Chapter 6b-f, Cellular Membrane

Question 1

What is the boundary that separates the living cell from its surrounding

Answer 1

The plasma membrane

Question 2

What is special about the plasma membrane?

Answer 2

It exhibits selective permeablility.
Selective permeabilty:allows some substances to cross it more easily than others

Question 3

What is the basic scturcutre of the cell memebrane?

Answer 3

The phospholipid bilayer

Question 4

If poreins and carbohydrates are part of the membrane compostion, making it a what?

Answer 4

Mosaic

Question 5

What force does phospholipid use between the fatty acid tails of one another

Answer 5

van der Waal forces

Question 6

Are membrane lipids able to move in plane of the membrane

Answer 6

Yes, that makes the membrane more fluid and dyamic

Question 7

What is most of the movement found on the lipid/protein layer of the membrane

Answer 7

Lateral movements, but some movements vertically (flip-flop) traversely across the membrane

Question 8

Why are flip-flop movemnets way less frequent if thye cytoplasmic and extracellular sides are polar?

Answer 8

Difficult to cross the hydrophobic inner layer if surroundings is polar, the hydrophillic head must cross the hydrophobic layer which is difficult

Question 9

Which plasma membrane componetn can be either found on its surfrace or embedde in the membrane structure?

Answer 9

Proteins

Question 10

What are the types of membrane proteins? Where are they located?

Answer 10

Peripheral Proteins: bound to the surface of the membrane.
Integral Proteins:penetrate the hydrophobic core.
Transmembrane Protein: Integral proteins that span the membrane.

Question 11

How cna the proteins be anchored in the lipid bilayer

Answer 11

Thep ortein can contain both hydrophillic and hydrophobic amino acids. Which allows the protein to slot it’s self into the membrane, allowing it to anchor its self to both polar and non polar regions of the membrane

Question 12

What are the 6 functions of the membrane proteins

Answer 12

1.Transportation
2.Enzymes
3.Receptors
4.Cell-Cell recognition
5.Intercelluar Joining
6. Attachment Proteins

Question 13

Describe the six functions of membrane proteins

Answer 13

1.Transportation
-Channel and carriers allow substances to move through the plasma membrane
2.Enzymes
-Increases/speeds up the speed of the reaction
3.Receptors
-Able to detect signaling molecule such as a hormone, or a neurotransmitter and binds to signaling molecule and undergoes signal transduction
4.Cell-Cell recognition
-Can invovle proteins and carbohydrates, An example is a chain of carbohydrates used to be detected as a tag. Specific proteins can recognize this “tag” and signal a specific reponse/interaction
5.Intercelluar Joining
-Can hold cell together. Such as tight junctions
6. Attachment Proteins
-hold the cytoskelton to the associated extracellular matrix
-Extracellular matrix is formed by collagen and other proteins. Parts of this matrix can bind to attachment proteins
These attachment proteins then bind to the cytoskeleton on the other side, creating a thrid but firm structure. Cytoplasm is then supported by cytoskeleton and outside with extracellular matrix.

Question 14

What are the functons of carbohydrates in the cell membrane

Answer 14

Bonding covalently to proteins or lipids to form (Glyoproteins and Glyolipids)
Located on the exteral side of the plasma membrane and varies in size amoug species,individuals and even cell types in a indvidual
Carbohydrates plays an imporant role in cell-cell recognition
Cells recognize each other by binding to the surface molecules, often carbohydrate, on the plasma membrane.

Question 15

What is permeability refer to?

Answer 15

To the rate of passive diffusion of molecules across the membrane

Question 16

What is the fluditiy of the cell?

Answer 16

Fluidity refers to the ability to move molecules in the membrane, and the viscosity of the cell membrane.

Question 17

How can the fluidity and permeabiltiy of the plasma membrane change?

Answer 17

It can change depending on its compostion and the enviorment.
Can be affected by the diffusion of proteins and other molecules inside cells, thus affecting their function.
This property can be affected by phospholipid strucutre,cholesterol compostion in the membrane and the tempature
Membrane fluidity can affect membrane permeability

Question 18

What plays a huge impact on membrane permeability

Answer 18

Transport proteins associated with the membrane

Question 19

What is the function of cholesterol in animal cell membranes

Answer 19

At warm temperatures, cholesterol decreases membrane fluidity by restraining the movement of phospholipids.
At cool temperatures, cholesterol increases membrane fluidity by preventing phospholipids from packing tightly
Acts as “buffer”

Question 20

What is the polarity of Cholesterol

Answer 20

Cholesterol is amphipathic: has a hydrophillic hydroxyl group and a hydrophobic region of interconnected carbon rings

Question 21

How do fatty acids effect membrane fluidity?

