transport Flashcards
What is diffusion
Diffusion is the net movement of particles (molecules or ions) from an area of higher concentration to an area of lower concentration
What happens when molecules diffuse in both directions
Molecules will diffuse both ways, but the net movement will be to the area of lower concentration. This continues until particles are evenly distributed throughout the liquid or gas
What is the concentration gradient
The concentration gradient is the path from an area of higher concentration to an area of lower concentration. Particles diffuse down a concentration gradient
Is diffusion an active or passive process
Diffusion is a passive process — no energy is needed for it to happen
Which molecules diffuse through cell membranes
Small, non-polar molecules such as oxygen and carbon dioxide can diffuse easily through spaces between phospholipids
Why can water diffuse across plasma membranes
Water is small enough to fit between phospholipids, so it can diffuse across plasma membranes even though it is polar. This process is called osmosis
How does the concentration of CO2 affect its diffusion across the plasma membrane
CO2 molecules diffuse from an area of higher concentration (in the cell cytoplasm) to an area of lower concentration (in the tissue fluid surrounding the cell)
What factors affect the rate of diffusion
The rate of diffusion is affected by the concentration gradient, the thickness of the exchange surface, the surface area, and the temperature
How does the concentration gradient affect the rate of diffusion
The higher the concentration gradient, the faster the rate of diffusion
How does the thickness of the exchange surface affect the rate of diffusion
The thinner the exchange surface, the faster the rate of diffusion because the particles have a shorter distance to travel
How does the surface area affect the rate of diffusion
The larger the surface area, the faster the rate of diffusion (e.g., a larger cell membrane)
How does temperature affect the rate of diffusion
The warmer it is, the faster the rate of diffusion because particles have more kinetic energy and move faster
What is facilitated diffusion?
Facilitated diffusion is the process by which larger molecules, ions, and polar molecules move across the cell membrane through carrier proteins or channel proteins, down their concentration gradient.
Does facilitated diffusion require energy?
No, facilitated diffusion is a passive process and does not require energy. It moves particles down their concentration gradient.
How do carrier proteins assist in facilitated diffusion?
Carrier proteins help move large molecules into or out of the cell by attaching to them, changing shape, and releasing them on the opposite side of the membrane.
How does facilitated diffusion work for channel proteins?
Channel proteins form pores in the membrane that allow charged particles to diffuse through, down their concentration gradient.
How is active transport different from facilitated diffusion?
Active transport moves molecules against their concentration gradient, unlike facilitated diffusion which moves particles down their gradient. Active transport requires energy from ATP.
How does active transport use carrier proteins?
In active transport, a molecule binds to a carrier protein, the protein changes shape, and the molecule is moved across the membrane against its concentration gradient using energy (ATP).
Can you provide an example of active transport?
An example of active transport is the movement of calcium ions (Ca2+) across the membrane, where they are moved from an area of low concentration to an area of high concentration using energy.
What is the role of ATP in active transport?
ATP provides the energy needed for active transport to move molecules against their concentration gradient using carrier proteins.
What is endocytosis?
Endocytosis is the process by which cells take in large substances by surrounding them with a section of the plasma membrane, which then pinches off to form a vesicle inside the cell containing the ingested substance.
What types of substances can be taken in by endocytosis?
Endocytosis is used for substances too large to be taken in by carrier proteins, such as proteins, lipids, carbohydrates, and even microorganisms or dead cells (by white blood cells).
Does endocytosis require energy?
Yes, endocytosis requires energy in the form of ATP, similar to active transport.
How does exocytosis work?
Exocytosis is the process where cells release substances, such as digestive enzymes or hormones, by vesicles pinching off from the Golgi apparatus and fusing with the plasma membrane to release their contents outside the cell.
What substances are released during exocytosis?
Substances such as digestive enzymes, hormones, and lipids are often released through exocytosis. Membrane proteins may also be inserted into the plasma membrane instead of being released outside the cell.
Does exocytosis require energy?
Yes, exocytosis requires energy in the form of ATP.
What is osmosis?
Osmosis is the diffusion of water molecules across a partially permeable membrane, moving from an area of higher water potential (higher concentration of water molecules) to an area of lower water potential (lower concentration of water molecules).
What is water potential?
Water potential is the potential of water molecules to diffuse into or out of a solution. Pure water has the highest water potential, and all solutions have a lower water potential than pure water.
How does osmosis work in a cell?
Water moves in or out of a cell by osmosis, depending on the water potential of the surrounding solution.
What happens to animal cells in a solution with a lower water potential than the cell?
In a solution with lower water potential, water will move out of the animal cell by osmosis, causing the cell to shrink or shrivel.
What happens to animal cells in a solution with a higher water potential than the cell?
In a solution with higher water potential, water will move into the animal cell by osmosis, causing the cell to swell and possibly burst (lysis).
What happens to plant cells in a solution with lower water potential than the cell?
In a solution with lower water potential, water will move out of the plant cell by osmosis. The plant cell will become plasmolysed, with the plasma membrane pulling away from the cell wall.
What happens to plant cells in a solution with higher water potential than the cell?
In a solution with higher water potential, water will move into the plant cell by osmosis. The plant cell will become turgid (firm) as it fills with water but does not burst because of the rigid cell wall.
