Cell Biology & Genetics Overview

Cell Theory
- All living organisms are composed of cells.
- The cell is the basic unit of life.
- All cells arise from pre-existing cells.
Types of Cells
- Prokaryotic: No nucleus, smaller, simpler (e.g., bacteria).
- Eukaryotic: Contains a nucleus, larger, more complex (e.g., plant and animal cells).
Cell Organelles
- Nucleus: Contains DNA, controls cell activities.
- Mitochondria: Powerhouse of the cell, ATP production.
- Ribosomes: Protein synthesis.
- Endoplasmic Reticulum: Rough (with ribosomes) and Smooth (lipid synthesis).
- Golgi Apparatus: Modifies and packages proteins.
- Lysosomes: Digestion and waste removal.
Cell Membrane
- Phospholipid bilayer, selectively permeable.
- Proteins embedded for transport and signaling.

Basic Concepts
- Gene: A unit of heredity, composed of DNA.
- Alleles: Different forms of a gene.
- Genotype: Genetic makeup.
- Phenotype: Observable characteristics.
Mendelian Genetics
- Dominant and recessive traits.
- Law of Segregation: Alleles segregate during gamete formation.
- Law of Independent Assortment: Genes for different traits can segregate independently.
DNA Structure and Replication
- Double helix composed of nucleotides (adenine, thymine, cytosine, guanine).
- Semi-conservative replication process.
Mutations
- Changes in DNA sequence can lead to genetic diversity but may cause diseases.

Theory of Evolution
- Proposed by Charles Darwin.
- Natural selection: Organisms better adapted to their environment tend to survive and reproduce.
Key Concepts
- Common descent: All species share a common ancestor.
- Speciation: Process by which new species arise.
- Adaptation: Traits that improve survival and reproduction.
Evolutionary Evidence
- Fossils, comparative anatomy, molecular biology, and embryology.
Mechanisms of Evolution
- Genetic drift, gene flow, and mutation contribute to genetic variation and evolution.

Major Systems
- Skeletal System: Provides structure, support, and protection; produces blood cells.
- Muscular System: Facilitates movement, posture, and heat production.
- Circulatory System: Transports blood, nutrients, gases, and waste.
- Respiratory System: Facilitates gas exchange (oxygen and carbon dioxide).
- Digestive System: Breaks down food, absorbs nutrients, and eliminates waste.
- Nervous System: Controls body functions and responses through signaling.
- Endocrine System: Regulates body processes through hormones.
- Immune System: Defends against pathogens and diseases.
- Reproductive System: Produces gametes and hormones, facilitates reproduction.
Key Organs
- Heart, lungs, liver, kidneys, brain, stomach, intestines, skin.
Homeostasis
- Maintenance of a stable internal environment despite external changes.

Cell Theory states all living organisms are made of cells, the cell is the fundamental unit of life, and all cells originate from pre-existing cells.
Prokaryotic cells lack a nucleus, are generally smaller, and simpler; examples include bacteria.
Eukaryotic cells have a nucleus, are larger, and more intricate, found in plants and animals.
The nucleus houses DNA and regulates cell activities, playing a critical role in cell function.
Mitochondria are known as the cell's powerhouse, responsible for ATP production, supplying energy.
Ribosomes are essential for protein synthesis, translating genetic information into proteins.
The Endoplasmic Reticulum consists of Rough ER, involved in protein synthesis, and Smooth ER, which synthesizes lipids.
The Golgi Apparatus modifies and packages proteins for distribution.
Lysosomes contain enzymes for digestion and removal of cellular waste.
The cell membrane, composed of a phospholipid bilayer, is selectively permeable, allowing certain substances to pass, with embedded proteins facilitating transport and signaling.

A gene represents a unit of heredity made of DNA, determining traits in organisms.
Alleles are different variations of a gene that can influence specific traits.
Genotype refers to the genetic constitution of an organism, while phenotype encompasses observable traits.
Mendelian Genetics involves dominant and recessive traits with key laws including:
- Law of Segregation: Alleles segregate during the formation of gametes.
- Law of Independent Assortment: Different genes for different traits segregate independently during gamete formation.
DNA has a double helix structure made of nucleotides (adenine, thymine, cytosine, guanine) and replicates through a semi-conservative process.
Mutations may alter DNA sequences, leading to genetic diversity, though they can also result in diseases.

The Theory of Evolution, proposed by Charles Darwin, explains how natural selection leads to the survival and reproduction of organisms better adapted to their environments.
Key concepts include:
- Common descent, indicating that all species share a common ancestor.
- Speciation, the process through which new species develop.
- Adaptation, traits enhancing survival and reproduction.
Evolutionary evidence is gathered from fossils, comparative anatomy, molecular biology, and embryology.
Evolution is influenced by mechanisms such as genetic drift, gene flow, and mutation that create genetic variation.

Major bodily systems include:
- Skeletal System: Provides structure, support, protection, and produces blood cells.
- Muscular System: Facilitates movement, supports posture, and generates heat.
- Circulatory System: Responsible for the transport of blood, nutrients, gases, and waste.
- Respiratory System: Enables gas exchange of oxygen and carbon dioxide.
- Digestive System: Breaks down food, absorbs nutrients, and eliminates waste.
- Nervous System: Controls bodily functions and responses through signaling.
- Endocrine System: Manages body processes via hormone regulation.
- Immune System: Protects against pathogens and diseases.
- Reproductive System: Produces gametes and hormones, essential for reproduction.
Key organs include the heart, lungs, liver, kidneys, brain, stomach, intestines, and skin.
Homeostasis refers to the maintenance of a stable internal environment despite external fluctuations, crucial for proper bodily function.