Cellular Biology Basics: A Comprehensive Guide
Cellular Respiration
Glycolysis
Glycolysis is the breakdown of glucose, a process also known as the splitting of sugars. It produces 4 ATP molecules but requires 2 ATP molecules to function.
Krebs Cycle
The Krebs cycle occurs in the inner membrane of the mitochondria and completes the breakdown of pyruvic acid molecules to carbon dioxide. This process forms 2 ATP molecules, and chemical energy is released and captured in the form of NADH, FADH2, and ATP.
Electron Transport Chain (ETC) & ATP Synthase
The ETC is a sequence of electron carrier molecules that transfer electrons and release energy during cellular respiration. ATP is converted to ADP when one phosphate is removed, leaving only two phosphates. ADP is converted back to ATP when a phosphate is added to complete the three phosphates.
Fermentation
During fermentation, animal cells create lactic acid, which can cause muscle contractions. During exercise, proteins enter muscle cells, and lactic acid contributes to muscle contraction. Fermentation in yeast cells produces ethanol, a type of alcohol.
Cell Structure and Function
Nucleus
The nucleus is located in the center of the cell and acts like the brain. It stores information like a computer, and when needed, the nucleus retrieves and provides that information.
Vesicles
Vesicles are sacs that transport substances across cell walls. When a substance cannot pass through the cell wall, it uses a vesicle for transport.
Golgi Apparatus
The Golgi apparatus is known as the post office of the cell. It modifies proteins as they enter the organelle, where enzymes modify them before being sent to their destination.
Common Features in Plant and Animal Cells
- Nucleus (generally, excepting red blood cells and some other specialty cells)
- Cell membrane
- Mitochondria
Features Exclusive to Plant Cells
- Chloroplasts
- Cellulose (‘woody’) cell wall
DNA, Steroids, and Molecules
DNA
The letters A, T, C, and G in DNA form sequences that are sent to the membrane, determining traits like physical appearance and personality. DNA is a nucleic acid, one of the three vital components for life and function.
Steroids
Steroids are a large class of organic compounds with a characteristic molecular structure containing four rings of carbon atoms (three six-membered and one five-membered). Two functions of steroids in cells include being components of cell membranes and protecting the cell (cholesterol) and participating in the production of sex hormones (testosterone and estrogen).
Cholesterol, the most abundant steroid in the body, is formed in brain tissue, nerve tissue, and the bloodstream. It plays a role in producing hormones like testosterone, estrogen, progesterone, aldosterone, and cortisone. The body also uses cholesterol to make membranes and bile acids. Additionally, cholesterol contributes to the production of Vitamin D.
Carbon
Carbon has 6 neutrons, 6 protons, and 4 valence electrons.
Organic Molecules
Any molecule containing Carbon-Hydrogen (hydrocarbon) bonds or Carbon-Carbon bonds is considered organic. Examples include methane, ethane, alcohols, and DNA.
Inorganic Molecules
Inorganic molecules are essentially any molecules that do not contain carbon. Examples include carbon dioxide (CO2), water (H2O), oxygen (O2), and ammonia (NH3).
Monomers and Polymers
Monomers are small molecules, mostly organic, that can join with other similar molecules to form very large molecules called polymers. All monomers can form chemical bonds with at least two other monomer molecules.
Hydrolysis
Hydrolysis is the process of splitting a compound into fragments by adding water. This reaction breaks down polymers into simpler units, such as starch into glucose.
Dehydration Reaction
A dehydration reaction is a chemical reaction that involves the loss of a water molecule from the reacting molecule. A water molecule (H2O) consists of two hydrogen atoms and one oxygen atom connected by covalent bonds, meaning they share electrons. Water molecules are polar because oxygen has a partial negative charge, and hydrogen has partial positive charges, leading to “hydrogen bonding.”
Cohesion and Adhesion
Cohesion is the attraction between like molecules, while adhesion is the attraction between unlike molecules.
Capillary Action in Plants
In plants, stomata, or pores in leaves, allow for gas exchange. Wind helps pull water out of these pores. Due to the pressure decrease caused by water being drawn out, water is pulled up the xylem tubes within the tree. This mechanism, called “capillary action,” requires tubes with a small diameter and occurs because of water’s adhesion to the tube walls and cohesion within the water itself (surface tension).
Enzyme Activity
In a saliva experiment, saliva breaks down starch over time. The enzymes in saliva act as catalysts to break down the starch. Amylase, an enzyme in saliva, breaks down starch in crackers, explaining the different reactions observed with iodine compared to iodine with a regular cracker.