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Summary BIOL1000 Block 1: Metabolism, Respiration + Photosynthesis
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- University Of The Witwatersrand (wits)
This document is a summary of week 5 of ILS block 1. It includes metabolism, respiration and photosynthesis.
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INTRODUCTION TO METABOLISMThe duties of the cell
● Assembling polymers
● Motility
● Reproduction
● Feeding
● Breathing
All of the above require energy to perform all of these duties
This energy comes from:
● Chemical reactions, which is termed metabolism
● Metabolism: the breaking down of chemical compounds
CATABOLISM
● Breakdown of chemical compounds to release energy (usually ATP)
Main catabolic pathways
● Many catabolic pathways have been developed
1. Aerobic respiration: Chemical compound + oxygen = carbon dioxide + water +
energy
a. This pathway occurs in most eukaryotic and prokaryotic cells
2. Anaerobic respiration: Chemical compound = product + energy
a. Occurs in many prokaryotic cells
3. Fermentation: Chemical compound = fermented product + energy
a. Occurs in eukaryotic and prokaryotic cells
,Chemical compound
● These are the fuel for the reactions
○ As they are broken down to generate the energy
● Carbohydrates, proteins, lipids are chemical compounds
● Many organisms make their own chemical compounds
○ Proteins: DNA - amino acids - proteins
○ Lipids: fatty acids - oils
○ Carbohydrates: monosaccharides - polysaccharides
○ The production of these chemical compounds in the body of the organism
is called anabolism
■ Anabolism: the construction of macromolecules from smaller units
(e.g. building carbohydrates, proteins and lipids)
METABOLISM = CATABOLISM + ANABOLISM
Energy binds metabolism and catabolism together
,NUTRIENTS
● A constant supply of nutrients is required to ensure that catabolism and
anabolism can occur/remain balanced
● These nutrients come from food that is consumed
● The way that these nutrients are obtained differs in animals and plants
1. Animals: Consumed food is catabolised to produce ATP energy
2. Plants: obtain energy from the sun to break it into oxygen, compounds, and
energy
ENERGY AND LIFE (CH6)
Bioenergetics
● A living cell is a miniature chemical factory where thousands of reactions occur
● Metabolism is the totality of the organism's chemical reactions
,Energy in other forms
● Energy: the capacity to perform work
● From a global perspective, energy has many definitions
○ I.e. light energy, heat energy, mechanical energy
● Therefore energy is divided into two main types:
1. Potential energy - energy of position; it is stored and waiting to be used for a
task
2. Kinetic energy - energy of motion; energy that is being used to perform a
particular task
Potential energy is transformed into kinetic energy and any energy can be
converted to heat
Energy in a biological perspective
● We refer to a flow of energy in biology
○ Energy flows from the sun in the form of light/heat energy
■ This flow of energy is essentially kinetic energy
○ Kinetic energy is then taken in by plants during photosynthesis and
converted into chemical energy, which is potential energy
■ E.g glucose is potential energy
THERMODYNAMICS
First law of thermodynamics
Energy can be transferred and transformed, but cannot be created or destroyed
● The total amount of energy in the universe remains constant
● However when energy conversions are happening, there is a loss of heat energy
, ○ So where does extra energy come from? It is being replaced by energy
that is derived from the sun
● Heat energy is kinetic energy - atoms are continuously bouncing around each
other
Second law of thermodynamics
Every energy transfer or transformation that occurs increases the entropy of the
universe
● Entropy: a measure of disorder or randomness in the universe
● Heat energy increases the entropy of the universe
● Entropy is decreased/balanced out by putting in work (i.e kinetic energy)
GIBBS FREE ENERGY
● There are 2 types of reactions: those that require input of energy and those that
don’t
● Spontaneous processes are the ones that don’t require energy
○ They are energetically favourable
○ More energy comes out than is put in
○ Exemplified by catabolic processes (breakdown of molecules)
● Non-spontaneous processes require energy input
○ Energy is taken in for the reaction
● Free energy is the energy that is available to do work at the end of a
spontaneous or nonspontaneous reaction
, ● G is change in enthalpy - change in entropy (i.e how much energy is left in terms
of your reaction)
● G is an indication of stability of a reagent and product
○ A high G means the reagent is unstable
■ A reagent/product with high energy wants to get rid of that energy
to transform into a more stable state
○ A low G means that the reagent or product is stable
○ Chemical reactions aim to proceed towards a state of equilibrium (i.e.
maximum stability and lowest G)
Link between energy and metabolism
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