Unit 2: Cell Structure and Function #3

Question 1

What does selective permeability mean?

Answer 1

It means that some substances can cross the membrane more easily than others.

Question 2

What has easy passage across the membrane?

Answer 2

Small non polar, hydrophobic molecules like hydrocarbons, CO2, O2, or N2.

Question 3

What has a difficult or protein assisted passage across the membrane?

Answer 3

Hydrophilic, polar molecules, large molecules, ions like sugar and water.

Question 4

What are the two types of transport across a membrane?

Answer 4

Passive and active transport.

Question 5

What is passive transport?

Answer 5

The transport of a molecule that does not require energy from the cell because a solute is moving with its concentration/electrochemical gradient, involved in the import of materials and export of waste

Question 6

What are the three types of passive transport?

Answer 6

Diffusion, osmosis, and facilitated diffusion.

Question 7

What is diffusion?

Answer 7

Spontaneous process resulting from the constant motion of molecules from a high to low concentration, down the concentration gradient, and diffuse directly across the membrane (even this is selectively permeable).

Question 8

What is osmosis?

Answer 8

The diffusion of water down its concentration gradient across a selectively permeable membrane (the diffusion of water from areas of low solute concentration to areas of high solute concentration)

Question 9

What is facilitated diffusion?

Answer 9

The diffusion of molecules through the membrane via transport proteins which increases the rate of diffusion for small ions, water, and carbohydrates

Question 10

What are the two types of transport proteins?

Answer 10

Channel proteins and carrier proteins, and each transport protein facilitates movement for a specific substance

Question 11

Why is facilitated diffusion passive transport and not active transport?

Answer 11

It is still passive transport because the substances the proteins are helping are moving down their concentration gradient and no energy is required

Question 12

What are channel proteins?

Answer 12

They provide a channel for molecules and ions to pass, they are hydrophilic;ic and are usually gated channels and only allow passage when there is a stimulus?

Question 13

What are the channel proteins for water called?

Answer 13

Aquaporins

Question 14

What are carrier proteins?

Answer 14

Proteins that undergo conformational changes for substances to pass (opening and closing on either end)

Question 15

What is active transport?

Answer 15

Transport of a molecule that requires energy because it moves a solute against its concentration gradient

Question 16

How does ATP work as energy?

Answer 16

ATP can transfer the third or terminal phosphate group to the transport proteins which changes the shape of the transport proteins to better move a substance

Question 17

What are the types of active transport?

Answer 17

Pumps, cotransport, exocytosis, endocytosis

Question 18

What is membrane potential?

Answer 18

Unequal concentration of ion across the membrane results in an electrical charge (electrochemical gradients), and the cell is usually negative in the cytoplasm compared to the extracellular fluid, and this electrochemical gradients is the energy for other things to happen, like cells reacting

Question 19

What are electrogenic pumps?

Answer 19

Proteins that generate voltage, or an electric gradient, across membranes, which can be used later as an energy source for cellular processes. (So basically an ion pump that creates a electrical gradient that can later make ATP if the ions go through an ATP synthase.

Question 20

Describe the sodium potassium pump.

Answer 20

Animal cells regulate their concentrations of Na+ and K+ through this pump, and 3NA+ get pumped out of the cell which K+ get pumped it, and this results in net charge of +1 to the fluid outside the cell. K+ in the cell also leak out easily causing an overall negative charge inside of a cell.

Question 21

What is a proton pump?

Answer 21

An integral membrane protein that builds up a proton gradient across the membrane, and pumps H+ (or protons) out of the cell, used by plants, fungi, and pacteria

Question 22

What is cotransport?

Answer 22

The coupling of downhill diffusion of one substance with an uphill transport of another substance, using the energy stored in electrochemical gradients (made by pumps) to move substances against their concentration gradient

Question 23

How do plants use cotransport for sugars and amino acids?

Answer 23

With the Sucrose-H+ cotransporter, where sucrose can travel into a plant cells against its concentration gradient only if it is coupled with H+ that is diffusing down its electrochemical gradient.

Question 24

How are large molecules transported in and out of the cell?

Answer 24

Through exocytosis and endocytosis

Question 25

What is exocytosis?

Answer 25

The secretion of molecules via vesicles that fuse to the membrane, and once fused, the contents of the vesicle are released to the extracellular fluid (ex. Nerve cells releasing neurotransmitters)

Question 26

What is endocytosis?

Answer 26

The uptake of molecules from vesicles fused from the plasma membrane (opposite of exocytosis)

Question 27

What are the types of endocytosis?

Answer 27

Phagocytosis (cell eating), pinocytosis (cell drinking) and receptor-mediated endocytosis.

Question 28

What is phagocytosis?

Answer 28

When a cell engulfs particles that are later digested by lysosomes: the cell surrounds the particle with pseudopodia (goes up to surround it with microfilaments) and packages particles into food vacuoles

Question 29

What is pinocytosis?

Answer 29

Nonspecific uptake of extracellular fluid containing dissolved molecules, taken in a protein coated vesicle which helps mediate the transport of molecules.

Question 30

What is tonicity?

Answer 30

The ability of an extracellular solution to cause a cell to gain or lose water, and it depends on the concentration of solutes than CANNOT pass through the cell membrane

Question 30

What is receptor-mediated endocytosis?

Answer 30

Specific uptake of molecules via solute binding to receptors on the membrane, allows cell to get large quantities of specific substance, use a protein coated vesicle to enter the cell

Question 31

What are the types of solutions a cell can be in?

Answer 31

Isotonic, hypertonic, and hypotonic

Question 32

What is osmoregulation?

Answer 32

Cells being able to regulate their solute concentrations and maintain water balance, different types of cells (plants vs animals) will react differently

Question 33

What happens with a cell in an isotonic solution

Answer 33

They have no net movement of water, equal concentration of solutes inside and out, water diffuses into the cell at the same rate as it diffuses out

Question 34

What happens with a cell in a hypertonic solution?

Answer 34

Cells lose water to their extracellular surrounding, the concentration of solutes is higher outside of the cell, water will move to the outside fluid and cells shrivel and die (plant cells can plasmolyze were the vacuole shrinks and the membrane pulls away from the cell wall)

Question 35

What happens with a cell in a hypotonic solution?

Answer 35

Cells immersed in this gain water, and the concentration of solutes is lower outside the cell, so the cell gains water, animal cells swell and lyse (explode) which plant cells work well and maintain turgor pressure.

Question 36

What is water potential?

Answer 36

A physical property that predicts the direction water will flow, includes solution concentration effects and physical pressure

Question 37

How does water flow?

Answer 37

From areas of high water potential to areas of low water potential. from low solute to high solute concentration or to high pressure to low pressure areas