UNIT 4: CELL METABOLISM

Metabolism = A process that involves using energy to build or break down molecules

Photosynthesis and cellular respiration involve making and breaking energy-rich molecules

Autotrophs (self feeders)= make their own food from “inorganic”substances and energy

Ex: Plants, algae, certain bacteria

Heterotrophs (different feeders)= obtain their nutrients by feeding on other organisms

Ex: Animals and Fungi

OBTAINING NUTRIENTS: 2 STRATEGIES

Happens in: autotrophs

Goal: Converting light energy into chemical energy (glucose)

Glucose: carbohydrate monomer

C6H12O6

PHOTOSYNTHESIS

carbon dioxide + water + light →glucose + oxygen

6CO2 + 6H2O + → C6H12O6 + 6O2

PHOTOSYNTHESIS EQUATION

Reactants Products

Happens in: autotrophs AND heterotrophs (ALL organisms)Goal: converting

chemical energy (glucose) into USABLE energy (ATP) ATP = adenosine

triphosphate

CELLULAR RESPIRATION

ATP is a USABLE form of energy for the cell

Energy is released from ATP by breaking the bonds between phosphate groups

Why ATP? It ’s efficient, relatively simple, and the energy is relatively easy to access

WHY ATP?

Bond Breaks

Here!

Glucose + oxygen → Energy + Carbon Dioxide + Water

C6H12O6 + 6 O2 → ATP + 6 CO2 + 6 H20

CELLULAR RESPIRATION EQUATION

Reactants Products

CO2 + H20 + Energy (Light) → C6H12O6 + O2

C6H12O6 + O2 → Energy (ATP) + CO2 + H2O

COMPARING PHOTOSYNTHESIS AND

RESPIRATION

IMPORTANT COMPARISON!: the reactants of

one reaction are the products of the other reaction!

ATP MODELING ACTIVITY

H and OH:

BLUE

Adenine:

ORANGE

Ribose: RED

Phosphoric

Acid: YELLOW

*CUT OUT! BUT DO

NOT CUT DASHED

LINES YET!

PHOTOSYNTHESIS!

LEAVES of plants

Very large leaves (Ex: Rain Forest Leaves) are used to capture A LOT of sunlight

Pores at the bottom of leaves (stomata) take in carbon dioxide and release oxygen

WHERE ON THE PLANT DOES PHOTOSYNTHESIS TAKE PLACE?

Takes place in the chloroplasts (in leaf cells)!

2 Main Processes:

1) Light Reactions (aka light dependent reactions)

2) Calvin Cycle (aka light-independent reactions)

PHOTOSYNTHESIS SUMMARY

Thylakoids are stacked to form grana

Light Reactions take place in the thylakoid membrane

Calvin Cycle takes place in the stroma

CHLOROPLAST STRUCTURE

Purpose:

1) absorb light

2) produce oxygen

3) transfer sun energy to electrons

Requires a green pigment called chlorophyll to absorb sunlight

Where: thylakoid membrane

PART 1: LIGHT REACTIONS

Join with a molecule called NADP+ (an electron acceptor)

Sunlight splits water into hydrogen and oxygen

Hydrogen binds with NADP+, becoming NADPH, and gets sent to the Calvin Cycle

WHAT HAPPENS TO THE ELECTRONS ENERGIZED BY SUNLIGHT?

SUMMARY OF LIGHT REACTIONS

Start With:

Sunlight, water,

NADP+

End with:

Oxygen, NADPH,

ATP

Purpose: produce glucose from CO2

Uses electrons from NADPH and energy from ATP (broken back into ADP and P)

Does not require light

Where: stroma

PART 2: CALVIN CYCLE

SUMMARY OF CALVIN CYCLE

Start With:

CO2 , NADPH, and

ATP

End with:

Glucose and

NADP+

Notice that the products of the light reactions are used in the

Calvin Cycle!

How are excited electrons and ATP from light rxns used in

the Calvin Cycle? The H is needed for glucose and the

energy is required to carry out the entire process.

1. Intensity of light

2. Concentration of carbon dioxide

3. Temperature.

FACTORS AFFECTING THE RATE (SPEED) OF PHOTOSYNTHESIS

Sunlight hits clusters of pigment called Photosystems I and II

This excites electrons and joins them with protein carriers and finally NADP+

ATP is created when protons flow through an enzyme called ATP synthase

Explanation continued on next slide…

SO HOW DO WE GET ATP?

CELLULAR RESPIRATION!

