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The Working Cell
Enzymes are essential proteins in cellular processes, acting as biological catalysts that speed up chemical reactions by lowering the activation energy required for these reactions to begin.
af معاذ العساف 8 år siden
1351
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2- non-competitive inhibitors.
Change the shape of enzymes active site.
1- competitive inhibitor.
Compete for the active site. Block substrate from entering the active site.
Energy released by hydrolysis reaction.
ATP = ADP + Phosphate group + Energy
Composed of:
3- Three phosphate group.
2- Ribose sugar ( Five-carbon sugar ).
1- Adenine ( nitrogenous base ).
ATP, is the immediate source of energy. that power most forms of cellular work.
2- Anabolism: build up a complex molecule.
1- Catabolism: break down a complex molecule.
Glucose + Oxygen >> Cellular Respiration >> Carbon dioxide + water.
The other 66% generates heat.
Cells convert about 38% of the chemical energy in their fuel to energy for cellular work.
- During every energy transformation, some energy is lost as heat.
- Energy conversions increase the entropy (disorder) of the universe.
- Plant cells convert light energy to chemical energy.
- State that the energy in the universe is constant and energy can be transferred and transformed, but cannot be created or destroyed.
Potential energy, is energy that matter possess as a result of its location or structure.
Chemical energy is the most important type of energy for living organisms; it is the energy that can be transformed to power the work of the cell.
Chemical energy, is the potential energy available for release in a chemical reaction
Molecules possess potential energy because of the arrangement of electrons in the bonds between their atoms.
Example: Water behind a dam.
Kinetic energy, is the energy of motion.
Light energy, another type of kinetic energy, can be harnessed to power photosynthesis.
Thermal energy (Heat), is a kinetic energy associated with random movement of atom or molecules.
Endocytosis
There are three kinds of endocytosis :-
The 3 types of endocytosis
Receptor-mediated endocytosis.
Pinocytosis or "cellular drinking"
It takes in any and all solutes dissolved in the droplets. not specific
Process: The cell gulps droplets of fluid into tiny vesicle.
Phagocytosis or "cellular eating"
Example: an amoeba takes in a food particle via phagocytosis.
2- The vacuole then fuses with a lysosome, whose hydrolytic enzymes digest the contents of the vacuole.
1- The cell engulfs a particle by packaging it within a membrane-enclosed sac, large enough to called vacuole.
A cell use Endocytosis process to import large molecule.
A cell membrane fold inward enclosing materials from the out side
Exsocytosis
Exocytosis Process :-
The vesicle fuses with the plasma membrane, and the vesicle's contents spill out of the cell.
A transport vesicle filled with macromolecule buds from Golgi apparatus and moves to the plasma membrane.
A cell use Exocytosis process to export bulky materials.
such as Proteins and polysaccharides.
Active Transport Process :-
Figure 4.5 - Page 56
The phosphate group detaches, and the transport protein returns to its original shape.
The protein change shape in such a way that the solute is released on the other side of the membrane.
Thet ATP transfers a phosphate group to the transport protein.
A solute molecules (in the cytoplasm) attach to specific binding site on the transport protein.
ATP molecule supplies the energy for most active transport.
Active Transport: the transport that requires energy to move a solute against its concentration gradient.
Facilitated Diffusion is a type of passive transport. Because it does not require energy.
Transport protein, provides a hydrophilic channel that some molecules or ions use as a tunnel through the membrane.
e.g. Aquaporins, protein channel allows the entry or exit of water molecules. (3 billion molecule per second)
Polar or charged substances can move across a membrane with the help of specific transporter protein in a process called facilitated diffusion.
Oxygen enter the cell. Carbon dioxide passes out of the cell. Both are essential for metabolic. Both are Small, nonpolar. (cross easily).
The molecules diffuses down its concentration gradient.
Passive Transport: diffusion across a membrane with no energy investment.
a solute is a substance that dissolve in a liquid solvent, producing a solution.
Equilibrium, Molecules still move back and forth, but there is no net change in concentration. (when the concentration is the same.)
Concentration gradient means from high concentration to low concentration.
Osmosis is the diffusion of water across a membrane.
Solvent Molecules move from lower concentration of solute to higher concentration of solute.
Water cross a membrane by passive transport.
Diffusion, the tendency for particles of any kind to spread out evenly in an available space.
Molecules move from lower concentration of solute to higher concentration of solute.
Much of the traffic across cell membranes occurs by diffusion.
Molecules vibrate and move randomly as a result of a type of energy called thermal energy (heat). . One result of this motion is diffusion.
- Polar molecules do not cross easily. (Require transport protein).
e.g. Glucose.
- Non-polar molecules cross easily.
e.g. Carbon dioxide - Oxygen.
Many ions and molecules require transport protein to enter or leave the cell.
6- Transport of substance across the membrane.
5- Intercellular junctions: a protein attach adjacent cells.
4- Cell-Cell recognition: their attached carbohydrates function as identification tags that are recognized by membrane proteins of other cells.
- recognition allows cells to reject foreign cells.
3- Enzymatic activity: enzymes grouped in a membrane to carry out sequential steps of a metabolic pathway.
2- Signal transduction: Receptor for chemical messengers (signaling molecules).
1- Help maintain cell shape and coordinate changes.
2- Embedded and attached proteins.
1- Bilayer of phospholipids.
