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MCAT Biochem > Biochem #8 > Flashcards

Biochem #8 Flashcards

1
Q

cell (plasma) membrane

A

: semipermeable phospholipid bilayer.
o Barrier that only some things can pass through passively while others can’t or have to find a different method of transportation.
o Fat-soluble compounds can cross easily while larger water-soluble compounds must seek alternate entry.
o Regulates what gets in and out, protects the interior of the cell, intracellular and intercellular communication, signal transduction via the receptors on it.

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2
Q

what easily diffuses through the plasma membrane and what has to find alternate entry?

A

o Fat-soluble compounds can cross easily while larger water-soluble compounds must seek alternate entry.

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3
Q

glycoprotein coat

A

created when carbohydrates are associated with membrane bound proteins.
o The cell wall of plants, bacteria, and fungi contain higher levels of carbohydrates.

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4
Q

phospholipids

A

move rapidly in the plane of the membrane via diffusion, spread throughout

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5
Q

lipid rafts

A

collections of similar lipids with or without associated proteins that serve as attachment points for other biomolecules.
 Important for signaling.

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6
Q

flippases

A

assist in the transition or flip of phospholipids between layers (or just lipids)
o What is on the surface of the cell can be regulated

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7
Q

the surfaces of cells can be ____

A

regulated, such as what is on them.

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8
Q

cell membrane: steroid and cholesterol provide ___ while waxes provide ____

A

fluidity

stability

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9
Q

lipids in the cell membrane

A

o Primarily phospholipids but some free fatty acids. Steroid molecules and cholesterol lend to fluidity of the membrane while waxes are present for membrane stability.
o Fatty Acids and Triacylglycerols
 Fatty acids: carboxylic acids that contain a hydrocarbon chain and terminal carboxyl group.
 Triacylglycerol (triacylglyceride): storage lipids involved in human metabolic processes.
• Unsaturated fatty acids: healthier, liquid at room temperature, more double bonds, fluidity in the membrane.
o Chylomicrons: used to transport triacylglycerols from the intestine whose fatty acids are used in the membrane.
• Saturated fatty acids: the main components of animal fats and tend to exist as solids at room temperature, unhealthy, decrease membrane fluidity.
o Phospholipids (glycerophospholipid)
 When one of the fatty acid chains in triacylglycerol is exchanged for a polar phosphate group head.
 Hydrophobic interactions cause phospholipids to assemble into micelles (small monolayer vesicles) or liposomes (bilayered vesicles) due to hydrophobic interactions.
 In the cell membrane
 Can also serve as second messengers in signal transduction.

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10
Q

triacylglycerol in cell membrane

A

storage lipids involved in human metabolic processes.
• Unsaturated fatty acids: healthier, liquid at room temperature, more double bonds, fluidity in the membrane.
o Chylomicrons: used to transport triacylglycerols from the intestine whose fatty acids are used in the membrane.
• Saturated fatty acids: the main components of animal fats and tend to exist as solids at room temperature, unhealthy, decrease membrane fluidity.

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11
Q

saturated vs. unsaturated fatty acids in cell membrane

A

unsaturated: more double bonds, more fluidity
saturated: decrease membrane fluidity

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12
Q

how do you get from triacylglyercol to phospholipid (glycerophospholipid)

A

 When one of the fatty acid chains in triacylglycerol is exchanged for a polar phosphate group head.

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13
Q

sphingolipids and cell membrane

A

 Important for the cell membrane.
 Very similar in structure to phospholipids, some just differ in the identity of their hydrophilic regions.
 Role (internet): the regulation of cell growth, differentiation, diverse cell functions, and apoptosis.

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14
Q

steroids are derived from ______

A

cholesterol

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15
Q

how does cholesterol act during high and low temperatures?

A

 Important for membrane fluidity roles: high temp  limits movement and holds the membrane together. Low temp  prevents formation of crystal structures and increases fluidity.

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16
Q

how do waxes act in the cell membrane?

A

 Extremely hydrophobic and are rarely found in the cell membranes of cells.
• Only in hydrophobic part for stability and rigidity.
 Consists of long chain fatty acid and long chain alcohol, very high melting point.
 Mainly extracellular function of protection and waterproofing.

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17
Q

integral proteins

A

associated with the interior of the plasma membrane and can include both transmembrane proteins and embedded proteins

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18
Q

transmembrane proteins

A

pass completely through the lipid bilayer (transporters, channels, and receptors)

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19
Q

embedded proteins

A

associated with only the interior or exterior surface of the cell membrane.

