MCAT BIO CH.6 PART 1 Flashcards
What is the function of nucleus?
Contain and protect DNA; transcription; partial assembly of ribosomes
Number of membranes surrounding nucleus?
2
What is the function of mitochondria?
Produce ATP via the krebs cycle and oxidative phosphorylation
Number of membranes surrounding mitochondria?
2
What is the function of ribosomes?
Synthesis of proteins
Number of membranes surrounding ribosomes?
0
What is the function of the RER?
Synthesis/modification of secretory, membrane-bound and organelle proteins
Number of membranes surrounding RER?
1
What is the function of the SER?
Detoxification and glycogen breakdown in liver; steroid synthesis in gonads
Number of membranes surrounding SER?
1
What is the function of the Golgi apparatus?
Modification and sorting of protein, some synthesis
Number of membranes surrounding Goldgi apparatus?
1
What is the function of the lysosomes?
Contain acid hydrolase that digest various substances
Number of membranes surrounding lysosomes?
1
What is the function of the peroxisomes?
Metabolize lipids and toxins using H2O
Number of membranes surrounding peroxisomes?
1
What is the nucleus surrounded by?
The nuclear envelope
What occurs in the nucleus in eukaryotes? Where does translation occur?
Replication, transcription and splicing; translation
Eukaryotic genome are organized into________, while the genome of prokaryotes is_______?
Linear molecules of double-stranded DNA; single circular DNA molecule
What is a chromosome?
Separate linear DNA molecule
What is a locus?
Specific location on the chromosome where the genes can be mapped
What happens to the gene in heterochromatin form?
Turned off and inaccessible
What happens to the gene in euchromatin form?
More loosely packed and allow genes to be activated
What is the purpose of nuclear matrix?
To support and provide overall structure and regulating gene expression
What are “domains” in the nucleus?
Chromosomal regions
What is the purpose of the nucleolus?
Ribosome factory
What does the nucleolus include?
RNA polymerases, rRNA, protein components the ribosome
What role would the loops of DNA in the nucleolus play?
DNA will serve as template for ribosomal RNA production
The nucleolus is responsible for the transcription of mRNA, tRNA and rRNA by_____?
Transcription of rRNA by RNA polymerase I
Transcription of tRNA and mRNA are done by RNA poly I?
False: other polys
How is the ribosome assembled in the nucleolus?
Partially
When does the ribosome become active, based on its production?
Remains inactive untila assembly is completed in the cytoplasm
What separates the nucleus from the cytoplasm?
Nuclear envelope
How many layers are composed of the nuclear envelope?
Two lipid bilayer membranes
What is the space between the nuclear membranes contiguous with?
With the lumen of the ER
Where are nuclear pores located?
Punctuated the nuclear envelope
What is the function nuclear pores?
Allows passage into and out of the nucleus
What size of molecules can enter the nucleus by diffusion?
Molecules smaller than 60 kilodaltons
What sequence do larger proteins require to enter the nucleus?
Nuclear localization sequence
What happens to proteins with the nuclear localization sequence?
Translated into the cytoplasm and then imported into the nucleus by specific transport mechanisms
Does RNA transport itself out through diffusion?
No, through a specific transport system rather than freely diffusing into the cytoplasm
The mitochondrion is the site of ______?
ATP synthesis and oxidative phosphorylation
What does the matrix include, what type of enzymes?
Pyruvate dehydrogenase and the enzymes of the Krebs cycle
What occurs in the inner membrane of the mitochondria?
Electron transport chain and ATP synthase
What are cristae, based on the mitochondria?
Inner membrane projections into the matrix
What from the inner membrane in mitochondria allows for the proton gradient for ATP synthesis?
Its impermeable to the free diffusion of polar substances
What are structural components of the outer membrane of mitochondria?
Smooth, contains large pores that allow free passage of small molecules
What is the space between the mitochondria membranes?
Intermembrane space
Why is the inner membrane folded into cristae in mitochondria?
Increase surface area
How is the genome of mitochondria?
