Biology 224 Liberty University (Dr. Brophy) Chapter 5

_____________________ are Amphipathic.

Phospholipids

Each phospholipid layer is called a_______________

leaflet

Cannot pass hydrophobic membrane center.

Polar Molecules

Can generally diffuse through membranes.

Nonpolar Molecules

__________________________ are embedded in Phospholipid bilayer.

Proteins

Protein content of membranes varies from ____________ times more Lipid molecules than Protein molecules.

15-70

Less closely associated with the membrane.

Peripheral Membrane Proteins

Loosely bound to the membrane.

Peripheral Membrane

Peripheral Proteins are bound by what bonds?

Hydrogen or Ionic Bonds

What are Peripheral Proteins bound to?

Transmembrane Proteins or the Heads of Phospholipids

The exposed portions of Peripheral Proteins are usually ____________ for binding.

polar

More closely associated with the membrane.

Integral Membrane Proteins

Exposed portions are usually__________________for binding.

non-polar

What are two types of binding in Integral Membrane Proteins?

-Transmembrane
-Lipid-anchored

________________________________transverse the membrane with domains forming a-helices.

Transmembrane Proteins

Transmembrane Proteins are bound to the __________________.

Cytoskeleton

Have a lipid covalently attached to the Protein.

Lipid-anchored Proteins

Phospholipids in the membrane are not covalently bound.

True

Phospholipids are not free to move between leaflets.

True

Since Phospholipids are not free to move between leaflets, a special protein ________________ is needed to do this using the energy from__________________.

Flippase, ATP

The most common Phospholipids have an even number of ___________________(18-20).

Carbons

What are the factors affecting membrane fluidity?

- fewer hydrophobic interactions (higher fluidity)
- shorter hydrocarbon chains
-more unsaturated hydrocarbon chains
- more cholesterol will make membrane more fluid at low temperatures, less fluid at higher temperatures.

Carbohydrates in membranes occur only as _____________ and _______________.

Glycolipids and Glycoproteins

_____________________________occur in the exterior leaflet of t he Plasma Membrane.

Carbohydrates

What does Glycolipids and Glycoproteins function as in the Plasma Membrane?

antigens, identifying the cells of organisms(cell surface recognition).

_____________________ shields the cell from the immune system of other cells.

Glycocalyx

How are Phospholipids synthesized?

by the smooth ER and inserted into the membrane.

What allows Phospholipids to be spread throughout the Endomembrane System?

Lateral Diffusion

The membranes of what are connected by vesicles?

-Nucleus
-ER
-Golgi
-Plasma Membrane
-Mitochondria
-Chloroplast

Can extract a lipid from one membrane, diffuse through the Cytoplasm, and insert it into any other membrane.

Lipid Exchange Proteins

The _____________________and ____________________synthesize various types of lipids then transferred to other organelles by Lipid Exchange Proteins.

Mitochondria, Chloroplast

Most Transmembrane Proteins are synthesized where?

Rough ER

___________________________ are left in the ER membrane as they are synthesized, forming Transmembrane Proteins.

Hydrophobic a helices

From the ER, Proteins can be moved to other membranes by _________________.

vesicles

Where does Glycosylation of Proteins occur in Membrane Synthesis?

Rough ER

Where are Oligosaccharides synthesized?

In the Lumen of the ER on a Dolichol lipid.

Where are Oligosaccharides transferred during membrane synthesis?

as a unit to the R/Side group of an Asparagine amino acid on the protein.

In the ________________, an Oligosaccharide chain can be synthesized and transferred to the Oxygen of a _____________________or ____________________amino acid.

Golgi, Serine or Threonine

Proteoglycans are often secreted from the cell to help form the __________________.

Extracellular Matrix

Proteoglycans are also components of _______________.

Mucus.

Molecules are passed through membranes, by either ________________or___________________transport.

passive or active

Passive Transport

simple and facilitated diffusion; down/with concentration gradient

Active Transport

up/against concentration gradient; requires ATP

Passive Transport does not require the input of outside energy.

True

What does passive transport depend on?

the Kinetic Energy of the solute molecule

Kinetic Energy

energy in motion

All molecules are in constant motion.

True

Passive Diffusion

the net movement of a substance from an area of high concentration to an area of low concentration.

When can passive diffusion occur?

for nonpolar molecules diffusing through the phospholipid bilayer, or through channel or carrier proteins.

What are the respiratory gases that are the primary examples of molecules that move by Passive Diffusion through Membranes?

Oxygen, Nitrogen and Carbon Dioxide

Passive Diffusion is due to what?

Kinetic Energy

What does the rate of diffusion depend upon?

-Electrical Charge
-Temperature
-Concentration
-Molecular Size

Diffusion over short distances is very effective.

True

What is Facilitated Diffusion?

The diffusion of macromolecules and polar molecules through membranes using proteins.

In facilitated diffusion, the proteins may be described as what?

channel or carrier/transporter proteins

What are Channel Proteins?

transmembrane proteins that form channels through the membrane through which certain molecules can diffuse.

_________________Proteins may be gated and only transport when the "gate" is opened.

Channel

_______________________ channels open when a signal molecule (ligand) is bound.

Ligand-gated

____________channels open when a membrane is depolarized, by a change in the electrical charge across the membrane.

Voltage-gated

___________________Proteins bind the solute which is then carried through the membrane, usually by a conformational change in the protein.

Transporter

Uniports

transports one solute molecule.

Symport

transports two in same direction.

Antiports

transports two in different directions.

What is the definition of Primary Active Transport?

the transport of a substance, with a pump, against its concentration gradient with the direct expenditure of energy.

In Primary Active Transport, what is often the energy source used?

ATP

What is an example of Primary Active Transport with the use of ATP?

Sodium Potassium pump

Puming two_____________at uneven rates results in an electrical charge across the ______________________________.

cations, plasma membrane

Osmosis

the diffusion of water through a semipermeable membrane.

What is the name of the pores in which water diffuses?

Aquaporins

Where are Aquaporins found?

plant cells, kidney cells, and RBCs of animals.

What are the three conditions (solutions) in which a cell may be placed?

-Isotonic
- Hypotonic
-Hypertonic

Isotonic Solution

the same solute concentration and water as the cell, cell volume does not change.

Hypertonic Solution

solution has a higher solute concentration than the cell(less water), so cell looses volume

Hypotonic Solution

solution has a lower solute concentration (more water) than cell, so cell gains volume.

Brings large sized materials into cells using Vesicles formation.

Endovytosis

____________________ uses receptors to concentrate materials before bringing them in.

Endocytosis

In Endocytosis, after the vesicle imports material from outside the cell, it can fuse with a _____________________________.

Primary Lysosome

In Endocytosis, __________________ are digested to monomers before they are transported to the cytoplasm.

Macromolecules

What is the function of Exocytosis?

discards materials from cells using vesicles.

What adds phospholipids to Plasma Membrane?

Exocytosis