biological membranes Flashcards
What is the function of biological membranes?
Biological membranes regulate the movement of substances in and out of cells, facilitate cell signaling, provide structural support, and enable compartmentalization within cells.
What is the fluid mosaic model?
A model describing the plasma membrane as a phospholipid bilayer with embedded proteins that move dynamically.
What are the components of the plasma membrane?
Phospholipids, cholesterol, proteins (intrinsic and extrinsic), glycolipids, and glycoproteins.
What is the role of phospholipids in the membrane?
They form a bilayer, with hydrophilic heads facing outwards and hydrophobic tails facing inwards, creating a selectively permeable barrier.
Why is the plasma membrane described as selectively permeable?
It allows certain molecules (small, non-polar) to diffuse freely while restricting others (large, charged, or polar molecules).
What is the role of cholesterol in membranes?
Cholesterol provides membrane stability, regulates fluidity, and prevents excessive movement of phospholipids.
What is the difference between intrinsic and extrinsic proteins?
Intrinsic proteins: Span the bilayer, acting as transporters or receptors.
Extrinsic proteins: Sit on the membrane surface, aiding in signaling and adhesion.
What are glycoproteins and glycolipids, and what are their functions?
Glycoproteins: Proteins with attached carbohydrate chains; involved in cell recognition and signaling.
Glycolipids: Lipids with attached carbohydrate chains; involved in membrane stability and immune response.
What are the main types of transport across membranes?
Simple diffusion, facilitated diffusion, osmosis, active transport, endocytosis, and exocytosis.
What is simple diffusion?
The passive movement of molecules from an area of high concentration to low concentration down a concentration gradient.
What types of molecules can pass through the membrane by simple diffusion?
Small, non-polar molecules such as oxygen and carbon dioxide.
What is facilitated diffusion?
The passive movement of larger or charged molecules across the membrane via channel or carrier proteins
What are channel proteins?
Intrinsic proteins that form pores in the membrane, allowing specific ions to pass through.
What are carrier proteins?
Proteins that change shape to transport specific molecules across the membrane.
What is osmosis?
The diffusion of water molecules across a partially permeable membrane from an area of high water potential to low water potential.
What is water potential?
A measure of the tendency of water to move from one area to another, solute potential + pressure potential
What happens to an animal cell placed in a hypotonic solution?
water enters by osmosis, causing the cell to swell and potentially burst (lysis).
What happens to an animal cell in a hypertonic solution?
Water leaves by osmosis, causing the cell to shrink (crenation).
What happens to a plant cell in a hypotonic solution?
Water enters, causing the cell to become turgid.
What happens to a plant cell in a hypertonic solution?
Water leaves, causing plasmolysis (cell membrane pulls away from the cell wall).
What is active transport?
The movement of molecules against a concentration gradient using ATP and carrier proteins.
What is endocytosis?
The process of engulfing substances into vesicles for transport into the cell.
What is exocytosis?
The process of vesicles fusing with the plasma membrane to release substances outside the cell.
What is phagocytosis?
A type of endocytosis where large particles or cells are engulfed by the membrane and enclosed in a vesicle
