Bio ATP
• As matter and energy flow through different organizational levels of living
systems, chemical elements are recombined in different ways to form different
products
• As a result of these complex chemical processes, energy is transferred from one
system of interacting molecules to another
• Light is the initial energy source for almost all biological systems
• Cellular respiration and photosynthesis are important parts of the carbon cycle,
the pathways through which carbon is recycled in the biosphere
o While cellular respiration releases carbon dioxide into the environment,
photosynthesis pulls carbon dioxide out of the atmosphere
o The exchange of carbon dioxide and oxygen during photosynthesis and
cellular respiration worldwide helps to keep atmospheric oxygen and carbon dioxide at stable levels
he purpose of photosynthesis is to transform light energy into chemical energy
o The energy is stored in molecules of glucose
• Chemical formula for photosynthesis:
Sunlight + CO2 + H2O → C6H12O6 +O2
• Photosynthesis occurs in 2 stages:
1. Light Reactions / Light Dependent Reactions
2. Dark Reactions / Light Independent Reactions / Calvin Cycle
• The light reactions take place in the chloroplast’s thylakoid membrane. Oxygen,
NADPH & ATP are produced. The oxygen is released, while the NADPH & ATP
are used to power the dark reactions
• The dark reactions take place in the chloroplast’s stroma. These reactions do not
require the presence of light to occur. Carbon dioxide combines with the
hydrogen (H) released from NADPH to produce C6H12O6 (glucose). NADPH+, ADP & a phosphate group are produced, which can then be recycled back into
NADPH and ATP during the light reactions ADP & a phosphate group are produced, which can then be recycled back into NADPH and ATP during the light reactions
Photosynthesis and cellular respiration are complementary processes for cycling
carbon dioxide and oxygen as well as transferring energy in ecosystems
• The products of photosynthesis (glucose & oxygen) are the reactants of cellular
respiration. The products of cellular respiration (carbon dioxide & water) are the
reactants for photosynthesis
o Photosynthesis makes the glucose used in cellular respiration to make
ATP. The glucose is then turned back into carbon dioxide, which is used
in photosynthesis.
o While water is broken down to form oxygen during photosynthesis, in
cellular respiration oxygen is combined with hydrogen to form water
o While photosynthesis requires carbon dioxide and releases oxygen,
cellular respiration requires oxygen and releases carbon dioxide. It is the
released oxygen that is used by us and most other organisms for cellular
respiration.
In the absence of oxygen, only a few ATP are produced from glucose
o Without oxygen, organisms can split glucose into just 2 molecules of
pyruvate
• In the presence of oxygen, many more ATP are made
o With oxygen, organisms can break down glucose all the way to carbon
dioxide, which produces 36-38 ATP molecules
• Oxygen is the final electron acceptor at the end of the electron transport chain of
aerobic respiration.
o The electron transport chain produces the bulk of ATP in the cellular
respiration process
o The electron transport chain step of cellular respiration does not take
place if oxygen is not present
o If oxygen is present, more ATP can be produced because the ETC step
can occur
• ATP is still produced even if oxygen is not present, just not as much. However,
this method produces ATP faster than the process involving oxygen!
ATP is the molecule which stores the cell’s chemical energy
o Cells release the chemical energy stored in the products of
photosynthesis as ATP
o When the cell needs energy to do work, certain enzymes release the
energy stored in the chemical bonds of ATP
• This is accomplished by breaking off the last phosphate of the ATP molecule
Both aerobic & anaerobic respiration produce ATP
• Aerobic respiration produces more ATP (approx. 36-38 ATP molecules) in the
presence of oxygen and occurs in the cytoplasm and the mitochondria
• Anaerobic respiration produces a little ATP (only 2 ATP molecules) without
the presence of oxygen and occurs only in the cytoplasm
o Anaerobic respiration is AKA fermentation. There are 2 types of
anaerobic respiration/fermentation:
▪ Lactic Acid fermentation – used to make cheese, yogurt,
buttermilk. Occurs in the muscles when oxygen levels are low,
causing a build up of lactic acid, which is what makes you sore.
▪ Alcoholic fermentation – occurs in yeast & some bacteria, cause
bread dough to rise. Produces ATP & ethyl alcohol from glucose during anaerobic respiration, allowing organisms to generate energy without the presence of oxygen.
Light energy is collected on the top/surface of the plant leaf, while gases such as
CO2, O2 & H2O are taken and released on the underside of the leaves.
• Exchange of gases & waste in a leaf cell occurs through pores called stomata
• Stomata open during the day when light hits the plant, and close at night
o The stomata opens & closes by changes in the tugor (pressure) in the
guard cells on either side of the stomata
o Stomata remaining open expose the plant to the risk of losing water
through transpiration (“plant sweat”).
▪ Plant leaves are also covered in a waxy cuticle to help prevent
water loss.
o Water absorption via the root system of the plants also helps compensate
for the water lost through transpiration. Water is transported through the
plant in the xylem, while sugars are transported through the plant in the
phloem.3