ability of a cell to distinguish one type of neighboring cell from another
Membrane carbohydrates may be bonded to lipids or proteins making glycolipids or glycoproteins respectively
Selective permeability and structure:
1. Small molecules and ions move across the plasma membrane in both directions
Example: sugar, amino acids and other nutrients enter a
muscle cell and metabolic waste leave The muscle cell takes in oxygen and expels
carbon dioxide Muscle also regulates the concentrations of
inorganic ions, such as Na, K, Ca, Cl by shuttling them one way or the other across the membrane
Movement of molecule depends on the interaction of the molecule with the hydrophobic interior of membrane Nonpolar molecules can dissolve in the
lipid bilayer easily Polar molecules and water extremely
small can cross bilayer slowly Passage of water occurs via aquaporins Carrier proteins- bind to molecules and
change shape to shuttle them across membrane
Membrane Transport
Passive Transport
Diffusion Osmosis
Tonicity
Isotonic Hypertonic
Hypotonic
Facilitated Diffusion
Carrier proteins
Channel proteins
Active transport
Sodium-potassium
pumpCotransport
Vesicular Transport
Exocytosis Endocytosis
Pinocytosis Phagocytosis
Receptor-mediated
endocytosis
Water potential A property predicting the direction in
which water will flow
Formula: Ψ = ΨS + ΨP
Water Potential ΨS = -iCRT
i = ionization constant (1 for sucrose) C = osmotic molar concentration R = Pressure constant (R= 0.0831 liter bars/mole
°Kelvin T = temperature
Calculations: Calculate the osmotic potential using
the following data. Answer should be in bars.
C = 0.32 T =21 °C *must convert to Kelvin