Honors Biology CELL ENERGETICS

Place the events of the light-dependent reactions in the appropriate order.

1.)The light absorbed by chlorophyll causes a transfer of electrons and H+ from H20 molecules already present. This causes the H20 to split into molecular 0xygen (02) and a H+ ion. 2.) The O2 is released (we breathe it) and the H+ bonds to NADP+ creating NADPH 3.)ATP is formed through photophosphorylation. (ADP gets a phosphate group added to it creating ATP) 4.) The NADPH and the ATP created here go on to fuel the reactions in the second part of photosynthesis - The Calvin Cycle

Compare the net ATP yield from a single glucose molecule that completes the cellular respiration pathway to the ATP yield per glucose molecule undergoing fermentation.

36ATP(38 for plants)......2 ATP

What is the pacemaker of cellular respiration?

Allosteric enzymes at certain points in the respiratory pathway respond to inhibitors and activators that help set the pace of glycolysis and the citric acid cycle. Phosphofructokinase, which catalyzes an early step in glycolysis is one such enzyme. It is stimulated by AMP (derived from ADP) but is inhibited by ATP and by citrate. This feedback regulation adjusts the rate of respiration as the cell's catabolic and anabolic demands change.

What types of cells/human systems are predominantly affected by mitochondrial diseases?

Neurological, gastrointestinal, cardiac, respiratory, endocrinal, opthalmological, ------- homoplasmic mtDNA mutations

What gas is produced in the light-dependent reactions?

Oxygen gas

Where does photosynthesis occur?

Photosynthesis takes place inside plant cells in small things called chloroplasts.

What is the source of energy for all ecosystems?

The sun. (light)

Describe the function of chlorophyll.

absorbs sunlight and uses its energy to synthesise carbohydrates from CO2 and water.

Identify the two phases of photosynthesis.

light-dependent phase (the "Light Reactions") and light-independent phase (the "Dark Reactions")

What happens when oxygen is not present during cellular respiration?

respiration without oxygen present is anaerobic respiration. & fermentation occurs when oxygen is not present.

What is the role of mitochondria within the human body?

the production of energy, in the form of adenosine triphosphate (ATP). The cell uses this energy to perform the specific work necessary for cell survival and function.

In what state/phase of photosynthesis is sugar (glucose) produced?

the second stage

Where is energy stored in ATP?

the third phosphate group

Describe the role of proteins in cellular respiration.

to assist in transferring electrons from one molecule to another.

Why do cells need energy?

to do work

What is ATP?

Adenosine triphosphate (ATP) is a nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism.

What is the role of coenzyme A in cellular respiration?

Acetyl-CoA is produced during the second step of aerobic cellular respiration, pyruvate decarboxylation, which occurs in the matrix of the mitochondria. Acetyl-CoA then enters the citric acid cycle. Acetyl-CoA is also an important component in the biogenic synthesis of the neurotransmitter acetylcholine. Acetyl-CoA

What is the chemical equation for photosynthesis?

(6)CO2 + (6)H2O + light → C6H12O6 + (6)O2

What is the chemical equation for cellular respiration?

(6)O2 + C6H12O6 → (6)CO2 + (6)H2 + Energy

Why do plant leaves change colors before they are shed each autumn?

(preparing for winter)During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer. They begin to shut down their food-making factories. The green chlorophyll disappears from the leaves.

How many rounds of the Calvin cycle are necessary to produce one glucose molecule?

6

How are ATP and ADP cycled?

ATP (adenosine triphosphate) is an ubiquitous energy carrier molecule and it gives up its energy by breaking the phosphoanhydride bond between the last and second last phosphate groups and thereby phosphorylating (adding a phosphate to) a target molecule, most likely inducing a change in its conformation that leads to activation or direct action. When that bond is broken, the ATP loses one phosphate and becomes ADP (adenosine diphosphate), which is less energetic and infrequently used to provide additional energy for the cell. The ADP must then be 'recharged' during cellular respiration or photosynthesis where energy (derived from nutrients or light) is used to add a phosphate onto ADP, recreating the phosphoanhydride bond and producing ATP.

If you ride a bicycle as fast as you can, your muscles may begin to feel weak and have a burning sensation. Explain what accounts for this muscle fatigue.

Anaerobic respiration takes place when you demand your muscles to do vigorous work. Normally, aerobic respiration takes place but when energy is needed immediately, anaerobic respiration takes place. During anaerobic respiration, the body produces lactic acid, which leads to the burning sensation. Your lungs deliver oxygen to the muscles much slower than the rate you need, since you're putting your muscles through an extensive exercise, and this leads to muscle fatigue.

Why is cellular respiration an aerobic process?

Cellular Respiration is an aerobic process because it requires the use of oxygen to enter and ultimately carry out the Kreb's Cycle. This requirement for oxygen makes it aerobic.

What types of molecules can be used as fuel for cellular respiration?

Cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP. Carbohydrates, fats, and proteins can all be used as fuels in cellular respiration, but glucose is most commonly used as an example to examine the reactions and pathways involved.

