Bio I - 6

Question 1

What is the plasma membrane?

Answer 1

It is a boundary that separates the living cell from its surroundings

Question 2

What is selective Permeability?

Answer 2

It means that the plasma membrane allows some substances to cross it more easily than others

Question 3

What is the most abundant lipid in the plasma membrane?

Answer 3

Phospholipids

Question 4

What does ampithetic molecule mean?

Answer 4

It contains hydrophobic and hydrophilic regions

Question 5

What does the fluid mosaic model state?

Answer 5

That a membrane is a fluid structure with a mosaic of various proteins embedded in it

Question 6

What are membranes made of?

Answer 6

Proteins and lipids

Question 7

What is a freeze fracture study?

Answer 7

Freeze fracture is a specialized preparation technique that splits a membrane along the middle of the phospholipid bilayer

Question 8

What did the phrase fracture study support?

Answer 8

The fluid mosaic model

Question 9

True or false
Phospholipids in the plasma membrane can move within the bilayer. 

Answer 9

True

Question 10

How do the lipids and proteins move in the bilayer?

Answer 10

They drift laterally

Question 11

Does a molecule ever flip flop transversely across the membrane?

Answer 11

Rarely

Question 12

What happens to the membrane when temperatures cool?

Answer 12

Membranes switch from a fluid state to a solid state

Question 13

At What temperature does the membrane solidify?

Answer 13

It depends on the type of lipid

Question 14

Are membranes rich and unsaturated fatty acids are _______ than those rich in saturated fatty acids. 

Answer 14

More fluid

Question 15

True or false
Membranes must be more solid to work properly.

Answer 15

False. They must be more fluid

Question 16

What is cholesterol?

Answer 16

It is a steroid

Question 17

How does cholesterol affect the membrane?

Answer 17

At warm temperatures cholesterol restrains movement of phospholipids. At cool temperatures it maintains fluidity by preventing tight packing.

Question 18

What do proteins determine?

Answer 18

Most of the membrane specific functions

Question 19

What is a membrane composed of?

Answer 19

It is a collage of different proteins embedded in the fluid matrix of the lipid bilayer

Question 20

What are peripheral proteins?

Answer 20

They are proteins that are bound to the surface of the membrane

Question 21

What are integral proteins?

Answer 21

They are proteins that penetrate the hydrophobic core

Question 22

What are integral proteins called that span the membrane?

Answer 22

Transmembrane proteins

Question 23

The Hydrophobic regions of an integral proteins consist of one or more stretches of _________ often coiled into __________

Answer 23

Non polar amino acids
Alpha helices

Question 24

What are the six major functions of membrane proteins?

Answer 24

Transport
Enzymatic activity
Signal transduction
Cell cell recognition
Intercellular joining
Attachment to the cytoskeleton an extra cellular matrix

Question 25

When is the asymmetrical distribution of proteins lipids and associated carbohydrates in the plasma membrane determined?

Answer 25

When the membrane is built by the ER and Golgi apparatus

Question 26

True or false. Hydrophobic nonpolar molecules such as hydrocarbons can dissolve in the lipid bilayer and pass through the membrane rapidly

Answer 26

True

Question 27

Do polar molecules cross the membrane easily?

Answer 27

No

Question 28

What do transport proteins do?

Answer 28

They allow for passage of hydrophilic substances across the membrane

Question 29

What are channel proteins?

Answer 29

They are a type of transport proteins that have a hydrophilic channel that certain molecules or ions can use as a tunnel

Question 30

What are aquaporins?

Answer 30

They are channel proteins that facilitate the passage of water

Question 31

What are carrier proteins?

Answer 31

They are transport proteins that bind to molecules and change the shape to shuttle them across the membrane

Question 32

What is a passive transport?

Answer 32

It is the movement of ions and other atomic or molecular substances across cell membranes without need of energy input

Question 33

What is active transport?

Answer 33

It is the movement of ions or molecules across the cell membrane into a region of higher concentration assisted by enzymes and requiring energy

Question 34

What is diffusion?

Answer 34

Diffusion is the tendency for molecules to spread out evenly into the available space

Question 35

What is dynamic equilibrium?

Answer 35

At dynamic equilibrium as many molecules cross one-way as cross in the other direction

Question 36

Diffusion follows the natural concentration gradient. What is the natural concentration gradient?

Answer 36

When a molecule moves from higher concentration to lower concentration of molecules

Question 37

Does diffusion require input of energy And a carrier protein?

Answer 37

No

Question 38

What is osmosis?

Answer 38

Osmosis is the diffusion of water across a selectively permeable membrane

Question 39

Water diffuses across a membrane from the region of _____ to the region of _____

Answer 39

Lower solute concentration Higher solute concentration

Question 40

What is tonicity?

Answer 40

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

Question 41

What is a isotonic solution?

Answer 41

The solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

Question 42

What is a hypertonic solution?

Answer 42

When the solute concentration is greater than the inside of the cell and therefore the cell loses water

Question 43

What is a hypotonic solution?

Answer 43

The solute concentration is less than that inside the cell and therefore the cell gains water

Question 44

What happens when a plant cell is in a hypotonic solution?

Answer 44

It swells until the wall opposes uptake; the cell is now turgid/ firm

Question 45

What happens to a plant cell and an isotonic state?

Answer 45

There is no net movement of water into the cell; the cell becomes flaccid/ limp and the plant may wilt

Question 46

What is facilitated diffusion?

Answer 46

It is when transport proteins speed the passive movement of molecules across the plasma membrane

Question 47

What do channel proteins include?

Answer 47

Aqua Porins, for facilitated diffusion of water Ion channels that open or close in response to a stimuli/gated channels

Question 48

What to channel proteins provide?

Answer 48

They provide corridors that allow a specific molecules or ions across the membrane

Question 49

What is active transport?

Answer 49

Active transport moves substances against their concentration gradient

Question 50

Does active transport require energy?

Answer 50

Yes The energy is usually in the form of ATP

Question 51

What is active transport performed by?

Answer 51

The specific proteins embedded in the membranes

Question 52

What does active transport allow cells to do?

Answer 52

It allows cells to maintain concentration gradients that differ from their surroundings

Question 53

What is one type of active transport system?

Answer 53

The sodium potassium pump

Question 54

What is bulk transport?

Answer 54

It Is the transport of larger molecules across the membrane

Question 55

What does the bulk transport process require?

Answer 55

It is an active transport process that requires input of energy and a carrier protein

Question 56

What are two bulk transport systems?

Answer 56

Exocytosis and endocytosis

Question 57

What is exocytosis?

Answer 57

It is when transport vesicles migrate to the membrane, fused with it, and release their contents

Question 58

What type of cells use exocytosis to export their products?

Answer 58

Secretory cells

Question 59

What is endocytosis?

Answer 59

The cell takes in macromolecules by forming vesicles from the plasma membrane

Question 60

What are the three types of endocytosis?

Answer 60

Phagocytosis – larger molecules (cellular eating), pinocytosis – smaller molecules (cellular drinking) Receptor mediated endocytosis