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20
Q

membrane-associated proteins (peripheral)

A

may be bound through electrostatic interactions with the lipid bilayer (lipid rafts or other transmembrane or embedded proteins)
 Ex: G proteins

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21
Q

carbohydrates and the cell membrane

A

o Generally attached to the protein molecules on the extracellular surface of cells.
o Hydrophilic, glycoproteins interact with water to form coat around the cell.
o Can act as signaling and recognition molecules (ABO blood type antigens)

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22
Q

membrane receptors

A

o Transmembrane proteins that can activate facilitated diffusion and active transport.
o Ex: ligand-gated ion channels.
o Ex: G protein couple receptor  signal transduction cascade
o Mainly proteins but can be carbohydrates and lipids in viruses.

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23
Q

what are the types of cell junctions?

A

Cells can form cohesive layer of intracellular junctions that are useful for communication between cell and cell and cell and extracellular matrix.

cell adhesion molecules (allow the cell-cell junctions to occur)
gap junctions
tight junctions
desmosomes
hemidesmosomes
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24
Q

cell adhesion molecules

A

proteins that allow cells to recognize each other and contribute to proper cell differentiation and development. Makeup cell cell junctions.

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25
gap junctions
Junctions (connexons): allow for direct cell-cell communication and are often found in small bunches together.  Made up of connexin: make the pores of gap junctions. One connexon is composed of 6 monomers of connexin.  Permit movement of water and some solutes directly between cells.  Random locations around the cell.
26
tight junctions
prevent solutes from leaking into the space between cells via a paracellular route.  Found in epithelial cells and function as a physical link between the cells as they form a single layer of tissue.  Continuous band around the cell  Can lead to transepithelial voltage difference.
27
desmosomes
bind adjacent cells by anchoring to their cytoskeletons.  Formed by interactions between transmembrane proteins associated with intermediate filaments inside adjacent cells.  Found in interface between two layers of epithelial tissue.  Hemidesmosomes: attach epithelial cells to underlying structures, especially the basement membrane.
28
hemidesmosomes
attach epithelial cells to underlying structures, especially the basement membrane.
29
Transport of ____ molecules occurs rapidly through the cell membrane via diffusion, while ____ require more specialized transport processes.
small nonpolar | ions and larger molecules
30
passive transport
spontaneous processes that do not require energy (ΔG<0), use concentration gradient to supply energy.  Thermodynamic motivator is increase in entropy simple diffusion, osmosis, facilitated diffusion
31
simple diffusion
substrates move down their concentration gradient directly across the membrane.  There is potential energy in the chemical gradient  Only particles that are freely permeable to the membrane are able to undergo simple diffusion.
32
osmosis
specific kind of simple diffusion that concerns water; water will move from a region of lower solute concentration to one of higher solute concentration.  Higher water concentration to lower water concentration.  Hypotonic: when the concentration of solutes inside the cell is higher than the surrounding solution, the solution is hypotonic. Water moves into the cell.  Hypertonic: the solution is more concentrated than the cell, water will move out of the cell.  Isotonic: when the solutions inside and outside are equimolar. • Still movement, just no net movement.  Osmotic pressure is one driving force behind this. It is a colligative property: a physical property of solutions that is dependent on the concentration of dissolved particles but not on the chemical identity of those dissolved particles. • Ex: two compartment container and one has more concentrated solution. Only water can pass thru the semipermeable membrane. Water will flow from low solute concentration to high solute concentration only until the hydrostatic pressure in the higher concentrated section counterbalances the tendency of water to flow across the membrane. • “sucking pressure” (against cell membrane in cells). Water will move to the compartment with the highest osmotic pressure.
33
hypotonic solution
when the concentration of solutes inside the cell is higher than the surrounding solution, the solution is hypotonic. Water moves into the cell.
34
hypertonic solution
the solution is more concentrated than the cell, water will move out of the cell.
35
water moves toward _____
higher concentration of solutes
36
define an isotonic situation and is there any movement of water?
when the solutions inside and outside are equimolar. | • Still movement of water, just no net movement.
37
osmotic pressure
It is a colligative property: a physical property of solutions that is dependent on the concentration of dissolved particles but not on the chemical identity of those dissolved particles. • Ex: two compartment container and one has more concentrated solution. Only water can pass thru the semipermeable membrane. Water will flow from low solute concentration to high solute concentration only until the hydrostatic pressure in the higher concentrated section counterbalances the tendency of water to flow across the membrane. • “sucking pressure” (against cell membrane in cells). Water will move to the compartment with the highest osmotic pressure.
