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PBD > Cells & Membranes > Flashcards

Cells & Membranes Flashcards

1
Q

What scientist first discovered that living things are made of cells? (He was the first to SEE the cell)

A

Robert Hooke, 1665

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2
Q

What are the common features of all cells? (6)

A
  • All cells have a cell membrane
  • All cells are made from the same materials: carbohydrates, proteins, nucleic acids, minerals, fats, and vitamins
  • All cells are able to regulate influx and eflux of nutrients, waste products, ions, and other materials
  • All cells contain DNA, RNA, and other proteins
  • All cells can reproduce themselves and are the result of reproduction
  • All cells require a supply of energy
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3
Q

Describe the two major classifications of cells

A

Prokaryotic cells: Lack membrane bound organelles. Many single cell organisms are prokaryotic. Some form of prokaryotic organism can be found nearly every terrestrial environment.

Eukaryotic cells: Contain a nucleus and other membrane bound organelles. In an evolutionary sense they are more advanced than prokaryotic cells. The cells of all multicellular organisms are eukaryotic.

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4
Q

What is the one thing PROKARYOTES have that EUKARYOTES do not?

A

Cell walls containing peptidoglycan

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5
Q

True or False: Prokaryotes undergo mitotic division

A

FALSE. Prokaryotes reproduce by binary fission or conjugation

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6
Q

What are the 7 parts of The Cell Theory? What parts were the original, made after Hook saw cells?

A

(1, 2, and 3 were the original cell theory)

  1. All living things are made of one or more cells
  2. Living cells come only from other living cells
  3. The cell is the fundamental unit of structure and function in all living organisms
  4. Activity of an organism is dependent on total activity of independent cells
  5. Basic metabolic processes of life occur within cells
  6. Cells contain (and pass on) hereditary information in the form of DNA
  7. All cells within organisms of similar species have essentially the same basic chemical composition
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7
Q

According to his slides, what is the “one definition of what it means to be alive”?

A

Living things are cellular organizations capable of reproducing themselves

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8
Q

What are covalent bonds?

A

Covalent bonds are bonds that involve sharing of electrons between atoms

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9
Q

What are polar bonds?

A

Covalent bonds in which the electrons are shared unevenly between atoms

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10
Q

What are non-polar bonds?

A

Covalent bonds in which the electrons are shared evenly. True non-polar bonds occur between identical atoms (ie N2 or O2)

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11
Q

What is a polar molecule?

A

Molecule in which the polar bonds are arranged in such a way as to create an uneven distribution of charge in the molecule as a whole (ie H2O)

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12
Q

What is a nonpolar molecule?

A

Molecule in which the polar bonds are arranged in such a way as to cancel eachother out (ie CO2)

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13
Q

What pieces make up the polar head of a phospholipid?

A

Choline, Phosphate, and Glycerol

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14
Q

What do “saturated” and “unsaturated” mean in terms of phospholipids?

A

The tails of phospholipid can be either saturated (saturated with hydrogen bonds, no double bonds) or unsaturated (contain “kinks” where double bonds are)

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15
Q

A fatty acid is a long hydrocarbon chain topped with a….

A

Carboxyl group

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16
Q

What are liposomes? Why are micelles different?

A
  • Bilayers formed in aqueous solutions, form spheres

- Micelles are spheres as well but they are a monolayer with polar heads outside and tails inside

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17
Q

Lipid bilayers are highly permeable to…

A

Nonpolar, thus lipid soluble, compounds

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18
Q

Lipid bilayers have a low permeability to…
Extremely low permeability to…
Virtually impermeable to…

A

Low: Small polar molecules
Extremely low: Large polar molecules
Virtually impermeable: Ions

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19
Q

Why is the membrane impermeable to ions in solution?

A

Ions in solution take on “waters of hydration” - water molecules surround the ions. To permeate the membrane, an ion would have to shed its waters of hydration and pass through a nonpolar environment. This is highly energetically unfavorable, thus extremely unlikely to occur.

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20
Q

Why is it important that membranes have such low permeability to ions?