Answer 21

Fatty acids vary in length of hydrocarbon chains as well as in the number and location of double bonds

Question 22

Which membrane is more fluid? One with short or long fatty acid chains and why?

Answer 22

Short fatty acids create less thick plasma membrane than longer fatty acids chains. They also have less van der Waal forces between the hydrophobic tails.

Question 23

Which membrane is more fluid? One with saturated or unsaturated fatty acid chains and why?

Answer 23

Unsatured fatty acids chain are more fluid due to more space betwen the chains, less dense overall and thus becomes more fluid

Question 24

What has a direct impact on membrane permeabiltiy?

Answer 24

Transport proteins have a direct impact on membrane permeability because they facilitate the diffusion of hydrophilic substances and large molecules

Question 25

What is diffusion?

Answer 25

Diffusuion is the tendency for molecules to spread out evenly to the available space.

Question 26

How does diffusion work?

Answer 26

It is the diffusion of the population of molecules that may exhibit a net movement in one direction. Movement is from higher to lower concentration / along the concentration gradient It is a dynamic equilbrium, many molecules cross both ways. Overall is no movement

Question 27

What substances would easily pass though the lipid bilayer of the plasma membrane?

Answer 27

Hydrophobic/non polar and small molecules like O2 and CH4 Big molecules with hydrophillic functional groups or Ions will not travel through like Sucrose or Salts Water does not count, it does passively diffuse into the cell, but not at a rate that is needed. Uses proteins to move the water

Question 28

What are the types of diffusion?

Answer 28

Simple diffusion:no transport protein is invovled, Small hydrophobic molecules usually cross the membrane through passive diffusion. Ex: O2,CO2,CH4 Facilitated diffusion:transport proteins speed and/or allows the movement of molecules across the membrane. Ex:Glucose

Question 29

What are transport proteins and what are the two kinds?

Answer 29

Channel proteins have hydrophilic channels that certain molecules or ions can use as a tunnel. Carrier proteins bind to the molecules and changes the shape to shuttle them across the mumbrane. Transport proteins are proteins that help faciliate transport across the membrane when there are natural restrictions.

Question 30

What is passive transport? What are the three examples?

Answer 30

Passive transport is defined as the movement of molecules across a selectively permeable membrane without the use of energy. Includes simple diffusion, facilitated diffusion and osmosis. Simple diffusion and facilitated diffusion refer to the movement of solutes. Solutes diffuse down (or with or along) their concentration gradient (so substances move from an area of high concentration to an area of low concentration).

Question 31

What is osmosis?

Answer 31

Osmosis is the diffusion of water across a selectively permeable membrane. Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration.

Question 31

How is water moved through the membrane?

Answer 31

Moves across the membrane slowly. Use Aquaporins (channels) in the membrane. (small pores or openings for water molecule)

Question 32

What is tonicity?

Answer 32

The ability of a solution to cause a cell to gain or lose water comparatively.

Question 33

What are the three tonics?

Answer 33

Isotonic: solutions have equal solute concentration comparatively Hypertonic: solutions have higher solute concentration comparatively Hypotonic: solutions have lower solute concentration comparatively

Question 34

What happens with a cell without a cell wall when placed in an isotonic, hypotonic and hypertonic solution in relation to the cell's intracellular environment?

Answer 34

Isotonic: No net water movement across the plasma membrane (cell remains the same) Hypotonic: Cell gain water (cell lyses/grows until bursts) Hypertonic: Cell loses water (shirvels/crenates)

Question 34

How do cell waters maintain water balance?

Answer 34

A plant cell in a hypotonic solution swells until the wall opposes uptake: the cell is now turgid(firm) If the cell and its surroundings are isotonic, there is no net movement of the water in the cell; the cell becomes flaccid and limp In a hypertonic environment, plant cells lose water; eventually, the membrane pulls away from the wall, a usually lethal effect called plasmolysis

Question 35

What is active transport?

Answer 35

Active transport moves substances against their concentration gradient This requires energy, usually in the form of ATP Active transport is performed by specific carrier proteins embedded in the membrane Active transport allows cells to maintain concentration gradients that differ from their surroundings.

Question 36

What is secondary active transport?

Answer 36

Active transporters can drive the transport of molecules through a different transporter through the creation of an electrochemical gradient

Question 36

What is an electrochemical gradient and how can it be achieved

Answer 36

ECG is the gradient of charge and concentration of compounds between the inside and outside of the cell. Formed from chemical carriers Can be achieved with the help of carriers and ATP, creating a charge disparity between the outside and inside of the cell.