A single circular DNA molecule
What does the mitochondria genome code for?
rRNA, tRNA, proteins, and ETC components, parts to he ATP synthase complex
What is the evolutionary theory of mitochondria?
Endosymbiotic Henry of mitochondria; independent unicellular organism living within larger cells
What does mitochondrial exhibit that is important with reproduction?
Maternal inheritance
Why is the mitochondrial only inherited from the mother?
The cytoplasm of the egg becomes the cytoplasm of the zygote
What does the sperm contribute in reproduction?
Only genomic nuclear DNA
Why is the rough ER called rough?
Large number of ribosomes bound to its surface
What is the purpose of the ribosomes for the rough ER?
Site of protein synthesis for proteins targeted to enter the secretory pathway
What type of enzymes may be present in the smooth ER although its usually not actively involved in protein processing?
Steroid hormone biosynthesis enzymes for gonads or degradation of environmental toxins in the liver
What does the ER do that’s important with protein localization?
Key role in directing protein traffic to different parts of the cell
Where do proteins that are translated on free cytoplasmic ribosomes go?
Peroxisomes, mitochondria, nucleus or in cytoplasm
Where do proteins that are translated on the rough ER ribosomes go?
- Secreted into extracellular environment
- Integral plasma membrane proteins
- In the membrane or interior of the ER, Golgi apparatus or lysosomes
Based on the rough ER, which membranes is it in contiguous with?
Interior of the ER, Golgi Apparatus, lysosomes, and the extracellular environment
Proteins synthesized on the rough ER are transported in vesicles to which location first?
From the ER to the Golgi apparatus
After the proteins go to the Golgi apparatus, where does it go? (Based on ER)
To the plasma membrane or lysosome
What decides if a protein is translated on the rough ER or not?
Determined by the sequence of the protein itself
All proteins, even the ones from the rough ER, begins translation where?
Start translation in the cytoplasm
Which proteins have the signal sequence to continue translation on rough ER?
Secreted proteins and lysosome proteins
Where is the signal sequence from ER ribosomal proteins?
Amino acid sequence at their N-terminus
How is the signal sequence from ER ribosomal proteins recognized? What does it then do?
By the signal recognition particle (SRP); binds to the ribosome
One the ribosome-SRP complex is made, what occurs to it, based on ER?
Rough ER has STP receptors that dock the ribosome-SRP complex on the cytoplasmic surface along with the polypeptide and the mRNA
What happens to the polypeptide since the complex gets bound to the STP receptors, based on ER?
Translation pushes the polypeptide into the ER lumen, signal peptide first
What happens after rough ER ribosomal translation is complete?
Signal peptidase removes the signal peptide from the polypeptide
Where is the signal peptidase located?
In the ER
What happens to secreted proteins after the signal peptide is removed, based on ER?
The protein is transported in the interior of vesicles, through the Golgi, to the plasma membrane, released by exocytosis
What are transmembrane domains and where are they located?
Hydrophobic amino acid residues located on integral membrane proteins
Where do the transmembrane domains pass through, based IMN (integral membrane proteins)?
Through lipid bilayer membranes
What are transmembrane domains basically, based on IMN?
Signal sequences found int he interior of the protein but NOT AT THE N-TERMINUS
During translation, the transmembrane domains are threaded through what?
The ER membrane
What type of initial post-translation modification of proteins may occur in the rough ER?
Disulfide bond formation, glycosylation
What is the default target for proteins that go through the secretory path based on protein traffic for ER?
Plasma membrane
What are needed for the protein to end up elsewhere than the plasma membrane (ex. Golgi, ER, lysosome)?
Targeting signals
Proteins that are made in the cytoplasm but need to be sent to an organelle are apart of the secretory pathway. T/F
False
What sequence do proteins made in cytoplasm but need to be transported to a different organelle, need?
Localization signals
What is the structure of the Golgi Apparatus?
Group of membranous sac stacked together
What are the functions of the Golgi?
- Modification of proteins made in RER
- Sending proteins to destinations
- Synthesis of macromolecules
Based on the modification of proteins made in RER, what is the Golgi especially important for?
