TEAS Cellular Respiration and Photosynthesis SE

Cell Respiration

1. What is cellular respiration?

Imagine your body is a phone that needs to be charged to work.

• Your cells are like tiny machines.

• Your cells need energy to do their jobs.

• Your cells get usable energy by breaking down glucose (sugar).

• That process is called cellular respiration.

• Much of this process happens in the mitochondria, often called the powerhouse of the cell.

Super easy definition: Cellular respiration is how cells break down glucose to make usable energy called ATP.

Glucose = fuel

The sugar the cell breaks down to get energy.

Mitochondria

Mitochondria = energy-making site

Where most cellular respiration takes place in eukaryotic cells.

Adenosine triphosphate (ATP)

ATP = usable energy

The energy supply cells use to do their work.

Memory trick: G → M → A

• Glucose = fuel

• Mitochondria = where most of the process happens

• ATP = usable energy

Think: Fuel goes in, energy comes out!

2. Understand the equation

Your notes give you this equation:

What does each part mean?

O₂

O₂ = Oxygen

The cell uses oxygen to help release energy from glucose during aerobic cellular respiration.

Memory trick: Oxygen helps the process.

C₆H₁₂O₆

C₆H₁₂O₆ = Glucose

This is the chemical formula for glucose, a simple sugar that provides fuel for the cell.

Memory trick: Glucose = gas for your cell.

CO₂

CO₂ = Carbon dioxide

This is a waste product of cellular respiration. It travels in the blood to the lungs and is breathed out.

Memory trick: CO₂ goes out.

H₂O

H₂O = Water

Water is another product made during cellular respiration.

Memory trick: H₂O = water. You may already know this from chemistry!

ATP

ATP = Usable energy

ATP stands for adenosine triphosphate. Cells use it to power activities such as moving substances, building molecules, and muscle contraction.

Memory trick: ATP = energy money the cell can spend.

4. How to read the equation

Think of it as a recipe.

• Before the arrow (→): What goes in.

• After the arrow (→): What comes out.

• The arrow: Means “produces” or “turns into.”

Goes in (reactants)	Comes out (products)
Oxygen (O₂)	Carbon dioxide (CO₂)
Glucose (C₆H₁₂O₆)	Water (H₂O)
	ATP (usable energy)

The easiest memory trick:

Sugar + Oxygen → Energy + Waste

More completely: glucose and oxygen are used to produce carbon dioxide, water, and ATP.

5. What happens step by step?

Step 1: Get glucose

Glucose comes from the food you eat. Your digestive system breaks carbohydrates down into simple sugars such as glucose.

Why Do We Need Oxygen?

Step 2: Get oxygen

You breathe in oxygen, and your blood carries it to your cells.

Cellular Respiration -

Step 3: Make ATP

Cells break down glucose through several reactions. In aerobic respiration, oxygen helps the process produce ATP efficiently. Most ATP is produced through processes associated with the mitochondria.

Step 4: Produce waste

Carbon dioxide and water are formed. Carbon dioxide is carried to the lungs and breathed out.

6. Important TEAS facts to memorize

cellular respiration

Term	Remember this
Cellular respiration	Breaks down glucose to make usable energy
Glucose	Fuel; a simple sugar
Oxygen	Used in aerobic respiration
Mitochondria	Main site of aerobic respiration in eukaryotic cells
ATP	Usable energy for cell activities
Carbon dioxide	Waste product breathed out
Water	Product of respiration
Reactants	Substances that go into a reaction
Products	Substances made by a reaction

Two extra facts that can help you ace the TEAS

• Glycolysis is the first stage of cellular respiration. It happens in the cytoplasm, not inside the mitochondria.

• Cellular respiration occurs in plants, too! Plants use glucose to make ATP. Photosynthesis makes sugars using light energy, while cellular respiration releases usable energy from those sugars.

Last thing to remember: Glucose is the fuel, oxygen helps release its energy, mitochondria are the main site, ATP is the usable energy, and carbon dioxide and water are products.

1. What is the main purpose of cellular respiration?

To produce usable energy in ATP

Cellular respiration breaks down glucose and captures energy in ATP.

2. Which molecule provides fuel for cellular respiration?

Glucose

3. Where does glycolysis occur?

cytoplasm

Which gas is used in aerobic cellular respiration?