38
facilitated diffusion
: simple diffusion for molecules that are impermeable to the membrane (large, polar, charged) because the energy barrier is too high for them to cross freely.  Requires integral membrane proteins to serve as transporters or channels for these substrates.  Ex: Carriers: only open to one side of the cell membrane at any given point • Substrate walks in, rotate and conformational change of the transporter, and then walks out the other side • Occluded state: the carrier is not open to either side of the phospholipid bilayer.  Channels: may be in an open or closed conformation and act like a tunnel for the particles to diffuse through.
39
active transport
net movement of a solute against its concentration gradient. o Always requires energy but the source of the energy can vary. o Primary active transport: uses ATP or another energy molecule to directly power the transport of molecules across a membrane.  Ex: transmembrane ATPase  Ex: maintains membrane potential in neurons o Secondary active transport (coupled transport): harnesses the energy of one particle going down its concentration gradient to drive a different particle up its concentration gradient.  Symport: both molecules flow in the same direction across the membrane  Antiport: the molecules flow in opposite directions across the membrane  Used in the kidneys
40
endocytosis
IN occurs when the cell membrane invaginates and engulfs material to bring it into the cell. o Pinocytosis: endocytosis of fluids and dissolved particles. o Phagocytosis: ingestion of large solids such as bacteria o Vesicle-coating proteins: initiate and carry out invagination  Ex: clathrin o Receptors are embedded in the plasma membrane.
41
exocytosis
OUT secretory vesicles fuse with the membrane, releasing material from inside the cell to the extracellular environment. o Ex: of neurotransmitters from synaptic vesicles.
42
primary active transport
uses ATP or another energy molecule to directly power the transport of molecules across a membrane.  Ex: transmembrane ATPase  Ex: maintains membrane potential in neurons
43
secondary active transport
(coupled transport): harnesses the energy of one particle going down its concentration gradient to drive a different particle up its concentration gradient.  Symport: both molecules flow in the same direction across the membrane  Antiport: the molecules flow in opposite directions across the membrane  Used in the kidneys.
44
symport
secondary active transport | both molecules flow in the same direction across the membrane
45
antiport
secondary active transport | the molecules flow in opposite directions across the membrane
46
pinocytosis
endocytosis of fluids and dissolved particles.
47
phagocytosis
ingestion of large solids such as bacteria
48
Vesicle-coating proteins
initiate and carry out invagination |  Ex: clathrin
49
membrane potential
): the difference in electrical potential across cell membranes.
50
what is resting membrane potential and what does it shoot to during depolarization?
-40 to -80, +35
51
nernst equation
is used to determine the membrane potential.
52
sodium potassium pump
 Intracellular: high K+ but low Na+, pumps 3 Na+ out for every 2 K+ pumped in.  Maintains the negative resting potential of the cell.  Leak channels also let K+ and Na+ diffuse • More L+ leak channels.  Stable resting membrane potential via the leak channels and the pump.
53
outer mitochondria membrane
highly permeable due to many large pores that allow the passage of ions and small proteins. Surrounds the inner mitochondrial membrane with the intermembrane space in between.
54
inner mitochondria membrane
: much more restricted. Has many foldings, cristae, which increase the available surface area for the integral proteins associated with the membrane.  Encloses the mitochondrial matrix, where the citric acid cycle produces high-energy electron carriers used in the electron transport chain.  No cholesterol.
55
where is the pH gradient in the mitochondria?
o There is no pH gradient between the cytoplasm and the intermembrane space.  Gradient is between the intermembrane space and the matrix (more H+ in the intermembrane space due to proton
56
describe the fluid mosaic model
This model states that the components of a membrane such as proteins or glycolipids, form a mobile mosaic in the fluid-like environment created by a sea of phospholipids.
57
phospholipids can move ______ in the plane of the membrane
rapidly | and they mix
58
is the process of a lipid flipping from the interior of the cell membrane to the exterior favorable or unfavorable?
unfavorable because it requires the polar head group to travel through the hydrophobic region of the membrane.
59
rate the following from most to least present in the plasma membrane: carbohydrates, lipids, nucleic acids, proteins
lipids (phospholipids and cholesterol) > proteins (membrane proteins, receptors, transporters) > carbohydrates (glycoproteins) > nucleic acids
60
are there a lot of nucleic acids in the cell membrane?
almost none.
61
fatty acid
carboxylic acids that contain a hydrocarbon chain and a terminal carboxyl group.
62
compare saturated and unsaturated fatty acids in the cell membrane
saturated: straight, unhealthy, reduce membrane fluidity, solid at RT unsaturated: bent, healthy, increase membrane fluidity, liquid at RT.