Modification of oligosaccharidse
The vesicle traffic too and from the Golgi are…?
Unidirectional
What is retrograde traffic based on the Golgi traffic?
Proteins hat reside in the ER may accidentally escape and must be brought back to the ER from the Golgi
Based on Golgi, the portion closest to the ER are called….and the portion further from the ER are called…?
cis stack, trans stack
What is the medial stack based on Golgi?
The middle stack
What happens to the proteins in the vesicle once they reach the Golgi?
Fuse with the cis stack
What occurs after the protein vesicle fused with the cis stack of the Golgi?
Modified and transferred to the medial stack, further modified and pass to the trans stack
How does the proteins leave the Golgi?
At the trans face in transport vesicles
What happens if the vesicle contains proteins anchored to its membrane?
These proteins will remain attached to the cel as cell-surface proteins
What is the constitutive secretory pathway based on Golgi?
Vesicles from the Golgi immediately to the cell surface
What is the regulated secretory pathway?
Specialized secretary cells store secretory proteins in secretory vesicles and release them at certain times
What is the lysosome responsible for?
Degradation biological macromolecules by hydrolysis
Does lysosome have a membrane?
Yes
Where are the lysosome proteins made?
In the RER
What is autophagy and which organelle processes it?
Self-eating and lysosome
What is phagocytosis and which organelle processes it?
Cell eating and lysosome
What is the purpose of macrophage?
Apart of the immune system, engulfing bacteria and viruses
Where do bacteria and viruses end up to be degraded?
End up in a phagocytic vesicle that will fuse with a lysosome
What is crinophagy and which organelle processes it?
Digestion of excess secretory proteins and lysosome
What happens after hydrolysis that occurs in the lysosome?
Release molecular building blocks into the cytoplasm for reuse
What enzyme is responsible for degradation in the lysosomes?
Acid hydrolase
What do the acid hydrolases need in order to be activated, based on lysosome?
Only hydrolyze substrate when they are in an acidic environment
What happens to the cell if the lysosome ruptures?
The enzymes will not damage the cell because the acidic fluid will be diluted
What is the peroxisome?
Small organelles that perform a variety of metabolic tasks
What do the enzymes produce as a byproduct in the peroxisome?
Produce hydrogen peroxide
Why is the byproduct from peroxisome important in the body? (H2O2)
Essential for lipid breakdown in many cell types
How to peroxisome assist in the liver?
Detoxification of drugs and chemicals
Why can hydrogen peroxide be contained in the peroxisome?
Contained an enzyme called catalase which converts it into H2O and O2
What do animal cells rely on instead of cell wall?
Internal cytoskeleton
What type of cells have a cell membrane and a cell wall?
Bacteria, plants and fungi
What do fungi have in the cell wall?
Chitin
All of the membranes of the cella re composed of what?
Lipid bilayer membranes
What are the three most common lipids in eukaryotic membranes?
Phospholipids, glycolipids, and cholesterol
Which lipid is most abundant in eukaryotic membrane?
Phospholipids
What is an example of a phospholipid in eukaryotic membrane?
Phosphatidyl choline
What is the structure phosphatidyl choline?
Two long hydrophobic fatty acids esterified to glycerol and a charged phosphoric choline group
Are phospholipids hydrophobic or hydrophilic?
Both
What is the structure glycolipids?
Fatty acids groups and carbohydrate side chains
Are glycolipids hydrophobic or hydrophilic?
Both
Why can the bilayer membrane reseal and repair itself easily?
Lowest energy state for these molecules
What do fatty acids form in the presence of water?
Micelles
What is the structure of a phospholipid?
Phosphate and glycerol head with two hydrophobic fatty acid tails, one unsaturated with a bent
What happens if a phospholipid is in the presence of water?
Forms a lipid bilayer
What type of molecule are cell-surface receptors?
Proteins
What are cell-surface receptors?
Bind extracellular signaling molecules and relay these signals into the cell
What are channel proteins?
Selectively allow ions or molecules to cross the membrane
What are the two types of membrane proteins?
