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Brooker Biology-Chapt 5

Terms in this set (75)

Phospholipid
molecule that has both a hydrophillic region and hydrophobic region
Phospholipid bilayer
a double layer of phospholipids that makes up a plasma membrane
Integral Proteins
Proteins that extend through the phospholipid bilayer.
Peripheral Proteins
A protein loosely attached to the surface of a membrane
cholesterol
steroid present in the plasma membranes of animal cells. A large amount of this in a phospholipid bilayer at High Temperatures reduces membrane fluidity, but at Lower Temperature prevents the membrane from solidifying.
Selective Permeability
Allows some substances to cross more easily than others
Diffusion
the movement of molecules from an area of higher concentration to an area of lower concentration, so that they spread out evenly reaching equilibrium
Osmosis
The diffusion of water across a selectively permeable membrane
Concentration Gradient
a difference in the concentration of a substance across a space
Transport Proteins
proteins that help to transport substances across cell membranes
Passive Transport
movement of materials through a cell membrane without using energy
Isotonic
a solution whose solute concentration equals that inside a cell; the cell will not change
Hypertonic
the solution with the greater concentration of solutes than that inside the cell; the cell will lose water to its environment--> Cell will shrivel up
Hypotonic
the solution with the lower concentration of solutes than that inside the cell; water will enter the cell -> Cell will swell and burst
Plasmolysis
As a plant cell shrivels its plasma membrane pulls away from the wall
Facilitated Diffusion
passive transport of ions or polar molecules across a plasma membrane by transport proteins
Active Transport
transport of a substance through a cell membrane against the concentration gradient; requires energy
Sodium-Potassium Pump
a carrier protein that uses ATP to transport sodium ions out of a cell and potassium ions into the cell against the concentration gradient; active transport, requires energy
Exocytosis
process by which a cell releases large amounts of material by vesicles
Endocytosis
the movement of a substance into a cell by a vesicle
Phagocytosis
A type of endocytosis in which microbes are taken in by immune cells of animals (mainly by macrophages)
diaphragm
controls the amount of light coming through the stage
Prokaryotic cell
cell lacking a nucleus and most other organelles; found only in bacteria
Eukaryotic cell
cell with a nucleus (surrounded by its own membrane) and other membrane-bound organelles
Membrane
a pliable sheet of tissue that covers or lines or connects organs or cells of animals
Membrane Structure
• Basic framework of the membrane is the phospholipid bilayer
• Membranes also contain proteins, carbohydrates, cholesterol
• Relative amounts of each vary.
Phospholipids in Membranes
• Are amphipathic molecules
• Hydrophobic region faces in
• Hydrophilic region faces out
Membrane Characteristics
1. Permability
2. Semifluid
Fluid Mosaic Model
Membrane is considered a mosaic of lipid, protein, and carbohydrate molecules.

Membrane exhibits properties that resemble a fluid because lipids and proteins can move relative to each other within the membrane
Glycolipids
Lipids with carbohydrate attached.
Leaflet
Half of a phospholipid bilayer
Membrane Permeability
degree to which a membrane allows a substance to pass through it
Cell membrane structure ensures
Essential molecules enter
Metabolic intermediates remain
Waste products exit
Proteins bound to membranes
1. Integral membrane proteins
2. Peripheral membrane proteins
Integral membrane proteins
1. Transmembrane proteins
2. Lipid anchored proteins
Transmembrane proteins
One or more regions that are physically embedded in the hydrophobic region of the phospholipid bilayer.

Many function in transport.
Lipid anchored proteins
Covalent attachment of a lipid to an amino acid side chain within a protein.
Peripheral membrane proteins
Noncovalently attached, either to:
integral membrane proteins that project out from the membrane.
the polar head groups of phospholipids.

May modify the activity of transmembrane proteins.
Membranes are Semifluid
Individual molecules remain in close association yet move within the membrane.

Semifluid- most lipids rotate freely around their long axes and move laterally within their membrane leaflet.

"Flipflop" of lipids from one leaflet to the opposite leaflet does not occur spontaneously.
Flippase requires ATP to transport lipids from one leaflet to another.
High Permeability
Gases
CO2
N2
O2
Ethanol
Very small uncharged polar molecules
Moderate Permeability
Water & Urea
Low Permeability
Polar Organic Molecules such as Glucose
Very Low Permeability
Ions
&
Charged polar molecules and macromolecules (Amino Acids, ATP, Proteins, Polysaccharides, Nucleic Acids (DNA & RNA))
Diffusion
movement of solute from an area of higher concentration to an area of lower concentration
Diffusion is affected by
1. Temperature
2. Size of the molecules involved
3. Mixing Area
Types of Diffusion
1. Passive diffusion
2. Facilitated diffusion
Passive Diffusion
Diffusion of a solute through a membrane without transport protein; solute moves through plasma membrane.
Facilitated diffusion
Diffusion of a solute through a membrane with the aid of a transport protein (channel or transporter).
Types of Transport
1. Passive Transport
2. Active Transport
Passive Transport
no energy is needed to transport molecules across the membrane; they go from high to low concentration
Active Transport
energy is needed to move molecules across the cell membrane; moving against the gradient
Channels
____ in the membrane control the movement of ions across the membrane. Some are passive while others are active.
Integral Membrane Proteins
1. Transmembrane proteins
2. Lipid anchored proteins
Transmembrane Proteins
1. One or more regions that are physically embedded in the hydrophobic region of the phospholipid bilayer.
2. Many function in transport.
Lipid anchored proteins
Covalent attachment of a lipid to an amino acid side chain within a protein.
Proteins bound to membranes are:
1. Integral membrane proteins
2. Peripheral membrane proteins
Peripheral membrane proteins
Noncovalently attached, either to:
1. integral membrane proteins that project out from the membrane.
2. the polar head groups of phospholipids.