A
  • Key feature that allows for separation of charge across the membrane
  • Allows for voltage across the membrane, or “membrane potential” (MP)
  • MP helps drive many cellular processes including active transport and electrical signaling
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21
Q

True or False: Passive diffusion is not the only way to traverse the membrane

A

False - actual cell membranes are not pure lipid bilayers

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22
Q

Actual cell membranes (at physiological temperatures) are stiffened to various degrees by….

A

Cholesterol

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23
Q

What is cholesterol made of?

A

Polar head group, rigid steroid ring structure, and nonpolar hydrocarbon tail

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24
Q

What is the “transition temperature” or cell membranes? What factors determine it?

A
  • Temperature in which cell membranes melt into the liquid phase
  • Factors that determine it:
    Length of fatty acid tails (longer = higher TT)
    Degree of saturation (more DB = lower TT)
    Cholesterol (lowers TT)
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25
Q

How does cholesterol sometimes have an opposite effect on cell membrane (Doesn’t increase stiffness)?

A
  • In the liquid phase, cholesterol increases viscosity by limiting lateral movement, thus “stiffens the membrane”
  • At lower temperatures, cholesterol interferes with ordering and alignment of the fatty acid tails, which helps to keep the membrane fluid (lowers TT) (keeps cell fluid in gel phase)
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26
Q

Most of a cell membrane in a living cell is in the _____ phase at physiological temperature.

A

liquid

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27
Q

What is “phase separation” in cell membranes

A

Occurs when spatially distinct regions of a membrane are in a different phase at the same temp (depends where cholesterol is)

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28
Q

What are glycolipids? Why are glycolipids important in cell membranes?

A
  • Lipids with a sugar group on the polar head
  • They are thought to function in cell recognition processes
  • May also help regulate concentrations of specific ions (especially calcium) at the membrane surface
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29
Q

What is the purpose of ion channels in the cell membrane?

A
  • Gate the flow of ions across the cell membrane, establishing resting membrane potential and controlling action potentials and other electrical signals
  • Can be ligand gated or voltage gated
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30
Q

What are peripheral proteins? Why are they important?

A
  • Proteins that adhere only temporarily to the cell membrane. They attach to either transmembrane proteins, or to the peripheral regions of the lipid bilayer
  • The reversible attachment of proteins to biological membranes has been shown to regulate cell signaling and many other important cellular events, through a variety of mechanisms.
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31
Q

What is the difference between transmembrane and integral proteins?

A
  • An integral membrane protein (IMP) is a type of membrane protein that is permanently attached to the biological membrane. All transmembrane proteins are IMPs, but not all IMPs are transmembrane proteins.
  • Transmembrane span the entire bilayer, from one side to the other. Not all IMP’s do
32
Q

Protein:Lipid ratio is highest where? Lowest?

A

Highest: (from High to Low) Mitochondrial inner membrane and sarcoplasmic membrane
Lowest: Myelin (0.23), Mouse liver cells (0.85), retinal rods (bovine)

33
Q

What are the 4 ways for a solute to traverse the cell membrane?

A
  • Passive diffusion (favors uncharged and nonpolar molecules, no membrane bound proteins required)
  • Facilitated diffusion (aka passive transprort, requires membrane transport proteins but driven by concentration, no energy required)
  • Active transport (requires membrane transport protein, requires additional energy source because solute moves against concentration gradient)
  • Endocytosis/Exocytosis
34
Q

What is the difference between primary and secondary active transport?

A
  • Primary: directly uses ATP
  • Secondary: doesn’t directly use ATP, sometimes uses another molecules concentration gradient to generate energy to move another molecule against its gradient
35
Q

The rate of passive diffusion is driven by…

A

concentration gradient (kinetics graph is a straight line)

36
Q

How are the kinetics of carrier-mediated diffusion and passive diffusion different?

A

Passive diffusion rate is linear with respect to solute concentration. Carrier-mediated is curved, because eventually the carriers would be saturated and a maximum velocity (Vmax) is reached

37
Q

What is Symport? Antiport? Uniport?

