Biology

• All life consists of cells
• Cells can be seen with a normal light microscope
• Electron microscopes allow us to see finer details of subcellular structures
• Magnification is calculated by image size divided by object size
• Eukaryotic cells have a nucleus containing DNA (e.g., plant and animal cells)
• Prokaryotic cells lack a nucleus and have DNA in a ring called a plasmid
• Both eukaryotic and prokaryotic cells contain similar organelles
• The cell membrane is semi-permeable, allowing certain substances to pass through
• Plant cells and most bacteria have an additional cell wall made of cellulose
• Cytoplasm is the liquid where most chemical reactions take place
• Mitochondria is where respiration occurs, releasing energy for the cell
• Ribosomes are where proteins are synthesized
• Plant cells also contain chloroplasts for photosynthesis and a permanent vacuole for storage
• Bacteria multiply by binary fission, doubling in number every 10 minutes
• Stem cells are unspecialized cells found in embryos and meristems
• Mitosis is the process of cell division for growth and repair
• Cells specialize based on the function they need to fulfill
• Diffusion is the movement of molecules from high to low concentration
• Osmosis is the diffusion of water across a semi-permeable membrane
• Active transport uses energy to move substances against a concentration gradient
• Tissues form organs, which work together in organ systems
• Enzymes are biological catalysts that break down larger molecules into smaller ones
• Enzymes are specific and work on a lock and key principle
• Enzymes have an active site where substrates bind, forming a complex
• Substrates must be the right shape to fit the active site for the complex to form
• The rate of enzyme activity increases with temperature as molecules have more energy
• However, if the active site changes shape, the substrate no longer binds, leading to denaturation of the enzyme
• In experiments, amylase is mixed with starch at different temperatures or pH levels
• The time taken for the starch to be broken down is calculated and plotted against pH or temperature
• The lowest point on the curve represents the optimum temperature or pH for enzyme activity
• Food tests can identify nutrients: iodine turns black in the presence of starch, Benedict's solution turns orange with sugars, Biuret reagent turns purple with proteins, and cold ethanol goes cloudy with lipids
• The respiratory system involves breathing and gas exchange
• Air moves through the trachea, bronchi, bronchioles, and into the alveoli for gas exchange
• Oxygen binds to hemoglobin in red blood cells and is transported to cells for respiration
• Carbon dioxide, a byproduct of respiration, is exhaled
• The heart is part of the circulatory system, a double circulatory system
• Deoxygenated blood enters the heart through the vena cava into the right atrium
• Blood is pumped to the lungs for oxygenation and then circulated to the body
• The left side of the heart has thicker walls to pump blood to the body, while the right side pumps to the lungs
• The heart's electrical pulses cause muscle contractions for the heartbeat