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What does it mean when the cell membrane is semi-permeable?
 certain substances (usually small molecules) to pass while restricting others (large molecules).
What are three basic processes for transporting materials in and out of a cell?
diffusio
Carrer-mediated/facilitated transport
Vesicular transport
Key points of a passive process
Does not use the cells’ energy (from respiration)
Substances move from areas of high concentraion to lower concentration ( witht the concentration gradient)
Key points of an active process
Uses the cells’ energy
Sbstances move from low to high concentration (against the concentration gradient)
What is diffusion?
A passive process where particles move from areas of high concentration to low concentration until equilibrium is reached.
eg. oxygen or alcohol
Why does diffusion occur in gasses and liquids?
Because the molecules in gases and liquids are constantly moving
How do lipid-soluble molecules move through a semi-permeable membrane?
They diffuse through the lipid membrane as the membrane itself is made of lipids
Describe the movement of molecules in diffusion
They move in random directions and straight lines until they hit another molecule or a barrier.
Deflected molecules continue in straight lines until they hit another obstacle.
Molecules moving away from high concentration experience fewer collisions and stay on their straight paths longer.
What is net diffusion?
The overall movement of particles from high to low concentration, even though some molecules move randomly against the gradient.
What is concentration gradient/diffusion gradient?
The difference in concentration that drives diffusion
How does the concentration gradient affect diffusion rate
A steeper gradient (greater difference in concentration) results in a faster diffusion rate.
What is osmosis
The diffusion of water molecules through a differentially permeable membrane from an area of higher water concentration to an area of lower water concentration.
How is osmosis different from regular diffusion
Osmosis specifically involves the movement of a solvent (water) to balance the concentration of a solute across a membrane.
What determines water concentrataion in a solution
The proportion of water compared to dissolved solutes like sugar or salt
In which direction does water move during osmosis?
From an area of low solute concentration (high water concentration) to an area of high solute concentration. (low water concentration)
What happens as water moves into a high-solute concentration area?
The solution becomes diluted, lowering the solute concentration
What happens as water laves an area of low solute concentration?
The solute concentration in that area increases
What is osmotic pressure?
The pressure caused by differences in solute concentration on either side of a differentially permeable membrane
How does solute concentration affect osmotic pressure?
The higher the solute concentration, the higher the osmotic pressure
What is facilitated transport?
A process where proteins in the cell membrane allow molecules to be transported across the membrane
What are the two types of proteins involved in facilitated transport?
channel proteins
carrier proteins
What is the role of proteins involved channels in facilitated diffusion?
They provide a pathway for water-soluble molecules to cross the membrane without interacting with the hydrophobic inner portion
Why can’t larger molecules pass through protein channels?
The channels are very small in diameter, and larger molecules are too big to fit
How does carrier mediated transport work?
Carrier proteins change shape when specific substances bind to them opening on the other side of the membrane to release the substances
Wat are the important characteristics of the carrier proteins?
specificL only bind to a particular molecule.
Can become saturated: Once all carriers are occupied, rate of transport cannot increase
Regulated by hormones
What is facilitated diffusion?
A type of carrier-mediated transport where substances are moved from a higher to a lower concentration via a protein, in a passive process
What are examples of substances transported by facilitated diffusion?
Glucose, amino acids, and other water-soluble molecules that are too large to diffuse through the membrane
What is active transport?
A process that requires energy (ATP) to move substances against the concentration gradient ( from lower to higher concentration) via carrier proteins.
How does active transport differ from facilitated diffusion?
Active transport requires energy and does not depend on the concentration gradient, while facilitated diffusion is passive and relies on the gradient.
What is vesicular transport?
The movement of substances across the cell membrane in membranous sacs (vesicles), requiring energy to form the vesicles.
Why is vesicular transport considered an active process?
Because energy from the cell is needed to form the vesicles
What is endocytosis
The process by which a cell takes in materials by enfolding and enclosing them in a vesicle
What are the two types of endocytosis
phagocytosis (cell eating) wen the material is solid particles
Pinocytosis (cell drinking) when the material is liquid.
How does endocytosis occur?
The process in which the contents of a vesicle inside the cell are moved to the outside by fusing the vesicle with the cell membrane
What happens during exocytosis?
The vesicle formed inside the cell migrates to the membrane, fuses with it, and releases its contents into the exxtracellular fluid.
Examples of substances released through exocytosis
Saliva, breast milk, and mucus
