KA3 Flashcards
What is the fluid mosaic model?
The fluid mosaic model describes the structure of the plasma membrane, which consists of a phospholipid bilayer and a patchwork of protein molecules.
What are the properties of the phospholipid molecule?
The head is charged and hydrophilic (attracted to water), and the tail is uncharged, non-polar, and hydrophobic (repelled by water).
What are integral membrane proteins?
Integral membrane proteins are embedded within the lipid bilayer, often spanning the entire membrane, and interact extensively with the hydrophobic region of the phospholipids.
What are peripheral membrane proteins?
Peripheral membrane proteins are bound to the surface of the membrane, typically by ionic or hydrogen bonds, and have hydrophilic R groups.
How do hydrophobic interactions contribute to membrane protein positioning?
Hydrophobic R groups in integral membrane proteins allow strong hydrophobic interactions, which hold the proteins within the phospholipid bilayer.
What are transmembrane proteins?
Transmembrane proteins are integral membrane proteins that span the entire width of the membrane.
What is the function of the phospholipid bilayer?
The phospholipid bilayer acts as a barrier to ions and most uncharged polar molecules, controlling the movement of substances across the membrane.
What molecules can pass through the phospholipid bilayer by simple diffusion?
Small molecules such as oxygen and carbon dioxide can pass through the bilayer by simple diffusion.
What is facilitated diffusion?
Facilitated diffusion is the passive transport of substances across the membrane through specific transmembrane proteins.
How do channel proteins function?
Channel proteins form water-filled pores across the membrane and allow selective diffusion of specific ions or molecules.
What is the function of gated channels?
Gated channels change their conformation to allow or prevent diffusion, and can be controlled by specific signals, like ligand binding or changes in voltage.
What are ligand-gated channels?
Ligand-gated channels are controlled by the binding of signal molecules, which open or close the channel.
What are voltage-gated channels?
Voltage-gated channels open or close in response to changes in membrane potential or ion concentration.
How do transporter proteins work?
Transporter proteins bind to a specific substance, undergo a conformational change, and transfer the solute across the membrane.
What is active transport?
Active transport is the movement of substances across the membrane against their concentration gradient, requiring energy (usually from ATP).
What are pump proteins?
Pump proteins mediate active transport by transferring substances across the membrane against their concentration gradient, using energy from ATP hydrolysis.
What is the role of ATPases in active transport?
ATPases hydrolyze ATP to provide the energy for conformational changes in transport proteins, moving substances across the membrane.
What is the electrochemical gradient?
The electrochemical gradient combines the concentration gradient and the electrical potential difference, determining the movement of charged solutes.
What is membrane potential?
Membrane potential is the electrical potential difference across the membrane, created by a difference in charge between the two sides of the membrane.
What is the function of the sodium-potassium pump?
The sodium-potassium pump uses ATP to transport sodium ions out of the cell and potassium ions into the cell, establishing both concentration and electrical gradients.
How many sodium and potassium ions are transported by the sodium-potassium pump?
For each ATP hydrolyzed, three sodium ions are transported out of the cell, and two potassium ions are transported into the cell.
Why is the sodium-potassium pump important for cell metabolism?
It is found in most animal cells and accounts for a high proportion of the basal metabolic rate, helping maintain ion gradients across the membrane.
How does the sodium-potassium pump help in the small intestine?
The sodium gradient created by the sodium-potassium pump drives the active transport of glucose in the small intestine.
What is glucose symport?
Glucose symport is the transport of glucose and sodium ions simultaneously in the same direction, using the sodium gradient created by the sodium-potassium pump to move glucose against its concentration.
What happens when the sodium potassium pump becomes phosphorated?
Phosphorylation changes the confirmation shape of the sodium potassium pump. This changes the pumps affinity for ions.
