chapter 17 p1 Flashcards
activity depends on metabolic reactions and processes continually taking place in individual cells.
A few examples of these metabolic activities include:
active transport, which is essential for the uptake of nitrates by root hair cells, loading sucrose into sieve tube cells, the selective reabsorption of glucose and amino acids in the kidney, and the conduction of nerve impulses
anabolic reactions, such as the building of polymers like proteins, polysaccharides, and nucleic acids essential for growth and repair
movement brought about by cilia, flagella, or the contractile filaments in muscle cells.
All of these metabolic activities require energy.
Energy flow through living organisms:
The total amount of energy in the universe hasn’t changed from the time of the Big Bang. when the universe began, until now.
The universe is gradually cooling as it expands because this energy is being dispersed over a larger area.
This is inevitable and irreversible.
Energy cannot be created or destroyed.
Radiation from the Sun is used to fuel the metabolic reactions and processes necessary to keep organisms alive before, eventually, being transferred back to the atmosphere as heat
diagram of the transfer of energy though ecosystems
Photosynthesis:
- Organisms make use of the energy in the bonds of organic molecules, such as glucose.
- These bonds are formed during photosynthesis in plants and other photosynthetic organisms
- Light is trapped by chlorophyll molecules.
- This energy is used to drive the synthesis of glucose from carbon dioxide and water.
Respiration:
All organisms need to respire.
Respiration is the process by which organic molecules, such as glucose, are broken down into smaller inorganic molecules, like carbon dioxide and water.
The energy stored within the bonds of the organic molecules is used to synthesise adenosine triphosphate (ATP).
Two of the most important chemical reactions in the living world are…
photosynthesis and respiration.
Photosynthesis is the reaction behind the production of most of the biomass on the earth.
Respiration is the process by which organisms break down biomass to provide the ATP needed to drive the metabolic reactions that take place in cells.
The two reactions are intimately linked (Table 1). The raw materials for one are the products of the other so they are interrelated throughout the living world.
The overall reactions for photosynthesis and respiration are as follows:
comparison of respiration and photosynthesis
bond energy
A general rule in biochemistry is that energy is used to break bonds, and energy is released when bonds are formed.
The same quantity of energy is involved whether a particular bond is being broken or formed - This is called the bond energy.
Whether an overall reaction is exothermic (releases energy) or endothermic (takes in energy) depends on…
the total number and strength of bonds that are broken or formed during the reaction.
The atoms in small inorganic molecules like water and carbon dioxide are joined by strong bonds that release a lot of energy when they form but require a lot of energy to break.
Organic molecules like glucose and amino acids contain many more bonds than small inorganic molecules.
These are weaker bonds compared with those in inorganic molecules and, therefore, release less energy when they form and require less energy to be broken.
In respiration large organic molecules are
broken down forming small inorganic molecules.
The total energy required to break all the bonds in a complex organic molecule is less than the total energy released in the formation of all the bonds in the smaller inorganic products.
The excess energy released by the formation of the bonds is used to synthesise ATP.
Organic molecules contain…
large numbers of carbon-hydrogen bonds, particularly lipids.
Carbon and hydrogen share the electrons almost equally in bonds that form between them.
This results in a non-polar bond which does not require a lot of energy to break.
The carbon and hydrogen released then form…
strong bonds with oxygen atoms, forming carbon dioxide and water, resulting in the release of large quantities of energy.
The reverse happens in photosynthesis when organic molecules are made from small inorganic molecules.
The energy required to build these molecules comes from the Sun.
Energy transfer:
the energy required to form a particular type of bond (e.g. 0-H) is equal to the amount of energy released when the bond is broken.
When bonds are broken, the bond energy is given a positive sign, e.g. breaking an 0-H bond: +464 kJ/mol.
When bonds are formed, the bond energy is given a negative sign, e.g. making an 0-H bond: -464 kJ/mol.
what is ATP
ATP is the universal energy currency in cells.
The bond energy in the ATP molecule is used to drive essential metabolic processes.
The production of ATP is therefore fundamental to all forms of life.
role of ATP in energy transfer diagram