May modify the activity of transmembrane proteins.
NA/K Pump
1. Pumps 3 Na+ out and 2 K+ ions in
2. Takes ATP
Ion Channel
Protein channel in a cell membrane that allows passage of a specific ion down its concentration gradient.
Which of the following statements best describes the chemical composition of biomembranes?

A) Biomembranes are bilayers of proteins with associated lipids and carbohydrates.
B) Biomembranes are composed of two layers--one layer of phospholipids and one layer of proteins.
C) Biomembranes are bilayers of phospholipids with associated proteins and carbohydrates.
D) Biomembranes are composed of equal numbers of phospholipids, proteins and carbohydrates.
E) Biomembranes are composed of lipids with proteins attached to the outer surface.
C) Biomembranes are bilayers of phospholipids with associated proteins and carbohydrates.
Carbohydrates of the plasma membrane

A) are associated with a protein or lipid
B) are located on the outer surface of the plasma membrane
C) can function as cell markers for recognition by other cells.
D) All of the above
E) A and C only
D) All of the above
A transmembrane protein in the plasma membrane is glycosylated at two sites in the polypeptide sequence. One site is Asn--Val--Ser and the other site is Asn--Gly--Thr. Where in this protein would you expect these two sites to be found?

A) in transmembrane segments
B) in hydrophilic regions that project into the extracellular environment
C) in hydrophilic regions that project into the cytosol
D) could be anywhere
E) B and C only
B) in hydrophilic regions that project into the extracellular environment
The tendency for Na+ to move into the cell could be due to

A) the higher numbers of Na+ outside the cell, resulting in a chemical concentration gradient.
B) The net negative charge inside the cell attracting the positively charged Na+.
C) the attractive force of K+ inside the cell pulling Na+ into the cell.
D) All of the above
E) A and B only
E) A and B only
What structural features of a membrane are major contributors to its selective permeability?

A) phospholipid bilayer
B) transport proteins
C) glycolipids on the outer surface of the membrane
D) peripheral membrane proteins on the inside of the membrane.
E) both a and b
E) both a and b
What is the name given to the process in which solutes are moved across a membrane against their concentration gradient?

A) diffusion
B) facilitated diffusion
C) osmosis
D) passive diffusion
E) active transport
E) active transport
Large particles or large volumes of fluid can be brought into the cell by

A) facilitated diffusion
B) active transport
C) endocytosis
D) exocytosis
E) all of the above
C) endocytosis
Which one of the following biological macromolecules is least likely to be a component of a biomembrane?

A) Lipids
B) Carbohydrates
C) Proteins
D) Nucleic acids
E) All of these macromolecules are common components of biomembranes.
D) Nucleic acids
A solute crossing a biomembrane from a region of high concentration to a region of low concentration without the aid of a transport protein is most accurately referred to as:
A) selective permeability.
B) active transport.
C) passive diffusion.
D) facilitated diffusion.
E) fluidity.
C) passive diffusion.
True or False: Due to its structure, cholesterol adds to the fluidity of biological membranes.
A) True
B) False
A) True
Which of the following is not a type of transport protein?
A) Transporters
B) Channels
C) Antiporters
D) Symporters
E) All of the choices are forms of membrane transport proteins.
E) All of the choices are forms of membrane transport proteins.
A beaker of water is divided into two compartments, A and B, by an artificial lipid bilayer. The concentration of Na+ in compartment A is 1.0 M, while the concentration of Na+ in compartment B is 1.5 M. With regards to Na+ concentration, compartment A would be referred to as __________, while compartment B would be referred to as __________.
A) isotonic; hypertonic
B) hypertonic; hypotonic
C) hypotonic; isotonic
D) hypotonic; hypertonic
E) hypertonic; isotonic
D) hypotonic; hypertonic
Which one of the following statements about Na+/K+-ATPase pumps is incorrect?
A) Na+/K+-ATPase pumps are an example of an electrogenic pump.
B) A typical animal cell utilizes thousands of Na+/K+-ATPase pumps to maintain ATPase gradients across the cell membranes.
C) The Na+/K+-ATPase pump results in 2 K+ being released into the cytosol and 3 Na+ being released into the extracellular space.
D) A Na+/K+-ATPase pumps alternates between two different conformations known as E1 and E2.
E) Some animal cell types, like neurons, utilize a majority of their ATP to operate pumps like the Na+/K+-ATPase pump.
B) A typical animal cell utilizes thousands of Na+/K+-ATPase pumps to maintain ATPase gradients across the cell membranes.

Refer to pages 114 and 115.
Vesicles destined for exocytosis are typically derived from
A) mitochondria.
B) smooth endoplasmic reticulum.
C) lysosomes.
D) the Golgi apparatus.
E) vacuoles.
D) the Golgi apparatus.

Refer to pages 115 and 116.
Which one of the following statements about endocytosis is incorrect?
A) Endocytic vesicles can be formed when a receptor molecule binds a specific cargo molecule.
B) All cell types are capable of phagocytosis, a form of endocytosis.
C) Internalization of extracellular fluid is a form of endocytosis.
D) Endocytosis is an invagination of the plasma membrane.
E) All of these statements about endocytosis are correct.
B) All cell types are capable of phagocytosis, a form of endocytosis.
A solute crossing a biomembrane from a region of low concentration to a region of high concentration with the aid of a transport protein and energy is most accurately referred to as
A) selective permeability.
B) active transport.
C) passive diffusion.
D) facilitated diffusion.
E) fluidity.
B) active transport.
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