63
how do you get from triacylglycerol to glycerophospholipid
remove a fatty acid and add a phosphate with a polar head group
64
define rigidity
inability to be bent or forced out of shape
65
because carbohydrates are generally _____, interactions between glycoproteins and water can form _______ around the cell
hydrophilic | a coat
66
what is another name for gap junctions
connexons
67
what is transferred through gap junctions?
water and some solutes
68
what is the paracellular route?
it is the route that can be taken by some small molecules between cells tight junctions block this off in places such as epithelial tissue.
69
what is the difference between desmosomes and hemidesmosomes in what they connect?
desmosomes: primarily found at interface between two layers of epithelial tissue hemidesmosomes: attach epithelial cells to underlying structures such as the basement membrane.
70
compare the 3 classes of membrane proteins
1. transmembrane proteins: channels or receptors 2. embedded proteins: most likely have catalytic activity linked to nearby enzymes 3. peripheral proteins: cell signaling or recognition molecules.
71
give an example of a peripheral protein
cytochrome c from oxidative phosphorylation
72
can paracellular transport happen past gap junctions?
yes
73
what types of molecules need more specialized transport processes to get across the cell membrane?
small, nonpolar molecules diffuse rapidly through the cell membrane while ions and larger molecules require more specialized processes.
74
compare active and passive transport
active transport is nonspontaneous and requires energy to occur.
75
how is diffusion, facilitated diffusion, and osmosis affected by temperature?
they increase
76
what is the main thermodynamic motivator in most passive transport situations?
increase in entropy.
77
when substances flow from higher to lower concentration it results in _____
an increase in entropy.
78
in the example of water and the semipermeable membrane with salt concentration, there is a net flow of water into the other container until ____
the hydrostatic pressure from the water in the salt compartment opposes the osmotic pressure of the water into that container.
79
what is a colligative property
it is a property that does not depend on the identity of dissolved particles but the concentration of those dissolved particles.
80
what substances cannot participate in simple diffusion
large, polar, charged
81
describe the process of carrier facilitated diffusion
only open to one side of the membrane at a given moment | substrate binds to transport protein, conformational change, spins, dissociation on other side
82
what are the two types of facilitated diffusion methods?
carrier or channel
83
what is the occluded state of a carrier protein?
when the carrier is not open to either side of the phospholipid bilayer.
84
describe the process of channel facilitated diffusion
channels can be in an open state (open to both sides) or closed state (open to neither side)
85
contrast carrier and channel facilitated diffusion
when active, carrier is open to one side of membrane at a time while channel is open to both. The channel method has more rapid transport kinetics.
86
what is another name for secondary active transport?
couple transport
87
what are the names of proteins assisting with endocytosis?
vesicle-coating proteins | Ex: clathrin
88
compare some of the important examples of endocytosis and exocytosis
endocytosis: phagocytosis of bacteria by macrophages exocytosis: neurotransmitter release into the synapse
89
osmotic pressure is considered a ______ pressure because water will move toward the compartment with the highest ____ pressure
sucking | osmotic pressure
90
maintaining membrane potential requires ______ because ions may _____ diffuse through the cell membrane over time using ____ channels
energy passively leak channels
91
discuss the permeability of the outer mitochondrial membrane
it is highly permeable due to many large pores that allow the passage of ions and small proteins
92
how is the stable resting membrane potential maintaineed?
it is maintained stably via the leak channels and the Na+/K+ pump. The pump pumps 3 Na out for every 2 K it pumps in but there are more potassium leak channels so the membrane is held up.
93
do all cells in the body have a resting membrane potential?
all cells in the body have a characteristic resting membrane potential depending on the cell type.
94
what is osmotic pressure? It is the pressure needed to ____ osmosis
stop
95
fluid flows from ___ to ____ osmotic pressure
low to high
96
the citric acid cycle occurs in the ______
mitochondrial matrix
97
what is special about the inner mitochondrial membrane
it lacks cholesterol
98
what is the pH gradient between the cytoplasm and the inter-membrane space?
there is none because the outer mitochondrial membrane is so permeable there is constant balance.
99
in the equations used to calculate membrane potential, why is 61.5 used as a shortcut?
it is assuming we are physiological temperature which is approximately 310 K
100
unsaturated lipids have a ____ melting point than saturated lipids
lower
101
the movement of any solute or water by diffusion or osmosis is dependent only on the concentration gradient of ______
the molecule of interest
102
what is the least likely resting membrane potential in cells?
0

MCAT Biochem (12 decks)

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