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)
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