Cell division and cycle

• Cell Energy: Life on Earth depends on the energy produced by our closest star, the sun.
• Energy from the sun travels through space in the form of light.
• H is transferred from food to NAD.
• H is transferred from H2O to NADP8.
• Sunlight filters down through the forest, eventually falling on green leaves.
• Leaves are able to trap this sunlight and use it to manufacture food.
• When you eat, you are getting energy that originally came from the sun.
• The energy in fruits, vegetables, and grains is captured by plants.
• Since cows and hens eat grains, when you eat milk and eggs you are getting energy from the sun second-hand.
• Your body uses energy continuously.
• The ultimate source of energy is sunlight.
• The conversion of energy from one form to another is accomplished by many chemical reactions.
• Energy conversion is a basic biological process upon which all living things depend.
• The activities of all living things require energy.
• Most of the activities of cells require energy, too.
• Cell growth and the active transport of molecules across membranes require energy.
• The immediate source of energy for cells is the energy stored in chemical bonds of organic molecules.
• Energy may be stored in many organic molecules, especially carbohydrates such as sugars and starches.
• These molecules are called food molecules.
• The most common food molecule is the sugar glucose.
• A cell may have a large supply of energy stored in the chemical bonds of sugars.
• In order to use this energy, a cell must transfer the energy in its sugar molecules to a substance called adenosine triphosphate, or ATP.
• The energy in the food, say in a sugar molecule is analogous to your peso bill and the energy in ATP is like the change or coins in your pocket.
• Business transactions (as in the operation of vending machines) require smaller denominations.
• The same is true for cellular processes; they are fueled by the energy stored in ATP.
• Each ATP is composed of the base adenine and the sugar ribose.
• The ribose is bound to a chain of three phosphates.
• The phosphate molecules are connected by energy-containing bonds.
• If the cells need energy, it can break the last phosphate bond, thus liberating the energy that held the second and third phosphates together.
• When the last phosphate bond is broken, the molecule of ATP becomes a molecule of adenosine diphosphate (ADP) and a molecule of phosphate (P).
• The production of ATP from the complete breakdown of glucose is called respiration.
• Respiration uses oxygen to break sugars down into carbon dioxide and water.
• In everyday language, people often speak of breathing as respiration.
• Lactic acid fermentation can occur in the cells of humans when there is not enough oxygen available for the aerobic stages of respiration.
• As the yeast cells grow, they produce more and more carbon dioxide which forms tiny bubbles in the dough, causing the dough to increase in volume.
• In lactic acid fermentation, no carbon dioxide is given off, instead, pyruvic acid combines with hydrogen from NADH to produce lactic acid according to the following equation: CH 3 COCOOH +2NADH CH 3 CHOHCOOH + 2NAD + (pyruvic acid) (lactic acid).
• The yeast that is used to leaven bread carries out alcoholic fermentation.
• During strenuous exercise, your muscle cells may not receive enough oxygen to process all the pyruvic acid through the steps of aerobic respiration, instead, your muscle cells produce lactic acid.
• After strenuous exercise, you must continue to breathe heavily to allow your cells to convert the accumulated lactic acid back to pyruvic acid.
• When lactic acid builds up in your muscles, it causes the muscles to ache.