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PHYSIOL 2130 > Module 3: Cells > Flashcards

Module 3: Cells Flashcards

1
Q

What is the function of the Golgi apparatus?

A

Responsible for packaging proteins from the rough ER into membrane-bound vesicles. Two types of vesicles include 1) secretory vesicles and 2) storage vesicles.

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2
Q

What is the function of the secretory vesicle?

A

Produced by the Golgi apparatus and used to transport various types of proteins out of the cell for use in other parts of the body.

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3
Q

What is the function of ribosomes?

A

Ribosomes are dense granules of RNA and protein. Responsible for manufacturing proteins from amino acids.

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4
Q

What are the two types of ribosomes?

A

1) Fixed ribosomes, which are attached to the ER and 2) Free ribosomes, which float in the cytoplasm. Free ribosomes often form groups of 10-20 known as polyribosomes.

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5
Q

What is the function of lysosomes? What type of vesicle are they?

A

Act as the digestive system of the cell. Contain several enzymes used to destroy damaged organelles, kill bacteria, and break down other kinds of biomolecules. They are one type of storage vesicles produced by Golgi apparatus.

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6
Q

What is the function of mitochondria? How many mitochondria are there?

A

Where most of the body’s ATP is generated. Number of mitochondria determined by particular cell’s energy needs (e.g. muscle cells have increased energy demands when they are regularly exercised).

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7
Q

What is the function of the endoplasmic reticulum?

A

Continuation of the cell’s nuclear membrane. Site for synthesis, storage, and transportation of proteins and lipids.

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8
Q

What are the two types of ER? What does each synthesize?

A

1) Rough (or granular) and 2) smooth (or agranular) endoplasmic reticulum. Rough ER is the site for protein synthesis and is covered with rows of ribosomes. Smooth ER is the site for synthesis of lipids and fatty acids.

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9
Q

What is the function of the cell/plasma membrane?

A

Regulates the passage of substances into and out of cell. Also plays important role in detecting chemical signals from other cells and in forming physical links with adjacent cells.

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10
Q

What is the function of centrioles?

A

Cylindrical bundles of microtubules responsible for directing movement of DNA strands during cell division.

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11
Q

What is the function of the nucleolus?

A

Dense body within nucleus which contains the specific DNA that produces RNA found in ribosomes.

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12
Q

What is the function of the phospholipids in the cell membrane?

A

Phospholipids are the most abundant components of the cell membrane and form a phospholipid bilayer.

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13
Q

What is the location of the phospholipid heads?

A

Face out into the water base solutions inside and outside of the cell.

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14
Q

What is the location of the phospholipid tails?

A

Oriented away from the aqueous and extra and intracellular solutions into the cell membrane.

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15
Q

Which part of the phospholipid is hydrophilic? Hydrophobic?

A

The head is hydrophilic and the tail is hydrophobic.

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16
Q

What is the function and location of the cholesterol molecules in the cell membrane?

A

Cholesterol molecules help make membrane impermeable to some water soluble molecules and help keep membrane flexible over wider temperature range. They are inserted into the non-polar lipid layer of the membrane.

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17
Q

What is the function and location of enzymes in the cell membrane?

A

Form of associated protein which act as catalysts for certain reactions immediately inside or outside membrane. They can be attached to either the intracellular or extracellular surface of membrane.

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18
Q

What is the function and location of the carbohydrate molecules in the cell membrane?

A

Form a protective layer called glycocalyx. Glycocalyx plays key role in immune response of cell and in recognition of other cells in the body. Associated with extracellular membrane proteins or lipids.

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19
Q

What is the function and location of membrane spanning proteins in the cell membrane?

A

Act as gates or channels that control movement of certain substances into and out of cell. Embedded in the phospholipid bilayer and span the entire width of the membrane.

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20
Q

What is the function of location of structural proteins in the cell membrane?

A

Some support and strengthen membrane while others may anchor some cell organs to the intracellular side of membrane. Generally attached to the inside surface of cell membrane.

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21
Q

How do phospholipids arrange in water?

A

Phospholipid bilayer.

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22
Q

What are some water-soluble and fat-soluble substances? Which can travel through membrane?

A

Water- soluble substances include ions, glucose, urea, and most of the other molecules in living organisms. Fat-soluble substances include oxygen, carbon dioxide, and steroid hormones. Water-soluble substances cannot readily penetrate membrane, while fat-soluble substances can penetrate the fatty-acid portion of membrane with ease.

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23
Q

What are the 5 functions of membrane proteins?

