ch 7-Membrane Structure and Function

The movement of molecules from an area of higher concentration to an area of lower concentration is callled __________ A)diffusion B)endocytosis C)phagocytosis D)active transport e)osmosis

A)diffusion

who is play key roles in regulating transport in membrane ?

Proteins built into the membrane

Hydrophilic molecules including ions and polar molecules do not cross the membrane________

easily

amphipathic lipids

polar ends and non-polar tails

The main electrogenic pump of plants, fungi, and bacteria is a ________

proton pump

How molecules move

randomly and in straight lines until bump into something else

fluidity of membranes

-phospholipids can move within bilayer -mostly lipids and proteins move laterally -rarely they flip across membrane

what the two combined forces, collectively called the electrochemical gradient?

1-A chemical force 2-An electrical force

Carbohydrates on the extracellular side of the plasma membrane vary among species? 1-TRUE 2-FALSE

1-TRUE

Membranes must be solid to work properly 1-false 2-true

1-false

Two functions of a cell membrane:

1. separation from environment 2. selective permeability

sugars can permeability \cross the membrane 1-true 2-false

2-false

Proteins determine most of the membrane's functions 1-false 2-true

2-true

transport proteins

A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.

Permeability

Ability of rock or soil to allow water to flow through it

Phospholipid molecules in a membrane are arranged with their ___ on the exterior and their ___ on the interior. A)Hydrophobic heads...hydrophilic tails B)Hydrophilic tails....Hydrophobic heads C)Nonpolar heads...Polar tails D)hydrophobic tails ....hydrophilic head

B)Hydrophilic tails....Hydrophobic heads

Which of the following types of molecules are the major structural components of the cell membrane? A) phospholipids and cellulose B) nucleic acids and proteins C) phospholipids and proteins D) proteins and cellulose E) glycoproteins and cholesterol

C) phospholipids and proteins

The Role of Membrane Carbohydrates in Cell-Cell Recognition

Cells recognize each other by binding to molecules, often containing carbohydrates, on the extracellular surface of the plasma membrane

which pumps help store energy that can be used for cellular work?

Electrogenic

Active transport

Energy-requiring process that moves material across a cell membrane against a concentration difference

How can dissolve in lipid and pass through the membrane? 1-Hydrophobic (nonpolar) molecules 2-Hydrophilic molecules

Hydrophobic (nonpolar) molecules

which channel protein that open or close in response a stimulus (gated channels)

Ion channels

facilitated diffusion

Movement of specific molecules across cell membranes through protein channels

Hypertonic

Solute concentration is greater than that inside the cell; cell loses water

Hypotonic

Solute concentration is less than that inside the cell; cell gains water

electrochemical gradient,

The combination of forces that acts on membrane potential.

fluid mosaic model

The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids.

The sodium-potassium pump is one type of (active\passive) transport system

active

The sodium-potassium pump is the major electrogenic pump of _______

animal cells

Channel proteins called _______ greatly facilitate the passage of water molecules

aquaporins

peripheral proteins

bound to the surface of the membrane

Voltage is created

by differences in the distribution of positive and negative ions across a membrane

3. The concentration of calcium in a cell is 0.3%. The concentration of calcium in the surrounding fluid is 0.1%. How could the cell? A)passive transport B)diffusion C)active transport D)osmosis E)any of the above

c)active transport

transport proteins, called _________, bind to molecules and change shape to shuttle them across the membrane

carrier proteins,

Plasma membranes are selectively permeable, regulating the ________

cell's molecular traffic

As temperatures cool, membranes switch from a ____ state to a ____ state

fluid,splid

Membrane carbohydrates may be covalently bonded to lipids

glycolipids

Membrane carbohydrates may be covalently bonded to proteins

glycoproteins

cholesterol in cell membrane

helps stabilize the membrane fluidity

Osmosis

lower solute concentration to the region of higher solute concentration

Cotransport

occurs when active transport of a solute indirectly drives transport of other substances

integral proteins

penetrate the hydrophobic interior of the lipid bilayer

How controlled exchange materials in the cell

plasma membrane

freeze fracture

splits a membrane along the middle of the phospholipid bilayer. When a freeze-fracture preparation is viewed with an electron microscope, protein particles are interspersed in a smooth matrix, supporting the fluid mosaic model.

Tonicity

the ability of a solution to cause a cell to gain or lose water

Osmoregulation

the control of solute concentrations and water balance

Membrane potential

the voltage difference across a membrane

Integral proteins that span the membrane are called________

transmembrane proteins

where specific some diseases are caused by malfunctions ?

transport systems

Membranes rich in ________fatty acids are more fluid than those rich in _______fatty acids

unsaturated ,saturated

How HIV enters the cell?

via Receptor CD4 and CCR5