85 Questions
What is the main function of NCX in many cell types?
Removing Ca2+ ions from plasma membranes, mitochondria, and endoplasmic reticulum
Where is NCKX2 mainly located and what function does it serve?
Neuronal cell membranes - Constituting a Ca2+ clearance mechanism
What is the primary role of Na+, K+-ATPase in animal cells?
Maintaining Na+ and K+ concentration differences across the plasma membrane
Which of the following statements about NCX is true?
It is important for removing Ca2+ ions from the plasma membranes
What role does NCX play in cellular function?
Regulating Ca2+ concentration
What is the main function of leak channels in cells?
Facilitate the flow of ions down the concentration gradient
How do ions pass through the selectivity filter in K+ channels?
By dehydrating and interacting with carbonyl groups
Where are aquaporins most abundant in cells?
Plasma membrane
Which of the following glands predominantly express aquaporins for water secretion?
Sweat glands
What role do hormone-responsive aquaporins play in animals?
Facilitate the formation of concentrated urine
In response to water deficit, what occurs in mammalian cells?
Activation of osmoreceptors
What is the process of a cell taking in fluids and small particles dissolved in it called?
Pinocytosis
Which process involves a cell engulfing a large particle, other cell, or pathogen?
Phagocytosis
What are the cup-shaped lipoprotein structures at the cell plasma membrane called?
Porosomes
Which process involves the release of large quantities of molecules from a cell?
Exocytosis
What is the term for a cell that engulfs pathogens through phagocytosis?
Phagocyte
What factor determines the speed of molecule diffusion across the cell membrane?
Size of the molecule and water association
What contributes to the resting membrane potential of a cell?
Active transport (Na+,K+-ATPase) and passive diffusion
Which ions contribute to the slight excess of positive charge on one side of the cell membrane?
Sodium (Na+)
What does the electrochemical gradient affect in terms of solute transport?
Charged solute transport
Which proteins can associate with the plasma membrane based on their topology?
Proteins containing hydrophilic and hydrophobic regions
What happens to the interior of the cell regarding electrical charge during resting membrane potential?
Turns more negative
What type of transport is simple diffusion?
Passive transport
In simple diffusion, the flow of solutes is always ________.
Down their concentration gradient
Which type of molecules can simply diffuse through the phospholipid bilayer?
Non-charged molecules
Facilitated diffusion involves the movement of molecules through ________.
Membrane channels or carriers
SGLT-1 working through facilitated diffusion is an example of solute transport depending on ________.
The solute's concentration gradient
Passive transport involves movement ________.
Down a solute's concentration gradient
What is the main reason why most polar molecules have restricted passage across the lipid bilayer of the cell membrane?
Hydrophilic nature
Which characteristic of molecules plays a significant role in determining their permeability across the cell membrane?
Molecular weight
What is the primary function of transport proteins in the cell membrane?
Transport of molecules and ions
In the context of membrane transport, what distinguishes channels from transport proteins (carriers)?
Channels selectively allow specific ions or molecules to pass through
Which type of diffusion involves the use of specific membrane proteins to facilitate the movement of molecules across the plasma membrane?
Facilitated diffusion
What is the primary characteristic of active transport that distinguishes it from passive transport mechanisms?
Moves molecules against their concentration gradient
What contributes to the resting membrane potential of a cell?
Passive diffusion of K+ ions into the cell
How does the electrochemical gradient affect solute transport?
It influences the movement of charged solutes
What type of molecules can associate with the plasma membrane based on their topology?
Proteins containing hydrophilic and hydrophobic regions
What is the main role of Na+,K+-ATPase in animal cells in the context of membrane potential?
Maintaining the electrical charge imbalance across the membrane
Which process primarily results in the interior of the cell becoming more negative during resting membrane potential?
Passive movement of negatively charged ions into the cell
How does the size and association with water affect molecule diffusion across the membrane?
Smaller, less associated with water molecules diffuse more rapidly
What is a distinguishing feature between channels and transporters in terms of solute interaction?
Channels interact more weakly with solutes compared to transporters
What is the state where transporter binding sites are not accessible for solutes?
Occluded state
What is the main function of gated ion channels?
