Cellular Respiration part 1: Overview of Cellular Respiration and Glycolysis
Call Kai
Learn
Practice Test
Spaced Repetition
Match
Flashcards
Knowt Play1/95
There's no tags or description
Looks like no tags are added yet.
96 Terms
Energy flows into an ecosystem as ____ and exits as ____
sunlight; heat
In an ecosystem, chemicals (matter) are ____ while energy ____
recycled; flows through (one way)
What do chloroplasts do in the ecosystem cycle?
Use light energy for photosynthesis to make organic molecules + O2 from CO2 + H2O
What do mitochondria do in the ecosystem cycle?
Use organic molecules + O2 for cellular respiration to make ATP, releasing CO2 + H2O
Products of photosynthesis are the ____ of cellular respiration (and vice versa)
reactants
What powers most cellular work?
ATP
The breakdown of organic molecules is ____ (exergonic or endergonic)
exergonic
Catabolic pathways do what?
Break down organic molecules and release energy (used to make ATP)
What can catabolic pathways be used for?
Making ATP to power cell work (like movement, transport, building molecules)
Fermentation is…
a partial breakdown of sugars that happens without O2
Does fermentation need oxygen?
No
Aerobic respiration is…
breaking down organic molecules using O2 to make ATP
Anaerobic respiration is…
like aerobic respiration, but uses a compound other than O2
Aerobic vs anaerobic respiration?
Aerobic = uses O2. Anaerobic = uses something other than O2
Fermentation vs anaerobic respiration?
Fermentation = partial sugar breakdown, no electron transport chain. Anaerobic respiration = full respiration using a non-O2 final acceptor
Cellular respiration includes…
both aerobic and anaerobic processes (but usually means aerobic)
Are fermentation and cellular respiration exergonic or endergonic?
Exergonic (both release energy)
Which fuels can be used in cellular respiration?
Carbohydrates, fats, and proteins
Why do we trace cellular respiration with glucose?
It's the simplest/most helpful example to follow
Summary equation for cellular respiration?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP + heat)
How many O2 are used to break down one glucose?
6
Is cellular respiration exergonic or endergonic?
Exergonic (ΔG is negative, about −686 kcal/mol)
Redox reactions are…
chemical reactions that transfer electrons between reactants (oxidation-reduction)
Oxidation is…
a substance losing electrons
Reduction is…
a substance gaining electrons
Why is gaining electrons called "reduction"?
It reduces the amount of positive charge
Memory hook for oxidation vs reduction?
OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons)
The reducing agent is the electron ____
donor (it gets oxidized)
The oxidizing agent is the electron ____
acceptor (it gets reduced)
Reducing agent vs oxidizing agent?
Reducing agent = gives electrons away (oxidized). Oxidizing agent = takes electrons (reduced)
In a redox reaction, what happens to the reducing agent's potential energy?
It loses electrons and loses potential energy
Do all redox reactions completely transfer electrons?
No, some just change how electrons are shared in covalent bonds
Example of a redox reaction that changes electron sharing?
Methane (CH4) burning with O2
During cellular respiration, glucose is ____ and O2 is ____
oxidized; reduced
In cellular respiration, what is the reducing agent?
Glucose (it loses electrons)
In cellular respiration, what is the oxidizing agent?
O2 (it gains electrons)
Glucose becomes ____ when it's oxidized
CO2
O2 becomes ____ when it's reduced
H2O
Why are carbs and fats excellent fuels?
They have lots of hydrogen (lots of electrons that can be moved to oxygen)
As hydrogen (with its electron) is transferred to oxygen…
energy is released that can be used to make ATP
A hydrogen atom =
one electron + one proton
In cellular respiration, glucose is broken down…
in a series of steps (not all at once)
Electrons from glucose are usually first transferred to…
NAD+ (a coenzyme)
What is NAD+?
A coenzyme that acts as an electron carrier (shuttle)
Remember: a coenzyme is…
an organic cofactor (NAD+ comes from the vitamin niacin)
NAD+ functions as an ____ agent during cellular respiration
oxidizing (it's an electron acceptor)
An electron acceptor is…
a molecule that takes electrons from another molecule
Oxidized form vs reduced form of NAD?
NAD+ = oxidized (empty). NADH = reduced (carrying electrons)
What does each NADH represent?
