Deck 5: Cell Membrane Structure and Function

Question 1

Membranes consist of a bilayer of ______________. The five major categories of protein within the bilayer are: ______________, ______________, ______________, ______________, and ______________ proteins.

Answer 1

Enzymes:
These are biological catalyst, which synthesize or break down biological molecules. Enzymes, which are found on the plasma membrane, are attached to membrane surface. For example, several kinases are acts as membrane enzymes.
Receptor proteins:
These are glycoproteins, which respond to specific messenger molecule that are present in bloodstream. When an outside messenger gets attached to these receptor proteins it gets activated and causes response inside the cell. It leads to opening and closing of membrane, or activation and inactivation of enzymes. It also helps in destroying then invading bacteria and viruses. For example, delta and notch proteins are acts as receptor proteins.
Recognition protein:
These are also glycoproteins, which identifies cells as self or non-self. It basically serves as identification tags. Each organism bear different recognition protein on their membranes on the basis of which body recognize self-cells and attack invading cells. For example, major histocompatibility proteins (MHC I and II) are acts as recognition proteins.
Connection proteins:
These proteins link plasma membrane to cell cytoskeleton and helps in maintaining the cell shape. It also forms connection between adjacent cells. For example, connexons are acts as connection proteins.
Transport proteins:
These proteins help in transport of specific material, or molecules across the plasma membrane. It basically regulates the movement of hydrophilic molecules and ions. For example, glucose transporters are acts as transport proteins.

Question 2

The general process by which fluids or particles are transported out of cells is called_____________. Does this process require energy? __________The substances to be expelled are transported within the cell in membraneenclosed sacs called_____________.

Answer 2

To maintain an equilibrium state, living cells have many mechanisms to acquire nutrients from their external environment and to expel out the cell waste.
The nutrient molecules pass through the phospholipid bilayer across the cell membrane or directly in to the cell by various processes, whereas the disposal of waste particles occur by a process called exocytosis.
Exocytosis process utilizes energy. During this mechanism the special membrane-bound sac like structures called vesicles play a role to diffuse out the metabolic waste from the cell.
So, the answer for the first blank is exocytosis the process of particles transport out of cells, Yes is the second answer as the transport of particles require energy, and the vesicles is the third answer that are membrane enclosed sacs.

Question 3

Animal cells are surrounded by__________ fluid. This fluid is_________ to the cytosol.

A) phospholipid; isotonic
B) plasma; hypertonic
C) interstitial; isotonic
D) interstitial; hypotonic

Answer 3

Cell is a small biological unit of all living things with a cell membrane enclosing its contents, and genetic material.
Phospholipids are the amphipathic lipid molecules acting as building blocks in cell membranes. They are composed of fatty acids and alcohol and are present as bilayer in the membrane to promote semi permeability.
When two solutions have same concentration of dissolved molecules they are termed as isotonic. The isotonic solutions are often present as extracellular fluids to balance molecule concentrations in a cell.
Hence, the option (a) is incorrect.
Plasma is a fluid majorly found in blood, where the blood cells are suspended. Plasma fluid maintains the stable environment and it acts as a medium to transport nutrients to the cell.
When a solution has high concentration of dissolved particles than any specific related fluid, then it is termed as hypertonic. The hypertonic solutions are often present as intracellular fluids to maintain the cell in equilibrium state.
Hence, the option (b) is incorrect.
Interstitial fluid is the major solution among the extracellular fluids that are present surrounding the cell and in between the cell spaces. This fluid plays a role in transfer of cell materials.
When a solution has lower concentration of dissolved particles than any specific related fluid, then it is termed as hypotonic. The hypotonic solution plays a role to maintain the cell equilibrium.
Hence, the option (d) is incorrect.
All the animal cells are surrounded by extracellular fluids and interstitial fluid is the major one. This fluid balances the nutrient levels of a cell by allowing them outside and inside the cell environment for various cellular operations. This fluid is isotonic to the cytosol to maintain the cell's equilibrium state.
Hence, the option (c) interstitial; isotonic is correct.

Question 4

Describe the following types of transport processes in cells: simple diffusion, facilitated diffusion, active transport, pinocytosis, receptor-mediated endocytosis, phagocytosis, and exocytosis.

Question 5

Describe and diagram the structure of a plasma membrane. What are the two principal types of molecules in plasma membranes, and what is the general function of each?

Question 6

Name the protein that allows facilitated diffusion of water. What experiment demonstrated the function of this protein?

Question 7

Predict and sketch the configuration that ten phospholipid molecules would assume if they were completely submerged in vegetable oil. Explain your prediction.

Question 8

Imagine a container of glucose solution, divided into two compartments (A and B) by a membrane that is permeable to both water and glucose. If some glucose is added to compartment A, how will the contents of compartment B change? Explain.

Question 9

A membrane that is permeable to some substances but not to others is described as being ______________. The movement of a substance through a membrane down its concentration gradient is called ______________. When applied to water, this process is called ______________. Channels that are specific for water are called ______________. The process that moves substances through a membrane against their concentration gradient is called ______________.

Question 10

Name four types of cell-to-cell junctions, and describe the function of each. Which are found in plants, and which in animals?

Question 11

Which of the following cannot enter a cell by simple diffusion?

A) water
B) sugar
C) estrogen
D) oxygen

Question 12

Sketch the configuration that 10 phospholipid molecules would assume if placed in water. Explain why they arrange themselves this way.

Question 13

Facilitated diffusion involves either ______________ proteins or ______________ proteins. Diffusion directly through the phospholipid bilayer is called ______________ diffusion, and molecules that take this route must be soluble in ______________ or be very small and have no net electrical charge.

Question 14

Glycoproteins are important for

A) binding hormones.
B) cell recognition by the immune system.
C) forming ion channels.
D) active transport through the membrane.

Question 15

What are the five categories of proteins commonly found in plasma membranes, and what is the function of each one?

Question 16

The three types of cell attachment structures in animal cells are: ______________, ______________, and ______________. The structures that interconnect plant cells are called ______________.

Question 17

Diffusion

A) is always facilitated.
B) occurs by active transport.
C) is increased when temperature increases.
D) requires aquaporin proteins.

Question 18

Define diffusion and osmosis. Explain how osmosis helps plant leaves remain firm. What is the term for water pressure inside plant cells?

Question 19

After each molecule, place the two-word term that most specifically describes the process by which it moves through a plasma membrane: Carbon dioxide: ______________; ethyl alcohol: ______________; a sodium ion:______________; glucose: ______________.

Question 20

Which of the following is not true of endocytosis?

A) It is a form of passive transport.
B) It includes pinocytosis.
C) It can occur in coated pits.
D) It is used by Amoeba to feed on Paramecium.

Question 21

Different cells have somewhat different plasma membranes. The plasma membrane of a Paramecium, for example, is only about 1% as permeable to water as the plasma membrane of a human red blood cell. Hypothesize about why this is the case. Is Paramecium likely to have aquaporins in its plasma membrane? Explain your answer.

Question 22

Define hypotonic , hypertonic , and isotonic. What would be the fate of an animal cell immersed in each of these three types of solution?