Unit 4 Part 2 - Cellular Respiration (Biology 9H)

Cellular respiration

• Process by which molecules (glucose & oxygen) are broken down to release energy (ATP) for the cell.

• Either aerobic (with oxygen) or anaerobic (w/o oxygen)

• 3 stages for aerobic= glycolysis, Krebs cycle, & electron transport chain

• 2 stages for anaerobic = glycolysis and fermentation

• Biochemical pathway : series of chemical reactions where products of one become reactants for the next

2 ways to convert glucose into ATP

1. Fermentation (anaerobic respiration) - makes 2 ATP & doesn’t need oxygen

2. Aerobic respiration - makes 36 ATP & needs oxygen

Mutualism

• Win-win relationship

• Ex.: bacteria benefit from living in our intestines since they get food & a warm environment.

• We benefit from having bacteria since we get short chain fatty acids which we digest.

Fermentation

• Occurs in the cytoplasm

• Lactic acid fermentation

  • Produces 2 lactic acid & 2 ATP

  • Occurs in bacteria & mammals

  • I.e. cheese, kimchi, yogurt, sauerkraut

• Alcoholic fermentation

  • Produces 2 alcohol (ethanol) & 2 CO2 & 2 ATP

  • Occurs in yeast

• Fermentation recycles NAD+ back to glycolysis

  • Important bc it results in glycolysis producing ATP even if there’s no oxygen (anaerobic)

Aerobic respiration equation & where it occurs

C₆H₁₂O₆  +  6O₂  ==> 6H₂O  + 6CO₂  +  ~36 ATP

Occurs in the mitochondria

Glycolysis

• First stage of cellular respiration

• Occurs in the cytoplasm of the cell

• Breaks down glucose into 2 3-C pyruvate molecules (used in aerobic respiration)

• Produces ATP and NADH

  • NADH = carries electrons to the Electron Transport Chain (final stage of aerobic respiration)

• Doesn’t use oxygen (anaerobic)

Krebs cycle

• Second stage of aerobic respiration

• Occurs in the matrix of mitochondria

• Adds electrons to NAD and FAD

• Produces NADH, FADH2, ATP, CO2

  • NADH and FADH2 → go to Electron Transport Chain

Electron Transport Chain

• Third stage of aerobic respiration

• Is a series of proteins

• Uses reactant O2 which is not from Krebs cycle

• Occurs in inner membrane of mitochondria

• Uses electrons carried by NADH and FADH2 molecules from Krebs cycle

• Produces ATP and water

NADH ⇒ NAD⁺ H⁺ + e^_

• As the e- (electron) goes down the chain → energy released

  • →ATP synthase (enzyme) makes ATP

  • Low energy electron @ the bottom of the chain combines w/ O2 and H+ to make water.

When is glucose used?

Glycolysis

When is oxygen used?

Electron Transport Chain

When is water made?

Electron Transport Chain

When is carbon dioxide (CO2) made?

Krebs cycle

When is ATP made?

Throughout cellular respiration, but mostly in the ETC for aerobic respiration

Why do you die when you are deprived of oxygen?

You need oxygen for cellular respiration in order to sustain your body, as the amount of ATP made by fermentation (anaerobic respiration), which doesn’t need oxygen, is not enough energy to survive.

What elements are sugar molecules made of?

Carbon, hydrogen, and oxygen

Why do organisms perform respiration instead of just using glucose?

Glucose is better for energy storage, while ATP is better for fuel and serves as an energy currency (fuels cellular processes) as it can be directly used.

What will happen if you forget to add yeast to your bread?

A) Dough will not taste sweet

B) Dough will contain alchohol

C) It will not rise

D) All of the above

C

How is it possible for plants to release carbon dioxide and oxygen at the same time? (About chemical reactions & the speed they occur)

Plants do photosynthesis (O2) and cellular respiration (CO2) simultaneously, but they do photosynthesis at a higher rate. The oxygen produced in photosynthesis is used in respiration; the oxygen they don’t use is then released by the plant to the atmosphere.

This means that during the daylight, there is more O2 being released than CO2 is being taken in.

What role do photosynthesis and cellular respiration play in forming carbon-based compounds?

• Carbon-based compounds = glucose

• Photosynthesis: makes glucose by taking CO2 from the atmosphere & bonding the carbons (w/ other elements) together

• Cellular respiration: breaks down glucose to release energy. CO2 is a waste product & returned to the atmosphere.

For photosynthesis and cellular respiration, are they endothermic or exothermic?

• Photosynthesis - endothermic

• Cellular respiration - exothermic

How is breathing related to cellular respiration?

When you breathe, you let in oxygen to your body which you need to perform cellular respiration to produce ATP. You also release the excess CO2 (product of respiration) when you exhale.

You take in O2 and get rid of CO2 through your lungs.

Do skin cells or the cells in your bicep muscles have more mitochondria? Why?

Bicep muscles because you use your muscles more often when you exercise. When exercising, you have to breathe in more oxygen to produce enough energy in respiration, and respiration occurs in the mitochondria. Your muscle cells use more ATP when exercising.

Why does a person breathe faster and deeper when they are exercising? Use the fact that when a person exercises, their muscle cells use much more ATP.

In order for aerobic respiration, the person needs to breathe in oxygen so they can make enough ATP, which they need more of when exercising. If they don’t breathe enough oxygen, they would have to do anaerobic respiration which doesn’t produce enough ATP/energy.

More carbon given off by respiration & decomposition than taken in by photosynthesis.

Is it a carbon source or sink, and is the Net Ecosystem Exchange (NEE) positive or negative? When does this occur?

• Carbon source

• NEE is positive

• Usually happens at night & in the winter, since photosynthesis doesn’t occur.

More carbon taken in by photosynthesis than given off by respiration & decomposition

Is it a carbon source or sink, and is the Net Ecosystem Exchange (NEE) positive or negative? When does this occur?

• Carbon sink

• NEE is negative

• Usually happens during the summer and day since there is a lot of light and photosynthesis occurs.