Convert mechanical stimuli to chemical or electrical signals
In which state of transporter proteins are the binding sites exposed to the outside?
Outward-open state
What conversion do mechanosensitive channels perform?
Convert mechanical stimuli to chemical or electrical signals
How do transporters differ from channels in terms of solute transfer?
Transporters undergo conformational changes for solute transfer, while channels do not
What type of transport requires energy and is always mediated by transporters (carrier)?
Active transport
Which type of transporter can be classified based on the direction of transport?
Uniport
What type of transporter moves 2 molecules in the opposite direction?
Antiporter
Which type of active transport is driven by a gradient generated by another active transporter?
Secondary active transport
In endocytosis, what is surrounded by an area of plasma membrane to form a vesicle inside the cell?
Ingested material
Which transporter works against the solute's concentration gradient and usually requires energy from ATP?
Na⁺/K⁺ ATPase
What is the primary function of porosomes at the cell plasma membrane?
Act as secretory portals for molecules to be released
Which process involves a cell exporting molecules such as neurotransmitters and proteins?
Exocytosis
What distinguishes phagocytosis from pinocytosis in terms of the substances taken in by the cell?
Size of particles engulfed
What is the main function of phagosomes in the context of cellular processes?
Engulf large particles during phagocytosis
In exocytosis, what structures at the cell plasma membrane are involved in releasing intra-vesicular contents?
Porosomes
What is a common characteristic of transport proteins?
Bind substrates at different locations through the membrane
Which type of transporter removes calcium from cells?
Na+/Ca2+ exchanger
How do most membrane proteins cross the lipid bilayer?
In a helical conformation
What distinguishes the Na+/Ca2+ exchanger in terms of energy usage?
Utilizes energy stored in sodium electrochemical gradient
Where does the Na+/Ca2+ exchanger transport calcium ions?
3 out of the cell and 1 Na+ into the cell
What is a common structural feature of transport proteins?
Accessible substrate binding sites on both sides of the membrane simultaneously
Which type of membrane transport protein forms pores for solutes to move across the membrane?
Channels
In which state of transporters are the binding sites for solutes exposed to the inside of the cell?
Inward-open state
What is the primary difference between channels and transporters in terms of solute interaction?
Transporters interact more strongly with solutes.
Gated ion channels convert mechanical stimuli into which type of signals?
Electrical
Which state of transporters indicates that the binding sites for solutes are not accessible?
Occluded state
What distinguishes transport proteins from channels in terms of solute transfer?
Transport proteins transfer solutes more actively.
What is the main function of aquaporins in cells?
Facilitation of osmotic water flow
How does the size of ions affect their passage through the selectivity filter of K+ channels?
Smaller ions are not recognized in the filter
Which type of glands predominantly express aquaporins to facilitate water secretion?
Sweat glands
What causes an increase in the expression of aquaporins in the kidneys' collecting ducts?
Increase in water deficit
How do leak channels differ from gated ion channels?
Leak channels are always open, while gated channels are essentially closed
What distinguishes aquaporins that are hormone-responsive in animals?
They play a role in urine concentration
What type of transport involves the movement of molecules against the solute's concentration gradient and usually requires energy from ATP?
Active transport
Which of the following is a characteristic feature of primary active transporters?
Saturable kinetics like enzymes
What is the term used for transporters that move 2 molecules in opposite directions?
Antiporters
Which type of active transport is driven by a gradient generated by a primary active transporter?
Secondary active transport
How does passive transport differ from active transport?
It involves movement of molecules down their concentration gradient
What is the main difference between passive simple diffusion and channel-mediated transport?
Involvement of membrane proteins
How does facilitated diffusion differ from simple diffusion?
Involves carrier proteins
What determines the direction of transport in facilitated diffusion?
Electric potential across the membrane
Which type of molecules are able to diffuse through the phospholipid bilayer in passive simple diffusion?
Small or non-charged molecules
What distinguishes passive facilitated diffusion from active transport?
Requirement of energy
Test your knowledge on transport proteins in the cell membrane and resting membrane potential. Understand the selective passage of molecules and how membrane potential is maintained in cells.
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