Biology: Module #5 Key Terms

Consumers (heterotrophs)

obtain energy by consuming other organisms

Electron transport chain

Electron transport chain is a series of electron carrier proteins that shuttle high-energy electrons during ATP-generating reactions. Energy from electrons is used by the proteins in the chain to pump H+ ions from the stroma into the thylakoid space. At the end of the electron transport chain, the electron themselves pass to a second photosystem called photosystem I. The Kreb's cycle and the electron transport chain generate the majority of ATP during cellular respiration and take place inside the mitochondria.

NADH

A carrier molecule and in the presence of oxygen, the electrons they hold are used to generate huge amounts of ATP. One of the reactions that occurs during glycolysis removes four electrons. These electrons are ina high-energy state and are transported to NAD+, also known as nicotinamide adenine dinucleotide. Each NAD+ molecule accepts a pair of high-energy electrons and a hydrogen ion. This molecule, now known as NADH, holds the electrons until they can be transferred to other molecules. In the presence of oxygen, these high-energy electrons can be used to produce even more ATP molecules.

ATP synthase

ATP synthase is a protein contained in the thylakoid membrane which spans the membrane and allows H+ ions to pass through it. Powered by the gradient, H+ ions pass through ATP synthase and force it to rotate, almost like a turbine being spun by water in a hydroelectric power plant. As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP. This process is known as chemiosmosis.

Producer (autotroph)

An organism that can make its own food.

Cellular respiration

Cellular respiration is a way to withdraw energy. Cellular respiration adds carbon dioxide to the atmosphere. Cellular respiration uses oxygen to release energy from food. Glycolysis is the process of energy conversion that releases energy from food in the presence of oxygen. The three stages are: Glycolysis, Krebs, and Electron transport. Photosynthesis and cellular respiration can be thought of as opposite processes. The chemical summary of cellular respiration is: Oxygen + glucose—> carbon dioxide + water + energy Look at image for the chemical summary in symbols (equation)

Glycolysis

During glycolysis, 1 molecule of glucose, a 6-carbon compound, is transformed into 2 molecules of pyruvic acid, a 3-carbon compound. The first stage of cellular respiration. The first set of reactions in cellular respiration during which one molecule of glucose ( a 6 carbon compound) is transformed into 2 molecules of pyruvic acid (a 3-carbon compound). Glucose first enters a chemical pathway known as glycolysis. A small amount of energy is captured to produce ATP. Even though glycolysis is anaerobic, it is considered part of cellular respiration because its products are key reactants for the aerobic stages. Glycolysis occurs in the cytoplasm. One advantage of glycolysis is that it occurs so quickly that thousands of ATP molecules are created in milliseconds. This is helpful when the energy needed by a cell increases. The second advantage is that glycolysis does not require the use of oxygen. As a result, it can provide useable energy to the cell when oxygen is not available. However, if oxygen is available, the pyruvic acid and NADH that are created from glycolysis can be used for other processes in cellular respiration to produce additional ATP molecules.

Calorie

Energy is stored in a variety of macromolecules in the body, including fats, proteins, and carbohydrates. The energy is measured in a unit known as a calorie. A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degrees Celsius. There are 100 of these calories in 1 food calorie (that is seen on the food label). When measuring calories, fat tends to have 9,000 calories (9 food calories) of energy per gram, while protein and carbohydrates have 4,000 calories (4 food calories). The cells in the body release and use this energy over time using the process of cellular respiration.

Heterotrophs

Heterotrophs are organisms that obtain food by consuming other living things. Ex. mushrooms absorb nutrients from decomposing organisms.

Fermentation

If oxygen is not present, another anaerobic pathway, fermentation, makes it possible for the cell to keep glycolysis running, generating ATP to power cellular activity.

Kreb's Cycle

In the second stage of cellular respiration, of Kreb's cycle, a little more energy is converted. During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions.

Matrix

Innermost compartment of mitochondrion and the site of the Krebs cycle reactions. Once inside the matrix, 1 carbon atom from pyruvic acid becomes part of a molecule of carbon dioxide, which is eventually released into the air. The other 2 carbon atoms from pyruvic acid rearrange and form acetic acid, which is joined to a compound called coenzyme A. The resulting molecule is called acetyl-CoA. At the beginning of the Krebs cycle, the three-carbon compound known as pyruvic acid created from glycolysis passes through the two membrane walls of the mitochondrion. As a result, it moves into a region located in the matrix.

FADH2

NAD+ and FAD (flavine adenine dinucleotide). At five places, electron carriers accept a pair of high-energy electrons, changing NAD+ to NADH and FAD to FADH2. FAD and FADH2 are molecules similar to NAD+ and NAPH, respectively.

Photosynthesis

Photosynthesis is a process that deposits energy. Photosynthesis removes carbon dioxide from the atmosphere. Photosynthesis releases oxygen. The global balance between cellular respiration and photosynthesis is essential to maintain Earth as a living planet. Photosynthesis is the process of plants converting energy of sunlight into chemical energy stored in the bonds of carbohydrates. In plants, photosynthesis takes place inside chloroplasts. Photosynthesis involves two sets of reactions: light-dependent reactions and light-independent reactions. Photosynthesis uses the energy of sunlight to convert water and carbon deoxide (reactants) into high-energy sugars and oxygen (products). Photosynthesis usually produces 6-carbon sugars (Ex. C6H12O6 as the final product, It is the process that autotrophs use to synthesize molecules of high-energy carbohydrates by trapping light energy. Photosynthesis and cellular respiration can be thought of as opposite processes.

Anaerobic

Process that does not require oxygen. Glycolysis, however, does not require oxygen, nor does it rely on an oxygen-requiring process to run. Glycolysis is therefore said to anaerobic ("without air").

Aerobic

Process that requires oxygen. Pathways of cellular respiration that require oxygen are said to be aerobic ( in air) Example: The Kreb's Cycle and the electron transport chain are aerobic processes.

Electron transport

The final stage of cellular respiration, the electron transport requires reactants from the other two stages of the process

Autotrophs

autotrophs are organisms that make their own food by capturing sunlight energy and synthesizing high-energy carbohydrates (Ex. sugars and starches that can be used as food). There are two kinds of autotrophs; photoautotrophs and chemoautotrophs. Plants, algae, and some bacteria are able to use light energy from the sun to produce food.