Cell Membrane And Membrane Transport

Question 1

What are phospholipids?

Answer 1

They are the base make up for cell membranes
They consist of hydrophilic phosphate head and hydrophobic lipid tail.

Question 2

What is the nature of phospholipids in an aqueous environment

Answer 2

The phospholipids form a bilayer where the hydrophilic heads are on the outer side and the hydrophobic tails are on the inside(away from the water and aqueous environment)

Question 3

What is the currently accepted model of the membrane structure and why is it named so?

Answer 3

It is the fluid mosaic model.
This name is given since the membrane isn’t a solid ridgid layer but rather a fluid elastic layer
And the word mosaic is added considering the various components it is comprised of.

Question 4

Describe the fluid mosaic model

Answer 4

There is a double layer of phospholipids (the lipid bilayer)

The lipid bilayer is fluid with many proteins floating in it freely suspended

Proteins, glycolipids, glycoproteins and cholesterol contribute majorly to the properties of a semi permeable membrane

Question 5

What do glycoproteins do in the bilipid layer

Answer 5

They play an important role in cellular recognition and immune response and help protect the cell

Question 6

What do proteins do in the bilipid layer

Answer 6

Proteins form channels and are responsible for the movement of substances and solutes.

Question 7

What do glycolipids do in the bilipid layer

Answer 7

Act as surface receptors and stabilize the memebrane

They also help in the formation of tissues

Question 8

What does cholesterol do in the plasma membrane

Answer 8

It acts as a packing molecule and regulates the fluid structure of the membrane

Question 9

What are substances that pass through the semi permeable easily? How do complex substances pass through?

Answer 9

Substances that pass through easily are water oxygen and carbon dioxide.

More complex substances require proteins for their transport as the bilipid layer might prevent them from entering.

Question 10

How do water molecules pass easily through the plasma membrane even considering the hydrophobic lipid layer?

Answer 10

Water are small molecules and are usually not recognized by the hydrophobic lipids and hence can pass through easily

Question 11

______________ molecules can.move through the membrane by diffusion

Answer 11

Lipid soluble molecules

Question 12

What are carrier proteins in the bilipid layer

Answer 12

They form a passageway for substances to move against their concentration gradient

Question 13

What are transmembrane proteins used for?

Answer 13

To form a passageway for substances that cannot pass through the plasma membrane easily

Question 14

The two major type of transport across the cell membrane?

Answer 14

Passive transport and active transport

Question 15

Give examples of passive transport

Answer 15

Diffusion
Facilitated diffusion
Osmosis

Question 16

Give examples of active transport

Answer 16

pumps and endocytosis

Question 17

What is the main difference between active and passive transport?

Answer 17

Passive transport doesn’t require energy and the substances move with the concentration gradient. (Osmosis water moves with the water concentration gradient)

Active transport required energy as it moves against the concentration gradient.

Question 18

What is a concentration gradient

Answer 18

A gradient or change in values occurs when the two environments (inside and outside of the cell) have different concentrations of a solute.
The solute tries to reach equilibrium (by moving down the concentration gradient) where the difference no longer exists and hence substances are always moving.

Question 19

What is simple diffusion

Answer 19

Molecules move directly through the memebranes without the help or support of proteins and passageways and they move down the concentration gradient

Oxygen and carbon dioxide

Question 20

State an example where we might see simple diffusion in the lungs.

Answer 20

The blood cells in the lungs take in oxygen and diffuse out carbon dioxide.

Question 21

Facilitated diffusion

Answer 21

Diffusion that is assisted by proteins to form a passageway.
This is required as the plasma membrane doesn’t allow for direct movement of these substances.
It is also passive transport and moves down the concentration gradient.

Question 22

Examples of facilitated diffusion/types?

Answer 22

Channel mediated diffusion and carrier mediated diffusion

Question 23

What is channel mediated diffusion

Answer 23

Channel mediated diffusion is when proteins hydrophilic (water loving) passageways for ions to pass through.

Question 24

Carrier mediated diffusion

Answer 24

Protein channels do not remain as a passageway but rather change shape to translocate the substance.

Question 25

Example of carrier mediated diffusion is

Answer 25

Glucose into muscle cells

Question 26

What is osmosis

Answer 26

It is the diffusion of water
It works against the concentration gradient of solutes
But it works down the concentration gradient of water.
Through a semi permeable membrane without the use of ATP

Question 27

How do we determine the direction of translocation of water?

Answer 27

If the environment that a cell is in:

Hypotonic (less concentration of water than cells) the water moves out of the cell.

Isotonic: when the cell and out of cell have same water concentration.

Hypertonic: when there is higher water concentration so water moves into the cells.

Question 28

Example of use of isotonic solutions

Answer 28

It is used as IV water so blood cells do not take effect based on the concentration of water

Question 29

Water uses _____________ protein channels to move through

Answer 29

Aquaporin

Question 30

Water moves from hypotonic to hypertonic. true or false

Answer 30

True

Question 31

What is active transport

Answer 31

Lower concentration of solute to higher concentration

Moves against concentration gradient

It requires ATP

Proteins act as carriers or passages for movement

Question 32

What are sodium potassium pumps

Answer 32

These pumps exchange sodium ions and potassium ions between the membrane.
This requires energy to do so as the ions are pumped to higher concentration areas.
For every 3 sodium ions pumped out, 2 potassium ions are taken in and hence they create an unbalanced charge level.
The change in unbalanced charges creates a gradient for another active transport processes

Question 33

What are the proton pumps

Answer 33

Hydrogen ions are moved out of the cell through the protein.

These ions pair up outside the cell to transport other materials or perform other processes

Question 34

Vesicular transport meaning (cytosis)

Answer 34

The process by which large molecules are moved into the cell.
The molecules go through the plasma membrane and form a membrane around itself taking the structure of a vesicle.
This process requires energy and is active transport.
It is of two types:
Endocytosis and exocytosis.

Question 35

What are the types of endocytosis

Answer 35

-phagocytosis
-pinocytosis
-Receptor mediated cytosis

Question 36

What is receptor mediated cytosis

Answer 36

Engulfing/internalization of particles according to the receptors on the membrane

Question 37

What is endocytosis

Answer 37

Particles are surrounded by the invagination of the cell membrane.
The vesicle buds of the cell membrane and into the cytoplasm
The vesicle is digested by the lysosome.

Question 38

What is exocytosis

Answer 38

The vesicle carrying export materials moves to the perimeter of the cell
The membrane of the vesicle fuses with the plasma membrane
Contents are expelled into the intercellular space.

Question 39

What is pinocytosis

Answer 39

Poni cytosis is a type of endocytosis which is involved in the internalization of liquid materials.

Question 40

What is phagocytosis

Answer 40

It is a type of cytosis that is involved in the internalization of solid particles and substances

Question 41

What are the steps that occur in phagocytosis

Answer 41

Microbe attaches to the phagocyte

Microbe is engulfed or surrounded by the invagination of the memebranes

Engulfed microbe is called a phagosome

Phagosome fuses with a lysosome to make a phagolysosome

The microbe is digested and the insisted particles form a residue

A residue is carried out of the cell through exocytosis.