THE PROCESS THROUGH

WHICH YOUR CELLS

OBTAIN USABLE ENERGY

By the end of this unit you should be able to:

Describe the purpose of cellular respiration in living

organisms

Compare glycolysis, Kreb’s cycle, and the electron transport

chain

Summarize the reactants and products of cellular respiration

Describe the structure of the mitochondria

OBJECTIVES

EQUATION

Glucose + Oxygen → Energy + Carbon Dioxide + Water

C6H12O6 + 6 O2 → ATP + 6 CO2 + 6 H2O

CELLULAR RESPIRATION SUMMARY

Location: Mitochondria (Eukaryotes), Cell Membrane (Prokaryotes)

Goal: Produce ATP from Glucose

Main Processes:

1) Glycolysis

2) Kreb’s Cycle

3) Electron Transport Chain

RECALL: WHAT IS ATP?

It is a molecule that “stores” energy in its

bonds

When used, the energy in ATP can act on other

compounds like an enzyme, and either break

their chemical bonds, or form them

ATP stands for “Adenosine Triphosphate”

STRUCTURE OF A MITOCHONDRION

1.Glycolysis occurs in cytoplasm of cell

2.Kreb’s Cycle occurs in matrix

3.ETC occurs in inner membrane

TWO TYPES OF RESPIRATION

Aerobic

With oxygen

Makes a lot of ATP

Includes all 3

steps

• Anaerobic

• Without oxygen

• Makes a little ATP

• Only glycolysis

PART 1: GLYCOLYSIS

Purpose: Glucose is broken down into two

smaller molecules (pyruvate – 3 carbons),

send electrons to ETC

Occurs in: Aerobic AND Anaerobic

Location: cytoplasm

Reactants: Glucose

Products: Pyruvate, NADH, ATP

GLYCOLYSIS

An enzyme splits

the glucose into 2

pieces, called

“Pyruvate”. The

process is called

“Glycolysis”.

The split also

produces 2 ATP

Molecules

ATP

ATP

PART 2: KREB’S CYCLE

Purpose: Pyruvate broken down into CO2, send

electrons to ETC

Occurs in: Aerobic respiration ONLY

Location: matrix

Reactants: pyruvate

Products: NADH, FADH2, ATP, and CO2

KREBS/CITRIC ACID CYCLE

The two Pyruvate

molecules enter the

mitochondria and

undergo reactions

which produce 2

more ATP

Molecules, plus

CO2 molecules as

waste

The CO2 leaves the

cell

The ATP is

available for use by

the cell for energy

ATP

ATP

CO2

PART 3: ELECTRON TRANSPORT CHAIN

Purpose: Electrons from NADH and FADH2 are passed to oxygen → Water

ATP is made using ATP Synthase

Occurs in: Aerobic respiration ONLY

Location: Inner Membrane

Reactants: Oxygen

Products: Water, ATP

ELECTRON TRANSPORT CHAIN

Inside the

Mitochondria,

oxygen (O2), the

final e- acceptor,

is used to drive

additional

reactions that

produce 32 more

ATP molecules

The process is

called Electron

Transport

Water (H2O) is

also produced, and

exits the cell

ATPATP

ATPATP

ATP

ATPATP

ATP

ATPATP

ATP

ATP

ATP

ATP

ATP

ATP

ATP

ATP

ATP

ATPATP

O2

H2O

ENERGY YIELD

2 ATP from Glycolysis

2 ATP from Kreb’s Cycle

32-34 ATP from Electron Transport Chain

36-38 Total ATP!!!

ANAEROBIC RESPIRATION

(FERMENTATION)

Glycolysis only (occurs where in the cell?

Cytoplasm)

Occurs in the absence of oxygen

Goal: break down glucose

▪Produce 34-36 ATP fewer than aerobic cell resp

Two Types: Lactic Acid and Alcoholic

LACTIC ACID FERMENTATION

Happens in: Animals, prokaryotes

Produces: lactic acid and ATP

Examples in Everyday Life: Muscle cells during

exercise, yogurt, pickles, etc.

LACTIC ACID FERMENTATION

ALCOHOLIC FERMENTATION

Happens in: Yeast and other microorganisms

Produces: alcohol (ethanol), CO2 and ATP

Examples in Everyday Life: Yeast causes bread to

rise!

ALCOHOLIC FERMENTATION

RESPIRATION CHART

PROCESS O2 NEEDED END PRODUCT

GLYCOLYSIS

KREBS

ELEC. TRANS.

FERMENT.