ENERGY

Organisms obtain their energy by breaking down complex high-energy biomolecules

(otherwise known as food)

AUTOTROPH

Can utilize sunlight as an energy source

Plants and photosynthetic bacteria & protists

HETEROTROPH

Must consume organic matter to obtain energy (in the form of

chemical energy) Animals, fungi and non-

photosynthetic bacteria & protists

Energy

High energy compounds (ie carbohydrates, fats and alcohols) are broken down to low energy compound (ie water, carbon dioxide and oxygen)

Chemical reactions in the body can be exergonic (release energy) aka catabolic

Chemical reactions in the body can be endergonic (require energy) aka anabolic

Often exergonic and endergonic reactions in the body will be complimentary

Exergonic and Endergonic Reactions

Example of complimentary exergonic and endergonic reactions

Example of complimentary exergonic and

endergonic reactions

ENZYMES

Enzyme Structure

Some are pure proteins Some require COFACTORS to work (usually

inorganic metal ions) Eg. iron, copper, calcium, zinc, potassium Some require COENZYMES to work (an

organic substance) Eg. a vitamin

Enzyme Structure

Enzymes have an active site and a regulatory region The active site (formed by folds in the protein) is where

substrate binds to the enzyme The regulatory region is where cofactors coenzymes or enzyme

inhibitors can alter the function of an enzymeSubstrate

Active site

Regulatory region

Products

Enzyme inhibitor

Some quick facts.Enzymes …

Act at both the intra and extracellular level Act on SUBSTRATE and yield PRODUCT Reduce the ACTIVATION energy required to

start a reaction in the body Are very specific, each individual type of subs

trate is acted upon by a specific enzyme

The “Lock and Key” model of enzyme activity

The enzyme provides a perfect fit for a particular substrate

The “Induced Fit” model of enzyme activity

The substrate induces the enzyme to change shape to create a tighter fit

Factors Affecting Enzyme Activity

pH Most biological enzymes operate

at a neutral pH range of 6-8 If enzymes are at a pH outside

their optimum range, their shape will change and they will be less efficient.

Enzyme

Cells

Carbonic Anhydrase

Trypsin Pepsin

Location Blood Small Intestine

Stomach

Opt. pH 7.6 7.4 8.0 2.0

Factors Affecting Enzyme Activity

Temperature Most biological enzymes have an optimum

temperature of 37° If an enzyme is exposed to temperatures higher than

optimum, it will permanently denature. If an enzyme is exposed to temperatures lower than

optimum, it will become inactive until temperature returns to optimum.

The enzymes of other organisms have optimum temperatures suited to the environment in which they live

Factors Affecting Enzyme Activity

Enzyme Concentration An increase in enzyme conc. will cause an

increase in reaction rate but won’t increase the yield.

Substrate concentration Reaction rate will initially increase as unoccup

ied enzymes take on substrate but will then plateau.

Inhibition Other molecules can block the active site or r

egulatory region of an enzyme.

Increasing substrate concentration

PhotosynthesisPhotosynthesis

Photosynthesis

The process in which light energy is transformed in to chemical energy

Performed by Plants Algae Some protists (eg phytoplankton) Photosynthetic bacteria

What makes leaves so ideal for photosynthesis?Flat = large surface area to volume ratioMany stomata = efficient import of CO2 and

export of O2

Thin with many air chambers = diffusion of CO2

Xylem = transports reactants inPhloem = transports products outChloroplasts = photosynthetic pigment

concentrated in dedicated organelles

Chloroplasts

The Photosynthetic Equation

Photo = lightSynthesis = put together

It is a complex series of reactions that can be summarized as:

12H2O + 6CO2 → 6O2 + C6H12O6 + 6H2O

6 of the water molecules on either side of the equation cancel each other out to give:

6H2O + 6CO2 → 6O2 + C6H12O6

Photosynthesis OverviewPhotosynthesis Overview

6H2O + 6 CO2 --> C6H12O6 + 6 O2

Light Dependent Stage

H2O --> O2

requires Light E

Light Independent Stage

CO2 --> 2x3C sugars

Light-dependent reaction

Inputs: sunlight, water, NADP, ADP & Pi

Outputs: oxygen, ATP & NADPH

A not-so-simple explanation of the process

A simplified version of the process

Light-dependent reaction

Occurs in the granaLight energy is used to split water in to two H+

ions and O2 gas

The O2 is released as waste

With the power of the two free electrons One H+ ion fuses ADP to Pi to form ATP One H+ ion fuses to NADP to form NADPH

