Lesson 3
Science
1. Biology
Biology is the study of living organisms and their interactions with the environment.
Cell Structure
Nucleus
Control center; contains DNA and genetic information
Mitochondria
Powerhouse of the cell; produces ATP energy
Cell Membrane
Controls what enters and exits the cell
Ribosome
Protein synthesis; found on rough ER and cytoplasm
Endoplasmic Reticulum
Rough ER (protein), Smooth ER (lipid synthesis)
Golgi Apparatus
Packages and modifies proteins for transport
Plant vs Animal Cells
Plant Cells Only:
- Cell wall (rigid structure)
- Chloroplasts (photosynthesis)
- Large central vacuole
Animal Cells Only:
- Centrioles (cell division)
- Lysosomes (digestion)
- Small, multiple vacuoles
Human Body Systems
- Circulatory: Heart, blood vessels; transports nutrients and oxygen
- Respiratory: Lungs; gas exchange (O₂ in, CO₂ out)
- Digestive: Stomach, intestines; breaks down food for nutrients
- Nervous: Brain, spinal cord; controls body functions
- Skeletal: Bones; provides structure and protection
- Muscular: Muscles; enables movement
2. Chemistry
Chemistry is the study of matter, its properties, and how it changes.
Basic Concepts
- Atom: Smallest unit of matter that retains element properties
- Element: Pure substance made of one type of atom (e.g., O, H, C)
- Compound: Two or more elements chemically bonded (e.g., H₂O, NaCl)
- Molecule: Two or more atoms bonded together (e.g., O₂, CO₂)
- Mixture: Two or more substances physically combined (not chemically bonded)
Atomic Structure
Proton (+)
In nucleus
Determines element
Neutron (0)
In nucleus
Adds mass
Electron (-)
Orbits nucleus
Involved in bonding
States of Matter
Solid
Fixed shape and volume; particles tightly packed
Liquid
Fixed volume, takes container shape; particles flow
Gas
No fixed shape or volume; particles spread out
pH Scale
- 0-6: Acidic (lower = more acidic)
- 7: Neutral (pure water)
- 8-14: Basic/Alkaline (higher = more basic)
3. Physics
Physics is the study of matter, energy, and their interactions.
Newton's Laws of Motion
- Law of Inertia: An object at rest stays at rest; an object in motion stays in motion unless acted upon by an external force.
- F = ma: Force equals mass times acceleration. More force = more acceleration; more mass = more force needed.
- Action-Reaction: For every action, there is an equal and opposite reaction.
Basic Formulas
Speed: s = d/t (distance ÷ time)
Velocity: speed with direction
Acceleration: a = (v₂ - v₁)/t
Force: F = ma
Work: W = F × d
Power: P = W/t
Density: D = m/V
Pressure: P = F/A
Energy Types
- Kinetic Energy: Energy of motion (KE = ½mv²)
- Potential Energy: Stored energy (PE = mgh for gravitational)
- Thermal Energy: Heat energy from particle motion
- Chemical Energy: Energy stored in chemical bonds
- Electrical Energy: Energy from moving electrons
4. Earth Science
Earth science covers geology, meteorology, and astronomy.
Layers of the Earth
- Crust: Thin outer layer; where we live (5-70 km thick)
- Mantle: Thick layer of hot rock; causes plate movement
- Outer Core: Liquid iron and nickel; creates magnetic field
- Inner Core: Solid iron and nickel; extremely hot
Plate Tectonics
- Convergent: Plates collide → mountains, trenches, volcanoes
- Divergent: Plates separate → rifts, mid-ocean ridges
- Transform: Plates slide past each other → earthquakes
Weather vs Climate
- Weather: Short-term atmospheric conditions (daily/weekly)
- Climate: Long-term average weather patterns (decades)
- Factors: Latitude, altitude, proximity to water, ocean currents
5. Scientific Method
The systematic approach to investigating phenomena and acquiring knowledge.
Steps of the Scientific Method
- Observation: Notice something interesting or puzzling
- Question: Ask a question about the observation
- Hypothesis: Make an educated guess (testable prediction)
- Experiment: Design and conduct a test
- Analysis: Collect and analyze data
- Conclusion: Accept or reject hypothesis based on results
Key Terms
- Variable: Factor that can change in an experiment
- Independent Variable: What you change (manipulate)
- Dependent Variable: What you measure (result)
- Control: Standard for comparison; kept constant
- Theory: Well-tested explanation supported by evidence
- Law: Statement describing consistent natural phenomena
PUPCET Science Tips
- ✓Review basic concepts - focus on high school science fundamentals.
- ✓Memorize key formulas - especially physics equations.
- ✓Understand processes - photosynthesis, cell division, water cycle.
- ✓Know the periodic table basics - element symbols and atomic numbers.