Science test notes


🧫 Cell Biology & Related Topics – Study Notes

🔹 1. Parts of a Cell

🔸 Common to Both Plant & Animal Cells

Cell Part

Function

Cell membrane

Controls what enters and leaves the cell; maintains homeostasis.

Cytoplasm

Jelly-like substance where chemical reactions take place.

Nucleus

Contains DNA and controls cell activities.

Mitochondria

Produces energy through cellular respiration (“powerhouse of the cell”).

Ribosomes

Make proteins.

Endoplasmic Reticulum (ER)

Transports materials; Rough ER has ribosomes, Smooth ER does not.

Golgi apparatus

Modifies, sorts, and packages proteins for transport.

Lysosomes

Contain enzymes that break down waste (mainly in animal cells).

🔸 Plant Cells Only

Cell Part

Function

Cell wall

Provides structure and protection; made of cellulose.

Chloroplasts

Contain chlorophyll for photosynthesis (make food using sunlight).

Large central vacuole

Stores water and nutrients; helps maintain cell shape.

🔹 2. Osmosis and Diffusion

Process

Definition

Example

Diffusion

Movement of particles from an area of high concentration to low concentration.

Oxygen moving into cells.

Osmosis

Diffusion of water through a selectively permeable membrane.

Water entering plant roots.

Key points:

  • Both are passive transport (no energy required).

  • Aim to reach equilibrium (balance of concentration).

🔹 3. Organ Systems (Human Body)

System

Major Organs

Function

Circulatory

Heart, blood, blood vessels

Transports oxygen, nutrients, and waste.

Respiratory

Lungs, trachea, diaphragm

Gas exchange – takes in oxygen, removes carbon dioxide.

Digestive

Mouth, stomach, intestines

Breaks down food into nutrients for energy.

Nervous

Brain, spinal cord, nerves

Controls body activities and responses.

Skeletal

Bones, ligaments

Provides support, structure, and protection.

Muscular

Muscles, tendons

Enables movement.

Excretory (Urinary)

Kidneys, bladder

Removes waste from the body.

Reproductive

Ovaries/testes, uterus, penis

Produces offspring.

Immune

White blood cells, lymph nodes

Defends against disease.

Integumentary

Skin, hair, nails

Protects body, regulates temperature.

Endocrine

Glands (pituitary, thyroid)

Controls hormones and metabolism.

🔹 4. Multicellular and Unicellular Organisms

Type

Description

Example

Unicellular

Made of one cell that performs all life functions.

Bacteria, Amoeba, Paramecium.

Multicellular

Made of many specialized cells that work together.

Humans, plants, animals.

Advantages of being multicellular:

  • Specialization (cells have different jobs).

  • Greater size and complexity.

🔹 5. Cell Technologies

🧬 DNA Testing

Definition:
A process that examines an individual’s DNA sequence to identify genetic information.

How it helps us understand cells & cell processes:

  • Reveals how genes control traits and diseases.

  • Helps identify genetic disorders.

  • Allows scientists to study how cells function and reproduce.

  • Improves our understanding of heredity and evolution.

✅ Advantages

  • Early disease detection (e.g., cancer, genetic conditions).

  • Personalized medicine (treatment tailored to individual DNA).

  • Helps solve crimes or identify people.

  • Improves understanding of human biology and evolution.

⚠ Disadvantages

  • Privacy concerns (DNA data misuse).

  • Cost – not affordable for everyone.

  • Possible discrimination (insurance or employment).

  • Results may cause emotional stress or uncertainty.

🌍 Availability

  • Widely available in developed countries (hospitals, ancestry companies).

  • Less accessible in poorer or rural areas due to cost and equipment needs.

  • Ethical and legal regulations vary by country.

💊 How Understanding Cells Helps Treat Diseases

  • Cancer: Understanding cell division helps develop treatments that stop uncontrolled growth.

  • Genetic diseases: Knowledge of DNA allows for gene therapy (fixing faulty genes).

  • Vaccines & antibiotics: Target specific cell structures in pathogens.

  • Stem cell research: Uses undifferentiated cells to repair damaged tissues.

🧠 Summary Table

Topic

Key Points

Cells

Basic unit of life; plant and animal cells share many parts but differ in wall, chloroplasts, and vacuole.

Osmosis/Diffusion

Movement of substances to maintain balance; vital for nutrient and water transport.

Organ Systems

Work together to maintain homeostasis.

Unicellular/Multicellular

One cell vs. many specialized cells.

Cell Tech (DNA Testing)

Advances medical research, diagnosis, and treatment; has ethical and access concerns.