Introduction to Biology and Cell Biology

• Biology is the scientific study of life, examining the structure, function, growth, origin, evolution, distribution, and taxonomy of living organisms
• Central themes in biology include cell theory, gene theory, homeostasis, evolution, and energy
• Cell theory posits that all living organisms are composed of cells, which are the basic units of life
• Gene theory explains that traits are inherited through genes, located on chromosomes
• Homeostasis refers to the ability of an organism to maintain a stable internal environment despite external changes
• Evolution describes the change in the characteristics of a species over several generations and relies on the process of natural selection
• Living organisms require energy and raw materials to maintain homeostasis, grow, and reproduce

Cell Biology

• Cell biology studies the structure, function, and behavior of cells
• A cell is the basic unit of life, capable of independent existence
• Cells are broadly classified into prokaryotic and eukaryotic types
• Prokaryotic cells lack a nucleus and other membrane-bound organelles; bacteria and archaea are prokaryotes
• Eukaryotic cells possess a nucleus and other membrane-bound organelles, such as mitochondria and endoplasmic reticulum; protists, fungi, plants, and animals are eukaryotes
• Key eukaryotic organelles include the nucleus (containing DNA), mitochondria (producing energy), ribosomes (synthesizing proteins), endoplasmic reticulum (involved in protein and lipid synthesis), Golgi apparatus (modifying and packaging proteins), lysosomes (degrading cellular waste), and the cell membrane (controlling the entry and exit of substances)
• The cell membrane is a phospholipid bilayer with embedded proteins, regulating the transport of substances into and out of the cell
• Cell communication involves various signaling pathways, including direct contact, local signaling (paracrine and autocrine), and long-distance signaling (endocrine)
• Cell division occurs through mitosis (for growth and repair) and meiosis (for sexual reproduction)
• Mitosis results in two identical daughter cells, while meiosis results in four genetically different daughter cells
• Cellular respiration, occurring in mitochondria, converts glucose and oxygen into energy (ATP), water, and carbon dioxide
• Photosynthesis, occurring in chloroplasts (in plants and algae), converts carbon dioxide and water into glucose and oxygen using sunlight

Genetics

• Genetics is the study of heredity and variation of inherited characteristics
• Genes are units of heredity composed of DNA, coding for specific proteins or functional RNA molecules
• The genome is the complete set of genetic material in an organism
• DNA (deoxyribonucleic acid) is a double-stranded helix composed of nucleotides: adenine (A), guanine (G), cytosine (C), and thymine (T)
• RNA (ribonucleic acid) is typically single-stranded and contains uracil (U) instead of thymine (T)
• DNA replication is the process by which DNA is copied, ensuring genetic information is passed on during cell division
• Transcription is the process by which RNA is synthesized from a DNA template
• Translation is the process by which proteins are synthesized from RNA
• Mutations are changes in the DNA sequence, which can be spontaneous or induced by mutagens
• Mutations can be harmful, beneficial, or neutral in their effect on the organism
• Mendelian genetics describes the principles of inheritance as proposed by Gregor Mendel, including the laws of segregation and independent assortment
• Law of segregation states that allele pairs separate during gamete formation
• Law of independent assortment states that genes for different traits are inherited independently of each other
• Genetic engineering involves the manipulation of an organism's genes to achieve a desired trait
• Common techniques in genetic engineering include gene cloning, recombinant DNA technology, and CRISPR-Cas9 gene editing
• Genomics is the study of entire genomes, including their structure, function, evolution, and mapping
• Epigenetics refers to changes in gene expression that do not involve alterations to the DNA sequence itself but can be heritable; examples include DNA methylation and histone modification

Human Anatomy

• Human anatomy is the scientific study of the structure of the human body
• Anatomy includes gross anatomy (macroscopic structures) and microscopic anatomy (histology)
• The human body is organized into several levels: cells, tissues, organs, and organ systems
• There are four main types of tissues: epithelial, connective, muscle, and nervous
• Epithelial tissue covers body surfaces and lines body cavities and forms glands
• Connective tissue supports, connects, and separates different types of tissues and organs in the body; examples include bone, cartilage, and blood
• Muscle tissue is responsible for movement and includes skeletal, smooth, and cardiac muscle
• Nervous tissue transmits electrical signals throughout the body
• The skeletal system provides support, protection, and movement; it is composed of bones, cartilage, ligaments, and tendons
• The muscular system enables movement, maintains posture, and generates heat
• The nervous system controls and coordinates bodily functions through electrical and chemical signals; it includes the brain, spinal cord, and peripheral nerves
• The endocrine system regulates bodily functions through hormones secreted by glands; examples include the pituitary, thyroid, adrenal, and pancreas
• The cardiovascular system transports blood, oxygen, nutrients, and waste products throughout the body; it includes the heart, blood vessels, and blood
• The respiratory system facilitates gas exchange, taking in oxygen and releasing carbon dioxide; it includes the lungs, trachea, and bronchi
• The digestive system breaks down food, absorbs nutrients, and eliminates waste; it includes the mouth, esophagus, stomach, intestines, liver, and pancreas
• The urinary system filters waste from the blood and maintains fluid and electrolyte balance; it includes the kidneys, ureters, bladder, and urethra
• The reproductive system enables sexual reproduction; it includes the testes and penis in males and the ovaries, uterus, and vagina in females
• The lymphatic system supports the immune system, removes waste, and absorbs fats; it includes lymph nodes, lymphatic vessels, and lymphoid organs (spleen and thymus)
• The integumentary system protects the body, regulates temperature, and provides sensory information; it includes the skin, hair, and nails