Biology: Cell Structure and Function

Cell Structure and Function

• Cell Theory:

  • All living organisms are composed of cells.
  • Cells are the basic unit of life.
  • All cells arise from pre-existing cells.

• Prokaryotic Cells:

  • Lack a nucleus and membrane-bound organelles.
  • DNA is circular and located in the nucleoid.
  • Examples: Bacteria and Archaea.

• Eukaryotic Cells:

  • Have a nucleus and membrane-bound organelles.
  • DNA is linear and packaged in chromosomes.
  • Examples: Animals, plants, fungi, and protists.

Genetics

• DNA Structure:

  • Double helix composed of nucleotides (A, T, C, G).

• Gene Expression:

  • Transcription (DNA to mRNA).
  • Translation (mRNA to protein).

• Mendelian Genetics:

  • Principles: Segregation and Independent Assortment.
  • Traits: Dominant vs. recessive alleles.

Evolution

• Natural Selection:

  • Mechanism of evolution proposed by Charles Darwin.
  • Organisms better adapted to their environment tend to survive and reproduce.

• Speciation:

  • Process by which new species arise.
  • Can occur through methods like allopatric or sympatric speciation.

Ecology

• Ecosystem Components:

  • Biotic factors: living organisms.
  • Abiotic factors: non-living elements (water, soil, climate).

• Food Webs:

  • Energy flow through trophic levels (producers, consumers, decomposers).

• Biomes:

  • Large ecological areas (e.g., deserts, forests, tundras) characterized by specific climate conditions and organisms.

Human Biology

• Organ Systems:

  • Major systems include circulatory, respiratory, nervous, endocrine, digestive, and reproductive.

• Homeostasis:

  • Maintaining stable internal conditions (e.g., temperature, pH).

• Immune System:

  • Protects body from pathogens (bacteria, viruses).
  • Involves innate (first-line defenses) and adaptive (specific responses) immunity.

Plant Biology

• Photosynthesis:

  • Process by which plants convert sunlight into chemical energy.
  • Occurs in chloroplasts; overall equation: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2.

• Plant Growth:

  • Controlled by hormones (auxins, gibberellins, cytokinins).
  • Adaptations to environments (e.g., xerophytes in deserts).

Microbiology

• Bacteria:

  • Classified by shape (cocci, bacilli, spirilla) and staining properties (Gram-positive, Gram-negative).

• Viruses:

  • Non-cellular entities that require a host to replicate.
  • Composed of genetic material surrounded by protein coat.

• Fungi:

  • Absorb nutrients through external digestion.
  • Important decomposers in ecosystems.

Biotechnology

• Genetic Engineering:

  • Manipulating DNA to transfer genes between organisms.

• CRISPR:

  • A powerful tool for genome editing that allows precise alterations to DNA sequences.

• Cloning:

  • Producing a genetically identical organism from a single cell.

Cell Structure and Function

• All living organisms are made up of cells, the fundamental unit of life.
• Cells arise from pre-existing cells.
• Prokaryotic cells lack a nucleus and membrane-bound organelles, their circular DNA is located in the nucleoid. Bacteria and Archaea are examples.
• Eukaryotic cells contain a nucleus and membrane-bound organelles. Their DNA is linear and organized into chromosomes. Animals, plants, fungi, and protists are examples.

Genetics

• DNA, a double helix composed of nucleotides (adenine, thymine, cytosine, and guanine), carries genetic information.
• Gene expression translates genetic information into functional proteins through transcription (DNA to messenger RNA, mRNA) and translation (mRNA to protein).
• Mendelian Genetics explains the inheritance of traits based on the principles of segregation (alleles separate during gamete formation) and independent assortment (alleles for different traits separate independently). Traits can be dominant, expressed when a single copy is present, or recessive, requiring two copies for expression.

Evolution

• Natural Selection, proposed by Charles Darwin, is the driving force of evolution: individuals with traits better suited to their environment are more likely to survive and reproduce, passing on those beneficial traits to their offspring.
• Speciation is the process by which new species evolve from existing ones. This can happen through allopatric speciation, where populations are separated geographically, or sympatric speciation, where new species arise within the same geographic area.

Ecology

• Ecosystems consist of biotic factors (living organisms) and abiotic factors (non-living elements like water, soil, and climate).
• Food webs illustrate the flow of energy through different trophic levels: producers (photosynthetic organisms), consumers (herbivores and carnivores), and decomposers (break down organic matter).
• Biomes are large ecological areas characterized by specific climate conditions and adapted communities of organisms, such as deserts, forests, and tundras.

Human Biology

• The human body is organized into interconnected organ systems, including the circulatory, respiratory, nervous, endocrine, digestive, and reproductive systems.
• Homeostasis maintains stable internal conditions, like temperature and pH, essential for survival.
• The immune system protects the body from pathogens (bacteria and viruses) through innate immunity (first-line defenses) and adaptive immunity (specific responses tailored to individual pathogens).

Plant Biology

• Photosynthesis, the process by which plants convert sunlight into chemical energy, occurs in chloroplasts. The overall reaction is: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
• Plant growth is regulated by hormones like auxins, gibberellins, and cytokinins. Plants exhibit adaptations to various environments, such as xerophytes in deserts.

Microbiology

• Bacteria are classified by shape (cocci, bacilli, spirilla) and staining properties (Gram-positive, Gram-negative).
• Viruses are non-cellular entities that require a host cell to replicate. They consist of genetic material encased in a protein coat.
• Fungi are heterotrophs that absorb nutrients through external digestion, playing a significant role in decomposition within ecosystems.

Biotechnology

• Genetic engineering involves manipulating DNA to transfer genes between organisms.
• CRISPR is a powerful tool for genome editing that allows for precise changes to DNA sequences.
• Cloning is the process of producing a genetically identical organism from a single cell.

Explore the fundamental concepts of cell biology, including the differences between prokaryotic and eukaryotic cells. This quiz covers cell theory, DNA structure, gene expression, and principles of Mendelian genetics. Test your knowledge on how these components contribute to the broader understanding of evolution and natural selection.