Study sheet: Cellular and Genetic Foundations

📋 Course Outline

1. Cell as Basic Life Unit
2. Animal and Plant Cell Structures
3. DNA Structure and Stability
4. Chromosomes and Genetic Organization
5. Genes and Alleles

📖 1. Cell as Basic Life Unit

🔑 Key Concepts & Definitions

• Cell : The basic structural unit of a living organism, so humans, animals, and plants are composed of cells.

📝 Essential Points

• The course distinguishes between animal cells and plant cells, and both are eukaryotic cells because they possess a nucleus.

💡 Memory Hook

Cell = building unit of a living organism, like a brick in a wall

📖 2. Animal and Plant Cell Structures

★ Must-know

📌 A plant cell has the same main components as an animal cell but additionally possesses a cellulose wall and chloroplasts.

• An animal cell contains:

  • a plasma membrane
  • a nucleus containing genetic information
  • rough endoplasmic reticulum
  • smooth endoplasmic reticulum
  • a Golgi apparatus
  • mitochondria
  • ribosomes

• Mitochondria participate in ATP production, while ribosomes, the endoplasmic reticulum, and the Golgi apparatus participate in protein synthesis.

Further detail

• The cellulose wall gives the plant cell a regular geometric shape, while chloroplasts enable photosynthesis.

💡 Memory Hook

Animal cell has the shared core; plant cell adds a cellulose wall and chloroplasts

📖 3. DNA Structure and Stability

🔑 Key Concepts & Definitions

• DNA : The genetic support of a living organism, found inside the cell nucleus.
• Nucleotide : Phosphoric acid, deoxyribose sugar, and a nitrogenous base.
• DNA structure : DNA consists of two antiparallel, opposing polynucleotide strands joined by hydrogen bonds between nitrogenous bases and arranged in a helical structure.

★ Must-know

• DNA contains four nitrogenous bases:
  • adenine
  • thymine
  • cytosine
  • guanine

Further detail

📌 A DNA molecule with more cytosine–guanine pairs has greater cohesion because these pairs form three hydrogen bonds, unlike adenine–thymine pairs, which form two.

💡 Memory Hook

More G–C pairs → more hydrogen bonds → greater DNA cohesion

📖 4. Chromosomes and Genetic Organization

📝 Essential Points

📌 The two chromosomes in each human pair are similar because one was inherited from the father and the other from the mother, and they carry the same genes in corresponding regions.

• A human cell has 46 chromosomes organized into 23 pairs.

• During some stages of cell division, DNA associates with histone proteins, which wrap and condense it into chromosomes.

💡 Memory Hook

DNA → histones → condensed chromosome

📖 5. Genes and Alleles

🔑 Key Concepts & Definitions

• Gene : A hereditary unit located on a chromosome and associated with a trait such as eye colour, leg length, or hair colour.
• Allele : A version of a gene that determines a particular form of a trait, such as a specific eye, leg-length, or hair-colour form.

★ Must-know

📌 Homologous chromosomes carry the same genes in the same corresponding regions, but they may carry different alleles inherited from the father and the mother.

Further detail

📌 When two different alleles are inherited for a trait, the dominant allele determines the visible trait described in the course.

💡 Memory Hook

Gene identifies the inherited trait; allele specifies its version

📊 Synthesis Tables

Animal and Plant Cells

Feature	Animal cell	Plant cell
Basic components	Plasma membrane, nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, and ribosomes	The same main components
Cellulose wall	Absent	Present; gives a regular geometric shape
Chloroplasts	Absent	Present; enable photosynthesis