Transcript
CELL THEORY
• ACCORDING TO CELL THEORY, ALL LIVING THINGS ARE COMPOSED OF CELLS
• HUMANS, E. COLI, SPIDERS, ALGAE – ALL OF THEM HAVE CELLS
• CELLS ARE CONSIDERED THE BASIC BUILDING BLOCKS OF LIFE
UNICELLULAR ORGANISMS
• ORGANISMS CONSISTING OF ONLY ONE CELL CAN CARRY
OUT ALL THE FUNCTIONS OF LIFE
• THESE INCLUDE BACTERIA AND PROKARYOTIC CELLS
• THE MAIN FUNCTIONS OF LIFE INCLUDE: METABOLISM,
RESPONSE TO CHANGING ENVIRONMENTS, HOMEOSTASIS,
GROWTH, REPRODUCTION AND NUTRITION
SURFACE AREA TO VOLUME RATIO
• CELLS MOVE THEIR NUTRIENTS, PROTEINS AND OTHER MOLECULES THROUGH THEIR
CYTOPLASM USING DIFFUSION
• AS CELLS GET LARGER, IT TAKES LONGER FOR NEEDED MOLECULES TO DIFFUSE
• THE RATIO CREATES A LIMIT ON THE POTENTIAL SIZE OF CELLS
𝑹𝒂𝒕𝒊𝒐 =𝑺𝒖𝒓𝒇𝒂𝒄𝒆 𝑨𝒓𝒆𝒂
𝑽𝒐𝒍𝒖𝒎𝒆
EMERGENT PROPERTIES
• ON THEIR OWN, INDIVIDUAL CELLS CAN PERFORM CERTAIN FUNCTIONS
• HOWEVER, WHEN THEY WORK TOGETHER IN A MULTICELLULAR
ORGANISMS, THE TEAMWORK LEADS TO NEW PROPERTIES
• THEY ARE CALLED ‘EMERGENT PROPERTIES’
• FOR EXAMPLE, CELLS IN THE HEART WORK TOGETHER TO CREATE A
PUMP: A SINGLE CELL COULD NOT PUMP BLOOD ON ITS OWN
SPECIALISATION
• ALL THE CELLS IN AN ORGANISM HAVE THE COMPLETE GENOME
(GENETIC SEQUENCE)
• HOWEVER, WHEN CELLS DIFFERENTIATE (SPECIALISE), THEY ONLY
EXPRESS SOME OF THE GENES, AND MAY TURN OFF OTHERS
• THE DIFFERENT EXPRESS CAUSES THE VARIOUS TYPES OF CELLS
• THE CELLS CAN THEN FORM SPECIALISED TISSUES LIKE SKIN, THE
STOMACH, BRAIN OR LIVER
STEM CELLS
• STEM CELLS ARE UNDIFFERENTIATED CELLS
• THEY ARE CAPABLE OF BECOMING ANY TYPE OF CELL
• MAINLY FOUND IN EMBRYOS: THESE CELLS CAN BECOME ABSOLUTELY ANY
TYPE OF CELL
• ADULT STEM CELLS ARE MORE LIMITED AND CAN ONLY BECOME SELECT CELL
TYPES
THERAPEUTIC STEM CELLS
• STEM CELLS CAN BE USED FOR TISSUE REPAIR AND ORGAN REPLACEMENT
• THEY HAVE THE POTENTIAL TO CURE DISEASES AND REPAIR INJURIES (I.E. SPINAL INJURY,
CYSTIC FIBROSIS)
• HOWEVER, THERE IS CONTROVERSY, SINCE THE BEST STEM CELLS ARE
HARVESTED FROM EMBRYOS
• THERE HAS BEEN CULTURAL AND RELIGIOUS OBJECTIONS TO STEM
CELL RESEARCH
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