Integral or peripheral
Where are integral membrane proteins located?
Embedded in the membrane and held by hydrophobic interactions
What are transmembrane domains?
Membrane-crossing regions
At which point in the secretory pathway would the insertion of transmembrane domains int the membrane occur?
As the protein is translated and threaded across the ER membrane
Where are integral membrane proteins located?
Stuck to integral membrane proteins
Integral proteins may have what base on the membrane?
Complex pattern of transmembrane domains and portions not within the membrane
What is the current understanding of membrane dynamics?
Fluid mosaic model
What is the fluid mosaic model?
The membrane is seen as a mosaic of lipids and proteins that are free to move back and forth fluidly
What does it mean when it states membrane has polarity?
Inside face and outside face remain different
All glycosylations are found…?
On the extracellular face
What is the exception to the fluidity of the membrane?
Some proteins are anchored to the cytoskeleton and cannot move in any direction
How does composition of lipids in the membrane affect fluidity of the membrane?
- Unsaturated fatty acids - Kink - Increase Fluidity
2. Saturated - Tightly packed - Less Fluidity
Other than the composition of the lipid membrane themselves, what interactions also are major determinant in the membrane fluidity?
Hydrophobic van der Waals interacts between the fatty acid side chains
Which type of fatty acids would have strong van der Waals?
Saturated
Which molecule plays an important role in maintaining optimal membrane fluidity?
Cholestrol
How does cholesterol play an important role in maintaining optimal membrane fluidity?
Fitting into the membrane interior
What is molarity?
Concentration of a solution (moles of solute) per volume (in liters) of solution
What is the equation for molarity?
(M) = # moles of solute / # liters of solution
What is molality?
Concentration in terms of moles of solute per MASS (kg) of solvent
What is the equation for molality?
Molality (m) = # moles of solute / # kg of solvent
Why is molality useful when measuring something involving temperature?
It does not change with temperature
Why is the molar and molal concentrations of dilute aqueous solution usually the same?
A liter of water has a mass of one kg
What is mole fraction?
The fraction of moles of a substance relative to the total moles in a solution
What is the equation of mole fraction?
mole fraction of S = Xsubscript s = # moles of substance S / total # moles in solution
When is mole fraction useful?
When more than one solute is present
What happens when ionic substances dissolve?
They dissociate into ions
What are electrolytes? Why?
Free ions in a solution; they can conduct electricity
What is partial dissociation of an ionic substance?
A certain percentage of the ions will remain paired
What are strong electrolytes?
Solutes that dissolve completely
What are weak electrolytes?
Remain ion-paired to some extent
What are nonelectrolytes?
Covalent compounds that don’t dissociate into ions
Which electrolytes are better conductors?
Solutions of strong electrolytes are better conductors of electricity than those of weak electrolytes
What is the van’t Hoff factor (i)?
Tells us how many ions one unit of substance will produce in a solution?
What is another term for van’t Hoff?
Ionizability (i)
If a molecule is non-ionic, what would be its ionizability factor?
1
What would be the ionizability of NaCl?
2 since it dissociates into Na and Cl
What would be the ionizability of CaCl2?
3 since it dissociates into 1Ca and 2Cl
What does the colligative properties depend on?
On the number of solute particles in the solution rather than the type of particle
What is an important key factor when calculating colligative properties?
The identity of the particle is not important
When stating for colligative properties, that 1M of solution of any solute, the change in colligative property will…?
Be the same no matter what the size, type or charge of the solute particles
If you have one mol of sucrose, how many number of particles in solution of 0.5 mol of NaCl?
The same because sucrose i is 1 and NaCl i is 2, so it would be the same
What are the four types of colligative properties?
- Vapor-Pressure Depression
- Boiling-point elevation
- Freeing-point depression
- Osmotic pressure
What is vapor pressure?
The pressure from the gaseous phase of a liquid that evaporated from the exposed surface of the liquid
How does the intermolecular forces and vapor pressure correlate?
