1. cells

• Cells and development
• Imaging development
• Cell


  Our earliest understanding - we had no idea that our bodies were actually made up of trillions of smaller units
• 3 basic components of the original Cell Theory

  • All organisms are composed of cells
  • Cell is the basic unit of life
  • Cells are produced by the division of pre-existing cells
• Modern cell theory


  • Cells contains hereditary information that can be passed on
  • All cells are essentially comprised of the same chemical mix
  • Cells carry out all the basic chemical and physiological processes within themselves (movement digestion etc)
  • Cellular activity depends on the activities of subcellular structures
• Cells are the basic building blocks of all living things, from micro-organisms to humans
• Fertilisation of oocyte


  1. Single cell

  2. Multicellular adults
• The average human being is composed of around 100 trillion cells
• 300 million cells die in the body every minute
• Each cell has about 10,000 times as many molecules as the Milky way has stars
• Efficiency


  Surface area increased, Nutrient/oxygen supply and waste disposal
• Specialisation


  Numerous small cells allow for specialisation, different cells have different functions
• Questions - Part 1

  • What are the four major points of modern cell theory?
  • Do cells work in isolation?
  • Why do we need different cell types?
• Plasma membrane


  Fluid mosaic model, separates living cells from nonliving surroundings, selectively permeable, Transport of selected molecules, incorporates receptors that allows the cell to respond to signals from outside

  
• Structure of the cell membrane - phospholipids, proteins and other macromolecules, around 7.5-10nm thick

  
• Cell membrane


  Critical for cell-cell communication
• A single signal reaching the cell membrane

  Can lead to many downstream alterations in cellular behaviour
• Cilia


  Protrusions from the cell surface, Motile - eg respiratory surfaces, fallopian tubes, Immotile - involved in cellular signaling
• Flagella


  Longer and fewer of them than cilia, Involved in cellular movement, and movement of materials along the outside of the cell
• Cilia were ignored for a long time, and thought to be an evolutionary leftover, but we have now associated a number of developmental disorders to issues of the cilia - the "ciliopathies"
• Oral-facial-digital (OFD) syndrome type I


  • X-linked, predominantly observed in females, multiple developmental abnormalities
• Cytoplasm


  Location of many of the cellular organelles, many complex cellular chemical reactions/metabolic pathways take place here
• Mitochondria


  Powerhouse of the cell - cellular metabolism, eg Krebs cycle (production of ATP), many in a single cell (300->1000 per cell), passed down maternally only, second location of DNA in a cell, genes code for many proteins required for mitochondrial function, mitochondria-rich cell types include skeletal and cardiac muscle, sperm tail (midpiece), renal tubular cells
• Defects in mitochondrial function can be minor - "exercise intolerance" or serious like Leber hereditary optic neuropathy (LHON)
• Endoplasmic reticulum - rough and smooth


  Interconnecting channels associated with storage, synthesis and transport within the cell, Rough ER - translation of mRNA into proteins by ribosomal complexes, production and processing of specific proteins, Smooth ER - site of carbohydrate metabolism, ion regulation, synthesis and metabolism of steroids and lipids, and some drug detoxification
• Disorders associated with aberrations in ER function include cerebral ischaemia, sleep apnoea, Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, the prion diseases, and familial encephalopathy with neuroserpin inclusion bodies
• Golgi


  Large cellular component, appears like a "stack of pancakes", sorts, modifies and packages cellular products before sending them into or out of the cell
• Vacuole


  Cellular space for water/other storage
• Lysosome


  A vesicle, produced by the Golgi, contain a variety of digestive enzymes, "suicidal bags of the cell"
• Peroxisome


  Bud off from the endoplasmic reticulum, rid host of toxins and break down long chain fatty acids
• Nucleus


  Contains the majority of the cellular DNA, DNA is wrapped around histone proteins, known as CHROMATIN, in non-dividing cells chromatin is dispersed throughout the nucleus in two major forms - heterochromatin (tightly packed, transcriptionally inactive) and euchromatin (loose, open, allows active transcription)
• Many disruptions to development are associated with mutations to the genomic DNA or with the regulation of gene expression
• RNA


  Involved in the regulation of gene expression
• Summary I


  • There are many different parts to the cell, all of which play a critical role during normal human development
• Questions - Part 2

  • What is contained within the cytoplasm?
  • What protects the nucleus from the external environment?
  • Why does the nucleus need protecting?
  • What are the organelles presented in this section?
  • What is the function of each of the organelles presented?
• Cellular differentiation and specialisation

  The concept of differentiation, particularly during development, Transcriptional control of cellular identity
• Totipotent, Pluripotent, Multipotent, Nullipotent (terminally differentiated)


  Cellular differences are the result of differences in gene expression, some genes expressed in all cells, others in specific cell types, specialised gene expression supports the development of specialised characteristics
• Transcription factors


  Proteins that directly regulate and drive gene expression by interacting with the regulatory region of a gene - its promoter, for a gene to be activated it requires the right transcription factors to be present in the right cells, in the right compartment of the cells (ie the nucleus), at the right time, some transcription factors are found in many cell types, some are specific to a particular cell type
• Transcription factors


  Proteins that directly regulate and drive gene expression by interacting with the regulatory region of a gene - its promoter
• Transcription factors


  • For a gene to be activated, it requires the right transcription factors to be present in the right cells, in the right compartment of the cells (ie the nucleus), at the right time
  • Some transcription factors are found in many cell types, some are specific to a particular cell type