A

1) Receptors for attachment of chemical hormones and neurotransmitters
2) Enzymes that help with chemical reactions or breakdown molecules
3) Ion channels or pores that allow water-soluble substances into cell
4) Membrane-transport carriers that transport molecules across membrane
5) Cell-identity markers, like antigens or glycoproteins

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24
Q

What are the 5 membrane-transport mechanisms?

A

1) Endocytosis/exocytosis (pinocytosis for small molecules)
2) Diffusion through lipid bilayer (for fat-soluble molecules)
3) Diffusion through protein channels (for water-soluble molecules)
4) Facilitated diffusion
5) Active transport

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25
Q

How can molecules leave or enter cell without crossing the membrane? What is this called for small molecules?

A

Exocytosis is when vesicles merge with the cell membrane to release substances. Endocytosis is when substances enter the cell after being surrounded by area of membrane. Pinocytosis is for small molecules, which will still be suspended in fluid in the vesicle. These processes require ATP.

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26
Q

What is diffusion? Molecules move according to which gradient?

A

Movement of molecules from area of high concentration to low concentration due to molecules’ random thermal motion. Molecules move according to chemical concentration gradient.

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27
Q

What gradient(s) do charged molecules diffuse according to? What if they are in opposite directions?

A

They move to areas of opposite charge and this is called their electrical gradient. They can also move according to their chemical concentration gradient. If the gradients are in opposite directions, ion movement depends on balance of two gradients and will stop moving when molecules reach electrochemical equilibrium.

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28
Q

What is electrochemical equilibrium?

A

When the electric force is equal to and in the opposite direction to the chemical force.

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29
Q

What does the diffusion of water-soluble substances through membrane require?

A

A pore, a channel, and concentration gradient.

30
Q

What are the 4 diffusion factors that limit the rate of movement of molecules through protein channels?

A

1) Size of protein channels (~0.8nm, for which sugar molecules are too large)
2) Charge on molecule because proteins that make up channels have charges on them
3) The greater the electrochemical gradient, the greater its rate of movement through channels
4) Number of channels in membrane (the more channels, the more ions that diffuse across membrane)

31
Q

How do protein carriers in facilitated diffusion work?

A

Molecules (water-soluble molecules like sugar that are too large for protein channels) attach to specific protein carrier and cause a change in protein’s shape. Protein then either opens up or rotates molecule to inner surface of membrane.

32
Q

Does facilitated diffusion require energy? What is it powered by?

A

It does not require energy (same as simple diffusion). It is powered by the concentration gradient of molecule.

33
Q

What limits the rate of transport of facilitated diffusion?

A

Rate of transport is limited by number of available proteins. Once system is saturated (all carriers occupied), it cannot operate any faster.

34
Q

What type of specificity does facilitated diffusion show? Can it be inhibited?

A

Shows chemical specificity where carrier protein will only interact with specifically shaped molecule. Can be competitively inhibited by molecules of similar shape.

35
Q

What are the similarities between facilitated diffusion and active transport?

A

They both require protein carriers, can be saturated, show chemical specificity, and show competitive inhibition.

36
Q

Does active transport require energy? Why?

A

Yes, it does require energy (ATP) because molecules move against their concentration gradients (low to high).

37
Q

How is ATP used to provide energy to carrier protein?

A

ATP is split to ADP and an inorganic phosphate (PE).

38
Q

How much water leaves and enters the cell?

A

The amount of water that diffuses into cell is exactly equal to water that diffuses out of cell; the volume of cell remains constant. It is possible, however, for concentration difference to develop across membrane.

39
Q

What is osmosis?

A

Net movement of water down its concentration gradient.

40
Q

What is a solute?

A

Substance that is being dissolve in liquid.

41
Q

What is a solvent?

A

Liquid that is doing the dissolving. In most cases, it will be water.

42
Q

What is a solution?

A

What you get when you dissolve solute in solvent.

43
Q

What would happen if a cell with high intracellular concentration of glucose is placed in a pure water solution?

A

Water would move down its concentration gradient, from high (pure water) to low (cell) concentration into the cell. This would cause the cell to swell.

44
Q

What are the 3 factors that affect osmosis?

A

1) Permeability of membrane to the solutes in the intracellular and interstitial fluids
2) Concentration gradients of solutes in the intracellular and interstitial fluids
3) Pressure gradient across cell membrane

45
Q

What is a particle that causes osmosis called?

A

Osmotically active particle.

46
Q

What is the unit used to describe number of osmotically active particles in a solution?

