Passive vs Active Transport Flashcards
What limits the size of a cell?
Surface area-to-volume ratio and rate of diffusion
Cells need to exchange materials efficiently, and a larger size can hinder this process.
What is passive transport?
Movement of substances across a cell membrane without the need for energy
It occurs from an area of high concentration to an area of low concentration.
Name three types of passive transport.
- Simple Diffusion
- Facilitated Diffusion
- Osmosis
What is a concentration gradient?
When the concentration of something builds up on one side of a membrane
It indicates a difference in concentration across a membrane.
Define simple diffusion.
Movement of molecules from high concentration to low concentration without energy or transport proteins
Only certain substances can diffuse freely, such as O₂ and CO₂.
What is facilitated diffusion?
Movement of molecules from high concentration to low concentration across the membrane with the help of transport proteins
It does not require energy.
What are the two types of transport proteins involved in facilitated diffusion?
- Channel Proteins
- Carrier Proteins
What is osmosis?
Movement of water molecules across a semi-permeable membrane from high solute concentration to low solute concentration
It does not require energy and uses aquaporins.
What happens to a cell in a hypotonic solution?
Water enters the cell, causing animal cells to swell and plant cells to become turgid
Hypotonic solutions have low solute concentration and more water outside the cell.
What occurs in a hypertonic solution?
Water leaves the cell, causing animal cells to shrink and plant cells to undergo plasmolysis
Hypertonic solutions have high solute concentration and less water outside the cell.
What characterizes an isotonic solution?
Equal water and solute concentration with no net movement of water
The cell remains the same size.
What is osmotic potential?
The capacity of a solution to lose water molecules through a selectively permeable membrane
It determines whether water will flow into or out of a cell.
List the factors affecting diffusion.
- Concentration gradient
- Diffusion distance
- Surface area
- Physical barriers
What is active transport?
Energy-consuming transport of molecules across a membrane against a concentration gradient
Energy is required to move substances in the opposite direction of diffusion.
Name the three types of active transport.
- Protein-mediated active transport
- Endocytosis
- Exocytosis
How does protein-mediated active transport work?
Integral proteins require energy to act as pumps or channels to move specific molecules against a concentration gradient
Energy comes from ATP.
What is endocytosis?
Cell membrane engulfs a particle by folding inward and encasing it
Energy is used to fold the membrane inwards.
What are the two types of endocytosis?
- Phagocytosis (cell eating)
- Pinocytosis (cell drinking)
Describe phagocytosis.
Endocytosis where a cell engulfs large particles by wrapping its membrane around them
It forms a vesicle containing the engulfed material.
What occurs during pinocytosis?
Cell takes in extracellular fluid and dissolved solutes by forming small vesicles
It is often called ‘cell drinking.’
What is exocytosis?
Process that allows substances to exit the cell by fusing vesicles with the plasma membrane
Energy is used for vesicle fusion and content release.
