Topic Two - Diffusion and Osmosis stuff Flashcards
what is diffusion
net movement of particles from a region of high concentration to a region of low concentration.
What is passive transport
Diffusion and Osmosis
no energy and it uses a concentration gradient
What is active transport
Movement across membranes that does require energy, low to high
Where can diffusion occur?
Liquid and gas, because the molecules are always moving
Diffusions occurs until…
equilibrium or homeostasis is reached
What factors affect the rate of diffusion
Large concentration gradient
Heat is applied
molecules are smaller
when movement occurs through a gaseous membrane
Why is diffusion important to life
Oxygen, food and waste products are some of the substances that move by diffusion. The substances are transported in the bloodstream, from where they can diffuse in and out of the cells.
Diffusion and Breathing
oxygen is inhales through the lungs, into the bloodstream and around the body.
Carbon dioxide waste from oxygen, exhaled via the lungs.
facilitated diffusion
When molecules are to large to pass through via regular diffusion, they are assisted by proteins in the membrane
What are the proteins that are involved in facilitated diffusion
Channel proteins
Carrier Proteins
Does facilitated diffusion require energy?
No
Carrier Proteins
Carrier proteins open and close along the membrane when open, molecules can pass through.
They bind to the molecules on one side of the membrane and release them on the other side.
Channel Proteins
form narrow passageways through whcih small ions can diffuse rapidly from where they are in high concentration and then to low concentration. Only ions of a specific size and shape can pass through a particular protein channel
Osmosis
The movement of water molecules across a semi-permeable membrane from a region of high-water concentrations to a low-water concentration. At the same time water is moving from a low solute concentration to a high solute concentration. Until Equilibrium or Homeostasis is reached
Dilute vs Concentrated
during osmosis, water molecules diffuse from pure water or a dilute solution to more concentrated solution.
Dilute Solutions have…
medium concentration of water molecules
Concentrated Solutions have…
a low concentration of water molecules
What is osmosis
osmosis is the movement of water molecules from a solution with a high concentration of water molecules to a solution with a lower concentration of water molecules, through a cell’s partially permeable membrane
Hypertonic
when the intracellular fluid has a higher water concentration than the extracellular fluid.
Hypotonic
When the extracellular fluid has a higher water concentration than the intercellular fluid
Isotonic
When the extracellular fluid and intercellular fluids are at the equal concentration
Animal Cells
- don’t have a cell wall
- dilute solutions - osmosis can cause animal cells to swell and burst LYSIS
- concentrated solutions - water loss causes the cells to shrink - CRENATION
- to remain healthy, animal cells need to maintain an isotonic water balance.
Lysis
When animals cells swell and burst
Crenation
Water loss causes the cells to shrink
The concentration of water + salt in blood is controlled by the ______
Kidneys
The Kidneys are controlled by the_______
Hypothalamus
Osmosis and plants
Root cells in plants absorb water through osmosis
SA increase - more water
water strengthens plant cells
Osmosis and cells
water and other small molecules pass through the plasma membrane.
Active Transport
Requires transport proteins (carrier proteins)
ATP/energy required
Transport against a concentration gradient
occurs through protein channels
Energy ATP binds to the protein and allows the particles to cross the membrane against the concentration gradient
Passive transport until equilibrium is reached, the movement of substances can continue through active transport.
In active transport…
diffusion is slow
some substances need to be accumulated in cells against the concentration gradient
For this to occur, energy must be used to move the needed substances across the cell membrane.
Examples of active transport
Cell metabolism produces wastes
Active transport enables cells to get rid of unwanted substances even when their concentration is much greater outside the cell.
Active transport in plants
the concentration of minerals in lower, the plant is higher. Active transport moves minerals against the concentration gradient
Active transport in humans
during digestion, the villi in the small intestine absorb the nutrient, overtime once equilibrium is reached, active transport is used to continue the concentration gradient.
Sodium Potassium Pump
Animal Cells have a high concentration of potassium ions but low sodium ions
The mechanism responsible for this is the sodium–potassium pump, which moves these two ions in opposite directions across the plasma membrane.
The sodium–potassium pump has a particular significance for excitable cells, such as nerve cells, which respond to stimuli.
Bulk Transport
Cells need to move large quantities of materials into or out of the cytoplasm, and the pores in the cell membrane cannot do this.
The process of bulk transport may achieve this. As with active transport, large amounts of energy are necessary for this to function.
There are two forms of bulk transport: endocytosis & exocytosis.
Exocytosis (exiting)
Exocytosis is the movement of substances out of a cell
A transport vesicle containing a particular
substance, maybe a waste product or a hormone, fuses with the plasma membrane releasing the substance to the outside of the cell
Endocytosis
Endocytosis is the movement of substances into the cell
Part of the plasma membrane encloses a substance
This section of the membrane then pinches off and forms a vesicle
There are two types of endocytosis, which differ according to the type of material taken in: phagocytosis & pinocytosis.
Phagocytosis
The bulk transport of solid materials into a cell
It can be selective, and the cell can discriminate between different kinds of particles
It involves the cell membrane engulfing the solid material, forming a vesicle, which moves into the cytoplasm
Pinocytosis
Occurs when a cell’s plasma membrane engulfs a drop of extracellular fluid, forming a vesicle, which moves into the cytoplasm
Factors affecting the rate of osmosis
Water potential gradient
membrane thickness
surface area
why do cells need buffering agents
to minimize the changes in pH of the internal environment
