class 7 bio
TRANSCRIPT
RESPIRATION, TERM WITH DUAL MEANING IN BIOLOGY: FIRST, THE PHYSICAL PROCESS BY WHICH LIVING THINGS (ORGANISMS) TAKE IN OXYGEN FROM THE SURROUNDING MEDIUM AND EMIT WASTE CARBON DIOXIDE—IN THIS SENSE IT IS VARIOUSLY KNOWN AS PHYSICAL RESPIRATION, BREATHING, VENTILATION OR GAS EXCHANGE; SECOND, THE CHEMICAL PROCESS BY WHICH FUEL MOLECULES SUCH AS SUGARS (SEE SUGAR METABOLISM) AND FATS ARE BROKEN DOWN WITHIN A CELL TO LIBERATE ENERGY FOR CELLULAR LIFE PROCESSES—IN THIS SENSE IT IS ALSO KNOWN AS CHEMICAL, BIOCHEMICAL, OR CELLULAR RESPIRATION.
Cellular respiration is similar in most organisms, from simple one-celled bacteria, amoebas, and diatoms to complex plants
like trees, and large animals such as elephants, whales, and
human beings (see also Metabolism; Photosynthesis). In
most organisms apart from prokaryotes (chiefly bacteria and blue-green algae) cellular respiration takes place in the
tiny sausage-shaped organelles within the cell called
mitochondria
CELLULAR RESPIRATION
In fact there are two versions of cellular respiration (both described in more detail in their separate articles, Aerobic Respiration, and Anaerobic
Respiration). Aerobic respiration requires oxygen to break down high-energy fuel molecules—typically a
simple sugar such as glucose (blood sugar)—through a series of chemical
stages. The results are carbon dioxide, water, and energy in the form of
molecules of ATP—the cell’s standard energy-carrier. The biochemical stages
in the breakdown of glucose form a circular pathway or cycle known as the
Krebs cycle or citric acid cycle.
Anaerobic respiration involves the breakdown of high-energy
molecules, again typically glucose, but without the need for oxygen
and therefore without the need for physical respiration (breathing).
This version incorporates the chemical pathway termed
glycolysis and results in lactic acid (see Fermentation). It occurs as a
matter of course in certain bacteria and other microbes called obligate anaerobes. It is also used as a reserve or emergency form of
obtaining energy in other organisms, usually when oxygen is
in short supply.
AEROBIC RESPIRATION AEROBIC
RESPIRATION, BIOCHEMICAL PROCESS IN LIVING THINGS WHEREBY SUGARS AND
SIMILAR SUBSTANCES, RESULTING FROM THE DIGESTION OF FOOD, ARE BROKEN DOWN IN
THE PRESENCE OF OXYGEN TO PRODUCE WATER, CARBON DIOXIDE, AND ENERGY. "AEROBIC" MEANS "WITH OXYGEN". THE REACTION CAN BE REPRESENTED BY THE
GENERAL CHEMICAL EQUATION
C6H12O6 + 6O2 → 6CO2 + 6H2O + ENERGY
THE WHOLE PROCESS OF AEROBIC RESPIRATION CONTAINS MORE THAN 20 CHEMICAL STEPS OR STAGES. THE FIRST SERIES OF STAGES IS KNOWN AS GLYCOLYSIS. THIS OCCURS IN THE JELLY-LIKE CYTOPLASM OF THE CELL,
AND IT IS ANAEROBIC—THAT IS, IT DOES NOT REQUIRE OXYGEN. IT RELEASES ONLY A SMALL PROPORTION OF
THE TOTAL ENERGY AVAILABLE FROM A FUEL MOLECULE OF GLUCOSE OR A SIMILAR SUGAR. (THE SECOND SERIES
OF STAGES IS KNOWN AS THE CITRIC ACID CYCLE, TRICARBOXYLIC ACID CYCLE, OR KREBS CYCLE. IT IS
AEROBIC—THAT IS, IT REQUIRES OXYGEN. IT RELEASES FAR MORE ENERGY, COMPARED TO GLYCOLYSIS, FROM
THE REMAINDER OF EACH SUGAR MOLECULE. THIS SERIES OF STAGES HAPPENS INSIDE THE TINY
ORGANELLES (PARTS INSIDE THE CELL) CALLED MITOCHONDRIA. THE FOOD MOLECULE IS BROKEN DOWN
IN A STEP-BY-STEP PROCESS THAT PRODUCES ATP MOLECULES AT ALMOST EVERY STAGE.
Anaerobic Respiration, also called anaerobiosis, biochemical process in living things whereby sugars and similar substances, resulting from
the digestion of food, are broken down to release energy in the absence of oxygen.
