Kim Thompson
Elizabeth Pawluk
Amanda Buchanan
Elyse Myrans
1B. Cells At Work
Cell Reactions and Energy
Metabolism: The sum of all chemical reactions in a cell.
Endergonic: require energy in order to proceed. Example: photosynthesis requires energy.
Exergonic: releases energy when carrying out a chemical reaction. Example, cellular respiration, releases
energy.
Anabolic reaction: reactions that build substances through a series of steps. (endergonic- requires energy)
Catabolic reaction: reactions that break down substances through a series of steps. (exergonic: releases
energy)
ATP: the energy molecule of the cell,
made from a nucleotide, composed of adenine, 5 carbon sugar ribose, and three phosphate groups
contains specialized bonds which are high energy bonds between phosphate groups
small molecule, therefore, it releases small amounts of energy that are useful for the cell
ATP Molecule
When energy is needed the bond between the second and third phosphate groups is broken,
this creates ADP and releases 30 kJ of energy per mole of ATP.
ATP ADP + P + Energy
o This can be reversed using cellular respiration
Enzymes
Catalyst: facilitate chemical reactions; speeds up or slows down chemical reactions, and allow chemical
reactions to be completed 10 billion times faster.
Enzymes: specialized protein molecules that function as a biological catalyst.
Essential to life, because though reactions would still occur, they would not occur fast enough to
maintain life.
Reactions are sped up by binding to substrates
o An enzyme binds with a substrate to form an enzyme substrate complex, this is when the
reaction occur. Reactions
occur at active sites on
the enzyme, which create
products.
Enzymes are reusable once the
products are released, ready to
bind to more substrates.
Each enzyme catalyses one
chemical reaction, this means enzymes are specific to particular substrates.
Lock and Key: 3-D shape of active site is designed to precisely fit and accept substrate molecules.
o Once the substrate (key) is in place in enzyme (lock) the chemical reaction can occur.
Competitive Inhibitors: Molecule with similar structure to substrate will compete to bind to
enzyme active site and will inhibit the function. Ex. Poisons- arsenic and cyanide)
Activation Energy: Energy required to activate a reaction, when enzymes bind to substrates they
lower the amount needed.
Presence of an enzyme makes reactions occur faster because energy is available for reaction,
rather than wasted of obstacles.
Example: digestion of food requires enzymes of specialized cells of the stomach, small intestine
and pancreas.
Cellular Respiration
Cellular Respiration: supplies cells with ATP energy.
Supplies heat to keep warm blooded animals warmer than their environment, as well as active
transport, muscle contraction and other endergonic reactions.
The fuel for cellular respiration is glucose.
Covalent bonds in glucose are slowly broken down in a series of reactions that are overall
exergonic. This energy released is used to make ATP.
Equation
C6H12O6 + 6O2 6CO2 +6H2O + Energy (in form of 36 or 38 ATP)
E glucose + water
n
e Exergonic reaction
r eg. Cellular respiration
g carbon dioxide + oxygen
y
Time
Steps of Cellular Respiration:
1. Glycolysis: the first stage; occurs in the cell’s cytoplasm under anaerobic conditions
C6H12O6 2 Pyruvate Molecules + 4ATP + 2NADH
The significance of glycolysis is to convert one molecule of glucose into 2 molecules of
pyruvate. During this process, 2 molecules of NADH are produced, as well as a net gain
of 2ATP molecules.
Four situations using Pyruvate
1. No O2, but need ATP lactic acid + NAD+
2. Have O2, do not need ATP fat formed (glycogen)
3. No glucose, O2 available, need ATP convert fat and protein to acetyl COA
4. O2, glucose, pyruvate need ATP pyruvate oxidation
2. Pyruvate Oxidation: occurs in the matrix of mitochondria
COA + 2Pyruvate +O2 + NAD+ 2Acetyl COA + 2NADH + CO2
3. Kreb Cycle- the second stage; occurs
within the matrix of the mitochondrion
under aerobic conditions
1. Oxaloacetate + 2Acetyl COA + O2
4CO2 + 2NADH + 2 FADH2 +
2ATP + oxaloacetate
Pyruvate oxidation and Kreb
cycle are shown in diagram.