Inputs Outputs

Water H2O ATP

Electron e- NADPH

NADP+

ADP + POxygen (“waste”)

Light-independent stageLight-independent stageOccurs in StromaDoes not need light, but NADPH and ATP

from previous stageNeeds CO2 and H+ ions Sugar molecules are synthesised from CO2

CO2 = oxidised state (low E compound)

C(H2O)n = reduced state (high E compound)

NADPH (carrier H+) is the reducing agent ATP is the energy source

Inputs Outputs

ATP ADP + P

NADPH NADP+

3C -> Glucose

Carbon reduction in Carbon reduction in CC33 Plants Plants

Calvin Cycle

Called C3 plants as the end product is a 3-carbon compound (PGAL), that goes on to form glucose.

Photosynthesis occurs in the mesophyll cells,

Carbon reduction in CCarbon reduction in C44 plants plants

Plants in hot, dry habitats and important crop plants such as corn, sugar cane

If light independent reaction took place in mesophyll cells, these plants would lose too much water from their open stomata.

One step occurs (in the mesophyll cells) to transport CO2 (in the form of oxaloacetate) to the bundle sheath cells,

Carbon reduction in CCarbon reduction in C44 plants plants CO2 combines with the 3-

carbon compound PEP (phophoenolpyruvic acid) to form oxaloacetate (4C)

A further reaction converts oxaloacetate (4C) to malate (4C).

Then a CO2 molecule leaves the cycle to nter the Calvin cycle, whilst the remaining 3C pyruvate returns to reform PEP.

C3 PLANTS C4 PLANTS

Putting Photosynthesis togetherPutting Photosynthesis together

2 x PGAL = fructose

fructose = glucose

fructose + glucose = sucrose

glucose x ∞ = starch

General Info on Cellular Respiration

Organisms can’t use glucose (2800 kJ) as energy, needs to be broken down to approx 1/100th of its size – ATP (30 kJ).

Breakdown is not 100% efficient (usually 36-38 ATP produced)

Remainder is lost as heat. Endothermic organisms trap this heat with layers of fat to maintain body temperature.

General Info on Cellular Respiration

The rate of respiration depends on the state of activity of the organism

Respiration involves 2 coupled reactions Energy is released by the breakdown of

glucose Energy is required for the production of ATP

There are 2 types of respiration Aerobic respiration (requires oxygen) Anaerobic respiration (does not require

oxygen)

Aerobic vs Anaerobic Respiration

Aerobic respiration

C6H12O6 + O2 → CO2 + H2O

Outside cells, to oxidise glucose need temp of 200° - Entire molecule oxidised simultaneously

Inside cells, oxidised gradually in small steps Steps summarized in to 3 stages

Glycolysis (produces pyruvate) Krebs Cycle (2 required per molecule of

glucose) Electron transport (harvests H+ from carriers)

Glycolysis

Occurs in cytosol – uses enzymes and vitamins as coenzymes

1 glucose (6C) converted to 2 pyruvate (3C)

Forms 2 ATP & 2 NADH (from NAD – nicotamide adenine dinucleotide)

Krebs Cycle Occurs in mitochondria Pyruvate initially broken down in to

CO2 and Acetyl-coA Joins with 4C molecule to form 6 C

molecule CO2 to form 5 C molecule, then again

to form 4 C molecule Further oxidation takes place to

reform original 4C Throughout cycle, constant oxidation

is fusing hydrogen to carrier molecules NAD → NADH and FAD → FADH2

Electron Transport Occurs in inner membrane of

mitochondria Produces 2-3 ATP per loaded receptor Electrons passed from one

cytochrome to next until accepted by O2- to form water

Return of released protons through ATP synthase carrier provides energy to produce ATP from ADP & Pi (phosphorylation)

Summarising Aerobic Respiration Vocabulary

Oxidation = removal of hydrogen Reduction = addition of hydrogen

A total of 36 ATP are formed except in the cells of heart, liver and kidneys where 38 are formed

Anaerobic respiration (in humans)

Occurs in muscles where oxygen supply exceeds demand The only stage that can occur is glycolysis So 1 glucose produces 2 ATP 2 NADH convert pyruvate to lactate (lactic acid) Lactate build up causes pH to fall and pain & muscle fatigue When activity returns to normal and oxygen becomes available,

lactate converted back to pyruvate to enter the Krebs Cycle.

Anaerobic respiration (in yeast)

Anaerobic respiration in yeast is called fermentation

Pyruvate is broken down in to CO2 and ethanol (alcohol)

What happens during starvation?- Autophagia (feeding of self)