"Anaerobic" means "without oxygen". It thus differs from the allied process of aerobic
respiration, which requires the presence of oxygen. Life processes such as growth and repair of tissues require energy, and this is
obtained by the chemical breaking of bonds in organic molecules such as sugars and other carbohydrates present in digested food. The chemical energy released by this process in
cells is transferred to molecules of adenosine diphosphate (ADP), which become converted to
adenosine triphosphate (ATP), forming the energy “bank” for the cell.
PRODUCTS OF ANAEROBIC
RESPIRATION
The process of anaerobic respiration
contains three main chemical
steps or stages. The starting
substance or "fuel molecule" is
usually the six-carbon sugar, glucose. The
chemical process by which this is broken down is
termed glycolysis. The results are
usually substances such as lactic acid (lactate), pyruvic acid (pyruvate) or
ethyl alcohol (ethanol). The
reaction can be represented by the general chemical
equation:
C6H12O6 → 2C3H4O3 + 2H2 + energy
ANAEROBIC RESPIRATION OCCURS IN THE CYTOPLASM OF THE CELL AND RELEASES
ONLY A SMALL PROPORTION OF THE TOTAL ENERGY CONTAINED IN THE FUEL
MOLECULES SUCH AS GLUCOSE SUGAR, YIELDING UP TO 8 MOLECULES OF THE HIGH-ENERGY ATP. IF OXYGEN IS AVAILABLE, THE PRODUCTS OF GLYCOLYSIS CAN BE USED
FURTHER IN THE OXYGEN-REQUIRING BREAKDOWN PROCESS OF THE CITRIC ACID OR KREBS CYCLE, TO YIELD UP TO ANOTHER 30 MOLECULES OF HIGH-ENERGY ATP. IN THIS WAY, GLYCOLYSIS BECOMES THE FIRST STAGE
OF AEROBIC RESPIRATION.
BREATHING, THE PROCESS WHERE BY AN ORGANISM (LIVING THING) OBTAINS OXYGEN FROM ITS SURROUNDINGS, TO TAKE PART IN
INTERNAL CHEMICAL REACTIONS WHICH BREAK DOWN FOOD TO RELEASE ENERGY. BREATHING
ALSO USUALLY GIVES OUT WASTE CARBON DIOXIDE AS AN UNWANTED BY-PRODUCT OF
THESE REACTIONS. BREATHING IS ONE ASPECT OF RESPIRATION, WHICH IS A TERM THAT
INCLUDES BOTH PHYSICALLY OBTAINING OXYGEN, AND ALSO USING IT IN CHEMICAL PATHWAYS
INSIDE CELLS TO RELEASE ENERGY—THE PROCESS OF CELLULAR RESPIRATION (SEE
RESPIRATION; AEROBIC RESPIRATION; ANAEROBIC RESPIRATION).
Circulatory System Circulatory System, in anatomy and physiology,
the course taken by the blood through the arteries, capillaries, and veins and back to the
heart. In humans and the higher vertebrates the heart is made up of four chambers: the right and
left auricles, or atria, and the right and left ventricles. The right side of the heart pumps oxygen-poor blood from the cells of the body
back to the lungs for new oxygen; the left side of the heart receives blood rich in oxygen from the lungs and pumps it through the arteries to the
various parts of the body. Circulation begins early in foetal life. It is estimated that a given portion
of the blood completes its course of circulation in approximately 30 seconds.
PORTAL CIRCULATIONIN ADDITION TO THE PULMONARY AND SYSTEMIC CIRCULATIONS DESCRIBED ABOVE, A SUBSIDIARY TO THE VENOUS SYSTEM EXISTS, KNOWN AS PORTAL CIRCULATION. A CERTAIN AMOUNT OF BLOOD FROM THE INTESTINE IS COLLECTED INTO THE PORTAL VEIN AND CARRIED TO THE LIVER. THERE IT ENTERS INTO THE OPEN SPACES CALLED SINUSOIDS, WHERE IT COMES INTO DIRECT CONTACT WITH THE LIVER CELLS. IN THE LIVER IMPORTANT CHANGES OCCUR IN THE BLOOD, WHICH IS CARRYING THE PRODUCTS OF THE DIGESTION OF FOOD RECENTLY ABSORBED THROUGH THE INTESTINAL CAPILLARIES. THE BLOOD IS COLLECTED A SECOND TIME INTO VEINS, WHERE IT AGAIN JOINS THE GENERAL CIRCULATION THROUGH THE RIGHT AURICLE. IN ITS PASSAGE THROUGH OTHER ORGANS, THE BLOOD IS FURTHER MODIFIED.
BUDBud, undeveloped or embryonic shoot of a plant. Buds contain the undeveloped leaves, stems, or flowers, and according to the mature structure into which they develop, are classified as either vegetative or flower buds. A bud growing at the end of a twig or shoot is called a terminal bud, and a bud that grows along the stem is known as a lateral bud. Although most lateral buds occur in the axils of leaves, they can appear elsewhere; they are then called adventitious.