Bio-Energy Notes

Photosynthesis Anaerobic Aerobic Cellular Respiration

Photosynthesis is the process..

in which green plants

use the energy of sunlight to convert water and

carbon dioxide into glucose (sugar) and oxygen.

6CO2 + 6H2O C6H12O6 + 6O2

carbon dioxide + water light——>sugars + oxygen

Autotrophs

Autotrophs are organisms that can make

their own food and sustain themselves without eating

other organisms

Plants, algae, certain other protists, and some prokaryotes

(bacteria) are autotrophs

Photoautotrophs…

are autotrophs that produce food using

light energy (photosynthesis)

Chloroplasts

Chloroplasts are concentrated in the cells of the mesophyll, the

green tissue in the interior of the leaf

Carbon dioxide enters the leaf and oxygen exits through pores called

stomata (singular—stoma).

Water absorbed by the roots is delivered to the leaves in veins

Chloroplast innermembrane

The inner membrane surround a

space filled with thick fluid called

stroma

Sugars are made from carbon

dioxide and water in the stroma

Inside the stroma are thylakoids,

which are..

flattened disc-shaped sacs.

The membranes of the thylakoid

contain chlorophyll molecules

that capture light energy.

Thylkaoids are stacked together into

stacks called grana

(Sunlight)Electromagnetic Energy

Light energy travels in waves and the distance between the crests of

two adjacent waves are called wavelength

Some light waves are shorter and have more

energy (violet waves), and other lights are longer and

have less energy (red

waves)

Pigments

light-absorbing molecules inside the thylakoid membrane

Pigments absorb some wavelengths of light and reflect/transmit

other wavelength

Different pigments absorb light of different wavelengths

Chlorophyll a

absorbs mainly blue-violet and red light and reflects

green light

Chlorophyll b

absorbs mainly blue and orange light and reflects

yellow-green

Photosynthesis light-dependent reactions

The light-dependent reactions take place within the thylakoid

and traps sunlight energy

Photosynthesis light-independent reactions (Calvin cycle)

The Calvin cycle takes place in the stroma and produces

high-energy sugars from carbon dioxide

Photosynthesis Phase 1: Light Reactions

The absorption of light is the first

step in photosynthesis.

Chloroplasts capture light energy

and converts it to chemical

energy and produces O2 gas as a

waste product

Water molecules are split to

create O2 gas

ATP and an electron carrier

called NADPH are also created

The light reactions occurs in the

thylakoid membrane

Photosystems

In the thylakoid membrane, chlorophyll and other pigments and

proteins are arranged into clusters called photosystems

Photosystem I and Photosystem II

Light energy is absorbed by the photosystems, which excites the

electrons of chlorophyll molecules

The electrons are then passed down an electron transport chain and

then to an electron carrier called NADPH

NADPH will bring these electrons to the Calvin cycle

Water & ATP

As electrons are being passed down, water is split into oxygen and H+ ions

H+ ions diffuse down an enzyme called ATP synthase

ATP synthase phosphorylates ADP to create ATP

ATP is then brought to the Calvin Cycle

Phase 2: Calvin Cycle

Takes place in the stroma of the chloroplast

It takes CO2 from the air and converts it to

glucose.

To do this, it uses the energy in ATP and the

electrons in NADPH (which were both made

in the Light Reactions)

The 1st sets of photosynthetic reactions work together

The light-dependent reactions trap sunlight energy in chemical form

(ATP & NADPH)

The 2nd sets of photosynthetic reactions work together

The light-independent reactions use that chemical energy to

produce high-energy sugars (glucose) from carbon dioxide.

C4 Plants

C4 Pathway helps plants maintain photosynthesis while

minimizing water loss

Keep their stomata closed during hot days, but can still

keep CO2 levels high to do photosynthesis

Ex: Sugarcane and Corn

CAM Plants

CO2 enters leaves only at night when it’s much cooler

Then, photosynthesis is completed during the day with

the stomata closed

Ex: Water-conserving plants

that live in deserts and other

places where water is limited

Cactus, Orchids, Pineapple

Cellular Respiration stages:

Glycolysis, the Krebs cycle(Citric acid cycle), Electron Transport Cycle (ETC:Oxidative Phosphorylation)

Step 1 of Cellular Respiration:Glycolysis-

an anaerobic process (does not use oxygen).

