Characteristics of life, Atomic Structure

• Living things share key characteristics: requiring energy and raw materials, cellular composition, maintaining homeostasis, response to stimuli, growth, reproduction, and adaptation.

Atomic Structure

• Atoms consist of: negatively charged electrons, positively charged protons, and neutral neutrons.
• Protons and neutrons reside in the nucleus, with electrons orbiting in shells.
• The first electron shell holds a maximum of 2 electrons, while the second can hold more.
• Atoms are the smallest unit of matter.
• Matter is any physical substance with mass that occupies space.
• Elements are pure forms of matter that cannot be broken down further and are composed of atoms.

Organic Compounds

• Proteins are composed of 20 different amino acids.
• Amino acids link via peptide bonds.
• Protein function is determined by its structure and can be disrupted by: denaturation (loss of biological function) and deamination (digestion).
• Lipids are insoluble in water.
• Triglycerides function in energy storage.
• Phospholipids are the primary component of cell membranes.
• Steroids, also insoluble, include cholesterol, vital for animal cell membranes and hormone production (including sex hormones).
• Carbohydrates contain a carbon backbone with hydrogen and oxygen atoms (C, H, O).
• Monosaccharides are simple sugars with 5 or 6 carbon rings.
• Disaccharides consist of two monosaccharides joined by a covalent bond.
• Polysaccharides are long chains of monosaccharides used by cells to store extra energy.
• Nucleic acids contain C, H, O, N, and P and include DNA and RNA.
• Nucleotides are smaller subunits of nucleic acids.
• In DNA, adenine (A) binds with thymine (T), and cytosine (C) binds with guanine (G).

Inorganic Compounds

• Inorganic compounds lack C-H bonds.
• Examples include salts, water, and gases.

Cells

• Cells are the smallest units of life.
• Cells provide basic structure and organization for organisms.

Eukaryotic Cell Organelles

• Eukaryotic cells (human, animal, plant, and fungi cells) possess three main components.
• Plasma membrane: the outer covering.
• Cytoplasm: the region inside the cell, excluding the nucleus.
• Nucleus: the cell's central control center.

Metabolism and Homeostasis

• Metabolism produces energy for cells.
• Homeostasis is an organism's state of internal stability, maintained by adjusting to external changes.
• Homeostasis involves variations within normal limits for factors like heart rate, blood pressure, and blood sugar.
• Water contributes to the properties of life and homeostasis.
• The body maintains homeostasis automatically.

pH Scale

• The pH scale ranges from 0-14, with 7 being neutral.
• Acidic solutions have a pH below 7, while basic solutions have a pH above 7.
• The body functions optimally around a neutral pH of 7.
• Acids are molecules that donate H+ ions in water.
• Bases are molecules that accept H+ ions in water.
• Acids and bases neutralize each other.

Cations vs. Anions

• Cations have a positive (+) electric charge.
• Anions have a negative (-) electric charge.

Tonicity

• Hypotonic solutions have a low osmotic concentration, causing cells to gain water.
• Hypertonic solutions have a high osmotic concentration, causing cells to lose water.
• Isotonic solutions have the same concentration inside and outside the cell, resulting in no net water movement.

Enzymes

• Enzymes are proteins that act as biological catalysts.
• Catabolism involves breaking down molecules.
• Anabolism involves combining molecules.

Passive vs. Active Transport

• Passive transport moves materials along a concentration gradient without energy expenditure.
  • Diffusion: movement from high to low concentration.
  • Osmosis: movement of water from low to high solute concentration.
  • Transport through channels: ions and water diffuse through protein channels in the plasma membrane; water channels are always open, gated channels require specific ionic charges.
  • Facilitated transport: molecules bind to membrane proteins for transport (e.g., glucose entering cells).
• Active transport moves molecules against the concentration gradient, requiring energy expenditure.
  • Like facilitated transport, it uses membrane proteins, but requires ATP.
  • Allows ions to move from low to high concentration.
  • Important for digestion; can utilize up to 50% of a cell's ATP.

Explore the fundamental characteristics of living organisms, including energy requirements, cellular composition, homeostasis, response to stimuli, growth, reproduction, and adaptation. Understand atomic structure, organic compounds, and their significance in biological processes.