A

Symport - Secondary active transport in which the solutes move in the same direction. One with its gradient, the other against (using energy from the other solute)

Antiport - Secondary active transport in which the solutes move in opposite direction

Uniport - Only one solute is moved

38
Q

True or False: Channels are used in syport and antiport

A

FALSE - They are not channels, they are transporters or carriers

39
Q

True or False: Symport and antiport can facilitate passive transport

A

TRUE - If they move the other solute in accordance with their chemical and/or electrical gradient, it is passive transport

40
Q

Describe the mechanism of the glucose carrier

A

Brings glucose INTO the cell.
Na+ binds to the carrier protein, this increases its affinity for glucose. Glucose then binds, and the carrier protein changes confirmation and opens on the opposite side (intracellular space). When Na+ leaves the protein, the affinity for glucose decreases, so glucose is released too. Net flux is inward for both sodium and glucose.

41
Q

__ driven carrier proteins regulate cytosolic pH.

A

Na+ (sodium hydrogen exchanger)

42
Q

What is cooperative binding?

A

Cooperative binding happens when the affinity of one molecule to a protein increases after the binding of another one
ie Na+ binding to the glucose carrier increases its affinity for glucose

43
Q

What makes Na+ bind to the glucose carrier in the first place?

A

Na+ electrochemical gradient goes into the cell. It is moving down its concentration gradient.

44
Q

Na+/K+ pump is a(n) ________________ mechanism

A

Primary active transport

45
Q

True or False: The sodium potassium pump is an antiporter

A

True

46
Q

The Na+/K+ pump moves # _+ out of the cell, and # _+ into the cell

A

3Na+ out of the cell, 2K+ into the cell

47
Q

In the sodium potassium pump, the ions are moving ___ their concentration gradient

A

Against

48
Q

Another function of the Na+/K+ pump is to _______ by regulating _______.

A

Maintain cell volume; osmolarity

49
Q

What are osmotically active particles?

A

Particles that interact with water but are impermeable to the plasma membrane (ie Ions)

50
Q

What is a Hypertonic solution? Hypotonic? Isotonic?

A 
Hypertonic = high solute conc., low water conc.
Hypotonic = low solute conc., high water conc.
Isotonic = Has the same solute conc. as the other side of the membrane
51
Q

The normal osmolarity for blood is approximately _____.

A

280 mOsm

52
Q

How does osmolarity relate to cell volume?

A

(Osmolarity of EXTRACELLULAR solution)
Hypertonic = shriveled (crenated) —> Water goes to the high concentration of solutes outside of the cell
Hypotonic = swollen –> water goes inside to the high concentration of solutes inside the cell
Very hypotonic = lysed cell

53
Q

How does the Na+/K+ pump help regulate osmolarity?

A

It reduces the number of inorganic solutes inside the cell

3Na+ out for every 2K+ in

54
Q

What is endocytosis? Exocytosis? How do these differ from diffusion/passive transport/active transport?

A

Endocytosis = Cells engulf material from their surroundings
Exocytosis = Cell secretes intracellular substances into the extracellular space
These differ from other types of transport because substances pass from one side of the cell to the other without ever directly crossing the lipid bilayer

55
Q

Describe the three subcategories of endocytosis

A

Phagocytosis (cellular eating): Cell engulfs large particles
Pinocytosis (cellular drinking): Cell ingests small particles or compounds in solution
Receptor mediated endocytosis: Membrane proteins called receptors bind to specific molecules, this causes the specific area to invaginate (example of cooperative binding)

56
Q

What is the mechanism for phagocytosis?

A

Cell engulfs large particle, forms phagosome
Phagosome breaks away from the cell membrane, eventually fuses with a lysosome
Lysosomal enzymes break down the contents

57
Q

What is the difference between a vacuole and a vesicle?

A

Vacuoles are formed during phagocytosis

Vesicles are formed during pinocytosis

58
Q

What is the mechanism for ingestion of LDL cholesterol

A
  • Receptor mediated endocytosis
    Cholesterol binds to apoprotein (forms LDL complex)
    LDL complex binds to LDL receptor
    LDL receptors have increased affinity for eachother, they move closer together.
    They form a coated pit, then break off into a vesicle.
    Time it takes: 10 minutes
    Forms “early endosome” where receptors are recycled and sent back to plasma membrane, and the contents are either transcytosed or forms a “late endosome” which is fused with lysosome and contents are degraded
59
Q

What is adapor protein? Clathrin? Dynamin?

