Cells, Tissues, Organs: Chemical Composition

Introduction

• Cells, tissues, and organs are composed of chemicals.
• Chemical reactions are important for bodily function.
• Chemistry studies elements, compounds, chemical reactions, and molecular structure.

Atomic Structure

• Atoms are the smallest particles of elements and maintain all characteristics of the element.
• The atomic nucleus contains protons and neutrons.
• Electrons orbit the nucleus in shells.

Elements, Isotopes, Compounds

• An element's atoms contain the same number of protons and electrons.
• A compound contains two or more elements.
• An isotope's number of neutrons varies.
• The periodic table arranges elements by increasing atomic number.
• An orbital is the area where an electron is found.
• Energy levels group orbitals and are represented as concentric circles surrounding the nucleus.

Bonds and Energy

• An ionic bond involves one atom gaining and another losing electrons.
• A covalent bond involves atoms sharing electrons.
• Hydrogen bonds are weak bonds that hold water molecules together.
• Within bonds, there is a exchange of electron donors, acceptors, and carriers
• Bonds contain energy.

Common Substances in Living Systems

• Water is the most abundant substance in cells and is a universal solvent.
• Water is a transport vehicle, absorbs and reduces heat, and protects bodily structures.
• Carbon dioxide is a waste product of cellular respiration.
• Photosynthesis uses carbon dioxide to produce usable energy sources.
• Carbon dioxide must be quickly removed from cells.
• Molecules' carbon content comes from carbon dioxide gas.
• Molecular oxygen forms from a covalent bond of two oxygen atoms.
• Atmospheric oxygen is required by organisms that breathe air and is necessary to convert food into ATP.
• The level of oxygen in the atmosphere is 21%.
• Ammonia is a byproduct of amino acid breakdown, which are building blocks of proteins and contain nitrogen.
• Ammonia is ultimately converted to urea in the liver.
• Mineral salts are composed of small ions.
• Calcium is used in muscle contraction and strengthen bones.
• Phosphate is used in ATP synthesis.
• Sodium, potassium, and chloride are necessary for muscle contraction and nervous transmission.

Carbohydrates

• Carbohydrates have a 1:2:1 ratio of carbon, hydrogen, and oxygen.
• Five- and six-carbon simple sugars are the smallest carbohydrates.
• Five-carbon sugars: deoxyribose and ribose.
• Six-carbon sugars: glucose and fructose.
• Carbohydrates' functions include energy storage and cell structure.

Lipids

• Lipids are insoluble in water.
• 95% of fats in the body are triacylglycerols.
• Saturated fats have fatty acids joined by single covalent bonds.
• Unsaturated fats have fatty acids joined by one or more double covalent bonds.
• Lipids' functions include energy storage, insulation, and protection.

Proteins

• Proteins contain carbon, oxygen, hydrogen, nitrogen, and sulfur.
• Amino acids are the building blocks of proteins.
• Proteins' functions are energy and structure.
• Enzymes are protein catalysts for chemical reactions.

Protein Structure

• Primary structure: amino acid sequence.
• Secondary structure: determined by hydrogen bonds.
• Tertiary structure: folding caused by interactions within peptide bonds and sulfur atoms.
• Quaternary structure: determined by spatial relationships between units.

Nucleic Acids

• Deoxyribonucleic acid (DNA) is the genetic material of the cell.
• Ribonucleic acid (RNA) is used in protein synthesis.
• This includes messenger RNA and transfer RNA.
• DNA has double helical chains in its structure.
• RNA has single chains in its structure.
• Nucleic acids comprise chains of nucleotides.
• Nucleotides encompass a nitrogen base, sugar, and phosphate group.
• Nitrogen bases are purines and pyrimidines.

Adenosine Triphosphate

• Adenosine Triphosphate (ATP) fuels cell function and maintenance.
• ATP molecules consist of sugar, adenine, and three phosphates.
• Energy is stored in the second and third phosphates.
• The breakdown of glucose provides energy to make ATP.

Movement of Materials In/Out of Cells

• Plasma membranes are selectively permeable.
• Only select materials can enter and exit cells due to the membranes' chemical structure.
• Water can enter and exit with ease.
• Diffusion is the movement of molecules from areas of high concentration to low concentration.
• Brownian movement is the random collision of diffusing molecules.
• Diffusion is accelerated by increased temperature.
• An example of diffusion includes oxygen-carbon dioxide exchange.
• Osmosis describes movement of water through a semipermeable membrane from high concentration to low concentration.
• Isotonic solutions have the same salt concentration outside the cell as inside.
• Hypotonic solutions have a salt concentration inside the cell higher than outside.
• Hypertonic solutions have a salt concentration higher outside the cell than inside.
• Active transport is used by cells to obtain sugars, amino acids, larger proteins, which are necessary for obtaining sugars, amino acids, larger proteins, and fats.
• Active transport needs energy in the form of ATP.
• Molecules move from areas of low concentration to areas of high concentration in this method.

pH

• pH is a negative logarithm of hydrogen ion concentration.
• Acids have pH values below 7.
• Bases have pH values above 7.
• Buffers help maintain pH levels.