Cell Respiration Review - AP Bio

Cellular

Respiration

Why We Live and Breathe

Food contains carbs, lipids and proteins (remember them?) The energy in these is stored in the chemical bonds. There’s more energy in these bonds than you think.

So, what would happen if your body didn’t
digest this food slowly? You would release all of that energy at one time and you'd explode!

Cellular respiration

The process of breaking the bonds in food in order to release the energy from the food. Your body then uses this energy to do work.

Coordinated step of redox reactions

Reduced - gains electrons/atoms
Oxidized - loses electrons/atoms

Glucose is oxidized as atoms are stripped from it. This results in the release of carbon dioxide.
Electrons and hydrogens released by glucose are picked up by electron carriers (NAD+ and FAD+)
These electrons & hydrogens will be added to oxygen to create water. Oxygen is reduced in this reaction.
The chemical energy that is released from the glucose molecule is stored as chemical energy in the ATP molecule.

Equation

You get glucose from the food you eat. It is released during the process of digestion
in your stomach and small intestine.

Oxygen is inhaled.

Carbon dioxide is exhaled. Water stays in your cells

ATP is your body’s energy storage molecule.

What is ATP?

ATP is the energy molecule in your body. Your body uses the energy from food to
make ATP molecules. These molecules are then sent to the cells in your body so that
they can use them to do work.

The ATP-ADP Cycle

Food gives you the
energy to recharge
the ATP battery.

The charged ATP
battery releases
energy in your cells
so that they can do
work.

The energy is
stored in the
triphosphate tail of
the ATP molecule.
Breaking off a
phosphate releases
the energy.

Releasing Energy

●To release the energy stored in ATP molecules,
bonds between their phosphate groups are broken
through hydrolysis.
●Hydrolysis is a chemical reaction in which a water
molecule splits another molecule.
● As a result of hydrolysis, energy is released and
ATP loses a phosphate to become ADP (Adenosine
diphosphate).

Multiple Choice

Which bond of the ATP molecule is broken in order to release energy?

• A
• B
• C
• D

Multiple Choice

Which cellular organelle is responsible for manufacturing ATP?

• Ribosome
• Nucleus
• Mitochondria
• Chloroplast

Multiple Choice

What are the parts of the ATP molecule?

• adenine, thylakoids, stroma
• stroma, grana, chlorophyll
• adenine, ribose, phosphate groups
• NADH, NAHPH, FADH

So how do you get the energy from the food?

Cellular respiration!

This process actually occurs in 3 steps:

1.

Glycolysis

2.

Citric Acid Cycle (aka. Kreb’s cycle)

3.

Electron transport chain

3 Processes Chart

Glycolysis

Citric Acid Cycle (Kreb's)

Electron Transport
Chain

Happens in cytoplasm
(anerobic)

Happens in mitochondria
(matrix)
(aerobic pathway)

Happens in mitochondria
(across inner
membrane) (aerobic)

Begins breaking down
glucose
Makes 2 ATP
Collects electrons &
hydrogens (NAD)

Completely oxidizes glucose & releases carbon dioxide
Collects electrons &
hydrogens (NAD & FAD)
Makes 2 ATP

Uses the flow of
hydrogens to make ATP
Oxygen fuels the chain by pulling e- towards it
Makes 32 ATP

So, you breathe in oxygen so that you can break down your food and make ATP
energy for your body. If you don’t get enough oxygen, you don’t make enough energy and you die.

​Glycolysis

​Breaks a 6-carbon glucose into 2, 3-carbon pyruvate molecules.
NAD+ is reduced as it picks up H+ and e- released from glucose oxidation to become 2 molecules of NADH.
2 ATP a required in the input phase to get the process started.
4 ATP are created, but since 2 were used to start the process, we say that glycolysis has a net gain of 2 ATP.

Glycolysis is an evolutionarily conserved process. In other words, it's been around for a long time and originated in a common ancestor.

Evidence:
Anaerobic process (early Earht's atmosphere was anaerobic)
Occurs in cytoplasm (all cells have cytoplasm)
Enzymes used in the process are similiar in all organisms. The genes that encode these enzymes are very similar across different organism types.

​Glycolysis & Evolution

Multiple Choice

What is the main function of glycolysis?

• To rearrange the glucose molecule to be broken down

• To recreated acetyl CoA for the Krebs cycle

• To absorb and store energy in the ATP molecules

• To split the glucose molecule to release energy

Multiple Choice

What are the products of glycolysis?