The weaker a substance’s intermolecular forces, the higher its vapor pressure (more easily it evaporates)
What are liquids said to be volatile?
Liquids with high vapor pressure
What happens when a solute is dissolved into a solvent?
More energy is required to enter the gas phase
Why is more energy required to enter the gas phase when a solute is dissolved into a solvent?
The solvent molecules need to break away from their interactions with the solute before they can enter gas phase
What happens if you add more solute to the same solution, based on vapor pressure?
Will decrease its vapor pressure
What is the boiling-point elevation referring to?
The increase in boiling point directly related to the number of particles in a solution and the type of solvent
Do we have to take in consideration the ionizability in the boiling-pint elevation?
Yes
What is the equation for boiling-point elevation?
delta Tsubscript b = ksubscriptb(i)(m)
Describe each component of the boiling-point elevation formula?
kb - solvent’s boiling point
i - solute’s van’t Hoff factor
m - molal concentration of the solution
What is the kb of water based on boiling point elevation?
kb = 0.5 degree celsius / m
What happens to the liquid when attempting to freeze hen a solute is present?
Less able to achieve solid state as solute particles interfere with arrangements of the solvent molecules
What is the formula for freezing-point depression?
delta T f = -k subscript f (im)
In the freezing-point depression, what does kf stand for?
The solvent’s freezing-point depression constant
In the freezing-point depression, what does i stand for?
The solute’s van’t Hoff factor
In the freezing-point depression, what does m stand for?
Molal concentration
What is the kf for water in freezing-pain depression?
1.9 degree celsius / molal concentration
According to which law explains diffusion?
Second law of thermodynamics
Why does diffusion lead particles to spread out and occupy all available space?
Maximizing entropy
A solute will always diffuse__________ (in which direction)? What does that mean?
Down its concentration gradient; from high to low concentration
What is the different between osmosis and diffusion?
Osmosis is diffusion in which solvent diffuses rather than solute
If a cell is placed in a hypotonic solution, what will happen to the cell?
Cell will burst
In osmosis, the direction is not permeable to what…?
To solutes
What does the work tonicity mean?
Describe osmotic gradient
What does isotonic solution mean?
The solvent concentration is the same inside and outside
What does hypertonic solution mean?
Solution has more total dissolved solutes than the cell
What does hypertonic solution mean?
Solution has less total dissolved solutions than the cel
What other isotonic terms may be used to describe osmosis?
isoosmotic, hyperosmotic, and hypoosmotic
Based on water moving down its concentration gradient, how would that be described in terms of cell?
Into a cell
What is the tendency of water based on particles presence and osmosis?
Moved towards where there are more particles
Osmosis describes the new movement of water across a ________from a region of _______?
semipermeable membrane from a low solute concentration to a region of higher solute concentration
What is the symbol for osmotic pressure?
Π
What is osmotic pressure?
The pressure it would take to stop osmosis from occurring
What is the osmotic pressure of a solution equation?
Π = MiRT
What is Π and what’s the units?
osmotic pressure, atm
Based on the osmotic pressure formula, what does the M symbolize?
Molarity of the solution
Based on the osmotic pressure formula, what does the i symbolize?
van’t Hoff factor
Based on the osmotic pressure formula, what does the R symbolize?
is the universal gas constant
What is the the universal gas constant?
0.0821 L-atm /K-mol
Based on the osmotic pressure formula, what does the T symbolize?
Temperature in kelvins
What is passive transport?
Any thermodynamically favorable movement of solute across a membrane
What are two types of passive transport?
- Simple diffusion
2. Facilitated diffusion
What is simple diffusion?
Diffusion of a solute through a membrane without help from a protein
What is facilitated diffusion?
Specific integral membrane proteins allow material to cross the plasma membrane down a gradient
What is an example in the human body of facilitated diffusion?
Glucose shuttled across RBC lipid bilayer by a protein
What are two types of protein that aid in facilitated diffusion?
- Channel proteins
2. Carrier proteins
What is selective permeability membrane?
Permeability to some things despite impermeability to most things
What are channel proteins?
