Cellular Respiration and Photosynthesis

the process used by the cells in plants and animals to break down sugar and turn it into energy to use at the cellular level

Breaks down food

Releases energy

Where does it occur?

Glycolysis occurs in the cytoplasm

Pyruvate oxidation occurs in the mitochondrial matrix

Krebs cycle occurs in the mitochondrial matrix

ETC/Chemiosmosis (oxidative phosphorylation) occur in the inner mitochondrial membrane

Equation

C6H12O6+6O2=6CO2+6H2O+Energy(ATP)

Reactants: suagrs and oxygen

Prodcuts: cardon dioxide, water and energy (ATP)

ETC: the redox reactions that move electrons along the membrane of the mitochondria

Chemiosmosis

H+ moves into the matrix through ATP synthase

Energy is released

Energy is used to phosphorylate ADP to form ATP through oxidative phosphorylation

New ATP is moved to cytoplasm by facilitated diffusion where it is used to drive reactions requiring energy

Other Aspects

Does not need oxygen to occur ( can be anaerobic)

Catabolic: breaks down complex molecules for the organism to use

Important Players

NADH: nicotinamide adenine dinucleotide

Produced throughout cellular repsiration

Used to carry energy

Loses its electrons at the electron transport chain (oxidized)

NADH=NAD+H+

The donated electrons drive ATP synthesis

For every NADH which is oxidized at the ETC: 3 ATPS are produced

FADH2: flavin adenine dinucleotide

Produced at the Krebs cycle

Carries energy

Loses electrons at the electron transport chain to produce ATP

FADH2=FAD+2H+

For every FADH2 in the ETC: 2 ATP are produced

Used for cellular processes that require energy

To release energy, ATP loses a phosphate group

ATP=ADP+inorganic phosphate+energy

To make ATP energy is required

Stages

During this stage substrate level phosphorylation occurs

Which is a process where a phosphate group is removed from a substrate molecule

The group is then combined with ADP to form ATP

Electron shuttles

Glycerol-Phosphate Shuttle

very common

Transfers electrons from cytosolic NADH to FAD to produce FADH

Aspartate Shuttle

Transfers electrons to NAD+

Forms NADH and produces ATP

Source of energy

Synthesizing carbohydrates (ex. glucose) using energy from the sun

Produces food

Captures energy

Where does it occur?

Plants have 40-200 chloroplasts

Chloroplast is a 2 layered membrane (stroma and thylakoid)

Stroma: the fluid-filled interior layer which surrounds the grana

Thylakoids: the layer of membrane bound sacs

The green pigment

Absorbs light to begin the photosynthesis process

Made up of a porphyrin ring and a long hydrocarbon tail

2 types

A: Methyl group: primary light absorbing pigment (CH3 is attached to ring)

B: Aldehyde group: absorbs photons that A did not absorb properly (-COH attached to ring)

Cartenoids (orange and yellow pigments) can be used to absorb light

Mainly absorb light which would damage the chlorophyll

They lose this energy through heat

Equation

6CO2+6H2O=C6H12O6+6O2

Reactants: carbon dioxide, water and sunlight

Products: sugars and oxygen

Hydrogen ions in the thylakoid layer cannot diffuse through membrane

ATP synthase provides pathway to move down concentration gradient

ATP synthase complex drives the phosphorylation of ADP to ATP

This is called photophosphorylation as light is required for it to occur

Other aspects

When a plant is low on water/NAD+ it goes through cyclic phosphorylation (just temporary phase)

Electrons in PS I pass backwards to cytochrome

Still produce PMF for the protons to move and continue the process

Concentration gradient powers ATP synthase by pumping protons down their concentration gradient

Two sets of reactions make up photosynthesis

Light-dependent reaction

Light energy is trapped and used to generate ATP and NADPH

Light-independent reaction

Energy of ATP and reducing power of NADPH are used to make an organic molecule which is high in energy

