Membrane Structure

Question 1

Describe the fluid mosaic structure of cell membranes

Answer 1

It is made up of phospholipids that spontaneously self- assemble into simple membranes in bilayers

Question 2

List five functions of membrane proteins

Answer 2

1. Cell-cell recognition
2. Intercellular Junctions
3. Transport
4. Signal Transduction
5. Enzymatic activity

Question 3

Explain how membranes exhibit selective permeability

Answer 3

They allow some substances to cross more easily than others. Many essential ions and molecules, such as glucose, require transport proteins to enter and leave the cell.

Question 4

Explain how the structure of phospholipid molecules is related to the structure and properties of cell membranes

Answer 4

phospholipids are polar and the structure/properties of cell membranes have hydrophobic and hydrophilic parts of the bilayer which makes it polar

Question 5

Diffusion

Answer 5

The spontaneous movement of a substance down its concentration gradient from where it is more concentrated to where it is less concentrated.

Question 6

Explain how some molecules move across the cell’s membrane by simple diffusion and some do not

Answer 6

the cells that can move across through simple diffusion are small and non polar and the ones that do not are either big or polar

Question 7

Describe the process of passive transport

Answer 7

A movement across a cell membrane that doesn’t require energy. Most of the traffic across a cell membrane is diffusion.

Question 8

Concentration gradient

Answer 8

A region along which the density of a chemical substance increases or decreases. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, substances tend to move from where they are more concentrated to where they are less concentrated.

Question 9

Explain osmosis

Answer 9

Osmosis is the diffusion of water across a selectively permeable membrane. The process occurs when water travels from the solute with more water to less water.

Question 10

Tonicity

Answer 10

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

Question 11

Distinguish between hypertonic, hypotonic, and isotonic solutions

Answer 11

A substance is hypertonic to another substance if it has a higher tonicity. A substance is hypotonic to another substance if it has a lower tonicity. Isotonic is when two solutions have the same tonicity.

Question 12

Outline the causes of cystic fibrosis in relation to Cl ion transport

Answer 12

A person with Cystic Fibrosis’ lungs don’t transport proteins out of the cell, resulting in less chlorine outside of the cell meaning that it is hypotonic compared to inside of the cell. The water thus is hypertonic so it moves into the cell leaving the surface dry and filled with bacteria to build up. Under normal circumstances, the transport channels actively work together to evenly transport both chlorine and sodium. This means that the two solutions inside of the cell and outside of the cell are isotonic to each other.

Question 13

Explain how animal and plant cells react to changes in tonicity

Answer 13

so animal cells if the blood cells get too big they burst and the plant cells membrane shrinks but the cell wall stays in tact

Question 14

Explain how transport proteins facilitate diffusion

Answer 14

One type of transport protein provides a hydrophilic channel that some molecules or ions use as a tunnel through the membrane. Another type binds its passenger, changes shape, and releases its passenger on the other side.

Question 15

Outline the discovery of aquaporins

Answer 15

When isolating the Rh proteins it seemed to consist of two proteins.

Question 16

Compare the processes of facilitated diffusion and active transport

Answer 16

Facilitated diffusion is a type of passive transport so it doesn’t require energy while active transport does require energy.

Question 17

Explain the process of active transport

Answer 17

It begins when the solute molecules on the cytoplasmic side of the plasma membrane attach to sites on the transport protein. Then ATP transfers a phosphate group to the transport protein. The protein changes shape in a way that the solute is released on the other side of the membrane and finally the phosphate group detaches and the transport protein returns to its original shape.

Question 18

Compare and contrast exocytosis, endocytosis, phagocytosis, pinocytosis

Answer 18

exocytosis is the movement of materials out of the cytoplasm of a cell by the fusion of the vesicles with the plasma membrane, endocytosis is the opposite of exocytosis and is the cellular uptake of molecules or particles via formation of new vesicles from the plasma membrane. Phagocytosis is cellular eating. It is also a type of endocytosis which a cell engulfs macromolecules into its cytoplasm. Finally, Pinocytosis is cellular drinking and is a type of endocytosis as well.

Question 19

What is selective permeability

Answer 19

A property of biological membranes that allows some substances to cross more easily than others and blocks the passage of other substances altogether