Cell Biology and Microorganisms

Endoplasmic Reticulum

  • Organelles in eukaryotic organisms only

  • Two types:

    • Rough Endoplasmic Reticulum (RER)

    • Contains ribosomes

    • Responsible for protein synthesis

    • Smooth Endoplasmic Reticulum (SER)

    • Lacks ribosomes

    • Responsible for synthesis and metabolism of lipids and sugars

Golgi Apparatus

  • Main purpose: packaging and shipping of products made in the endoplasmic reticulum

  • Operates as the shipping department of the cell

  • Materials made in the endoplasmic reticulum (ER) are sent to the Golgi in vesicles (membrane-bound bubbles) for processing and distribution

  • Processing might include adding address labels to ensure proper distribution

  • Final product could include sugars, lipids, proteins, and toxins

Nature's Assembly Line

  • Key organelles that contribute:

    • Nucleus

    • Contains DNA, the material that holds genetic instructions

    • Endoplasmic Reticulum

    • Manufactures proteins and lipids

    • Golgi Apparatus

    • Packages and distributes those products

  • Analogy: Like an assembly line in a factory

    • Example: DNA in the nucleus gives instructions for producing cell phones,
      which are proteins made in the ER, then shipped out by Golgi

Mitochondria

  • Known as the powerhouse of the cell

  • Responsible for energy production through aerobic respiration

  • Energy source: Combines sugars with oxygen to produce ATP (adenosine triphosphate)

  • ATP is the energy currency of the cell, stored in its phosphate bonds

  • Aerobic means it requires oxygen for this process

  • Notable trait: abundant in cells that need high energy

Cytoskeleton

  • Only present in eukaryotic cells without a cell wall

  • Functions similarly to a skeleton in vertebrates

  • Framework of long, thin protein filaments providing structure and shape

  • Used for cellular transport, analogous to roadways

  • Components can move and allow proteins to traverse within the cell

  • Vital in all eukaryotic cells, particularly those lacking a rigid outer wall

Eukaryotic Microorganisms

  • Focus on fungi, protozoa, and helminths

  • Fungi:

    • Pathogenic fungi exist but many are beneficial (e.g., mushrooms in ecosystems)

    • Example of pathogenic fungi: Yeast infections (e.g., thrush)

    • Example of beneficial fungi: Penicillium mold used to produce penicillin

    • Two forms of fungi:

    • Yeasts: Unicellular, reproduce by budding (asexual)

    • Molds: Multicellular, reproduce by spore production (can be sexual or asexual)

Fungal Nutrition

  • Heterotrophic Organisms: Acquire food by consuming other organisms

    • Heterotrophs are known as the consumers in an ecosystem

    • Key terms:

      • SAPROBES: Feed on dead or decaying matter

      • PARASITES: Feed on living hosts, causing harm

Pathogenic Roles of Fungi

  • True Pathogens: Cause disease in healthy individuals often (e.g., athlete's foot, ringworm)

  • Opportunistic Pathogens: Require an immunocompromised host to cause disease (e.g., vaginal yeast infections, thrush in babies)

Protozoa

  • Informal category of organisms that don't fit into fungi, plants, or bacteria

  • Generally unicellular and heterotrophic

  • Key diseases:

    • Trichomonas vaginalis: Sexually transmitted infection

    • Giardia: Waterborne infection causing diarrhea

    • Malaria: Caused by Plasmodium, transmitted via mosquitoes

  • Life Cycle: Usually complex with multiple stages and hosts

Helminths

  • Group of worms infecting humans and other animals

  • Classified as animals

  • Reproductive cycle mainly involves laying microscopic eggs, often in a host's gastrointestinal tract

  • Notable examples:

    • Pinworms: Common in children, transmitted via contact after scratching

Viruses and Prions

  • Acellular Organisms: Not made of cells; not placed on the tree of life

  • Can infect any cellular organism

  • Viruses:

    • Obligate intracellular pathogens: Need host cells for replication

    • Historical importance: Notable pandemics caused by viruses include COVID-19, Ebola

    • Structure consists of genetic material (DNA or RNA, not both) surrounded by a protein coat

Viral Replication Steps

  1. Attachment: Virus binds to host cell

  2. Entry: Virus enters the host cell

  3. Replication and Gene Expression: Uses host cell to replicate and express viral proteins

  4. Assembly: New viral particles are assembled

  5. Release: Viruses are released from the host cell, often killing it

Types of Viral Infections

  • Acute Viral Infections: Short-lived; no integration of viral genome (e.g., flu)

  • Latent Viral Infections: Integrated genome remains dormant; no symptoms until reactivation (e.g., herpes)

  • Chronic Viral Infections: Continuous replication; persistent symptoms (e.g., HIV)

Cultivation of Viruses

  • Viruses must be cultured within live host cells

  • Techniques:

    • Inoculation in animal models or embryos (e.g., chicken eggs) for producing vaccines

    • HeLa Cells: Immortal cell line derived from Henrietta Lacks, significant for scientific research and vaccine development