4. Electron Transport Chain: occurs in the cristae of mitochondria.
Products are: 6H2O + 34 ATP
Forms of Cellular Respiration:
Aerobic respiration- cellular respiration using oxygen
Anaerobic respiration- cellular respiration without the presence of oxygen, also known as
fermentation.
o Prokaryotic cells use this, eukaryotic cells can also, but using either lactic acid
fermentation or alcoholic fermentation.
o Lactic Acid Fermentation
Inefficient, does not add to ATP already produced, but is necessary to regenerate
coenzymes that allow glycolysis to continue.
Eukaryotic cells, convert pyruvic acid from gycolysis into lactic acid
Occurs in cytoplasm
Equation: pyruvic acid lactic acid
After strenuous exercising muscles are hurt because lactic acid builds up in
muscles as a result of anatomically producing energy
Lactic acid is toxic to cells, therefore causes pain. Excess amounts can cause
death
Lactic Acid is changed back to pyruvic acid with the presence of oxygen
o Alcoholic Fermentation:
Used by yeast (fungus) and other micro-organisms
pyruvic acid is broken down into ethanol and carbon dioxide
Like lactic acid fermentation, it is inefficient, does not add to ATP already
produced, but is necessary to regenerate coenzymes that allow glycolysis to
continue.
Equation: pyruvic acid alcohol + carbon dioxide
Example: wine brewing relies on yeast to ferment sugar to produce CO 2 +
alcohol
Summary Chart
Products NADH FADH2 ATP
Glycolysis 2 pyruvates 2 - 4 (net gain 2)
Acetyl COA 2 CO2 2 - -
Kreb’s Cycle 4 CO2 6 2 2
ETC 6 H2O - - 32 or 34
Protein Synthesis:
- proteins are always needed within the cell
- 2 steps:
1) Transcription: Protein-making instructions on DNA are copied into
RNA called messenger RNA (mRNA) which is then carried to
ribosomes on RER
2) Translationg: Transfer RNA (tRNA) brings required amino acids one
at a time to build the primary structure according to the mRNA
instructions. Peptide bonds link amino acids to make a polypeptide
which enters the RER where is takes its final shape, possibly a
quarternary structure. The RER sends protein as a vesicle to the golgi
apparatus where it may undergo further changes. If it is going to be
used outside of the cell, it is packaged in a new vesicle and is sent out
to the cell membrane. It is exported by exocytosis.
**See class notes for further information on protein synthesis.
Photosynthesis and Food Production:
Sunlight
CO2 + H2O ----------------- C6H12O6 + (H2O) + O2
Chlorophylla
sunlight
Carbon dioxide + water------------------ glucose + (water) + Oxygen
Chlorophylla
Photosynthesis makes all O2 and converts energy of sunlight into energy of sunlight into energy of
chemical bonds with carbohydrates
-Within chloroplasts chlorophyll capture light energy
-Energy converts CO2 from air and water from soil into glucose (endergonic reaction)
Light dependant Reactions – water turns into oxygen and hydrogen. Oxygen is released as a
product
-680nm of light energy goes to the cell, and then P680 e- is used to drive proton pumps from
stroma to the thykaloid space and eventually form ATP (see fig. 1, fig. 2)
-From P700 e- used to reduce NADP+ to NADPH
-Photolysis is the way by which water breaks down with light energy
fig.1.
fig. 2. Photosynthesis Electron Transport Chain
Light Independent reactions – carbon dioxide from air and hydrogen forms carbohydrate (glucose)
-The calvin cycle occurs in light dependant reactions. It takes 12 PGAL to get one glucose
molecule
Light (Dependent) Reactions Dark (Light Independent) Reactions
H20 CO2 +
NADPH + ATP + RUBP
H+ 02 ATP
+ glucose+RUBP
NADPH
-Occurs in thylakoid membrane -Occurs in the stroma
Net Equation – this is the ‘ingredients list’ that plants need to make a single molecule of glucose
only
Alternative types of food
Autotrophs – photosynthetic organisms that can make their own food
Most organisms are heterotrophs, which means they eat other organisms to gain energy
Chemoautotrophs – special bacteria that don’t have to rely on photosynthesis at all for survival.
Through chemical reactions they are able to make their own food.
-they release energy from inorganic substances (CO2) and use that energy to make organic
compounds (carbohydrates, amino acids) and other things that are needed by the organism to
survive
-these organisms date back to primitive earth, when there was a lack of oxygen for reactions like
photosynthesis, so this process was used. Today chemoautrophs exist in places like sea vents and
deep soil