Chapter 5 Flashcards
Phospholipid Bilayer
●The plasma membrane is common to all cells
●External surface lined with hydrophilic polar heads
●Cytoplasmic* surface lined with hydrophilic polar heads
●Nonpolar, hydrophobic, fatty-acid tails sandwiched in between
- Cytoplasm is the gelatinous liquid that fills the inside of a cell. It is composed of water, salts, and various organic molecules
Fluid Mosaic Model
●Phospholipid bilayer
●Protein molecules
● Some phospholipids and proteins have carbohydrate chains attached, making glycolipids and glycoproteins
●Cholesterol affects the fluidity of the membrane
Protein molecules- Fluid Mosaic Model
●Float around like icebergs on a sea
●Membrane proteins may be peripheral or integral
●Peripheral proteins are found on the inner surface
●Integral proteins are embedded in the membrane
What do channel proteins allow through the membrane?
Channel proteins allow charged or large molecules through the membrane. For example, channel proteins allow ions like sodium, potassium, and calcium, as well as larger molecules like glucose, to pass through the membrane.
What is the function of a channel protein?
The function of a channel protein is to move molecules from one side of the membrane to the other without binding to them and without using energy.
What is an example of an inherited disorder in channel protein?
Cystic fibrosis, an inherited disorder is caused by a
faulty chloride (Cl–) channel; a thick mucus collects in
airways and in pancreatic and liver ducts.
Carrier Proteins
- Selectively interacts with a specific molecule or ion so
that it can cross the plasma membrane. - Combine with the substance to be transported
- Assist passage of molecules through membrane
A suggested cause of Obesity - Carrier Protien
The inability of some persons to use energy for sodium- potassium (Na+–K+) transport has been suggested as the cause of their obesity
Cell Recognition Protein:
The MHC (major histocompatibility complex) glycoproteins are different for each person, so organ
transplants are difficult to achieve. Cells with foreign MHC glycoproteins are attacked by white blood
cells responsible for immunity.
Cell Recognition Proteins:
- Glycoproteins (Glycoproteins are molecules that comprise of protein and carbohydrate chains that are involved in many physiological functions including immunity.)
- Help the body recognize foreign substances
Receptor Protein: Relationship to Pygmies
Pygmies are short, not because they do not produce enough growth hormone, but because their plasma
membrane growth hormone receptors are faulty and cannot interact with growth hormone.
Receptor Proteins:
Is shaped in such away that a specific molecule can bind to it.
Allow a cell to respond to signals from other cells
Enzymatic Proteins:
Carry out metabolic reactions directly
Catalyzes a specific reaction. The membrane protein, adenylate cyclase, is involved in ATP metabolism.
What bacteria has enzymatic proteins?
Cholera bacteria release a toxin that interferes with the
proper functioning of adenylate cyclase; sodium (Na+) and water leave intestinal cells, and the individual may die from severe diarrhea.
Junction Proteins:
Attach adjacent cells
Tight junctions join cells so that a tissue can fulfill a function, as when a tissue pinches off the neural tube
during development. Without this cooperation between
cells, an animal embryo would have no nervous system.
Permeability of the Plasma Membrane
- The plasma membrane is differentially (selectively) permeable
- Allows some substances to move across the membrane Inhibits passage of other molecules
- Passive Transport:
No ATP requirement
Molecules follow concentration gradient - Active Transport
Requires a carrier protein
Requires energy
Passage of Molecules Across the Membrane
Energy Not Required (aka Passive)
- Diffusion
- Facilitated Transport
Energy Required
- Active Transport
-Bulk Transport
Diffusion
Diffusion is a spontaneous process in which a substance moves from a region of high concentration to a region of low concentration, eventually eliminating the concentration difference between the two regions.
Simple Diffusion
-A solution consists of:
A solvent (liquid), and
A solute (dissolved solid)
- Diffusion
Net movement of solute molecules down a gradient
Molecules move both ways, but net high to low
- Equilibrium:
When NET movement stops
Solute concentration is uniform
Example of Facilitated Transportation - Gas Exchange in Lungs
Energy is not required to move oxygen or carbon dioxide across membranes. Instead, these gases follow pressure gradients that allow them to diffuse. The anatomy of the lung maximizes the diffusion of gases: The respiratory membrane is highly permeable to gases; the respiratory and blood capillary membranes are very thin; and there is a large surface area throughout the lungs.
Osmosis
Osmosis is the process by which water molecules pass through a membrane from a region of higher water concentration to a region of lower water concentration.
The movement of water molecules through the cell membrane is caused by differences in the concentration of the solute on its two sides.
Osmosis
- Special case of diffusion
- Focuses on solvent (water) movement rather than solute
- Diffusion of water across a differentially (selectively) permeable membrane
- Solute concentration on one side is high, but water concentration is low
- Solute concentration on other side is low, but water concentration is high
- Water can diffuse both ways across membrane but the solute can’t
-Net movement of water is toward low water (high solute) concentration
What is Osmotic pressure?
is the pressure that develops due to osmosis
The amount of water contained within the cell creates a pressure
The cell membrane regulates the osmotic pressures of intracellular and intercellular fluids.
Types of Transport: Osmosis
Isotonic Solution
Hypotonic Solution
Hypertonic Solution
