Metabolism and Cell Energy

Topic Review

Q: Human liver cells membrane is composed of a phospholipid bilayer and associated proteins. What else are you expecting to find in the plasma membrane of human liver cells?

A: Cholesterol - a component of animal cell membranes

Lecture Question

Q: Where does the energy come from to support human activities?

A: from food, ATP

Core Concepts

1. Metabolism is the set of biochemical reactions that transform biomolecules and transfers energy

2. Kinetic Energy is energy of motion

3. Potential Energy is stored energy

4. The Laws of Thermodynamics govern energy flow in biological systems

Requirements of the Cell

• a membrane to separate the inside of the cell from the outside

• a way to encode and transmit information

• energy is needed to support all sorts of activities’

Adenosine Triphosphate (ATP)

• contains an adenosine group that is linked to three units of phosphate groups

• the energy levels stored in each bonds linking the phosphate group is different

• the highest energy bond is at the outer layer

• the bond linking the phosphate groups usually contains the highest potential energy

ATP In Cellular Activities

• involved in active transport

• energy will be released when the chemical bonds like the phosphate groups breaks, turning ATP into ADP

ATP In Organismal Activities

• physical functions of the human body burn ATP

• ATP is gained from carbohydrates

Metabolism

• the building or breaking down of carbon sources to harness or release energy

• ATP can be formed or consumed in this process

• the transformation of big molecules and energy doesn’t ever stop

Metabolic Classification

• Phototrophs

  • organisms that can obtain energy from sunlight

  • the most common are plants - they convert the energy they gain from sunlight to convert carbon dioxide and water into oxygen and sugar

  • Autotrophs - a secondary category: carbon from inorganic sources

    • Cyanobacteria; can utilize carbon from inorganic sources

  • Heterotrophs - a secondary category: carbon from organic compounds

    • Most Green Non-Sulfur Bacteria; can use sunlight energy but cannot produce oxygen and can obtain carbon from organic compounds

    • Heliobacteria; utilize sunlight energy but cannot convert carbon dioxide into sugar

• Chemotrophs

  • organisms that can’t obtain energy from sunlight but from chemical compounds

  • the most common are animals - breakdown the chemical compounds found in food

  • Autotrophs - a secondary category: carbon from inorganic sources

    • Sulfur-Oxidizing Bacteria; cannot use sun energy directly, it can produce energy through sulfur oxidizing reactions and can utilize carbon from inorganic sources

    • Hydrogen Bacteria; can synthesize organic matter themselves

  • Heterotrophs - a secondary category: carbon from organic compounds

    • Most Bacteria; cannot use sunlight energy directly nor use inorganic sources

Catabolism and Anabolism

• Catabolism - the breaking down of macromolecules (carbohydrates, proteins, fats, nucleic acids) through production of ATP, into subunits (sugars, amino acids, fatty acids, nucleotides)

• Anabolism - the building of subunits (sugars, amino acids, fatty acids, nucleotides) through consumption of ATP, into macromolecules (carbohydrates, proteins, fats, nucleic acids)

Kinetic Energy

• the energy of motion

• associated with any form of movement

• other forms of kinetic energy; light, electricity, thermal energy

  • Light - the movement of photons

  • Electricity - the movement of electrons

  • Thermal - the movement of particles/molecules

Potential Energy

• stored form of energy

• depends on the structure and position of an object

Chemical Energy

• form of potential energy held in the chemical bonds between pairs of atoms in a molecule

• strong bonds have less potential energy than weak bonds do

  • the more energy you need to break a bond, the less you will have in said bond

Packed Energy: ATP

• cells do not use all the energy they have at once

• cells package the energy into a chemical form that is readily accessible to the cell

Why is ATP the Currency of Energy?

• the chemical energy of ATP is held in the bond connecting the phosphate groups

• the broken of each bond between the phosphate group will release energy, so the ATP is called the currency of energy

First Law of Thermodynamics (The Law of Conservation of Energy)

• Energy is neither created nor destroyed

Second Law of Thermodynamics

• the total entropy of a system either increases or remains constant in any spontaneous process; it does not decrease

• Entropy - use to describe the amount of disorder in a system; the higher the energy the more disorder and vice versa

Microbiome

• the microbiome consists of microbes that are both helpful and potentially harmful

• the microbiome associated with the human body has more cells than human cells

• most are mutualists and commensals

• in smaller numbers are pathogens (promoting diseases)