Photosynthesis and Cellular Respiration

Photosynthesis and Cellular RespirationBiology

EasyShiksha.Com - A Way of Simple Learning

Energy and Livings Things

All organisms require energy to carry out life processes.

Most of the energy used by life on Earth comes from the sun.

You get energy from the food you eat.


How energy flows in living systemslight energy plant rabbit fox

[sun plants animals other animals]


Why do we need energy?

Energy is required for:

Growth

Reproduction

Movement

Transport of materials across the cell membrane


Plants and animals need each other to survive.


Storing Energy

Photosynthesis - light energy converted to chemical energy

--- The atmospheric by-product of photosynthesis is oxygen (O2)

Autotrophs – organism that uses energy from sunlight or inorganic compounds to make organic compounds (ex: plants, algae,

deep sea organisms)


Breakdown Energy

Cellular Respiration – process by which cell produces energy (ATP) from food

Heterotrophs – organisms that get energy from food by organic molecules (food) being broken down through cellular respiration

---have to consume other organisms to get energy!!!


ATP (Adenosine Triphosphate)

3 (tri) Phosphate groups provide energyWhen one phosphate is removed than energy is released

The phosphate groups are negatively charged and repel each other

Most of the energy that drives metabolism is supplied by ATP

“energy currency”



“photo” – Greek for light

“synthesis” – to make (Calvin Cycle)

Where photosynthesis occurs in a leafa.k.a mesophyll


Photosynthesis

What is photosynthesis?

Process plants use to make their own food

Plant cells contain chloroplast

Chloroplasts make photosynthesis possible

• Occurs in cell membranes in certain prokaryotes


Stages of Photosynthesis

Light Dependent Reactions

1. Absorption of light

2. Conversion of light Electron Transport Chain (ETC)

Makes ATP and NADPH (carries high energy electrons needed to make organic molecules)


Stages of Photosynthesis

Light Independent Reactions

3. Storage of energy Calvin Cycle

ATP and NADPH get fuel from ETC

Sugars are produced from carbon atoms (CO₂) and hydrogen atoms (NADPH)


Light Dependent Rxns

Light Independent Rxns


Chemical FormulaMust know the ENTIRE equation of

photosynthesis

6 CO2 + 6 H2O + light C6H12O6 +6O2

reactants products

Major atmospheric by-product!


Light Dependent Reactions

Electron Transport Chain

Occurs in thylakoids – clusters of pigment (ex: chlorophyll, which absorbs green & yellow, & carotenoids, which absorb red & orange

Grana – stacks of thylakoids

Pigments absorb light


Diagram of Light Dependent Reactions Note the arrows and circled molecules entering and leaving.


Steps in Light Dependant Reactions

1. light absorbed by chlorophyll

2. electrons excited and transfer electrons and hydrogen from H2O to NADP+ NADPH (electron carrier)

3. ADP + P ATP

4. ATP and NADPH power light independent reaction Required by dark reactions to generate sugars

(note: does not use CO2)



Calvin Cycle

Occurs in the stoma —an opening in a leaf or stem that enables gas exchange

Series of enzyme-assisted chemical reactions that produces a three-carbon sugar



Take CO2 from air and make sugar (glucose, starch)

Requires ATP, NADPH from ETC


Cellular Respiration

The process in which chemical energy stored in food molecules (carbohydrates, protiens, and fats) is released.


Aerobic – w/oxygen

Anaerobic – w/out oxygen

Occurs outside & inside of mitochondria


Metabolic processes

Stages of Cellular Respiration

1. Stage One---Glycolysis

• Glucose pyruvate

2. Stage Two---Aerobic and Anaerobic Respiration


Stage One - Glycolysis

- breaks down glucose to 2 pyruvates

- Why?

- Glucose (6-C) is too big to fit into the mitochondria

- Pyruvates are only 3 carbons!


Enzyme assisted anaerobic process that breaks down glucose (6-C) to pyruvate (3-C)

Requires energy to start breaking glucose down: Input 2 ATP

Output 4 ATP

Net Gain 2 ATP


Glycolysis

Where Glycolysis occurs? In cytoplasm, outside of mitochondria


Occurs w/in the mitochondria

NADH and FADH2 now contain energy that was in glucose and pyruvate


Stage Two – Kreb’s Cycle

Kreb’s Cycle

Starts with 2 carbon molecule

4 carbon molecule is recycled at the end

Makes 3 NADH, 1 ATP, 2 CO2 , and 1 FADH2

NO NADPH!!!


Stage Three – Electron Transport Chain

Occurs w/in mitochondria

Aerobic respiration

Receives NADH & FADH2 from glycolysis and Kreb’s cycle

Uses electrons to convert ADP + Pi to ATP

H ions, spent e-, and oxygen molecules form H2O


**(Note pathway of e-)**


What happens when oxygen is not present?

Fermentation occurs

Anaerobic process

Occurs in cytoplasm (outside of mito.)

Two Types:

Lactic Acid Fermentation

Alcohol Fermentation


Lactic Acid Fermentation

Prokaryotes have over a dozen kinds of fermentation (yogurt, cheese)

Pyruvate lactate

Allows glycolysis to continue in anaerobic conditions

Blood removes excess lactate


Alcohol Fermentation

Pyruvate ethanol

CO2 is released, e- transferred to make ethanol

Yeast is used to prepare certain foods and beverages



Production of ATP

Total amount of ATP depends on presence of oxygen

For each glucose molecule in aerobic respiration

Glycolysis (outside) – net 2 ATP

Kreb’s Cycle (inside) – 2 ATP

ETC (inside) – 34 ATP

TOTAL ATP: 38


Production of ATP (cont…)

Anaerobic Respiration

No oxygen present

Glycolysis (outside) – net 2 ATP

Fermentation (outside) – no ATP

No oxygen for H+ and e- to bind to, so go to make ethanol or lactate


Overall Pathway of Cell Respiration

2 ATP in

4 Net Gain = 2 ATP

38 Total

Inside mitochondriaOutside mitochondria

(a.k.a glucose)


Importance of Oxygen Remember, oxygen is needed to bond H+ and e- to make H2O

In Fermentation, no oxygen means H+ and e- go to lactate or ethanol


The chlorophyll absorbs the sunlight.


The sunlight is combined with water, Carbon Dioxide and nutrients from the soil.

CO2


The chlorophyll processes the ingredients and makes sugar(plant food) and oxygen.

Sugar + Air

O2


Animals including humans make the CO2 (carbon dioxide) plants need.They (the plants) make the O2 (oxygen) and food we need.


Education

Photosynthesis and Cellular Respiration