Biology Unit 4: Flow of Energy

What are the products of the Krebs cycle?

(1) 4 ATP (including 2 from glycolysis), (2) 10 NADH (including 2 from glycolysis), (3) 2 FADH_2

Describe electron carriers and the electron transport chain.

Electron carrier molecules are usually arranged in electron transport chains (ETCs). These accept and pass along energy-carrying electrons in small steps. In this way, they produce ATP and NADPH, which temporarily store chemical energy.

What are stomata? (singular: stoma)

Tiny pores in the epidermis of a plant leaf that control transpiration and gas exchange with the air.

List and describe the five compartments of the mitochondrion.

(1) the outer mitochondrial membrane: allows for the establishment of the inner membrane space, (2) the intermembrane space: holds protons that are pumped out of the matrix during electron transport, (3) the inner mitochondrial membrane: organizes the electron transport chain and holds ATP synthase, (4) the cristae: expand the surface area of the inner mitochondrial membrane, enhancing its ability to produce ATP, and (5) the matrix: site of ATP synthesis and the location of the Krebs cycle.

Compare and contrast lactic acid fermentation and alcoholic fermentation. Include examples of organisms that use each type of fermentation.

In lactic acid fermentation, pyruvic acid from glycolysis changes to lactic acid. This type of fermentation is carried out by the bacteria in yogurt. It is also used by your own muscle cells when you work them hard and fast. In alcoholic fermentation, pyruvic acid changes to alcohol and carbon dioxide. This type of fermentation is carried out by yeasts and some bacteria. It is used to make bread, wine, and biofuels.

What are guard cells?

The bean-shaped sclerenchyma cells in the epidermis; swell and shrink by osmosis to open and close stomata.

What are the products of photosynthesis? How are these products made?

Glucose and oxygen. They are made during cellular respiration.

What is mesophyll?

Specialized plant tissue inside leaves where photosynthesis takes place.

What is RuBisCo?

An enzyme that combines one molecule of CO_2 with a 5-carbon sugar called ribulose biphosphate (RuBP); the most abundant enzyme on Earth.

What is ATP synthase?

An ion channel and enzyme that uses the energy of hydrogen ions to chemically bond a phosphate group to ADP, producing ATP.

What is a chloroplast?

An organelle in the cells of plants and algae; site of photosynthesis.

What is a heterotroph?

An organism that gets food by consuming other organisms.

What is an autotroph?

An organism that makes its own food.

What is a producer?

An organism that produces food for itself and other organisms.

What is the epidermis?

In animals, it's the outer layer of skin that consists mainly of epithelial cells and lacks nerve endings and blood vessels; in plants, it's the outer layer of dermal tissue.

Explain why two turns of the Krebs cycle are needed for each molecule of glucose.

Two turns are needed because glycolysis produces two pyruvic acid molecules when it splits glucose.

Compare autotrophs to heterotrophs, and describe the relationship between these two groups of organisms.

Autotrophs make their own energy, while a heterotroph must eat another organism to be able to get energy. Heterotrophs can eat autotrophs or other heterotrophs.

What is alcoholic fermentation?

Type of anaerobic respiration that includes glycolysis followed by the conversion of pyruvic acid to ethanol and carbon dioxide and the formation of NAD+.

A single cell uses about 10 million ATP molecules per second. Explain how cells use the energy and recycle the materials in ATP.

An ATP molecule is like a rechargeable battery: its energy can be used by the cell when it breaks apart into ADP (adenosine diphosphate) and phosphate, and then the "worn-out battery" ADP can be recharged using new energy to attach a new phosphate and rebuild ATP. The materials are recyclable, but recall that energy is not!

What is the main advantage of aerobic respiration? Of anaerobic respiration?

A major advantage of aerobic respiration is the amount of energy it releases. One advantage of anaerobic respiration is that it lets organisms live in places where there is little or no oxygen. Aerobic respiration creates more ATP than anaerobic respiration.

