cellular respiration

what happens during cellular respiration

Cellular respiration involves many biochemical reactions. However, the overall process can be summed up in a single chemical equation: C6 H12 O6 + 6O2 ! 6CO2 + 6H2 O + energy (stored in ATP) Cellular respiration uses oxygen in addition to glucose. It releases carbon dioxide and water as waste products. Cellular respiration actually "burns" glucose for energy. However, it doesnt produce light or intense heat like burning a candle or log. Instead, it releases the energy slowly, in many small steps. The energy is used to form dozens of molecules of ATP.

where does cellular respiration take place

Cellular respiration takes place in the cells of all organisms. It occurs in autotrophs such as plants as well as heterotrophs such as animals. Cellular respiration begins in the cytoplasm of cells. It is completed in mitochondria. The mitochondrion is a membrane-enclosed organelle in the cytoplasm. Its sometimes called the "powerhouse" of the cell because of its role in cellular respiration. Figure 4.12 shows the parts of the mitochondrion involved in cellular respiration.

using glucose to make atp

Cellular respiration is the process in which cells break down glucose, release the stored energy, and use the energy to make ATP. For each glucose molecule that undergoes this process, up to 38 molecules of ATP are produced. Each ATP molecules forms when a phosphate is added to ADP, or adenosine diphosphate. This requires energy, which is stored in the ATP molecule. When cells need energy, a phosphate can be removed from ATP. This releases the energy and forms ADP again.

textbook_image

stage 2 the krebs cycle

The pyruvate molecules from glycolysis next enter the matrix of a mitochondrion. Thats where the second stage of cellular respiration takes place. This stage is called the Krebs cycle. During this stage, two more molecules of ATP are produced. Other energy-storing molecules are also produced (to be used to make more ATP in stage 3). The Krebs cycle requires oxygen. Anything that needs oxygen is described as aerobic. The oxygen combines with the carbon from the pyruvate molecules. This forms carbon dioxide, a waste product.

stage 3 electron transport

The third and final stage of cellular respiration is called electron transport. Remember the other energy-storing molecules from glycolysis and the Krebs cycle? Their energy is used in this stage to make many more molecules of ATP. In fact, during this stage, as many as 34 molecules of ATP are produced. Electron transport requires oxygen, so this stage is also aerobic. The oxygen combines with hydrogen from the energy-storing molecules. This forms water, another waste product.

stages of cellular respiration

Cellular respiration occurs in three stages. The flow chart in Figure dont purge me shows the order in which the stages occur and how much ATP forms in each stage. The names of the stages are glycolysis, the Krebs cycle, and electron transport. Each stage is described below.

stage 1 glycolysis

Glycolysis is the first stage of cellular respiration. It takes place in the cytoplasm of the cell. The world glycolysis means "glucose splitting". Thats exactly what happens in this stage. Enzymes split a molecule of glucose into two smaller molecules called pyruvate. This results in a net gain of two molecules of ATP. Other energy-storing molecules are also produced. (Their energy will be used in stage 3 to make more ATP.) Glycolysis does not require oxygen. Anything that doesnt need oxygen is described as anaerobic.

textbook_image

textbook_image

cellular respiration and photosynthesis

Cellular respiration and photosynthesis are like two sides of the same coin. This is clear from the diagram in Figure needed for photosynthesis. Together, the two processes store and release energy in virtually all living things.

textbook_image

fermentation

Some organisms can produce ATP from glucose anaerobically. One way this happens is called fermentation. Fermentation includes the glycolysis step of cellular respiration. However, it doesnt include the other, aerobic steps. There are two types of fermentation: lactic acid fermentation and alcoholic fermentation.

aerobic vs. anaerobic respiration

Both aerobic and anaerobic respiration have certain advantages. Aerobic respiration releases far more energy than anaerobic respiration does. It results in the formation of many more molecules of ATP. Anaerobic respiration is much quicker than aerobic respiration. It also allows organisms to live in places where there is little or no oxygen, such as deep under water or soil. For an entertaining review of aerobic and anaerobic respiration, watch this creative music video: MEDIA Click image to the left or use the URL below. URL:

textbook_image

lactic acid fermentation

In lactic acid fermentation, glycolysis is followed by a step that produces lactic acid. This step forms additional molecules of ATP. Lactic acid fermentation occurs in some bacteria, including the bacteria in yogurt. The lactic acid gives unsweetened yogurt its sour taste. Your own muscle cells can also undertake lactic acid fermentation. This occurs when the cells are working very hard. They use fermentation because they cant get oxygen fast enough for aerobic respiration to supply them with all the energy they need. The muscle cells of the hurdlers in Figure 4.15 are using lactic acid fermentation by the time the athletes reach finish line.