• 2 ATP; 2 NADH; 2 pyruvate

• 2 ATP; 2 NADPH; 2 pyruvate

• 2 ADP; 2 NADH; 2 pyruvate

• 2 ADP; 2 NADPH; 2 pyruvate

Multiple Choice

How does glycolysis lead to ATP synthesis?

• Glucose provides the phosphate to ADP to synthesize ATP

• Acetyl CoA is synthesized for the Krebs cycle

• Glycolysis splits the glucose molecule to create G3P

• High energy electrons are stored in NADH for the ETC

Multiple Choice

Justify that glycolysis evolved before oxygen was present in the atmosphere?

• Glycolysis splits a glucose molecule into 2 pyruvate molecules which does not require oxygen

• Glycolysis does not take place in the mitochondria and thus does not require oxygen

• Glycolysis does not require oxygen which represents that it evolved prior to free oxygen in the atmosphere

• Glycolysis takes place in all living organisms which means it evolved prior to free oxygen in the atmosphere

Multiple Choice

Where does glycolysis take place?

• Thylakoid

• Cytosol

• Mitochondrial matrix

• Cristae

The Intermediate Reaction (aka. pyruvate oxidation)

Occurs in the cytoplasm after glycolysis has taken place
Used to shuttle the carbons from glucose into the mitochondria
Co enzyme A oxidizes the pyruvate created in glycolysis into 2 molecules of Acetyl-CoA
Two CO2 molecules are released
NAD+ picks up the H+ and e- released from pyruvate oxidation to become NADH

​*This process is outside of the scope of the AP Bio curriculum. It's just good to know that the carbons from glucose don't magically appear in the mitochondria.

Multiple Choice

Krebs Cycle takes place in the:

• cytosol

• matrix

• intermembrane space

Multiple Choice

The waste product produced during the Krebs cycle is...

• oxygen

• carbon dioxide

• water

• ATP

Multiple Choice

The Krebs cycle is anaerobic.

• true

• false

Multiple Select

The Kreb's Cycle

• results in the total oxidation of glucose

• creates 2 ATP

• is also known as the Calvin cycle

• uses NADH and FADH2 to store high energy e- and H+

Multiple Choice

Which of the following is not an end product of the Kreb's cycle?

• FADH₂

• CO₂

• ATP

• pyruvate

Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping

​

​

Electron Transport Chain

​

The inner membrane is arranged into folds cristae, which increases the surface area available for the transport chain

​

The Third Stage of AEROBIC respiration

​

The hydrogen carriers (NADH and FADH2) are moving along and release high energy electrons and protons

​

The electrons are transferred to the electron transport chain, which consists of several transmembrane carrier I proteins

​

Step 1: Generating a Proton Motive Force

​

As electrons pass through the chain, they lose energy – which is used by the chain to pump protons (H+ ions) from the matrix

|

The accumulation of H+ ions within the intermembrane space creates an electrochemical gradient (or a proton motive force)​

Step 1: Generating a Proton Motive Force

​

• Highlight the electrons and the Hydrogen Ions!

The proton motive force will cause H+ ions to move down their electrochemical gradient and diffuse back into the matrix

​

(high to low concentration)​

​

Step 2: ATP Synthesis via Chemiosmosis

​

• Highlight the electrons and the Hydrogen Ions!

This diffusion of protons is called chemiosmosis and is facilitated by the transmembrane enzyme ATP synthase

​

As the H+ ions move through ATP synthase they trigger the molecular rotation of the enzyme, synthesizing ATP

​

​

​

Step 2: ATP Synthesis via Chemiosmosis

​

In order for the electron transport chain to continue functioning, the de-energised electrons must be removed

​

Oxygen acts as the final electron acceptor, removing the de-energised electrons to prevent the chain from becoming blocked

​

​

​

​

Step Three: Reduction of Oxygen

​

Oxygen also binds with free protons in the matrix to form water – removing matrix protons maintains the hydrogen gradient

​

In the absence of oxygen, hydrogen carriers cannot transfer energized electrons to the chain, and ATP production is halted

​

​

​

​

​

Step Three: Reduction of Oxygen

​

Multiple Choice

In what part of the mitchondria does the electron transport chain occur?

• Inner mitochondrial membrane (folds of the mitochondria)

• Outer mitochondrial membrane

• Cytoplasm

• Ribosomes

Multiple Choice

True or False: Water is produced as a byproduct during this stage of cellular respiration.