What is an electron transport chain?

A series of electron-transport molecules that pass high-energy electrons from molecule to molecule and capture their energy.

What is the electron transport chain?

A series of electron-transport molecules that pass high-energy electrons from molecule to molecule and capture their energy.

What is NADH?

A short-term energy carrier; temporarily stores energy during cellular respiration.

What is NADPH?

A short-term energy carrier; temporarily stores energy during photosynthesis.

What is a thylakoid?

A sub-organelle within the chloroplast; site of photosynthesis.

What is fermentation?

A type of anaerobic respiration that includes glycolysis followed by the conversion of pyruvic acid to one or more other compounds and the formation of NAD+.

What is anaerobic respiration?

A type of cellular respiration that does not require oxygen.

What is aerobic respiration?

A type of cellular respiration that requires oxygen.

Describe the flow of energy through a typical food chain (describing "what eats what"), including the original source of that energy and its ultimate form after use.

A typical food chain will start with an autotroph and go through several heterotrophs until they reach an apex predator. Once the energy flows from the system it gets recycle for future use in other organisms.

Name two types of fermentation.

Alcoholic fermentation and lactic acid fermentation.

What is pyruvate?

3-carbon product of glycolysis; also known as pyruvic acid.

What happens during the carbon fixation step of the Calvin cycle?

Building low-energy inorganic CO_2 into high-energy organic molecules like glucose.

Explain what might happen if the third step of the Calvin cycle did not occur. Why?

Carbon fixation could not happen again because they wouldn't be in the correct chemical formation to react with the incoming molecules of carbon dioxide.

What are organic molecules?

Carbon-containing molecules, such as carbohydrates, lipids, proteins, and nucleic acids that form the basis of life.

Describe what happens during glycolysis. How many ATP and NADH molecules are gained during this stage?

Enzymes split a molecule of glucose into two molecules of pyruvate. You gain two ATP and two NADH.

What process produces fuel for motor vehicles from living plant products? What is the waste product of this process?

Ethanol is produced by alcoholic fermentation of the glucose in corn or other plants. The waste product is carbon dioxide gas.

Describe the habitats of extremophiles.

Extremophiles live in harsh conditions, such as in the absence of sunlight and a wide range of water temperatures, some approaching the boiling point.

ATP and glucose are both molecules that organisms use for energy. They are like the tank of a tanker truck that delivers gas to a gas station and the gas tank that holds the fuel for a car. Which molecule is like the tank of the delivery truck, and which is like the gas tank of the car? Explain your answer.

Glucose is like the tank for the delivery truck because it can be broken down and built into several energy molecules. The delivery truck is good for big movements. ATP is like the tank on the car for small deliveries and used much more frequently than the large delivery truck.

What is a photosystem?

Group of molecules, including chlorophyll, in the thylakoid membrane of a chloroplast that captures light energy.

What is aerobic?

In the presence of oxygen.

Summarize the overall task of Stage III of aerobic respiration.

In this stage, energy from NADH and FADH_2, which result from the Krebs cycle, is transferred to ATP.

Describe the chloroplast's role in photosynthesis.

It is the site of photosynthesis.

What is an electron carrier?

Molecules that accept and temporarily hold high-energy electrons.

What is lactic acid fermentation?

Type of anaerobic respiration that includes glycolysis followed by the conversion of pyruvic acid to lactic acid and the formation of NAD+.

What is food?

Organic molecules, such as glucose, that organisms use for chemical energy.

Explain how the structure of a chloroplast (its membranes and thylakoids) makes its function (the chemical reactions of photosynthesis) more efficient.

Part of the photosynthesis reactions occurs in an internal membrane within the organelle. The chloroplast contains many of these internal membranes, making photosynthesis very efficient.

Which of the the two types of food making processes found among autotrophs is quantitatively more important to life on earth?

Photosynthesis

Name and describe the two types of food making processes found among autotrophs. Which is quantitatively more important to life on earth?