Oxygen

Which is a product of cellular respiration?

Carbon dioxide→ breathe out

6. What does ATP do?

Provides usable energy for cell activities

7. Where does most aerobic cellular respiration occur in eukaryotic cells?

mitochondria

8. What are reactants?

The substances that go into a reaction

starting substances

9. Do plant cells perform cellular respiration?

yes

10. Which statement best describes the overall process?

Oxygen and glucose produce carbon dioxide, water, and usable energy

1. What does aerobic respiration mean?

Aerobic = with oxygen.

Aerobic respiration is when your cells use glucose + oxygen to make ATP (usable energy).

Think of it like this:

Your cells need energy to work. They break down sugar using oxygen to make that energy.

Memory trick: 🫁 AEROBIC = AIR = OXYGEN

2. Why does it happen in the mitochondria?

Think of the mitochondria as a tiny power plant inside your cell.

• Your cell needs energy.

• The mitochondria help turn energy from glucose into ATP.

• ATP powers your cells so they can do their jobs.

Memory trick: Mitochondria = the cell's powerhouse!

3. What actually happens inside the mitochondria?

Step 1: Glucose gets broken down

Glucose starts breaking down in the cytoplasm before the later stages continue in the mitochondria.

Step 2: Oxygen helps

Inside the mitochondria, oxygen helps the process continue so the cell can produce lots of ATP.

Step 3: ATP is made

The mitochondria use energy from the breakdown of glucose to make ATP, which the cell can use.

Step 4: Waste products form

Carbon dioxide and water are produced. Carbon dioxide eventually gets breathed out.

What should you memorize for the TEAS?

• Aerobic = with oxygen.

• Mitochondria = main site of aerobic cellular respiration in eukaryotic cells.

• ATP = usable energy for the cell.

• Glycolysis = first step; happens in the cytoplasm.

• Oxygen = helps the cell make lots of ATP during aerobic respiration.

One-sentence memory trick: Sugar is the fuel, oxygen helps release its energy, mitochondria are the power plant, and ATP is the energy the cell can spend.

Cellular Respiration: Part 1 — Glycolysis + Pyruvate Oxidation 🧬

First, remember the big picture:

Your cell breaks down glucose to get energy in the form of ATP. This happens in several steps, and we're learning the first two.

1. Glycolysis — the first step

What does glycolysis mean?

Glycolysis = breaking down glucose.

Think of glucose as one big piece of sugar that the cell breaks into two smaller pieces.

• Glyco = sugar

• Lysis = breaking apart

Memory trick: Glycolysis = glucose gets split!

What happens during glycolysis?

1 glucose

One sugar molecule with 6 carbon atoms

2 pyruvate

Two smaller molecules with 3 carbons each

What the cell gets

2→ Net ATP

2→ NADH

2→Pyruvate

Glycolysis happens in the cytoplasm, the fluid inside the cell.

What are ATP, pyruvate, and NADH?

Adenosine triphosphate (ATP)

ATP = usable energy

The cell's energy supply. Glycolysis makes a net gain of 2 ATP.

Pyruvate = the next-step material

Glucose splits into 2 pyruvate molecules. These can move on to the next stage when oxygen-based respiration is taking place.

NADH = an energy carrier

Think of NADH as a little delivery truck carrying high-energy electrons to help make more ATP later.

Why is glycolysis called anaerobic?

• A = without

• Aerobic = with oxygen

• Anaerobic = without oxygen

Glycolysis does not require oxygen to happen. It takes place in the cytoplasm.

Memory trick: Glycolysis goes first and doesn't need oxygen.

One important detail: the cell invests 2 ATP to start glycolysis, then makes 4 ATP, leaving a net gain of 2 ATP.

That means:

4 ATP made} - 2 ATP used} = 2ATP net

2. Pyruvate oxidation — the transition step

preparing pyruvate for the next stage of cellular respiration.

After glycolysis, you have 2 pyruvate molecules. Before they can continue through the next stage, the cell changes them into a molecule called acetyl-CoA.

What happens step by step?

2 pyruvate

Made during glycolysis

Pyruvate oxidation

Happens in the mitochondrial matrix

Acetyl-CoA

Ready to enter the next stage

This step also produces NADH and releases CO₂.

What do the new words mean?