textbook_image

alcoholic fermentation

In alcoholic fermentation, glycolysis is followed by a step that produces alcohol and carbon dioxide. This step also forms additional molecules of ATP. It occurs in yeast, such as the yeast in bread. Carbon dioxide from alcoholic fermentation creates gas bubbles in bread dough. The bubbles leave little holes in the bread after it bakes. You can see them in the bread in Figure 4.16. The holes make the bread light and fluffy.

instructional diagrams

No diagram descriptions associated with this lesson

questions

Products of cellular respiration include

a. oxygen

-->  b. water

c. ADP

d. two of the above

For each glucose molecule that undergoes cellular respiration, what is the maximum number of ATP molecules that are produced?

a. 2

b. 4

c. 34

-->  d. 38

During cellular respiration, each ATP molecule forms when a phosphate is added to

a. alcohol.

b. glucose.

c. pyruvate.

-->  d. ADP.

In the first stage of cellular respiration, enzymes split a glucose molecule into two smaller molecules of

a. ADP

b. oxygen

-->  c. pyruvate

d. carbon dioxide

Cellular respiration occurs in

a. plants

b. protists

c. animals

-->  d. all of the above

Which stage of cellular respiration is anaerobic?

-->  a. glycolysis

b. electron transport

c. Krebs cycle

d. none of the above

The stage of cellular respiration that also occurs in fermentation is

-->  a. glycolysis.

b. electron transport.

c. Krebs cycle.

d. none of the above

How many molecules of ATP are produced during the Krebs cycle?

a. one

-->  b. two

c. three

d. four

When your muscle cells are working too hard for cellular respiration to keep them supplied with energy, they start producing ATP by

-->  a. lactic acid fermentation.

b. alcoholic fermentation.

c. aerobic respiration.

d. aerobic fermentation.

The matrix of a mitochondrion is the site of

a. glycolysis

-->  b. the Krebs cycle

c. alcoholic fermentation

d. lactic acid fermentation

Molecules that form during glycolysis include

a. pyruvate.

b. carbon dioxide.

c. ATP.

-->  d. two of the above

Which waste product is produced during the Krebs cycle?

a. water

b. alcohol

-->  c. carbon dioxide

d. lactic acid

_Cellular respiration uses oxygen in addition to glucose.

-->  a. true

b. false

_Cellular respiration takes place in the cells of all aerobic organisms.

-->  a. true

b. false

_Glycolysis takes place in the matrix of a mitochondrion.

a. true

-->  b. false

_The second stage of cellular respiration produces four molecules of ATP.

a. true

-->  b. false

An ATP molecule forms when a phosphate is added to ADP.

-->  a. true

b. false

Cells without mitochondria cannot break down glucose for energy.

a. true

-->  b. false

_A waste product of electron transport is water.

-->  a. true

b. false

All three stages of cellular respiration are aerobic.

a. true

-->  b. false

_The products of photosynthesis are the reactants of cellular respiration.

-->  a. true

b. false

_Fermentation produces ATP from lactic acid or alcohol.

a. true

-->  b. false

Water forms as a waste product during the second stage of cellular respiration.

a. true

-->  b. false

The final stage of cellular respiration is called electron transport.

-->  a. true

b. false

_second stage of cellular respiration

a. glycolysis

b. electron transport

c. cellular respiration

d. lactic acid fermentation

-->  e. Krebs cycle

f. alcoholic fermentation

g. mitochondrion

_organelle that is called the powerhouse of the cell

a. glycolysis

b. electron transport

c. cellular respiration

d. lactic acid fermentation

e. Krebs cycle

f. alcoholic fermentation

-->  g. mitochondrion

_process in which cells burn glucose for energy

a. glycolysis

b. electron transport

-->  c. cellular respiration

d. lactic acid fermentation

e. Krebs cycle

f. alcoholic fermentation

g. mitochondrion

_process in which yeasts in bread produce ATP from glucose

a. glycolysis

b. electron transport

c. cellular respiration

d. lactic acid fermentation

e. Krebs cycle

-->  f. alcoholic fermentation

g. mitochondrion

_process in which bacteria in yogurt produce ATP from glucose

a. glycolysis

b. electron transport

c. cellular respiration

-->  d. lactic acid fermentation

e. Krebs cycle

f. alcoholic fermentation

g. mitochondrion

_first stage of cellular respiration

-->  a. glycolysis

b. electron transport

c. cellular respiration

d. lactic acid fermentation

e. Krebs cycle

f. alcoholic fermentation

g. mitochondrion

_final stage of cellular respiration

a. glycolysis

-->  b. electron transport

c. cellular respiration

d. lactic acid fermentation

e. Krebs cycle

f. alcoholic fermentation

g. mitochondrion

diagram questions

No diagram questions associated with this lesson