Photosynthesis - uses the sunlight to make organic energy for the organism; makes more food than other ways of making food. Chemosynthesis - uses chemicals to make organic energy for organisms; only happens in areas of no sunlight and is very limiting for how large and productive those organisms can be.

Where does photosynthesis occur?

Photosynthesis takes place in the chloroplast.

What is a grana? (singular: granum)

Stacks of thylakoid membranes within the chloroplast.

What controls the opening of stomata?

Stomata are flanked by guard cells that swell or shrink by taking in or losing water through osmosis. When they do, they open or close the stomata.

Explain the role of stomata during photosynthesis.

Stomata must control the transpiration of water vapor and the exchange of carbon dioxide and oxygen.

Identify the sites of the Krebs cycle and the electron transport chain.

The Krebs cycle takes place within the matrix. The compartments are critical for the electron transport chain structure and function.

What is osmosis?

The diffusion of water molecules across a membrane.

What is special about RuBisCo?

The enzyme which catalyzes this reaction (nicknamed RuBisCo) is the most abundant enzyme on earth!

What is the main final product of the Calvin cycle? How many turns of the Calvin cycle are needed to produce this product?

The final product of the Calvin cycle is glucose. It takes six turns to reach a glucose molecule.

What is glycolysis?

The first stage of cellular respiration in which glucose is split to form two molecules of pyruvate (pyruvic acid) and two (net) molecules of ATP.

What is chlorophyll?

The green pigment in a chloroplast that absorbs sunlight, starting the light reactions of photosynthesis.

What is carbon fixation?

The process of building low-energy inorganic CO_2 into high-energy organic molecules, like glucose.

What is chemosynthesis?

The process of using the energy in chemical compounds to make food.

What is photosynthesis?

The process of using the energy in sunlight to make food (glucose).

What is the Krebs cycle?

The second stage of aerobic respiration in which two pyruvate (pyruvic acid) molecules from the first stage react to form ATP, NADH, and FADH2; also known as the citric acid cycle.

What is the citric acid cycle?

The second stage of aerobic respiration in which two pyruvate (pyruvic acid) molecules from the first stage react to form ATP, NADH, and FADH_2; also known as the Krebs cycle.

What is the Calvin cycle?

The second stage of photosynthesis in which carbon atoms from carbon dioxide are combined, using the energy in ATP and NADPH, to make glucose.

What is stroma?

The space outside the thylakoid membranes of a chloroplast; site of the Calvin cycle of photosynthesis.

What is electron transport?

The third stage of aerobic respiration in which the majority of ATP is produced.

What happens to the glucose molecules?

They are broken down to make ATP.

Why do bacteria that live deep below the ocean's surface rely on chemical compounds instead of sunlight for energy to make food?

This is because the sunlight doesn't reach the depths of the ocean where they live.

Defend this statement: ''Glycolysis is a universal and ancient pathway for making ATP.''

This is because this pathway occurs in the cytoplasm without the help of any organelles.

What is the maximum number of ATP molecules that can be produced during the electron transport stage of aerobic respiration?

This results in the formation of 34 ATP during the electron transport stage.

The fact that all organisms use similar energy-carrying molecules shows one aspect of the grand "Unity of Life." Name two universal energy-carrying molecules, and explain why most organisms need both carriers rather than just one.

Two of the most important energy-carrying molecules are glucose and adenosine triphosphate commonly referred to as ATP. These are nearly universal fuels throughout the living world and are both key players in photosynthesis.

What are the "raw materials" of photosynthesis? Where do these materials come from?

Water, CO_2- These molecules are from the surrounding environments. For example, Hydrogen, Oxygen, and Carbon in the atmosphere.

Explain how a leaf is like a factory.

You can think of a single leaf as a photosynthesis factory. A factory has specialized machines to produce a product. It's also connected to a transportation system that supplies it with raw materials and carries away the finished product.