BIO152 WK3 Lecture Notes

BIO152 WEEK 3

Introduction to energy generation

Cellular requirements
- In order to grow, calls require energy and building blocks
- Building blocks = C O N P S
- Building blocks are used to make macromolecules

Macromolecules
- Proteins; structural and functional
- Carbohydrates; functional e.g. starch, glycogen
- Lipids; structural and functional
- Nucleic acids; functional

Carbon sources
- Based on how they obtain their carbon, we classify organisms as either autotrophs
or heterotrophs
Autotrophs
- self-feeding
- they obtain carbon from CO2
- on the basis of how they obtain energy, we classify autotrophic organisms as
photosynthetic and chemosynthetic
Photosynthetic organisms
- Use solar energy
- E.g. CO2 + H2O  glucose   starch
- Green plants
- Photosynthetic bacteria
Chemosynthetic organisms
- Use chemical energy from the oxidisation of inorganic molecules
- E.g. NH3  NO2-  NO3-
- Nitrifying bacteria
Heterotrophs
- Feed off others
- Carbon is derived from assimilated compounds e.g. glucose, a 6-carbon sugar
- Energy is also obtained from these compounds
- Eng. Glucose   pyruvate    CO2
- Animals
- Most bacteria
- Non-green plant cells
Carbon sources
- Not all cells in a n organism are the same
- E.g. in plants, roots are heterotrophic, and leaves are autotrophic
- Cells can be fexible
- E.g. leaves; during the day, there is sunlight = autotrophic and at light, there is no
sunlight = heterotrophic

, Cellular metabolism
- Metabolism is all of the enzyme catalysed reactions in a cell
- Two phases; catabolism and anabolism
Catabolism
- Degradative reactions of metabolism
- Larger compounds are broken down into smaller ones
- E.g. glucose (6C)    6CO2 + 6H2O (arrows represent energy, ATP)
Anabolism
- Synthetic (building) reactions of metabolism
- Smaller compounds are combined into larger ones
- E.g. CO2 + H2O   glucose   (first arrows are solar, second is ATP)

Cellular processes
- Many cellular processes require energy
- E.g. anabolism, transport (active transport), mechanical work (muscle contraction)
- All of these processes require an input of energy as ATP

Nucleoside triphosphates
- Different nucleoside triphosphates differ only in their nitrogen bases
- Used in: polysaccharide synthesis (UTP), protein synthesis (GTP), lipid synthesis (CTP)
and RNA synthesis (CTP, GTP, UTP)

Deoxyribonucleoside triphosphates
- If we change the sugar from a ribose to a deoxyribose
- Used in DNA synthesis

ATP
- Energy carrier
- Energy transmiter
- Energy currency
- NOT an energy store
- Nucleoside triphosphate
ATP hydrolysis
- ATP energy is released by hydrolysis
- ATP  ADP + Pi + 30.5kJ (used for processes that require energy)
ATP generation
- ATP is generated by catabolism
- Two processes; fermentation and aerobic respiration
Fermentation
- Under anaerobic conditions (no O2)
- Lactic acid fermentation e.g. in the muscle in the absence of O2
- Glucose (6C)    pyruvate (3C)  lactic acid (3C)
- Ethanol fermentation e.g. in yeast in the absence of O2
- Glucose (6C)    pyruvate (3C)  ethanol (2C)
Aerobic respiration
- Fuel molecules (e.g. glucose) are completely oxidised by CO2