Intro to Cell Chapter 6

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Assuming that all had the same number of carbon atoms, which of the following types of molecules would have the most C-H bonds?

A Saturated fat

Triglycerides contain glycerol and ____

Fatty acid

Which of the following are soluble in water?
Terpenes
Prostaglandins
Steroids
ALL of these
NONE of these

NONE of these

Phospholipids always orient so their tails face.

Away from water

Nonpolar molecules tend to aggregate in water because they are forced to come into close proximity with each other due to

Hydrophobic interactions

The lipid layer tht forms the foundation of cell membranes is primarily composed of molecules called _____________________.

phospholipids

The plasma membrane is a thin sheet of lipid embedded with

proteins

Membrane proteins are not very soluble in water, because they possess long stretches of non-polar amino acids that

Hydrophobic

The hydrophobic tails are non-polar or polar?

The tails are non-polar!

On the outer surface of the plasma membrane there are marker molecules that identify the cell-type. Often these molecules are

Carbohydrate chains

The part of a membrane protein that extends through the phospholipid bilayer is primarily composed of amino acids that are

Non-polar

Which of the following protein classes are not found as membrane proteins?
Enzymes
Transport Proteins
Hormones
Identity Markers
Receptors

Hormones

Functions of the plasma membrane?

Selective transport of certain molecules and material, transport of water and bulk material, reception of information, expression of cellular identity.

Cholesterol functions in the plasma membrane to...

Maintain fluidity

A phospholipid molecule has a polar and a nonpolar end. Because of this, water molecules form

hydrogen bonds with the polar end of the phospholipid molecule.

The fluid mosaic model proposed by Singer and Nicolson in 1972 included that....

The cell membrane was composed of a phosopholipid bilayer with globular proteins actually inserted into the bilayer

Which of the following is not a component of an animal cell membrane?
Aquaporins
Polynucleotides
Glycolipids
Phospholipids
Cholesterol

Polynucleotides

If you were to replace the phosphate group of a phospholipid with a fatty acid chain, you would have

a triglyceride

If you mechanically shook a mixture of amphipathic lipids and water, what would you expect to see when you observe the solution using an electron microscope?

The lipids will have formed tiny vesicles filled with water

Which of these is NOT a lipid?
RNA
cholesterol
wax
phospholipid
steroids

RNA

Example of an unsaturated fat:

Olive oil. usually things that are liquid at room temp.

A function of cholesterol that does not harm health is its role _____.

as a component of animal cell membranes

Which statement most accurately describes how the structures of fats, steroids, and phospholipids compare?

Fats and phospholipids contain glycerol, steroids do not.

The plasma membranes of all known cells are largely composed of what class of macromolecules?

lipids

What most distinguishes lipids from other biomolecules is _____.

Their chemical properties

Steroids such as cholesterol are an important component of animal cell membranes but do not actually form the membrane. Why?

Lipids that form membranes are amphipathic with a polar region and a nonpolar region

What do phospholipids and triglycerides have in common?

They both have a glycerol backbone.

What type of functional group results when the alcohol group on glycerol reacts with the carboxylic acid group on a fatty acid?

Ester

Steroid hormones are large communication molecules thar are modified cholesterol molecules. How do they enter a cell?

Their lipid nature probably allowsthem to diffuse through the plasma membrane.

You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids. After testing the permeability of this membrane to glucose, you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to the membrane's permeability to glucose?

Permeability to glucose will increase

Which of the following crosses lipid bilayers the slowest?
A small, nonpolar molecule like O2
A small, polar molecule like water
A sodium ion
A large, polar molecule like glucose

A sodium ion

Which of the following crosses the lipid bilayer the fastest?
A small, nonpolar molecule like O2
A small, polar molecule like water
A sodium ion
A large, polar molecule like glucose

A small, nonpolar molecule like O2

________ is the net movement of substances to regions of lower concentration.

Diffusion

Both active transport and facilitated transport utilize specific ______________ proteins embedded in the cell membrane.

Carrier

Osmosis occurs as water can cross the lipid bilayer through ________________, specialized channels for water movement.

Aquaporins

The plasma membrane is a thin sheet of lipid embedded with

proteins

Membrane proteins are not very soluble in water, because they possess long stretches of non-polar amino acids that

are hydrophobic

A type of transport of a solute across a membrane, up its concentration gradient, using protein carriers driven by the expenditure of chemical energy is known as

active transport

The cell's transactions with the environment mediated by its plasma membrane include all of the following except

directing the synthesis of various food-digesting proteins

The actual transport of protons by the proton pump is mediated by a transmembrane protein which undergoes a change in its

conformation

Carrier-mediated transport is also called

facilitated diffusion

The type of diffusion that is specific and passive, and which becomes saturated if all of the protein carriers are in use is

facilitated diffusion

In a single sodium-potassium pump cycle, ATP is used up with the result that

3 sodium ions leave and 2 potassium ions enter.

The accumulation of amino acids and sugars in animal cells occurs through

secondry active transport (aka coupled transport)

During neuronal signaling, a change in membrane potential will cause sodium channels to open and let Na+ ions diffuse down their concentration gradient into the cell. Which of the following helps establish the concentration gradient necessary for this process to occur?

Na+/K+ pump

Which of the following factors does not affect membrane permeability?
-The saturation of hydrocarbon tails in membrane phospholipids
-
-Temperature
-The amount of cholesterol in the membrane

The polarity of membrane phospholipids

How can a lipid be distinguished from a sugar?

Lipids are mostly nonpolar.

True or false? Osmosis is a type of diffusion.

true

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

Amphipathic nature

Which of the following particles could diffuse easily through a cell membrane?
Oxygen
Hydrogen Ion
Sodium Ion
Glucose

Oxygen

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

True

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?

Hypotonic

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis

You know that a cell is in a(n) _____ solution when it _____.

hypertonic solution ... loses water

Which of the following molecules can cross the lipid bilayer directly without a transport protein?
Carbon Dioxide
Water
ions
sucrose
oxygen
proteins
lipids

Carbon Dioxide, water, oxygen, and lipids

Channels:

provide a continuous pathway across the membrane and allow water molecules and small ions to flow quickly across the membrane.

Only Carriers:

undergo a change in shape to transport solutes across the membrane, and transport primarily small, polar, organic molecules.

Both carriers and channels:

transport solutes down a concentration gradient, are integral membrane proteins, and provide a hydrophilic path across the membrane

Which statement most accurately describes the relationship between the permeability and fluidity properties of phospholipid bilayers and their structure?

Bilayers are more permeable as well as more fluid when they consist of shorter, unsaturated hydrocarbon tails.

What will happen to a red blood cell (RBC), which has an internal osmotic pressure equal to that of 0.9 % solution, if it is placed into a beaker of pure water?

The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.

Which statement most accurately summarizes a feature of passive transport?

It is a spontaneous process.

Lipid vesicles are formed so that they contain pure water. If these vesicles are transferred to a solution that contains a rather high concentration of solutes, what will be the net direction of water movement?

It will move out of the vesicles.

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