What are the end-products of fermentation?

Examples of fermentation end products include: Saccharomyces: ethyl alcohol and CO. Streptococcus and Lactobacillus: lactic acid.

What is the role of NADH and FADH2?

FADH2 : Carries electrons in the form of hydrogen atoms (1 proton and 1 electron) with 0 net charge. With 2 hydrogens FAD may use these electrons one at a time or 2 at a time, depending on which ever process it is in. NADH : Carries it's electrons in the form of hydrides (1 proton and 2 electrons) with -1 net charge. Since these electrons are in the hydride form they both must be used at the same time, there isn't an option to use 1 OR 2 only 2 electrons.

Describe feedback inhibition (also called a negative feedback loop).

Feedback inhibition is the phenomenon where the output of a process is used as an input to control the behavior of the process itself, oftentimes limiting the production of more product.

Compare and contrast fermentation with cellular respiration.

Fermentation is the process of getting energy from carbohydrates. Cellular respiration, is where electrons are put into oxygen, through the electron transport chain. Both these processes produce ATP for the cells. Cellular respiration is the process that occurs in the presence of oxygen but fermentation doesn't need oxygen.

What enters and exits each stage of cellular respiration?

Glycolysis: Glucose goes "in" and we convert 1 molecule of glucose into 2 molecules of pyruvic acid. Krebs: Each Acetyl CoA molecules goes "in" one at a time. In one "spin" of the cycle we generate 1 ATP molecule, 2 CO2 molecules, 3 NADH+H molecules and 1 FADH2 molecule ETC: NADH+H and FADH2 we've created throughout cellular respiration to generate more ATP in the mitochondria

Identify the three phases of cellular respiration.

Glycolysis: breaking down of glucose molecules from carbohydrates into molecules of pyruvate The Citric Acid Cycle(krebs): a series of steps, catalyzed by enzymes, which completely oxidize the Acetyl CoA molecule. Electron Transport Chain: a network of electron-carrying proteins located in the inner membrane of the mitochondrion. These proteins transfer electrons from one to another, down the chain, much in the way a bucket brigade passes buckets of water. These electrons will eventually be added, along with protons, to oxygen, which is the final electron acceptor.

Why is it necessary to release the energy stored in glucose in small amounts?

If it was all released at once, that much energy would cause the cell to combust/burn (theoretically. You don't have to worry about that ever happening)

How are electrons restored to the chlorophyll?

In the light reactions, the energy of light is used to "split water," stripping a pair of electrons from it (and causing the two hydrogens to be lost), thus generating molecular oxygen. The energy in light is transferred to these electrons, and is then used to generate adenosine triphosphate ( ATP ) and the electron carrier NADPH. These two products carry the energy and electrons generated in the light reactions to the stroma, where they are used by the dark reactions to synthesize sugars from CO2 .

Where does cellular respiration occur?

Mitochondria

What is the energy source for cellular processes?

Most cell processes use the same energy source, the rechargeable energy carrier, adenosine tri phosphate -- ATP.

What do the light-dependent reactions supply the Calvin cycle with?

NADPH and ATP

Compare and contrast the biochemical pathways of photosynthesis and cellular respiration.

cellular respiration - occurs in the mitochondria, first a glucose molecule goes through glycolysis, which produced 2 molecules of ATP and 2 molecules of pyruvate or pyruvic acid - each one of those either enters the krebs cycle and the electron transport chain, or if there isnt enough oxygen it goes into lactic acid cycle - which doesnt produce much energy and produced lactic acid (runners get this and the lactic acid causes muscle soreness), but anyway if there is enough oxygen, the pyruvate goes into the krebs cycle, in it a bunch of things happen to the pyruvate to turn it into different things, ending up in citric acid (krebs cycle is also called citric acid cycle), the krebs cycle produced some more ATPs and other molecules called NADPH and FADPH, after that it enters the stage that produces the most energy the electron transport chain - in this an electron is transported through a bunch of proteins called cytochromes and during this transport protons (H+ ions) are produced, they create a ph gradient between the sides separated by the cristae (inner wall of the mitochondria), and these ions travel through proteins that they call ATP synthease, while doing that they cause ATP to be made from ADP and inorganic phosphate. the electron transport chain produces 28 ATP molecules, giving the whole cycle a total of 32 ATP from one glucose molecule. Photosynthesis - occurs in the chloroplast, first light hits an electron in photosystem II, that excites the electron and it goes through an electron transport chain to reach photosystem I, during which it produces energy same way that the etc in respiration does, after that the electron gets hit by light again this time in photosystem I, it gets excited again ang goes through another etc, producing some more ATP as well as NADPH. these molecules are then used in the Calvin cycle, in which carbon dioxide is absorbed by the plant from the air and used to form 3 carbon sugars which are then combined to form glucose, oxygen is released as a byproduct of that.

How many molecules of ATP are produced per glucose molecule in glycolysis? In the Krebs cycle? In the ETC?

glycolysis: 2 ATP Krebs: 2 ATP ETC: 34 ATP