• True

• False

Multiple Choice

ATP synthesis by ATP synthase is driven by

• H⁺ movement

• electron movement

• NADH movement

• FADH₂ movement

Multiple Choice

What enzyme in the ETC is responsible for generating the ATP molecules?

• ATPase
• ATP synthase
• Hexokinase
• none of the above

Multiple Choice

When protons are pumped outside the matrix, across the inner membrane...

• water is made

• a concentration gradient of H⁺ ions (protons) is created

• NADH gets reduced

• CO₂ is produced

Multiple Choice

Oxidative phosphorylation results in the formation of

• Oxygen

• ADP

• ATP + H2O

• NADH

Multiple Choice

What will happen if there is a leakage in the inner membrane of mitochondria.

• no proton-motive force will be created

• chemiosmosis will be delayed

• no ATP will be produced

• no H2O will be produced

Multiple Choice

Why ETC must occur first before chemiosmosis?

• to produce H2O

• to produce ATP

• to create proton-motive force

Multiple Choice

What is the definition of electron transport chain.

• The process in which ATP is form as a result of the transfer of electrons from NADH and FADH2 occurs at the inner membrane of the mitochondrion of eukaryotes by a series of electron carriers.

• A sequence of electron carrier molecules embedded in inner membrane of mitochondria that shuttle electrons down a series of redox reactions that release energy used to make ATP.

• Energy-coupling mechanism that uses energy stored in the form of an H+ gradient across a membrane to drive cellular work.

• High concentration of proton (H+) in the intermembrane space of mitochondria resulting in proton gradient across the membrane known as proton-motive force.

Let's Review some Vocab...

Chemiosmosis - the flow of ions down their concentration gradient. (In the case of the ETC, this is the flow of H+ ions).
Oxidative phosphorylation - the creation of ATP using the electron transport chain in cell respiration
Proton motive force - the potential energy generated by a difference in proton concentration across a membrane

Phosphorylation

​Adding a phosphate group to a molecule

Substrate-level phosphorylation: Adding a phosphate directy to a molecule. Kinases are a group of enzymes that perform this reaction. In cell respiration, this occurs during glycolysis and the Kreb's cycle.

Oxidative phosphorylation: An electron transport chain (ETC) is used to create a proton motive force. These protons then flow through the enzyme ATP synthase, which then creates ATP. The movement of e- is driven by oxygen, who is the final e- acceptor.

Photophosphorlation: An ETC is usd to create a proton motive force. These protons then flow through the enzyme ATP synthase, which then creates ATP. These e- are excited when light energy (photons) hits chlorophyll pigments in photosystems 1 & 2.

Match

Match the types of phosphorylation with their definition.

• Substrate level

• Oxidative Phosphorylation

• Photophosphorylation

Phosphate added directly to ADP

Involves ETC, ATP synthase & O2; CR

Involves ETC, ATP synthase & light; PS

• Phosphate added directly to ADP

• Involves ETC, ATP synthase & O2; CR

• Involves ETC, ATP synthase & light; PS

Multiple Choice

The complete oxdiation of glucose in aerobic respiration occurs through which of the following sequences of metabolic rections?

• Glycolysis, ETC, Kreb's, pyruvate oxidation

• ETC, pyruvate oxidation, glycolysis, Kreb's

• Glycolysis, pyrvuate oxidation, Kreb's, ETC

• Pyrvuate oxidation, glycolysis, Kreb's, ETC

Multiple Choice

In the complete reactions of aerobic respiration, the energy for the majority of ATP synthesis is provided by

• splittng water to produce oxygen.

• high-energy phosphate bones from organic molecule intermediates in the CAC.

• a proton gradient across a membrane.

• the production of carbon dioxide and oxygen in the ETC.

Multiple Choice

What is the source of oxygen used to form water in teh compelte reactions of cellular respiration?

• glucose

• carbon dioxide (CO2)

• molecular oxygen (O2)

• pyruvate

Multiple Select

Which of the following statements are correct about an oxidation-reduction (redox) reaction?

• The molecule that is reduced gains electrons.

• The moelcule that is reduced loses elextrons.

• The molecule that is oxidized loses electrons.

• The molecule that is oxidized gains electrons.

Multiple Choice

Which process in eukaryotic cells will proceed normally wheterh oxygen is present or absent?

• glycolysis

• electron transport

• the Kreb's cycle

• chemiosmosis