Biomembranes Flashcards
What is the primary function of cell membranes?
To act as a selective barrier that regulate the movement of substances in and out of cell
What are the main components of cell membranes?
Phospholipids, proteins, cholesterol and carbohydrate
How do phospholipids contribute to membrane structure?
They form a bilayer where hydrophilic (water-attracting) heads face outwards and hydrophobic (water-repelling) tails face inward
How do ion channels regulate membrane potential?
Ion channels allow specific ions to flow across the membrane, which alters the electrical charge inside the cell and generates action potentials.
What role do proteins play in membrane function?
Proteins serve as channels, receptors, and enzymes that facilitate communication and transport across the membrane.
What is membrane permeability?
Membrane permeability refers to the ability of the membrane to allow substances to pass through; it is influenced by factors like lipid solubility and size.
What is the resting membrane potential?
The resting membrane potential is the electrical charge difference across the cell membrane when a cell is not actively sending signals, typically around -70 mV.
What factors influence the resting membrane potential?
Ion concentration gradients (like Na⁺ and K⁺), membrane permeability to different ions, and the activity of the sodium-potassium pump.
What is the sodium-potassium pump?
An ATP-driven pump that extrudes three sodium ions (Na⁺) from the cell and brings in two potassium ions (K⁺), helping maintain the ion gradients essential for membrane potential.
How do receptor proteins regulate cell signaling?
Receptor proteins bind to specific ligands (like hormones or neurotransmitters) and initiate intracellular signaling pathways that affect cell function.
What is the role of cholesterol in cell membranes?
Cholesterol helps maintain membrane fluidity and stability by preventing the fatty acid chains of phospholipids from packing too closely together.
What is facilitated diffusion?
A passive transport mechanism where molecules cross the membrane via specific transport proteins without the expenditure of energy
What is the function of active transport?
Active transport moves substances against their concentration gradient using energy, typically provided by ATP, ensuring necessary ion concentrations are maintained.
How do changes in membrane fluidity affect function?
Changes in fluidity can alter protein function, ion channel activity, and overall membrane integrity, impacting cell signaling and transport processes
What is a concentration gradient?
A concentration gradient refers to the difference in the concentration of a substance between two areas, which drives the movement of solutes from regions of higher concentration to regions of lower concentration.
What is an electrical gradient?
An electrical gradient is the difference in charge across a membrane, which can influence the movement of charged particles (ions) toward an area with the opposite charge.
How do concentration gradients affect solute transport?
Concentration gradients drive passive transport mechanisms, such as diffusion, allowing solutes to move down their gradient without the expenditure of energy
How do electrical gradients influence ion movement?
Electrical gradients pull positively charged ions (cations) toward negatively charged areas and negatively charged ions (anions) toward positively charged areas, impacting their transport across the membrane.
What is facilitated diffusion?
Facilitated diffusion is a passive transport process where specific molecules move across the membrane via protein channels or carriers, driven by their concentration gradient
What role do ion channels play in transport?
Ion channels are membrane proteins that allow selective passage of specific ions based on concentration and electrical gradients, contributing to the maintenance of membrane potential
What is the Na+/K+ ATPase?
The Na+/K+ ATPase is an active transport pump that moves sodium ions out of the cell and potassium ions into the cell against their concentration gradients, using ATP for energy.
How do gradients contribute to the resting membrane potential?
The resting membrane potential is established by the unequal distribution of ions (primarily Na+ and K+) across the membrane, created by concentration and electrical gradients maintained by pumps like Na+/K+ ATPase
What is osmosis, and how is it affected by concentration gradients?
Osmosis is the passive movement of water across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration, driven by concentration gradients
How do electrical and concentration gradients work together?
Together, electrical and concentration gradients create the electrochemical gradient, which determines the direction and magnitude of ion movement across membranes, influencing cell signaling and function.
What happens during depolarization in neurons?
During depolarization, there is a rapid influx of Na+ ions into the neuron due to both the concentration gradient and electrical gradient, causing the membrane potential to become less negative.
What is secondary active transport?
