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Membrane Structure

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Title: Slide 1 Author: Stephen D. Ebbs Last modified by: D P Althoff Created Date: 7/9/2005 3:53:30 PM Document presentation format: On-screen Show (4:3) – PowerPoint PPT presentation

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Title: Membrane Structure


1
Membrane Structure FunctionSpring 2013 -
Althoff Reference Mader Windelspecht Ch. 5)
Lec 05
2
  • ____________________ the boundary between
    the cells inside workings and the world outside
    it.
  • Keys to consider 1) ____________ for
    exchange between inside and outside the
    cell 2) _________________ are exchanged

3
A Little History
  • Beginning of 20th century researchers noted
    lipid soluble molecules entered cells more
    rapidly than water soluble molecules
  • In ______________________________ determined
    phospholipid content of a cell just enough to
    form a bilayer around the cells
    In ______________________________
    proposed proteins also part of membrane. Model
    they proposed was sandwich-like, further
    enhanced by Robertson in late 1950s.

4
A Little History
  • Robinsons ______ _________ model. late1950s

BILAYER PHOSPHOLIPID SANDWICH,
  • Singer Nicolson __________ model, 1972.

EMBEDDED PROTEIN MOLECULES
5
(No Transcript)
6
PHOSPHOLIPID
OUTSIDE THE CELL
INSIDE THE CELL
(similar to Mader p86 Fig. 5.1)
7
Components of the PLASMA MEMBRANE
Lipids
Proteins
  • Phospholipids bilayer (meaning 2 layers)
  • Exterior portions are hydrophilic (2 places)
  • Interior portion of the bilayer is hydrophobic
  • Provides essential structure to this portion of
    the cell
  • Protein molecules are embedded in the plasma
    membrane
  • Serve to stabilize and shape the plasma membrane
  • Various (many) proteins perform specific
    functions 1) channel 2) transport 3) cell
    recognition 4) receptors 5) enzymes 6) form
    junctions

8
PLASMA MEMBRANE A matrix of proteins
Proteins
  • Some proteins span the entire bilayer distance
    (__________________ proteins)
  • Some proteins reach the inside surface only

OUTSIDE
INSIDE
9
Fluidity of the Plasma Membrane
  • At room temperature, the __________________
    of the plasma membrane has the consistency of
    olive oil
  • Result ___________________
  • _____________________ those not attached to the
    cytoskeletoncan move within the fluid lipid
    bilayer
  • This fluidity is critical to the _________ of
    proteins, particularly enzymes which speed up
    chemical reactions

10
Lipid Movement
11
Plasma Membrane PROTEINS
  • CHANNEL proteins _________________, control
    passage of molecules
  • CARRIER proteins ____________ combine with a
    substance and move it across the membrane
  • CELL RECOGNITION proteins _________ looking
    for pathogens, alert immune system
  • RECEPTOR proteins __________, bind with other
    molecules resulting in shape change that brings
    about cellular response
  • ENZYMATIC proteins ________, facilitate/speed
    up metabolic reactions directly
  • JUNCTION proteins ___________________ form
    junctions between cells

12
CHANNEL
CARRIER
RECOGNITION
JUNCTION
RECEPTOR
ENZYMATIC
13
When Function Goes _____
  • CHANNEL proteins faulty chloride (Cl-) channel
    results in cystic fibrosis (thick mucus collects
    in airways, pancreatic ducts, liver ducts)
  • CARRIER proteins inability to use energy
    transport for sodium potassium (NaK-)transport
    may cause obesity for some
  • CELL RECOGNITION proteins can explain rejection
    of organ transplants, liked to MHC (major
    histocompatibility complex) glycoprotein
  • RECEPTOR proteins why some are pygmies.
    Membrane receptors faulty and cannot interact
    with growth hormone
  • ENZYMATIC proteins diarrhea impact of cholera
    bacteria toxin released on enzyme adenylate
    cyclase, which reduces water Na retention in
    large intestine

14
Plasma Membrane Permeability
  • _______________________________ the plasma
    membrane is choosy about the passage of
    molecules into and out of the cell.