Stored energy that can be used to make ATP
Think of NADH like…
a charged battery carrying energy-rich electrons
Dehydrogenases are enzymes that…
remove hydrogen (2 electrons + 1 H+) from a substrate and give it to NAD+
When dehydrogenase works, NAD+ receives ____ electrons and ____ H+
2; 1
In the reduction of NAD+, what is released into solution?
One hydrogen ion (H+)
Why are the electrons carried by NADH called "high energy"?
They have lots of potential energy that's released as they move toward oxygen
NADH passes its electrons to the…
electron transport chain (ETC)
In the ETC, electrons are passed to increasingly ____ carrier molecules
electronegative
Electrons move down the ETC through a series of…
redox reactions
What is the final (terminal) electron acceptor in aerobic respiration?
Oxygen (O2)
Path of electrons in cellular respiration?
Glucose → NADH → electron transport chain → oxygen
Why does the ETC release energy in steps instead of all at once?
To avoid one explosive reaction and capture the energy to make ATP
Think of the ETC like…
a staircase: electrons go down step by step instead of jumping off a cliff
"Falling down an energy gradient" means…
electrons moving from high potential energy (NADH) to low (O2), releasing energy at each step
Is the transfer of electrons from NADH to O2 exergonic or endergonic?
Exergonic
The energy released by the ETC is used to…
make (regenerate) ATP
What kind of molecules make up the ETC?
Mostly proteins
Where is the ETC located in eukaryotes?
Inner mitochondrial membrane
Where is the ETC located in prokaryotes?
Plasma membrane
3 stages of cellular respiration?
Glycolysis, pyruvate oxidation + citric acid cycle, oxidative phosphorylation
Where does glycolysis happen?
Cytosol (cytoplasm)
Where do pyruvate oxidation and the citric acid cycle happen?
Mitochondrial matrix
Where does oxidative phosphorylation happen?
Inner mitochondrial membrane
Glycolysis breaks glucose into…
two molecules of pyruvate
Pyruvate oxidation and the citric acid cycle do what?
Finish breaking down glucose
Which stage makes the most ATP?
Oxidative phosphorylation
Oxidative phosphorylation accounts for about ____% of the ATP made
90
Oxidative phosphorylation involves…
the ETC and adding inorganic phosphate to ADP
2 ways ATP is made in cellular respiration?
Oxidative phosphorylation and substrate-level phosphorylation
Substrate-level phosphorylation is…
an enzyme transferring a phosphate directly from a substrate molecule to ADP
Where does substrate-level phosphorylation happen?
Glycolysis and the citric acid cycle
Oxidative vs substrate-level phosphorylation?
Oxidative = ETC, makes most ATP (~90%). Substrate-level = enzyme directly moves phosphate to ADP, makes a small amount
Glycolysis means…
"sugar splitting"
Glycolysis breaks one glucose into…
two pyruvate molecules
How many carbons are in glucose vs pyruvate?
Glucose = 6. Each pyruvate = 3
Follow the carbons: where do glucose's 6 carbons end up after glycolysis?
In the two 3-carbon pyruvates
By-product of glycolysis besides ATP and NADH?
Two water molecules
2 phases of glycolysis?
Energy investment phase and energy payoff phase
What happens in the energy investment phase?
The cell spends 2 ATP to get glucose ready to split
What happens in the energy payoff phase?
4 ATP and 2 NADH are made
Why is glycolysis described as an investment and a payoff?
Early steps use ATP; later steps store more energy in ATP and NADH than was spent
Net yield of glycolysis per glucose?
2 ATP + 2 NADH (+ 2 pyruvate + 2 H2O)
Why is the net ATP of glycolysis 2 and not 4?
4 ATP made − 2 ATP invested = 2 net
How is ATP made in glycolysis: substrate-level or oxidative phosphorylation?
Substrate-level phosphorylation
Does glycolysis need oxygen?
No, it happens whether or not O2 is present
Do all living organisms perform glycolysis?
Yes, nearly all organisms do (it's very ancient)
If O2 is present, what happens to pyruvate and NADH after glycolysis?
Their energy is extracted by pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation
In the energy investment phase, glucose is split into two ____-carbon sugars
3 (glyceraldehyde 3-phosphate, G3P)