During glycolysis, glucose is broken down into 2 molecules of pyruvate (pyruvic acid)

Glyco = sugar, Lysis = break down

Glycolysis happens in the cytoplasm of cells.

Glycolysis uses….ATP to make … ATP

At the beginning of glycolysis, the cell uses up 2 molecules of ATP to start the reaction.

When glycolysis is complete, 4 ATP molecules have been produced. 

This gives the cell a net gain of 2 ATP molecules (since 2 ATP were used to help make the pyruvic acid).

This means that glycolysis produces 2 ATP for the cell.

NADH production

Electrons from glucose are given to an electron carrier called NADH, which brings the electrons to the Electron Transport Chain

 After glycolysis is finished, it will have produced:

2 ATP (net gain)

2 NADH (carrying high energy electrons)

2 pyruvate (to get ready to enter the Krebs cycle)

Where does the pyruvic acid and NADH go if oxygen is present?

If oxygen is present, the pyruvic acid molecules get ready to finish cellular respiration and enter the Krebs cycle (aerobic respiration).

Where does the pyruvic acid and NADH go if oxygen is not present?

 If oxygen is absent, the pyruvic acid molecules begin fermentation (anaerobic process)

Step 2:The Krebs Cycle

 During the Krebs Cycle, the pyruvic acid is broken down into carbon dioxide

The Krebs Cycle occurs in the mitochondrial matrix

Two Turns of the Krebs Cycle:

Remember, 1 glucose molecules turns into 2 pyruvates

Each pyruvate enters the Krebs Cycle, one at a time

Therefore, for each glucose molecule, there must be 2 turns of the Krebs Cycle

Electron Carriers

The Krebs Cycle produces more electron carriers that will bring electrons over to the Electron Transport Chain

These electron carriers are called NADH and FADH₂

For one turn of the Krebs Cycle, it produces 3 NADH and 1 FADH₂

-Therefore, in total, for 2 turns of the cycle, it produces 6 NADH and 2 FADH_2-

Krebs Cycle Produces:

The Krebs Cycle also produces one of the main products of cellular respiration, carbon dioxide

For one turn of the Krebs Cycle, it produces 2 molecules of CO₂

Kreb Cycle ATP

The Krebs Cycle also produces 1 ATP molecule for each turn

• So, for each turn of the Krebs Cycle:

  •  2 CO₂ molecules are released

  •  The energy yield is

    • 1 ATP

    • 3 NADH

    • 1 FADH₂

So how many energy molecules does the Krebs cycle make for ONE pyruvic acid?

The energy tally from 1 molecule of pyruvic acid is

• 1 ATP

• 3 NADH

• 1 FADH₂

• 2 CO₂
  

However, each glucose produces 2 pyruvic acids… So how many of each molecule is made for each GLUCOSE?

2___ATP

6__ NADH

2__ FADH₂

4__ CO₂

Step 3:The Electron Transport Chain

• Electron carrier NADH and FADH₂ passes electrons to the electron transport chain

•  As electrons “fall” from carrier to carrier and finally into O₂, energy is released in small quantities

•  The energy released is used by the cell to make 34 ATP!

Electron Transport Chain & Production of Water

• The electron transport chain is built into the inner membrane of the mitochondria

• The electrons from NADH and FADH₂ get passed down to O₂, the final electron acceptor

Each oxygen atom combines with 2 electrons and 2 hydrogen ions    (H⁺) to produce water, one of the products of cellular respiration

ATP Synthase: Production of ATP-

As electrons are being passed down, the ATP Synthase produces 34 molecules of ATP

The breakdown of glucose to produce ATP can be either:

Anaerobic or Aerobic

Anaerobic Respiration

does not require oxygen

Glycolysis & Fermentation

are anaerobic processes

Aerobic Respiration

requires oxygen

The Krebs Cycle and Electron

Transport Chain are aerobic processes

There are 2 types of Anaerobic Respiration(Fermentation)

Lactic Acid Fermentation

Alcohol Fermentation

Fermentation only produces 2 ATPS

2 ATPs are enough to keep your muscles contracting for

a short while when the need for ATP outpaces the delivery of O2