Energy Not Required
Energy Required
  • ACTIVE TRANSPORT
  • EXOCYTOSIS
  • ENDOCYTOSIS
  • DIFFUSION
  • FACILITIATED TRANSPORT

15
Some sugars, amino acids ions
3
Lipid-soluble molecules, H20,
1
gases
2
Some sugars amino acids
4
macromolecules
5
macromolecules
(Mader p89 Fig. 5.4)
16
Direction of molecule passage
Key process
DIFFUSION
  • Toward _______ concentration
  • Toward _______ concentration
  • Toward _______ concentration
  • Toward _______ of cell
  • Toward _______ of cell

FACILITATED TRANSPORT
ACTIVE TRANSPORT
EXOCYTOSIS
ENDOCYTOSIS
17
Requirement
Key process
  • Concentration gradient
  • Channels or carrier AND concentration gradient
  • Carrier plus energy
  • Vesicle fuses with plasma membrane
  • Vesicle formation

DIFFUSION
FACILITATED TRANSPORT
ACTIVE TRANSPORT
EXOCYTOSIS
ENDOCYTOSIS
18
PROCESS OF DIFFUSION (Mader p91 Fig. 5.5)
DIFFUSION is spontaneous and ___ chemical energy
is required
19
PROCESS OF OSMOSIS (Mader p93 Fig. 5.8)
20
_______ the Cell EUKARYOTIC CELLS
MULTICELLUAR ORGANISMS
  • Must make the ____________ between cells
  • Permits ________________ between cells
  • Permits _________________ between cells
  • Components and construction ______ between plants
    and animals
  • We consider these _________________
    structures examples for plants __________
    plasmodesmata examples for animals
    __________________

21
PLANTS -- Outside
CELL 1
CELL 2
CYTOPLASMA
PLASMODESMATA
CELL WALL -- PRIMARY
22
ANIMAL Extracellular Matrix
  • MESHWORK OF _______________________
  • Examples structural proteins
    ________________ matrix strength __________
    ______ resilience
  • Examples rigid packing gel permits
    ________________ of nutrients, metabolites, and
    hormones between blood and tissue cells

23
ANIMAL Extracellular Matrix
INSIDE
OUTSIDE
(Mader p99 Fig. 5.13)
24
Extracellular Matrix Rigid or Flexible?
  • RIGID ______ is rock solid because the
    extracellular matrix includes mineral salts
    (i.e., calcium salts) deposited outside the cell
  • FLEXIBLE _________

25
Animal Cell JUNCTIONS
ADHESION JUNCTIONS
  • _________ sheet of cells results
  • Attach to ____________, within the cell via
    cytoplasmic plaques, intercellular filaments
  • Common in heart, stomach, and bladder where
    ___________ must stretch

CELL 1
CELL 2
26
Animal Cell JUNCTIONS
TIGHT JUNCTIONS
  • ____________ fastening
  • Plasma membrane proteins _______ to each other
  • Common in kidney where urine passes through
    intestines have this type of lining to __________
    ______________ from entering lining

CELL 1
CELL 2
27
Animal Cell JUNCTIONS
GAP JUNCTIONS
CELL 1
CELL 2
  • Permits ______________
  • __________ plasma membrane channels join
  • Common in the ________ muscle _____________
    (stomach)
  • Permit _____________ to facilitate synchronous
    contraction

28
Know Where You Are Inside or Outside
the Eukaryotic Cell RELATIVE TO THE
_____________________
INSIDE looking out OUTSIDE looking in
COMPONENTS Cell wall (plants) Nucleus Ribosomes
Plasmodesmata (plants) Golgi
apparatus Extracellular matrix
(animals) Adhesion junctions (aniamls) Gap
junctions (animals)
Yes
No
No
Yes
29
Know What Requires Energy What Doesnt
Relative to _________________ of the Plasma
Membrane
Energy Required Direction of
passage
Passage type Diffusion Endocytosis Exocytosis
Active Transport Facilitated Transport
No
Yes
Toward outside
Toward lower concentration Toward
outside Toward higher concentration
Toward inside
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