Lesson 3
Science
1. Biology
The study of life and living organisms.
Cell Structure & Function
Nucleus
Control center; contains DNA
Mitochondria
Powerhouse; produces ATP
Ribosome
Protein synthesis
Endoplasmic Reticulum
Transport; Rough ER (proteins), Smooth ER (lipids)
Golgi Apparatus
Packages and modifies proteins
Cell Membrane
Controls entry/exit; selectively permeable
Genetics Basics
- DNA: Deoxyribonucleic acid; carries genetic information
- Gene: Segment of DNA that codes for a trait
- Chromosome: Structure containing DNA; humans have 46 (23 pairs)
- Allele: Different versions of a gene
- Dominant: Expressed when present (capital letter)
- Recessive: Only expressed when homozygous (lowercase)
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
- Nervous: Brain, spinal cord; controls body functions
- Skeletal: Bones; support and protection
- Muscular: Muscles; movement
- Excretory: Kidneys; removes waste products
2. Chemistry
The study of matter and its transformations.
Atomic Structure
Proton (+)
In nucleus
Determines element
Neutron (0)
In nucleus
Adds mass
Electron (-)
Orbits nucleus
Chemical bonding
Chemical Bonding
- Ionic Bond: Transfer of electrons (metal + nonmetal)
- Covalent Bond: Sharing of electrons (nonmetals)
- Metallic Bond: Sea of electrons (metals only)
- Hydrogen Bond: Weak attraction between polar molecules
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
Acids and Bases (pH Scale)
- 0-6: Acidic (lower = more acidic)
- 7: Neutral (pure water)
- 8-14: Basic/Alkaline (higher = more basic)
- Acids: Release H⁺ ions; taste sour
- Bases: Release OH⁻ ions; taste bitter, feel slippery
3. Physics
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. The greater the force, the greater the acceleration.
- Action-Reaction: For every action, there is an equal and opposite reaction.
Important Formulas
Speed: v = d/t
Acceleration: a = (v₂-v₁)/t
Force: F = ma
Weight: W = mg
Work: W = F × d
Power: P = W/t
Kinetic Energy: KE = ½mv²
Potential Energy: PE = mgh
Waves and Light
- Wavelength (λ): Distance between two consecutive crests
- Frequency (f): Number of waves per second (Hz)
- Wave equation: v = f × λ (speed = frequency × wavelength)
- Electromagnetic Spectrum: Radio → Microwave → Infrared → Visible → UV → X-ray → Gamma
4. Environmental Science
Understanding ecosystems and environmental issues.
Ecology Concepts
- Ecosystem: Community of organisms + their physical environment
- Food Chain: Linear pathway of energy transfer
- Food Web: Interconnected food chains
- Producers: Make their own food (plants, algae)
- Consumers: Eat other organisms
- Decomposers: Break down dead matter
Biogeochemical Cycles
- Water Cycle: Evaporation → Condensation → Precipitation → Collection
- Carbon Cycle: Photosynthesis, respiration, combustion, decomposition
- Nitrogen Cycle: Fixation → Nitrification → Assimilation → Denitrification
Environmental Issues
- Climate Change: Global warming due to greenhouse gas emissions
- Ozone Depletion: Destruction of protective ozone layer by CFCs
- Deforestation: Loss of forests; affects biodiversity and carbon storage
- Pollution: Air, water, and soil contamination
- Biodiversity Loss: Extinction of species; ecosystem imbalance
5. Scientific Method
The systematic approach to investigating natural phenomena.
Steps of the Scientific Method
- Observation: Notice something interesting
- Question: Ask a question about it
- Hypothesis: Make an educated guess (testable prediction)
- Experiment: Design and conduct a test
- Analysis: Collect and analyze data
- Conclusion: Accept or reject hypothesis
Key Terms
- Variable: Factor that can change
- Independent Variable: What you change (manipulate)
- Dependent Variable: What you measure (result)
- Control: Standard for comparison
- Constant: Factors kept the same
Units of Measurement (SI Units)
USTET Science Tips
- ✓Review fundamental concepts - focus on high school science basics.
- ✓Memorize key formulas - especially in physics and chemistry.
- ✓Understand processes - photosynthesis, respiration, cycles.
- ✓Practice problem-solving - apply concepts to real scenarios.