A

Osmole.

47
Q

What are the two units used to describe concentration of a solution?

A

1) Osmolality (equal to number of osmoles per kg of water)
2) Osmolarity (equal to number of osmoles per litre of solution)
We assume that these two units are the same.

48
Q

Example: What is the osmolality of a 1 molar solution of NaCl?

A

To make a 1 molar solution of NaCl, you take 1 mole of NaCl and add it to 1 kg of water. When NaCl is added to water, it dissociates into ions Na+ and Cl-. Each ion is capable of causing osmosis. Therefore, you have 2 osmotically active particles or 2 osmoles per kg of water. This is the concentration for this solution.

49
Q

Example: What is the concentration of a 1.5 molar solution of CaCl2?

A

When added to water, CaCl2 dissociates into 1.5 Ca2+ ion and 3.0 ions of Cl-. Each ion can cause osmosis; therefore, the concentration/osmolality of solution is 4.5 osmoles per kg solution.

50
Q

What is tonicity?

A

Ability of solution to cause osmosis.

51
Q

What is an isotonic solution?

A

Has the same concentration as body fluids. No osmosis would take place because concentrations of solution and inside cell are the same.

52
Q

What is a hypotonic solution?

A

Has lower concentration compared to cellular fluids. Causes osmosis into cell (cell would swell).

53
Q

What is a hypertonic solution?

A

Has higher concentration compared to the cell. Would cause osmosis out of cell (cell would shrink).

54
Q

What is the average concentration of a typical human cell?

A

Roughly 300 mOsm/kg water.

55
Q

Where does Na+ have a higher concentration?

A

Outside the cell.

56
Q

Where does Ca2+ have a higher concentration?

A

Outside the cell.

57
Q

Where does K+ have a higher concentration?

A

Inside the cell.

58
Q

Where does Cl- have a higher concentration?

A

Outside the cell.

59
Q

Why are cells not very permeable for Na+, Ca2+, and Cl-? What about K+?

A

Although there is a large concentration gradient for them, there are very few channels for them in membrane. For K+, however, the membrane is more permeable, so some will leak out down its concentration gradient.

60
Q

What is an electrical (or membrane) potential?

A

Charge difference between two points (inside vs outside of cell). Also called the membrane potential.

61
Q

What does electrolytic mean?

A

Solutions that contain ions.

62
Q

What is the resting membrane potential?

A

A very minute excess of anions accumulates along the inside of cell membrane and an equal number of cations accumulates outside the membrane. Because this potential difference is present even in resting cells, it is called the resting membrane potential.

63
Q

What is the value for resting membrane potential in mV?

A

-70 mV. It is negative because the negative inside is compared to the positive outside.

64
Q

What is the equilibrium potential? What is the relationship between the concentration gradient and equilibrium potential?

A

The electrical potential that must be applied to the inside of cell to stop movement of that ion down its concentration gradient. The larger the concentration gradient, the larger the equilibrium potential needed to stop movement of ion.

65
Q

What is the approximate equilibrium potential for K+?

A

-90mV

66
Q

What is the approximate equilibrium potential for Na+?

A

+60mV

67
Q

What is the approximate equilibrium potential for Cl-?

A

-70mV

68
Q

Example: Na+ and equilibrium potential.

A

Na+ has a strong concentration gradient pushing it into cell. To keep it out, you must apply a positive charge to inside of cell. +60mV is the charge just strong enough to keep Na+ from moving into cell.

69
Q

Example: K+ and equilibrium potential.

A

To keep K+ from moving out of cell, you must apply charge of -90mV to inside of cell because unlike charges attract (keeps K+ in cell).

70
Q

How many Na+ and K+ does the sodium/potassium pump pump into and out of the cell.

A

It pumps 3 Na+ ions out and 2 K+ ions in.

71
Q

Why is the sodium/potassium pump called an electrogenic pump?

A

It contributes to the resting membrane potential by making the inside of cell more negative (removes more Na+ than it replaces with K+).

72
Q

What are other functions of the sodium/potassium pump?

A

1) Without the pump, most cells would swell until they burst. Cell contains large number of proteins and other organic compounds to which cell membrane is impermeable. Many of these carry negative charge, so large number of positive ions are attracted around them. This increases number of particles inside cell, causing osmosis of water into the cell. Sodium/potassium pump pumps out 3 Na+ and pumps in 2 K+, reducing particles in cell. This causes osmosis of water out of cell, offsetting osmosis into cell (volume is constant).

PHYSIOL 2130 (6 decks)

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