Ch. 7 Membrane Structure and Function Dynamic

Where are membrane proteins and lipids synthesized and modified?

-in the ER -in the Er and Golgi apparatus - the inside and outside faces of membranes differ in molecular composition

amphipathic molecule

-phospholipid is an example -it has both a hydrophilic region and a hydrophobic region -most membrane lipids are this

Active transport

-uses energy, usually ATP, to move solutes against their gradients - an example = sodium- potassium pump

Which of the following plant cells would exhibit the most turgor pressure?

A cell placed in a hypotonic solution

Which of the following substances would be most likely to pass through the plasma membrane without the help of a transport protein?

A nonpolar molecule, such as a hydrocarbon

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process?

Endocytosis

Which of these statements describes some aspect of facilitated diffusion?

Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?

Membrane carbohydrates function primarily in cell-cell recognition.

Which of the following molecules are most abundant in the plasma membrane?

Phospholipids A phospholipid is an amphipathic molecule, meaning that it has both a hydrophilic region and a hydrophobic region.

plasma membrane

The boundary that separates a living cell from its surroundings and controls traffic into and out of the cell it surrounds.

Red blood cells contain approximately a 2% concentration of solutes. A red blood cell is placed into a solution that contains a 4% concentration of solutes to which the cell is not permeable. What will happen to the red blood cell?

The cell will decrease in size as water flows out of it.

Diffusion

The spontaneous movement of a substance down its concentration gradient

Which of the following is correct regarding integral proteins?

These proteins exhibit both hydrophilic and hydrophobic properties. Peripheral proteins are found on the surface of the plasma membrane. Integral proteins exhibit both hydrophilic and hydrophobic properties. Integral proteins carry out a variety of functions in the plasma membrane.

selective permeability

When a plasma membrane allows some substances to cross it more easily than others.

osmoregulation

adaptations in cell walls of cells that lack them

Why is energy required for active transport?

because it moves solutes against their concentration gradient

how does bulk transport across the plasma membrane occur?

by exocytosis and endocytosis

In facilitated diffusion, __________ proteins provide openings in the plasma membrane for substances to flow through without changing structure, and __________ proteins allow passage of substances through the plasma membrane after undergoing a subtle change in shape.

channel, carrier

What are the two gradients that ions can have?

concentration (chemical) and electrical (voltage)

isotonic

equal solute concentration on the inside and outside of membrane and solution...therefore no osmosis occurs

Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane?

exocytosis and smooth and rough ER

ion channels

faciliate the diffusion of ions across the membrane, here carrier proteins can undergo changes in shape

what is a membrane held together by mostly?

hydrophobic interactions, which are much weaker than covalent bonds

integral proteins are embedded where?

in the lipid bilayer

what are the two staple ingredients of membranes?

lipids and protiens

All cells have voltages across their membranes. This voltage is called a(n) __________ and is often maintained by __________.

membrane potential, elecrogenetic bumps

what happens in endocytosis?

molecules enter cells within vesicles that pinch inward from the plasma membrane

what are the three types of endocytosis?

phagocytosis, pinocytosis, receptor-mediated endocytosis

Which of the following cell structures exhibits selective permeability between a cell and its external environment?

plasma membrane

what do polar molecules and ions require to cross the membrane that hydrophobic substances don't require?

specific transport proteins

What does selective permeability of the plasma membrane control?

the exchange of molecules and ions with its surroundings

fluid mosaic model

the membrane is a mosaic of protein molecules bobbing in fluid bilayer of phospholipids

peripheral proteins are attached where?

the membrane surface

what does the electrochemical gradient determine?

the net direction of ionic diffusion

role of phospholipids in the structure and function of biological membranes?

they form selectively permeable structure

what do electrogenic and protein pumps do?

transport proteins that cotribute to electro chemical gradients

what happens in exocytosis?

transport vesicles migrate to the plasma membrane, fuse with it, and release their contents

what are the functions of membrane proteins?

transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix

cotransport of tow molecules occurs?

when a membrane protein enable the down hill diffusion of one solute to drive the uphill transport of the other

hypertonic

when the solution outside of a permeable membrane has a higher solute concentration than the cytosol

hypotonic

when the solution outside the permeable membrane has a lower solute concentration

osmosis

when water diffuses out through the permeable membrane of a cell

passive transport/ facilitated diffusion

where a transport protein speeds the movement of water or a solute across a membrane down its concentration gradient