Anabolic: builds molecules that are needed

Necessary for photosynthesis to occur

Photons are the energy that travels in waves

Each wavelength is associated with a different color on the electromagnetic spectrum

Pigment molecules are used to absorb visible light and appear as the colour of their light wavelength

The absorbance spectrum shows the amount of light different wavelengths can absorb

The action spectrum shows effectiveness of wavelengths promoting photosynthesis

Light is not absorbed by individual pigment molecules, it is absorbed by photosystems

Located in thylakoid membranes

Made of chlorophyll, accessory pigments and proteins

They contain

Photosystems in photosynthesis

PSI (P700): Chlorophyll A absorbs wavelength of 700nm

PSII (P680): Chlorophyll A absorbs wavelength of 680nm

Source of Energy

Sunlgiht

Electron Carriers

1. Light Reactions: Light energy and water produce ATP and NADPH

2. Calvin Cycle: Carbon dioxide and energy from ATP/NADPH produce glucose

In photosynthesis: ATP is produced using light energy and it is used to produce organic molecules

In cellular respiration: ATP is produced by breaking down organic molecules themselves

Chemiosmosis

both use this process similarly

Uses the energy in a hydrogen ion gradient to make ATP

In cellular respiration food is converted into ATP

Photosynthesis uses light energy to release ATP.

CO2

In photosynthesis, carbon dioxide is removed from the atmosphere

In cellular respiration, carbon dioxide is released into the atmosphere

Photosynthesis and cellular respiration can both occur in plants but photosynthesis is not possible in animals

Each of these processes is continuously happening for organisms to survive

Where?

Although each process is in different organelles, each takes place inside cells

PS is within the chloroplast

CR is in the cytoplasm and mitochondria

Photosynthesis uses water

Cellular respiration produces water

Light

Each process can occur in the light but cellular respiration does not require it

Redox Reactions

In photosynthesis, electrons travel from water to carbon dioxide

In cellular respiration, electrons transfer from glucose molecules to oxygen

Reaction Coupling

The glucose and O2 created in photosynthesis is used during cellular respiration to make CO2 and water

This shows that these reactions are coupled as they have common substances

Substances

Each process has similar substances involved but at different parts

The products and reactants are flipped (Products of PS are reactants of CR and vice versa) - but energy type varies (sun/ATP)

Stages

Both of these processes occur in different stages

Both processes occur in a mututally benficial releationship

One cannot occur without the other

They are interdependent to one another to complete their own functions

ETC

In photosynthesis: water is broken down into oxygen for electrons

Electrons from the transport chain are moved using electron molecules/carriers

Calvin cycle is used to make glucose

In cellular respiration: the Krebs cycle breaks down glucose

hydrogen carriers (NADH and FADH2) release electrons for the ETC

Electrons from the ETC are taken up by

Vital for Survival

Both CR and PS produce energy and living things must do at least one of them for survival

Reaction Types

Both are considered metabolic reactions/processes

PS is an anabolic reaction which builds complex molecules from small molecules

CR is a catabolic reaction which breaks down molecules to make them even smaller

Ways to make ATP

In Photosynthesis:

Absorbed light and energy is used to drive electrons from water to generate NADPH/drive protons across a membrane - these protons go through ATP synthase and make ATP

In Cellular Respiration:

Substrate level phosphorylation: ATP is formed directly in the enzyme catalyzed reaction and a phosphate group is removed and combined with ADP to make ATP

Oxidative Phosphorylation: indirectly forms ATP by using a number of redox reactions

Complications

In photosynthesis if the weather is too hot, photorespiration occurs

This is a problem because the production of carbohydrates decreases

This is decreased using C4 photosynthesis (using C4 plants: less photo respiration and more sugar production)

Can also be decreased using CAM plants which store water and allow for proper functioning

In cellular respiration, if the body does not produce ATP properly, the body will not function

Basic bodily functions will become a challenge, exhaustion will become common and death is possible