Cell Membranes

What is the primary function of cell membranes?

To enclose the contents of the cell and separate intracellular components from the external environment.

This allows them to control the internal conditions within the cell and the maintenance of homeostasis

What two key qualities promote homeostatic regulation in cell membranes?

Semi-permeability and selectivity.

Semi-permeability means only certain materials are able to freely cross the cell membrane

Selectivity means the cell is allowed to control the passage of any material that cannot pass the cell membrane

What are phospholipids composed of?

Its the base unit for cell membrane, made of a hydrophilic (water-loving) phosphate head and two hydrophobic (water-fearing) fatty acid/lipid tails.

What is the term used to describe the structure of the plasma membrane?

Fluid mosaic model.

How do unsaturated fatty acids affect membrane fluidity?

They have kinks that prevent tight packing, leading to a lower melting point and increased fluidity.

What role does cholesterol play in the membrane?

It regulates fluidity, stabilizes the membrane at high temperatures, and prevents crystallization at low temperatures.

What are the main types of membrane proteins?

Integral proteins and peripheral proteins.

What are glycoproteins and glycolipids involved in?

Cell recognition and attachment points for other cells.

What is passive transport?

Movement of molecules across the membrane that does not require energy and occurs down their concentration gradient.

What is the function of the sodium-potassium pump?

To generate an electrochemical gradient by exchanging three sodium ions for two potassium ions, using ATP.

What is the difference between primary and secondary active transport?

Primary active transport directly uses ATP, while secondary active transport uses an electrochemical gradient generated by primary active transport.

What types of substances can enter or exit the cell via vesicular transport?

Solid particles (phagocytosis), liquid particles (pinocytosis), and specific particles via receptors (receptor-mediated endocytosis).

What is osmosis?

The passive movement of water molecules across the membrane from low solute concentration to high solute concentration.

What is facilitated diffusion?

The passive movement of larger or polar molecules across the membrane with the help of membrane proteins.

What determines whether water moves into or out of the cell?

The solute concentration of the cell and the surrounding solution (isotonic, hypertonic, hypotonic).

What are the main functions of the cell membrane?

To enclose cell contents, separate intracellular components from the external environment, and maintain homeostasis.

What does semi-permeability in cell membranes allow?

It allows only certain materials to freely cross the cell membrane, regulating what enters and exits the cell.

What does amphipathic mean regarding phospholipids?

Phospholipids have both hydrophilic (water-loving) heads and hydrophobic (water-fearing) tails.

What occurs to phospholipids in an aqueous environment?

They spontaneously form a bilayer, with hydrophobic tails pointing inward away from water.

What roles do integral proteins have in cell membranes?

Integral proteins penetrate the bilayer and are permanently attached, playing key roles in transport and enzymatic functions.

How do peripheral proteins associate with membranes?

They are temporarily attached to one side of the membrane and interact with integral proteins or the cytoskeleton.

What are the functions of membrane proteins?

They serve roles in junctions, enzymes, transport, recognition, anchorage, and transduction.

What is glycosylation and its importance in membranes?

Glycosylation attaches carbohydrate chains to phospholipids and proteins, aiding in cell recognition and structural integrity.

What is the fluid mosaic model?

It describes the plasma membrane as a dynamic structure with a mosaic of components that allow mobility and fluidity.

How does cholesterol affect membrane fluidity?

Cholesterol stabilizes the membrane at high temperatures and prevents crystallization at low temperatures.

What is the significance of unsaturated fatty acids in membranes?

They increase fluidity due to kinks that prevent tight packing, resulting in lower melting points.

What methods do cells use to transport molecules across membranes?

Cells use passive transport (no energy required) and active transport (requires energy) to move substances.

What is the difference between uniport, symport, and antiport transport mechanisms?

Uniport transports one molecule in one direction, symport transports two molecules in the same direction, and antiport transports two in opposite directions.

What is osmosis in the context of membrane transport?

The passive movement of water across membranes from low to high solute concentration until equilibrium is reached.

How do active transport methods differ from passive transport?

Active transport requires energy to move substances against their concentration gradient, while passive transport moves them down their gradient.

What is the function of the sodium-glucose cotransporter?

It uses a sodium gradient to indirectly transport glucose in the kidneys and small intestine.

What is the role of vesicular transport in cells?

It allows materials to enter or leave the cell without crossing the membrane, through processes like endocytosis and exocytosis.

What processes are included under passive transport?

Passive transport includes diffusion, osmosis, and facilitated diffusion that do not require input of energy.

What are the three forms of endocytosis?

Phagocytosis (solid particle engulfment), pinocytosis (liquid particle engulfment), and receptor-mediated endocytosis.

What is the primary function of the sodium-potassium pump?

To generate an electrochemical gradient by exchanging three sodium ions for two potassium ions using ATP.

What is the main difference between primary and secondary active transport?

Primary active transport directly uses ATP for energy, while secondary active transport relies on the electrochemical gradient.