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30 Cards in this Set

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  • Back
Diffusion
the movement of molecules, other than water, from an area of high concentration to an area of low concentration. No ATP energy is used. eg. Perfume filling a whole room.
Molecules move like this naturally, so no chemical or cellular energy is needed.
How does the size of molecules, temperataure and concentration gradient affect diffusion
Size of the molecules, temperature, and the size of the concentration gradient affects the speed of diffusion. eg. large molecules diffuse slower that small ones, the greater the concentration difference the faster the rate of diffusion and increased temperature speeds up diffusion. The reason diffusion takes place faster is because of the increased number of collisions of the particles. When you heat up something the particles vibrate faster, collide more often and spread out faster. When the concentration is high, there is a greater number of particles in the solution. With a greater number of particles, there is a greater chance of collision and thus spreading out. Large molecules need more energy to begin moving and thus diffuse slower.
-Lipid-soluble molecules can diffuse through the membrane easily. Oxygen and carbon dioxide pass through easily. Water passes through easily even though it is lipid insoluble. (see protein lined pores)
Osmosis
Flow of water from a high concentration to a low concentration across a selectively permeable membrane. eg. water moving from the large intestine into the blood.
Facilitated transport
is also the movement of molecules from a high concentration to a low concentration. Lipid insoluble substances such as glucose and amino acids are taken across by "carrier proteins". These carrier proteins are embedded in the plasma membrane and will pick up, carry and regulate the rate that specific molecules move into the cell.No chemical energy is required in this process
.eg. amino acids, glucose and other breakdown products of food are absorbed by the small intestine.
Active Transport
It is the movement of molecules across a living membrane from an area of low concentration to an area of high concentration with the aid of a carrier protein and using energy or ATP.

The diagram below represents the sodium/potassium pump a kind of active transport
Two kinds of active transport
Endocytosis
Exocytosis
Endocytosis
Surrounding a substance with the cell membrane and the subsequent formation of a vesicle to bring these substances into the cell. Energy is used. The diagrams below shows endocytosis of a large particle.
Exocytosis
is the opposite of endocytosis. Materials are surrounded by a vesicle in the cytoplasm of the cell and released from the cell as the vesicle merges with the plasma membrane. Materials such as waste, useless cellular debris, or useful hormones for other cells are released in this manner. Energy is used.
There are two kinds of Endocytosis
Phagocytosis - involves the ingestion of large food particles or cellular debris
Pinocytosis - involves the ingestion of fluids or dissolved particles
What is a Solution
A solution is a combination of solute (a solid) that has been dissolved in a solvent ( a liquid like water)
Isotonic solution
is a solution where the solute concentration of the solution that the cell is in is the same as the solute concentration of the cell's cytoplasm.
Hypotonic solution
is a solution where the solute concentration of the solution that the cell is in is lower than the solute concentration of a cell's cytoplasm
Hypertonic solution
is a solution where the solute concentration of the solution that the cell is in is higher than the solute concentration of a cell's cytoplasm
What happens when cells are place in different kinds of solutions
Hypertonic solutions
The cells shrink or shrivel due to water leaving the cell. If a cell is placed in a hypertonic solution (higher solute concentration outside the cell) water will leave the cell, the net movement of water is from the inside to the outside of the cell. If blood cells are placed in a salt solution, the cell will shrink or "crenate". When this occurs in a plant cell it is said to plasmolyze. The blood cells below have shrunken (lost water) because they were placed in a salt solution.
Hypotonic solutions
The cells will swell due to water entering the cell. If a cell is placed in a hypotonic solution (lower solute concentration outside the cell) water will enter the cell, the net movement of water is from the outside to the inside of the cell. If blood cells are placed in a distilled water solution, the will swell or burst. This is called hemolysis in blood cells and lysis in non blood cells. In plant cells it is called turgor pressure because the plant cell wall prevents the cell from bursting.

The diagram below shows the effect of placing red blood cells into a hypotonic solution. After two minutes they have swelled.
Isotonic solutions
When a cell is placed in a solution where the solute concentration is the same on both sides of the cell membrane, the cell will neither shrink nor swell. 0.9% sodium chloride (salt) is isotonic to blood cells.
Surface Area and Volume
This is because the surface area allows the cell to obtain the necessary raw materials and get rid of the wastes that build up. Conversely a larger cell will not be able to supply the necessary raw materials to fuel a high metabolic rate or get rid of the resulting wastes, therefore it has a slower metabolic rate.
Fluid-Mosaic Model of the Cell Membrane
The cell membrane is made up a phospholipid bilayer (double layer) with proteins embedded in it. The phospholipid bilayer has a fluid consistency, comparable to light oil. Proteins are scattered throughout the membrane, they form the mosaic. (eg. stained glass windows are mosaics.
Phospholipid bilayer
The phospolipid bilayer is the structural element that forms the physical boundary of the cell membrane. Materials which can dissolve in fat, like alcohol, can move across phospholipid bilayer with ease. Water soluble substance are unable to cross through the bilayer and must enter the cell through channel proteins.
Proteins
are involved in the passage of molecules through the membrane.
Carrier proteins
a protein that selectively interacts with a specific molecule or ion so that it can cross the cell membrane to enter or exit the cell.
Integral membrane protein
Proteins which pass through the lipid bilayer of the membrane. Integral membrane proteins can have a single transmembrane domain or multiple transmembrane domains.
Peripheral membrane protein
Proteins that associate with the outer surfaces of the membrane lipid bilayer through non-covalent interactions with integral membrane proteins or the polar groups of the lipids.
plasma membrane
Protein
Responsible for cellular structure and function.
Plasma Membrane
The outermost membrane(s) of a cell.
Organelle
A subcellular compartment which carries out a particular function(s).
Nucleus
Prominent membrane-bound organelle in eukaryotic cells containing the DNA organized into chromosomes
Mitochondrion
A doubled-membrane organelle that carries out electron transport and oxidative phosphorylation and produces most of the ATP in eukaryotic cells. The inner membrane is often folded into numerous cristae.
Eukaryote
An organism in which the cells are compartmentalized. In particular, the cells have a distinct nucleus and cytoplasm. The eukaryotes, prokaryotes (= bacteria) and archaea make up the three major domains of life.
Prokaryote
Organisms with cells lacking a well-defined membrane enclosed nucleus as well as other membrane bound organelles. They include bacteria and cyanobacteria.