1. Mitochondrial matrix

The matrix is the fluid-filled space inside the inner membrane of the mitochondrion.

Memory trick: Matrix = the inside workspace.

2. Acetyl-CoA

Think of this as a package that delivers material into the next stage, called the citric acid cycle (also called the Krebs cycle).

Memory trick: Acetyl-CoA = the entry ticket to the next stage.

3. CO₂ (carbon dioxide)

During this step, carbon dioxide is released as a waste product.

Memory trick: CO₂ = carbon dioxide goes out.

4. Oxidation

In chemistry, oxidation means losing electrons. In this step, pyruvate is changed, carbon dioxide is released, and electrons are transferred to NAD⁺ to make NADH.

Memory trick: OIL RIG — Oxidation Is Loss, Reduction Is Gain (of electrons).

3. Compare the first two stages

What to know	Glycolysis	Pyruvate oxidation
Main job	Split glucose	Prepare pyruvate for the next stage
Location	Cytoplasm	Mitochondrial matrix
Starting material	Glucose	Pyruvate
Main result	2 pyruvate, net 2 ATP, 2 NADH	Acetyl-CoA, NADH, CO₂
Requires oxygen directly?	No	Part of aerobic respiration; depends on conditions that allow aerobic metabolism to continue

The listed results for pyruvate oxidation are for both pyruvate molecules from one glucose: 2 acetyl-CoA, 2 NADH, and 2 CO₂.

4. Quick TEAS memory recap

Glycolysis: Split glucose in the cytoplasm.

Pyruvate oxidation: Change pyruvate into acetyl-CoA in the mitochondrial matrix.

ATP: Usable energy.

NADH: Carries high-energy electrons.

CO₂: Waste product released.

Acetyl-CoA: Enters the citric acid cycle next.

Glucose → Pyruvate → Acetyl-CoA

1. Where does glycolysis happen?

Cytoplasm

2. Does glycolysis require oxygen?

no

3. What does one glucose molecule split into during glycolysis?

A. Two pyruvate molecules

4. What is the net ATP gain from glycolysis?

2 ATP

What does NADH do?

Carries high-energy electrons

6. What does pyruvate become during pyruvate oxidation?

Acetyl-CoA

7. Where does pyruvate oxidation occur?

Mitochondrial matrix

8. Which waste product is released during pyruvate oxidation?

carbon dioxide

Cellular Respiration: The Last 2 Stages 🧬

First, remember the order you've learned so far:

1→Glycolysis

Cytoplasm — glucose splits into 2 pyruvate

2→Pyruvate oxidation

Mitochondrial matrix — makes acetyl-CoA

3→Citric acid cycle (Krebs cycle)

Mitochondrial matrix — collects energy and releases CO₂

4→ Electron transport chain

Inner mitochondrial membrane — makes most ATP

1. Citric acid cycle (Krebs cycle)

What is it?

The citric acid cycle, also called the Krebs cycle, is a series of reactions that takes material from acetyl-CoA and helps the cell capture energy.

Think of it like a little recycling machine: material enters, reactions happen, carbon dioxide comes out, and energy carriers are filled up for the next stage.

What happens?

1. Acetyl-CoA brings a small carbon-containing group into the cycle.

2. The cell breaks down and rearranges molecules through a series of reactions.

3. Carbon dioxide (CO₂) is released as waste.

4. The cell produces a little ATP and loads up energy carriers called NADH and FADH₂.

5. Those carriers take energy-rich electrons to the electron transport chain.

Memory trick: The Krebs cycle loads the energy trucks for the next stage!

What do the hard words mean?

NADH

NADH = energy carrier

Think of it as a delivery truck carrying high-energy electrons to the next stage, where their energy helps make ATP.

FADH₂

FADH₂ = another energy carrier

It also carries high-energy electrons to the electron transport chain.

CO₂

CO₂ = carbon dioxide

A waste product released during the cycle. It eventually travels to your lungs to be breathed out.

What does the Krebs cycle produce?

For one glucose molecule, the cycle turns twice because one glucose produces two acetyl-CoA molecules.

Product	Amount
ATP	2
NADH	6
FADH₂	2
CO₂	4

Memory trick: The Krebs cycle makes 2 ATP, 6 NADH, 2 FADH₂, and 4 CO₂.