Secondary active transport uses the energy from the movement of one substance down its concentration gradient to drive the transport of another substance against its gradient, often mediated by co-transporters.
What drives the movement of ions across a membrane in passive transport?
a) ATP
b) Electrochemical gradient
c) Enzymes
d) Light energy
b) Electrochemical gradient
Which of the following best describes a concentration gradient?
a)Movement of solutes from high to low concentration
b) Movement of solutes from low to high concentration
c) Movement of solutes against the electrochemical gradient
d) No movement of solutes
a) Movement of solutes from high to low concentration
What happens when an ion moves down its electrical gradient?
a) It moves towards an area of opposite charge
b) It moves towards an area of the same charge
c) It moves randomly
d) It uses ATP for movement
a) It moves towards an area of opposite charge
What is the term for the combined influence of concentration and electrical gradients on ion movement?
a) Electrical potential
b) Osmotic pressure
c) Electrochemical gradient
d) Diffusion gradient
c) Electrochemical gradient
The movement of sodium ions into a cell when its concentration outside is higher than inside is an example of:
a) Simple diffusion
b) Active transport
c) Facilitated diffusion
d) Endocytosis
c) Facilitated diffusion
Which type of transport requires energy to move solutes against their concentration gradient?
a) Passive transport
b) Facilitated diffusion
c) Active transport
d) Osmosis
c) Active transport
What is the definition of passive diffusion?
Movement of solutes across a membrane from an area of higher concentration to an area of lower concentration
What is the mechanism of passive diffusion?
Driven by the concentration gradient; no transport protein or energy required
What is the definition of facilitated diffusion?
Passive movement of solutes across a membrane through specific carrier proteins or channels without using energy
Describe the mechanism of facilitated diffusion
Solutes move down their concentration gradient, but require a specific protein to facilitate their passage (e.g., glucose transporters).
What is the definition of active transport?
Movement of solutes against their concentration gradient using energy, usually in the form of ATP.
Describe the mechanism of active transport
Involves transport proteins (pumps) to move solutes from lower to higher concentration.
What is the definition of primary active transport?
Active transport where energy (typically from ATP hydrolysis) is directly used to pump solutes across a membrane.
Name an example of primary active transport
Sodium-potassium pump (Na+/K+ ATPase).
Define secondary active transport
Active transport that uses the energy stored in the electrochemical gradient of one molecule to drive the movement of another molecule against its gradient.
Describe the mechanism of secondary active transport
Often involves co-transport, such as symport or antiport (e.g., sodium-glucose co-transport).
Which of the following mechanisms requires no energy and allows solutes to move down their concentration gradient?
a) Primary active transport
b) Passive diffusion
c) Secondary active transport
d) Endocytosis
b) Passive diffusion
Which process involves water-soluble solutes passing through channels or pores in a membrane?
a) Passive diffusion
b) Aqueous diffusion
c) Facilitated diffusion
d) Secondary active transport
b) Aqueous diffusion
Which type of transport requires a transport protein but no energy?
a) Facilitated diffusion
b) Primary active transport
c) Osmosis
d) Pinocytosis
a) Facilitated diffusion
What distinguishes primary active transport from secondary active transport?
a) Primary active transport directly uses ATP, while secondary active transport uses the electrochemical gradient of another solute.
b) Primary active transport uses the concentration gradient, while secondary active transport does not.
c) Secondary active transport is slower than primary active transport.
d) Both use ATP directly.
a) Primary active transport directly uses ATP, while secondary active transport uses the electrochemical gradient of another solute.
Which of the following is an example of primary active transport?
a) Sodium-glucose co-transport
b) Glucose facilitated diffusion
c) Sodium-potassium pump (Na+/K+ ATPase)
d) Simple diffusion of oxygen
c) Sodium-potassium pump (Na+/K+ ATPase)
Which type of transport is responsible for moving glucose into a cell using sodium ions’ electrochemical gradient?
a) Passive diffusion
b) Facilitated diffusion
c) Primary active transport
d) Secondary active transport
d) Secondary active transport