Allow material that cannot pass through the membrane by simple diffusion to flow through
Ion channels are said to be ___? What does that mean?
Gated; the channel is open in response to specific environmental stimuli
What is a voltage gated ion channel?
Response to a change in the electric potential across the membrane
What is a ligand-gated ion channel?
Opens in response to binding of a specific molecule
The regulation of membrane potential by gated ion channel plays a key role in what part of the body?
Nervous system
Can ion channels move a ion against an electrochemical gradient?
No
What are carrier proteins?
Can transport molecules through membranes by facilitated diffusion
What do channel proteins form to allow the ion to flow through the semipermeable membrane?
Tunnel through the membranes
How is carrier proteins different than channel proteins?
Carrier proteins bind to the molecule and go through conformational change to let the molecule through
What are uniports based on carrier proteins?
Transport only one molecule across
What are symports?
Carry two substances across a membrane in he same direction
What are anti ports?
Carry two substances in opposite directions
What is a pore based on osmosis?
Tube through the membrane so large that its not selective
What type of molecules may not be able to cross a pore even though its not selective?
Molecule may not cross if it has the wrong charge and just barely small enough to cross
What is the composition of pores?
Polypeptides called porins
Where are pores present, based on other topics we’ve studied in different chapters?
Double nuclear membrane, outer mitochondrial membrane, gram-negative bacterial outer membrane
Why doesn’t eukaryotic membrane have pores?
Because pores destroy the barrier function of the membrane
What type of kinetics is exhibited in facilitated diffusion and why?
Saturation kinetics; finite number of integral membrane proteins
What is the flux?
The rate of diffusion
What is active transport?
Movement of molecules through the plasma membrane against a gradient
How is the input of energy processed for the active transport?
The transport process is coupled to a process which is thermodynamically favorable (delta G < 0)
For active transport, what can the gradient being pumped against involve?
Electric potentials that form a combined electrochemical gradient that must be pumped against
What is primary active transport?
The transport of a molecule is coupled to ATP hydrolysis
What is secondary active transport?
The transport process is not coupled directly to ATP hydrolysis
How is the secondary active transport processed, based on ATP?
ATP used first to create a gradient, and then the potential energy in hat gradient drives the transport of some other molecule
What is ATP called in the secondary active transport?
Indirect as its not ATP used to drive the transport
What is an example of secondary active transport?
Glucose driven against glucose concentration gradient by the co-transport of sodium ions down the sodium electrochemical gradient established by an ATPase pump
What is an example of an active transport that is the prime example of it?
Na + / K + ATPase
What is Na + / K + ATPase?
A transmembrane protein in the plasma membrane of all cells in the body
What is the activity provided by that Na + / K + ATPase?
Pump 3 Na + out of the cell, 2 K + into the cell, hydrolyze 1 ATP to drive these ions against their gradients
What happens to the sodium pumped outside of the cell on the Na + / K + ATPase?
Stays outside of the cell since plasma membrane is impermeable
What happens to the potassium pumped inside of the cell on the Na + / K + ATPase?
Movees down its concentration gradient by leaking outside through potassium leak channels
Why is the potassium leak channels important for the cell?
Maintain osmotic balance with its surroundings
What happens to the charge of the cell when potassium leaves?
The exist of potassiums positive creates an electric potential with a net negative charge on the interior of the cell
The concentration gradient provided by Na + / K + ATPase is the driving force behind______of many different molecules?
Secondary active transport
What are the three reasons the Na + / K + ATPase is important?
- Maintain osmotic balance
- Establish resting membrane potential
- Creates Na [M] gradient to drive 2nd active transport
Why is chloride so concentrated outside the cell?
The cell contains millions of negative charges on macromolecules inside the cell; Cl outside is to maintain negative charged substance outside concentrated
Based on the Na, K, Cl and Ca based on intracellular and extracellular concentration, tell me of their trends?
Ca2+: least amount intra and extra
Na+: little intra, lots extra, more than Cl for both
K+: lots intra, little extra,
Cl-: little intra, lots extra, less than Na+
