Living cells need energy Flashcards
(41 cards)
Why do all living cells require energy?
To carry out essential life processes such as active transport, movement of organelles and other structures, phagocytosis, pinocytosis, exocytosis/endocytosis and the synthesis of macromolecules.
Define energy.
The capacity to do work; the more energy an organism has, the more work it can do.
What are some examples of energy transformation?
Plants can convert light energy into chemical energy; muscle cells can convert chemical energy into movement.
What are autotrophs?
Organisms that synthesise organic molecules (e.g., proteins, nucleic acids, carbohydrates) from simple inorganic molecules (e.g., carbon dioxide, water, mineral ions).
What is the word equation for photosynthesis?
Carbon dioxide + water —> (light energy & chlorophyll) glucose + oxygen
What is the chemical equation for photosynthesis?
6CO2 + 6H2O —> (light energy & chlorophyll) C6H12O6 + 6O2
Describe photosynthesis.
The most fundamental chemical process to life, in which solar energy is converted into chemical energy in organic molecules that can be used by cells.
What is the main source of energy for life?
The sun.
Where does photosynthesis occur in photosynthetic eukaryotes?
In the chloroplasts. Enzymes that catalyse the many steps of photosynthesis are found in the grana and stroma.
Where does photosynthesis occur in photosynthetic prokaryotes?
In the cytoplasm, which contains the chlorophyll and necessary enzymes.
What are chemoautotrophs?
Organisms that are able to derive energy using chemicals in hostile environments.
What are heterotrophs?
An organism that derives its nutritional requirements from complex organic substances (other organisms, their products or their remains).
Describe chemical bonds.
Chemical bonds hold atoms together, and energy is required to break these bonds. Conversely, the formation of chemical bonds releases energy.
What happens when a chemical reaction occurs?
Some chemical bonds are broken and new ones are made as new combinations of atoms are formed.
What is a net output of energy derived from?
When the total energy released when new bonds are made is greater than the energy required to break the original bonds.
Describe energy in aerobic respiration.
The breakdown of glucose in the presence of oxygen releases energy, as the energy in the reactants is greater than the energy in the products. The amount of energy required to break the bonds in the reactants is less than the amount of energy released when the bonds in the product are formed. Some of this energy released can be used by the cell to do work, while the rest is lost as heat.
What is ATP?
Adenosine triphosphate is one of the most important energy storage compounds in cells.
What does ATP consist of?
Nitrogen base (adenine), bonded to a ribose sugar, which is bonded to three phosphate groups called a triphosphate.
What is significant about the third bond in a triphosphate?
The third phosphate group is held by an unstable bond. When this bond is broken, energy is released and can be used by the cell for processes requiring energy.
What happens when ATP releases the third phosphate?
It produces adenosine diphosphate (ADP).
What is the main process of synthesising ATP?
Cellular respiration (aerobic and anaerobic).
Describe the ATP cycle.
ATP breaks down to form ADP and Pi, releasing a constant amount of free energy which is available for cellular use. Some of this energy released from aerobic respiration is used to drive the synthesis of ADP and Pi into ATP (remaining energy is lost as heat). ATP is made again by adding a phosphate group to ADP.
Describe the equation for the ATP cycle.
ATP + water <—> ADP + phosphate + energy
What is cellular respiration?
Provides energy by breaking down energy-rich organic molecules into lower energy products; it releases more energy than required.
