Chapter 5

Question 1

Describe what is meant by the “fluid mosaic” model of the cell membrane.

Answer 1

The plasma membrane is a mosaic of components. These components give the membrane its fluid character

Question 2

What are the four main components of a plasma membrane?

Answer 2

Phospholipids cholesterol proteins and carbohydrates

Question 3

Amphiphilic

Answer 3

molecule has parts that are hydrophobic and parts that are hydrophilic integral proteins are integrated into the membrane structure

Question 4

selective permeability

Answer 4

certain substances are able to pass into or out of the cell while other ones are not

Question 5

concentration gradient

Answer 5

things move from an area of a high concentration to areas of a lower concentration of the same substance

Question 6

diffusion

Answer 6

passive random movement of a substance from an area of higher concentration to an area of lower concentration

Question 7

osmosis

Answer 7

the diffusion of water across the semi permeable membrane

Question 8

equilibrium

Answer 8

reached after the concentration gradient lessons over a period of time until the concentration is equal on both sides

Question 9

Aquaporins

Answer 9

special channel proteins that allow water to pass through the membrane at a very high rate

Question 10

Tonicity

Answer 10

the ability of an extracellular solution to influence the osmosis and therefore the volume of a cell

Question 11

Electrochemical gradient

Answer 11

a difference of electrical charge across the plasma membrane will also influence the diffusion of molecules

Question 12

Endocytosis

Answer 12

a type of active transport that moves large substances into a cell

Question 13

Exocytosis

Answer 13

the active process of moving large substances out of a cell

Question 14

Which molecular structures on the phospholipid are responsible for giving it the hydrophobic and hydrophilic nature.

Answer 14

The head is hydrophilic and the tail is hydrophobic

Question 15

Is the membrane-spanning region of an integral protein hydrophobic or hydrophilic?

Answer 15

It is hydrophobic because it is interacting with the hydrophobic region of the phospholipid bilayer

Question 16

How do peripheral proteins differ from integral proteins?

Answer 16

Peripheral proteins are only found on the surface of the membrane either internally or externally whereas integral proteins span across the entire surface throughout

Question 17

Describe the conditions under which carbohydrates are associated with the plasma membrane.

Answer 17

Carbohydrates are only present on the exterior surface where they can attach to proteins to form glycoproteins or carbohydrates can attach to lipids to form glycolipids

Question 18

What is the glycocalyx and why is it important to cells?

Answer 18

The glycocalyx includes glycoproteins and glycolipids it is highly hydrophilic and it helps to bring in substances to where they come into contact with this cell

Question 19

What is the function of the cholesterol found incorporated into the plasma membrane of animal cells?

Answer 19

The cholesterol extends the range of temperatures at which the membrane can maintain a functional fluidity

Question 20

Name several types of molecules that would likely be able to cross the plasma membrane. Name several types of molecules that would likely not.

Answer 20

Lipid soluble and other nonpolar molecules such as fat soluble vitamins, lipid based drugs, fat soluble hormones, oxygen, and carbon dioxide would be able to pass through whereas polar substances such as ions, simple sugars, and amino acids would not be able to

Question 21

What are the three types of transport we discussed in lecture and how are they different? How are they the same?

Answer 21

There is passive transport active transport and bulk transport passive transport does not require the cell to spend any energy active transport requires a cell to use energy often in the form of ATP and bulk transport is used when cells need to take in or remove larger molecules and particles that cannot pass through the membrane

Question 22

Which specific types of transport require energy and which do not?

Answer 22

Diffusion osmosis and facilitated diffusion do not require energy whereas active transport it does require energy

Question 23

Be able to discuss the factors that influence the rate of diffusion for a particular substance.

Answer 23

Some of the factors are the extent of the concentration gradient, the mass of the molecule, temperature, density of the median, solubility, surface area and thickness of the membrane, distance traveled, electrical charge, and pressure/filtration

Question 24

Understand how integral transmembrane proteins function as the two types of transport proteins in facilitated diffusion.

Answer 24

Channel proteins are integral transmembrane proteins which allow passage of a specific material into or out of a cell
Carrier proteins are integral transmembrane proteins that bind to a substance to allow it to pass into or out of a cell

Question 25

Know which parts of a channel protein are hydrophobic and which are hydrophilic and why.

Answer 25

The hydrophilic portion is exposed to the intercellular and extracellular fluids and the hydrophilic portion is the channel

Question 26

Be able to apply the concepts of hypo-, hyper-, and isotonic solutions in terms of which way the water would move across the semi-permeable membrane.

Answer 26

If a cell is in a hypotonic solution it will swell with water moving in, if it is in a hypertonic solution it will shrink with water moving out, and if it is an isotonic solution the water will be moving in and out equally and the cell will not change shape

Question 27

What is the main energy form that active transport uses?

Answer 27

ATP

Question 28

Be familiar with the sodium-potassium pump and how it works.

Answer 28

The sodium potassium pump is an antiporter that uses ATP to move three sodium into the cell and two potassium out of the cell across the cell membrane

Question 29

What is the difference between the uniporter, symporter, and antiporter transport protein pumps?

Answer 29

Uniporter pumps carry one specific ion or molecule, symporter pumps carry two different ions or molecules in the same direction, and antiporter pumps carried 2 different ions or molecules in different directions

Question 30

Given an example, be able to label transport as either primary or secondary active transport.

Answer 30

Primary active transport is solely dependent on ATP, while secondary active transport moves materials across the cell membrane due to the electrochemical gradient and commonly has a molecule that is attached such as hydrogen being transported with glucose

Question 31

How is bulk transport different from other forms of active transport?

Answer 31

Bulk transport is used when cells need to take in or remove larger molecules and particles that cannot pass through the membrane

Question 32

What are the three types of endocytosis we discussed?

Answer 32

Phagocytosis is the taking in of a large particle or cell, pinocytosis is the taking in of a small volume of extracellular fluid, and receptor mediated endocytosis is where receptor proteins in the plasma membrane allow for targeted endocytosis of a single specific type of substance