Notice that it makes only 2 ATP directly, but it makes 8 energy-carrier molecules (6 NADH + 2 FADH₂) to help produce much more ATP later.

One important detail: the cycle itself does not directly use oxygen in one of its reactions, but it depends on aerobic respiration continuing to regenerate the carriers it needs. That's why it's considered part of aerobic cellular respiration.

2. Electron transport chain (ETC)

This is the stage where the cell makes most of its ATP.

Imagine a water dam

Think of the mitochondrion as a power station.

• NADH and FADH₂ deliver high-energy electrons.

• Their electrons move through a series of protein complexes in the inner mitochondrial membrane.

• The released energy pumps tiny charged particles called protons (H⁺) across the membrane.

• The protons build up on one side, like water behind a dam.

• When protons flow back through a protein called ATP synthase, their movement powers ATP production.

Let's break down the hard words

Electron transport chain

A series of proteins that pass electrons along and use the released energy to pump protons.

Memory trick: ETC = an electron relay race.

Protons (H⁺)

Tiny positively charged particles. Their buildup across the inner membrane stores energy.

Memory trick: Protons pile up like water behind a dam.

ATP synthase

A protein that uses the flow of protons to make ATP from ADP and phosphate.

Memory trick: ATP synthase = the ATP-making machine.

Oxygen and water

Oxygen accepts the electrons at the end of the chain and combines with electrons and protons to form water.

Memory trick: Oxygen is the final electron acceptor.

What is chemiosmosis?

Protons flow across a membrane to help make ATP.

Picture a dam:

1. Protons are pumped to one side of the inner mitochondrial membrane.

2. They build up, creating stored energy.

3. They flow back through ATP synthase.

4. ATP synthase uses that energy to make ATP.

Memory trick: Chemiosmosis = protons flow → ATP grows!

How much ATP does the electron transport chain make?

Your notes say approximately 34 ATP per glucose. Some older textbooks use that estimate. Modern biology sources often estimate around 26–28 ATP from this stage, because the actual yield varies.

The key concept is that the electron transport chain produces most of the ATP during cellular respiration.

3. Quick comparison: Krebs cycle vs. ETC

What to know	Krebs cycle	Electron transport chain
Location	Mitochondrial matrix	Inner mitochondrial membrane
Main job	Produces energy carriers and releases CO₂	Uses electron energy to make most ATP
Uses NADH and FADH₂?	Produces them	Uses them
Oxygen's role	Needed indirectly for the cycle to continue	Directly accepts electrons at the end
Memory trick	Loads the trucks	Uses the trucks' deliveries to make ATP

4. Your final TEAS memory sheet

Glycolysis: Glucose splits. Cytoplasm. Net 2 ATP.

Pyruvate oxidation: Pyruvate becomes acetyl-CoA. Mitochondrial matrix.

Krebs cycle: Releases CO₂ and makes NADH, FADH₂, and 2 ATP per glucose.

Electron transport chain: Inner mitochondrial membrane. Electrons power proton pumping, and ATP synthase makes most ATP. Oxygen accepts electrons, and water forms.

The order to memorize:

Split → Prepare → Cycle → Power

Glycolysis → Pyruvate oxidation → Krebs cycle → Electron transport chain

1. What is another name for the citric acid cycle?

Krebs cycle

2. What is the main job of the Krebs cycle?

Produce energy carriers and release CO₂

3. Where does the electron transport chain occur?

Inner mitochondrial membrane

4. What does ATP synthase do?

Makes ATP using proton flow

5. What is chemiosmosis?

Proton flow that helps power ATP production

6. What is oxygen's role at the end of the electron transport chain?

It accepts electrons

Fermentation

a way for cells to keep making a little ATP without using oxygen.

Normally, cells use oxygen for aerobic cellular respiration to make lots of ATP. When oxygen isn't available or can't be used for that process, fermentation helps glycolysis keep going.

There are 2 types you should know:

1. Lactic acid fermentation

• Happens in human muscle cells when oxygen supply can't meet demand during intense exercise.

• Produces lactate.

• Allows glycolysis to keep producing a small amount of ATP.

2. Alcoholic fermentation

• Happens in organisms such as yeast.

• Produces ethanol (alcohol) and carbon dioxide (CO₂).

• Used in bread-making and brewing.

🧠 Easy memory trick

“Lactic = Legs; Alcoholic = Alcohol.”

