REQUIREMENTS OF A CELL 1. Genetic material that permits the production of identical cells ~ Deoxyribonucleic acid (DNA) – “blueprint” of a specific species. 2. Metabolic machinery for the maintenance of life-sustaining activities. 3. Cell membrane which enables the cell to exchange materials with its environment.
METABOLISM AND ITS PHASES 1. Anabolism – aka “ constructive phase ” ~ all chemical reactions that result into the formation of bigger or complex molecules from smaller or simpler molecules (synthesis). Metabolism - refers to the sum total of all the chemical reactions which occurs within a living cell e.g. Respiration, Digestion, Excretion , etc. Two Phases of Metabolism:
All anabolic activities are “endergonic” ~ energy-storing e.g. Photosynthesis in plants and synthesis of carbohydrates, lipids, proteins, etc in animals. 2. Catabolism – aka “ destructive phase ” ~ all chemical reactions that result into the breakdown of bigger or complex molecules into smaller or simpler molecules (analysis). All catabolic activities are “exergonic” ~ energy- releasing e.g. Respiration among animals.
ENTRY AND EXIT OF MATERIALS IN CELLS “ The ability of cells to exist and maintain life-sustaining activities depends on its ability to take in (food and nutrients) and get rid of substances (wastes or toxins).”
Major Process in the Entry and Exit of Materials 1. Active Transport – involves carrier molecules and cellular energy ~ requires or makes use of energy e.g. Exocytosis and Endocytosis 2. Passive Transport – does not involve carrier molecules and cellular energy ~ happens naturally therefore, no amount of energy is used.
ACTIVE TRANSPORT Requires the cell to spend energy stored in the chemical bonds of Adenosine triphosphate (ATP) and a system of carrier molecules. ATP - compound which by its breakdown in the body (to Adenosine diphosphate ) provides energy for physiological processes such as muscular contraction.
CYTOPLASM OUTSIDE THE CELL SOLUTE CARRIER PROTEIN CYTOPLASM OUTSIDE THE CELL SOLUTE CARRIER PROTEIN CYTOPLASM OUTSIDE THE CELL SOLUTE CARRIER PROTEIN
SOLUTE CYTOPLASM OUTSIDE THE CELL CARRIER PROTEIN CYTOPLASM OUTSIDE THE CELL CARRIER PROTEIN SOLUTE CYTOPLASM OUTSIDE THE CELL CARRIER PROTEIN SOLUTE
Two Processes under Active Transport 1. Endocytosis – entry of materials into the cell <ul><li>Phagocytosis - engulfing or taking in of solid particles – aka “cell eating” e.g. Amoeba and Leucocytes through the use of their pseudopodia after which a phagosome (large vacuole that encloses the particle) is produced. </li></ul>
b. Pinocytosis – taking in fluids – aka “cell drinking” ~ through the use of their pinocytic vesicle (cavity or pouch) after which a pinosome (vacuole that encloses the newly absorbed fluid) is produced . 2. Exocytosis – exit of materials from the cell; process of expelling a macromolecule through the help of the Golgi apparatus e.g. release of Insulin in the blood stream among animals and formation of cellulose among plants.
PASSIVE TRANSPORT A process that does not require energy nor protein carriers. Two Processes under Passive Transport 1. Diffusion – spontaneous and random movement of molecules from one place to another ~ direction of its motion is from a region of high concentration to a region of low concentration.
Concentration gradient – the difference between the concentration of two regions Net diffusion – the direction of greater movement of molecules Some facts regarding diffusion: <ul><li>Best exhibited by fluids </li></ul><ul><li>Motion of diffusing particles are always random </li></ul><ul><li>Net diffusion stops once equilibrium is attained </li></ul><ul><li>Even though net diffusion has already ceased, </li></ul><ul><li>diffusion does not stop </li></ul><ul><li>It may take place through membranes </li></ul>
2. Osmosis – diffusion of materials through a semipermeable membrane. Semipermeable membrane – permeable only to certain substances, especially allowing the passage of a solvent but not of the solute. Osmosis in Living Cells a. Hypotonic solution – contains lower concentration of dissolved materials (solutes) than the cell ~ aqueous solutions.
b. Hypertonic solution – contains higher concentration of dissolved materials (solutes) than the cell ~ saline/ brine, sugary solutions etc. c. Isotonic solution – contains the same concentration of dissolved materials (solutes) as that of the cell (neutral).
REACTION OF A CELL TO A HYPOTONIC SOLUTION The pressure caused by the entry of water into the cell is called, “turgor pressure” AQUEOUS SOLUTION IN PETRI DISH WATER RUSHES INSIDE THE CELL AQUEOUS SOLUTION IN PETRI DISH CELL SWELLS
BRINE SOLUTION IN PETRI DISH WATER RUSHES OUTSIDE THE CELL BRINE SOLUTION IN PETRI DISH CELL SHRINKS REACTION OF A CELL TO A HYPERTONIC SOLUTION The shrinking caused by the exit of water from the cell is called, “plasmolysis”
SOLUTION WITH THE SAME CONCENTRATION AS THE THE CELL WATER RUSHES OUTSIDE THE CELL REACTION OF A CELL TO AN ISOTONIC SOLUTION Since the cell loses and gains equal amounts of water, it neither swells nor shrinks. WATER RUSHES INSIDE THE CELL SOLUTION WITH THE SAME CONCENTRATION AS THE THE CELL
3. Facilitated diffusion – (aka “carrier-assisted transport ) similar to osmosis but the passage of particles is aided by “carrier proteins” SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE SOLUTE
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