A

When LDL receptors are bound, they have an increased affinity for Adaptor proteins. Adaptor proteins bind to the LDL receptors on the cytosolic side. Clathrin proteins bind to the adaptor proteins, to form an outer coating for the whole vessel. As the coated pit gets deeper, dynamin helps cut the vessel from the plasma membrane. (see photo on slide 41)

60
Q

What is the difference between constitutive and regulated secretory pathway?

A 
Constitutive = Unregulated, happens continually, no signal needed
Regulated = Needs a signal, such as a hormone or neurotransmitter. This is used for proteins that are stored then secreted on demand, such as insulin.
61
Q

How do neurotransmitters travel down nerve cells? (think synaptic transmission)

A

Synaptic vesicle breaks off from trans golgi network, the components are “delivered” to the plasma membrane. The synaptic membrane components are broken off and form a new vesicle directly OR are delivered to an endosome (then break off later). The neurotransmitter loads into the synaptic vesicle. The vesicle binds with the plasma membrane in response to an action potential, and neurotransmitter is released

62
Q

How is the membrane of the nucleus different from the cell membrane?

A
  • Contains an inner and outer lipid bilayer
  • Impermeable to many things that can permeate the cell membrane
  • At some places it is contiguous with the membrane of the ER
  • Has large distinctive pores specialized for transporting genetic material and related compounds in and out of the nucleus
63
Q

At least __ distinct proteins are involved in the construction of ribosomes

A

50

64
Q

The _______ is a specialized subnuclear structure where ribosomes are constructed

A

Nucleolus

65
Q

________ is the process of using mRNA to synthesize a protein

A

Translation

66
Q

Where can ribosomes be found?

A

Free in the cytoplasm or bound to the rough ER

67
Q

Free ribosomes are most likely to be involved in the synthesis of _______, while bound ribosomes are more likely to synthesize _______.

A

Free ribosomes: enzymes that facilitate reactions within the cytosol
Bound ribosomes: Membrane bound, lysosomal, and secretory proteins

68
Q

What are the functions of the endoplasmic reticulum?

A
  1. Synthesis (smooth = lipid, rough = protein)
  2. Transport (moves molecules through cisternal space from one part of the cell to another)
  3. Storage (stores newly synthesized molecules)
  4. Detoxification (smooth ER detoxifies both drugs and alcohol)
69
Q

What is the purpose of the golgi apparatus?

A
  • Receives lipids and proteins via vesicular transport from the ER
  • Modifies carbohydrate groups on some proteins
  • Packages other proteins for vesicular secretion
  • Produces polysaccharides and attaches them to proteins to form glycolipids
  • DOES NOT participate in protein synthesis directly
70
Q

What is the purpose of lysosomes?

A
  • Principle sites of intracellular digestion (inside is very acidic)
  • Break macromolecules down into smaller parts that can be recycled or extruded from the cell
71
Q

How many enzymes do lysosomes contain? What kind are they?

A

Contain about 40 types of hydrolytic enzymes, all of which are acid hydrolases

72
Q

Why is it important that acid hydrolases in lysosomes work only at low pH?

A

Because if lysosomes were to burst, the enzymes would eat up the cell. Since they only work at low pH, the enzymes would be denatured if the lysosome were to burst

73
Q

Why are mitochondria unique from other organelles?

A

They contain their own DNA and are self-replicated.

Also they have a double membrane

74
Q

Mitochondrial DNA is inherited from…

A

the mother (maternal DNA)

75
Q

_____ and _____ are concentrated in mitochondria, and used to make ATP in an _______ dependent manner.

A

Fatty acids and pyruvic acid, oxygen dependent (aerobic)

76
Q

Without a mitochondria, cells would depend entirely on ________ for ATP production.

A

Glycolysis

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