• Lactic acid → muscles

• Alcoholic → yeast makes alcohol

TEAS tip: Fermentation itself does not make extra ATP. Glycolysis makes a net 2 ATP per glucose, and fermentation regenerates NAD⁺ so glycolysis can continue without oxygen.

🌱 Photosynthesis

Think of a plant as a tiny food-making factory. It uses sunlight, water, and carbon dioxide to make sugar for energy.

1. What is photosynthesis?

Photosynthesis = the process plants use to make their own food using sunlight.

Plants need 3 main things:

• ☀ Sunlight = the energy source

• 💧 Water (H₂O) = absorbed through the roots

• 🌬 Carbon dioxide (CO₂) = taken in from the air

The plant uses these to make glucose (sugar) and releases oxygen (O₂).

The equation made easy

Photosynthesis chart

Word	Super easy meaning
Glucose	A type of sugar the plant makes and uses for energy
Chloroplast	The part of a plant cell where photosynthesis happens
Chlorophyll	The green pigment that absorbs light
Pigment	A substance that gives something its color
Organic chemicals	Carbon-containing substances living things use to grow and function

Memory trick: Plants take in C-W-L and make G-O.

• C = Carbon dioxide

• W = Water

• L = Light

• G = Glucose

• O = Oxygen

2. Where does photosynthesis happen?

Chloroplast = the food factory

Chloroplasts are organelles inside plant cells. They contain chlorophyll, which absorbs sunlight.

Remember:

• Chloroplast = where photosynthesis happens.

Chlorophyll = green pigment that captures light.

3. The two stages of photosynthesis

Photosynthesis has 2 main stages. Think of them as two steps in a factory.

Stage 1: Light-dependent reactions ☀

Needs light

• Uses sunlight and water.

• Makes ATP and NADPH, which carry usable energy.

• Releases oxygen (O₂).

Easy meaning: Captures sunlight and stores its energy for the next stage.

Stage 2: Calvin cycle 🌿

Also called the light-independent reactions or dark reactions.

• Does not directly require light.

• Uses CO₂, ATP, and NADPH.

• Builds small sugar molecules that can be used to make glucose.

Easy meaning: Uses the stored energy to build sugar.

What do ATP and NADPH mean?

You learned about ATP in cellular respiration!

• ATP = usable energy for cell activities.

• NADPH = carries high-energy electrons that help build sugar.

Memory trick: ☀ Light = Load energy. Calvin = Create sugar.

Important TEAS tip: The Calvin cycle doesn't directly need light, but it normally depends on products made during the light reactions. Dark reactions does not mean they only happen at night!

4. Photosynthesis vs. cellular respiration

These processes are almost opposites in what they do.

Photosynthesis 🌱	Cellular respiration 🔋
Happens in chloroplasts	Mainly happens in mitochondria
Uses CO₂ and water	Uses glucose and oxygen
Uses sunlight to make sugar	Breaks down glucose to make ATP
Releases oxygen	Releases CO₂ and water

Quick memory trick:

• Photosynthesis builds sugar.

• Cellular respiration breaks sugar down.

5. What you MUST know for the TEAS

Photosynthesis occurs in the chloroplasts.

Chlorophyll absorbs light energy.

Inputs: carbon dioxide + water + light.

Products: sugar + oxygen.

Light reactions need light; the Calvin cycle uses ATP and NADPH to build sugar.

Final memory sentence: Plants use sunlight, water, and CO₂ to make sugar and release oxygen. Light reactions capture energy; the Calvin cycle uses that energy to build sugar. 🌱

1. Where does photosynthesis occur?

Chloroplasts

Chloroplasts contain chlorophyll and are the main location of …..

2. What is the main job of chlorophyll?

Absorb light energy

Chlorophyll is the green pigment that absorbs light.

3. Which gas does a plant take in for photosynthesis?

carbon dioxide

Plants use carbon dioxide to build sugar.

4. Which product is released during the light reactions?

oxygen

Water is split during the light reactions, releasing oxygen.

5. What does the Calvin cycle do?

Uses ATP and NADPH to help build sugar

The Calvin cycle uses carbon dioxide and energy supplied by ATP and NADPH to build sugar molecules.

6. Do the dark reactions have to happen at night?

No, they do not directly require light