Cell Biology: Prokaryotic Cells

• Biology is the scientific study of life, examining the structure, function, growth, origin, evolution, and distribution of living organisms.
• It encompasses a broad range of fields, including anatomy, physiology, cell biology, genetics, ecology, and evolution.
• Biology seeks to understand the fundamental principles governing living systems and how they interact with their environment.
• The cell is the basic structural and functional unit of all known living organisms.
• Cell biology is the study of cells, their structure, function, and behavior.
• It includes examining cell organelles, cell division, cell signaling, and cell metabolism.
• Cell theory states that all living organisms are composed of one or more cells, the cell is the basic unit of life, and new cells arise from pre-existing cells.
• Cells are broadly classified into two types: prokaryotic and eukaryotic.

Prokaryotic Cells

• These cells lack a nucleus and other membrane-bound organelles.
• Bacteria and archaea are prokaryotes.
• Prokaryotic cells are generally smaller and simpler in structure than eukaryotic cells.
• They have a cell wall, a plasma membrane, cytoplasm, ribosomes, and a nucleoid region containing DNA.

Eukaryotic Cells

• Eukaryotic cells have a nucleus and other membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus.
• Eukaryotic cells are found in protists, fungi, plants, and animals.
• They are typically larger and more complex than prokaryotic cells.
• The nucleus contains the cell's DNA organized into chromosomes.

Cell Membrane

• The cell membrane, also known as the plasma membrane, is a selectively permeable barrier that surrounds the cell.
• It is composed of a lipid bilayer with embedded proteins.
• The cell membrane regulates the movement of substances into and out of the cell.
• It plays a role in cell signaling and cell adhesion.

Cytoplasm

• The cytoplasm is the gel-like substance within the cell, excluding the nucleus.
• It contains various organelles, cytoskeleton, and cytosol.
• Many metabolic reactions occur in the cytoplasm.

Nucleus

• The nucleus is the control center of the cell and contains the cell's genetic material (DNA).
• It is surrounded by a double membrane called the nuclear envelope.
• The nucleus regulates gene expression and controls cell growth and reproduction.

Mitochondria

• Mitochondria are the powerhouses of the cell, responsible for generating energy through cellular respiration.
• They have a double membrane structure, with an inner membrane folded into cristae.
• Mitochondria contain their own DNA and ribosomes.

Endoplasmic Reticulum (ER)

• The endoplasmic reticulum is a network of membranes involved in protein and lipid synthesis.
• There are two types of ER: rough ER (RER) and smooth ER (SER).
• RER is studded with ribosomes and involved in protein synthesis and modification.
• SER is involved in lipid synthesis, detoxification, and calcium storage.

Golgi Apparatus

• The Golgi apparatus processes and packages proteins and lipids synthesized in the ER.
• It consists of flattened membrane-bound sacs called cisternae.
• Proteins and lipids are modified, sorted, and packaged into vesicles for transport to other parts of the cell or for secretion.

Lysosomes

• Lysosomes are organelles containing digestive enzymes.
• They break down cellular waste, debris, and foreign materials.
• Lysosomes play a role in autophagy, the process of degrading and recycling cellular components.

Cytoskeleton

• The cytoskeleton is a network of protein filaments that provides structural support to the cell.
• It is involved in cell movement, cell division, and intracellular transport.
• The cytoskeleton consists of three main types of filaments: microfilaments, intermediate filaments, and microtubules.

Cell Division

• Cell division is the process by which a cell divides into two or more daughter cells.
• There are two main types of cell division: mitosis and meiosis.
• Mitosis is the process of cell division in somatic cells, resulting in two identical daughter cells.
• Meiosis is the process of cell division in germ cells, resulting in four genetically different haploid daughter cells (gametes).

Genetics

• Genetics is the study of heredity and variation of inherited characteristics.
• It examines how traits are passed from parents to offspring.
• Genes are the basic units of heredity and are composed of DNA.

DNA

• DNA (deoxyribonucleic acid) is the molecule that carries genetic information in all known living organisms.
• It is a double-stranded helix composed of nucleotides.
• Each nucleotide consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base.
• The four nitrogenous bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T).
• A pairs with T, and G pairs with C.

RNA

• RNA (ribonucleic acid) is a single-stranded molecule involved in protein synthesis.
• It is similar to DNA but contains ribose sugar instead of deoxyribose and uracil (U) instead of thymine (T).
• There are several types of RNA, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

Chromosomes

• Chromosomes are structures within the nucleus that carry genetic information.
• They are composed of DNA tightly coiled around proteins called histones.
• Humans have 46 chromosomes, arranged in 23 pairs.

Genes

• Genes are segments of DNA that code for specific proteins or RNA molecules.
• They are the fundamental units of heredity.
• Genes determine an organism's traits.

Genotype and Phenotype

• Genotype refers to the genetic makeup of an organism.
• Phenotype refers to the observable characteristics of an organism, which are influenced by both genotype and environmental factors.

Alleles

• Alleles are different versions of a gene.
• Organisms inherit two alleles for each gene, one from each parent.
• Alleles can be dominant or recessive.

Mendelian Genetics

• Gregor Mendel is considered the father of genetics.
• He formulated the basic principles of heredity through his experiments with pea plants.
• Mendel's laws include the law of segregation and the law of independent assortment.

Law of Segregation

• The law of segregation states that during gamete formation, the two alleles for each gene separate, so that each gamete carries only one allele for each gene.

Law of Independent Assortment

• The law of independent assortment states that alleles for different genes segregate independently of one another during gamete formation.

Mutations

• Mutations are changes in the DNA sequence.
• They can occur spontaneously or be caused by environmental factors such as radiation or chemicals.
• Mutations can be harmful, beneficial, or neutral.

Genetic Variation

• Genetic variation is the differences in DNA among individuals.
• It is essential for evolution and adaptation.
• Genetic variation arises through mutations, genetic recombination, and gene flow.

Gene Expression

• Gene expression is the process by which the information encoded in a gene is used to synthesize a functional gene product, such as a protein or RNA.
• It involves two main steps: transcription and translation.

Transcription

• Transcription is the process by which RNA is synthesized from a DNA template.
• It is catalyzed by RNA polymerase.
• The resulting RNA molecule is called messenger RNA (mRNA).

Translation

• Translation is the process by which the information encoded in mRNA is used to synthesize a protein.
• It occurs on ribosomes.
• Transfer RNA (tRNA) molecules bring amino acids to the ribosome, where they are linked together to form a polypeptide chain.

Genetic Engineering

• Genetic engineering is the process of manipulating an organism's genes.
• It involves techniques such as gene cloning, gene editing, and gene therapy.
• Genetic engineering has applications in medicine, agriculture, and industry.

Genomics

• Genomics is the study of entire genomes, including the complete set of genes and non-coding DNA sequences.
• It involves techniques such as DNA sequencing and genome mapping.
• Genomics has applications in understanding genetic diseases, developing new therapies, and improving crop yields.