1.1 intro to cells / cell theory Flashcards
cell theory?
living organisms composed of cells; cells as basic units of life; cells can only exist from pre-existing cells [implication?]; 1 or more cells
examples to question cell theory
- striated muscle cell
- giant algae (acetabularia)
- aseptate fungal hyphae
why does skeletal muscle not fit the cell theory?
challenges idea that cells are small and only contain 1 nuclei
- made up of muscle fibres which are enclosed in a membrane (fits)
- but they are much larger than most cells - 300mm+ (doesn’t fit)
- and they contain hundreds of nuclei [multinucleated] (doesn’t fit)
why does giant algae (acetabularia) not fit cell theory?
challenges idea that cells are small
- can grow up to 100mm in diameter
- only 1 nucleus
- complex structures like rhizoids (root-like structures, stalk and cap on top)
why does aseptate fungal hyphae not fit cell theory?
challenges idea that individual cells form basic units of life
- hyphae: long filaments of growth of fungal organisms w numerous branches
- hyphae can be septate (separated into sections) or aseptate (not in sections)
- aseptate hyphae: long, uninterrupted structures with numerous nuclei, and do not appear in the form of being made up of many conventional cells
- continuous cytoplasm
functions of life in cell
MERIGRAN Movement Excretion Respiration Irritability (response) Growth Reproduction Adaptability (regulation due to external changes) Nutrition (obtaining)
functions of life in paramecium
Paramecium:
• Movement – wave action of cilia on cell membrane allows paramecium to move around
• Excretion – cell membrane regulates the movement of molecules in and out of the cell, including the expulsion of metabolic wastes
• Respiration – mitochondria present within paramecium to facilitate cellular respiration
• Irritability (response) – proteins present on cell membrane help detect when contact is made with food (yeast, bacteria, etc) and cilia sweeps food towards the cell mouth
• Growth – Paramecium assimilates nutrients from food for growth
• Reproduction – via binary fission
• Adaptability – Contractile vacuoles can take in and expel water to maintain osmotic potential within the cell
• Nutrition – ingestion of food at cell mouth via phagocytosis and the formation of food vacuoles
functions of life in chlamydomonas
Chlamydomonas:
• Movement – presence of flagella allows for movement towards light
• Excretion – cell membrane regulates the movement of molecules in and out of the cell, including the expulsion of metabolic wastes
• Respiration – mitochondria present within cell to facilitate cellular respiration
• Irritability (response) – Contains an eyespot, an organelle reponsible for light detection
• Growth – Chlamydomonas assimilates nutrients from photosynthesis and environment for growth
• Reproduction – via mitosis
• Adaptability – Contractile vacuoles can take in and expel water to
maintain osmotic potential within the cell
• Nutrition – carries out photosynthesis via chloroplasts
2 constraints to cell size
• Large enough to store genetic material, resources (nutrients) and
cellular structures that allows for efficient adaptation to life on earth
• Small enough to maintain a high surface area to volume ratio for rapid exchanges of molecules with the external cellular environment
adaptations to maintain high surface area to volume ratio
• Cell division (increase cell numbers)
• Compartmentalisation due to presence of membrane bound
organelles
• Folding of cell membrane (e.g. microvilli and crista in mitochondria)
• Extensions (root hair cell)
what is emergent property
Emergent properties arise when the interaction of individual components produce new functions
example of a multicellular organism with emergent property from interaction of cellular components
- Caenorhabditis elegans is a multicellular organism that is able to carry out life functions due to the presence of specialised cells
- Almost one third of cells are nerve cells for coordination and response
- Muscle cells aid in locomotion by contraction to allow the organism to move by wriggling
- Presence of reproductive cells (both male and female)
- Distinct move and anus and intestinal cells to aid in digestion
- Emergent property – the organism is able to carry out complex functions of life, with these properties arising from the combined effort of multiple specialised cells
organisation of multicellular organisms (how cells group)
Cells may be grouped together to form tissues
Organs are then formed from the functional grouping of multiple tissues
Organs that interact may form organ systems capable of carrying out specific body functions
Organ systems collectively carry out the life functions of the complete organism
how do specialised cells develop
by differentiation [process during development where newly formed cells become more specialised and distinct from one another as they mature]
all cells share exact same genome
cell specialisation: some genes are expressed and not others
signals sent to deactivate certain genes and others are activated
totipotent stem cells do not have any genes deactivated; are able to turn into any other cell
what are stem cells?
undifferentiated / unspecialised cells that can replicate and have the ability to differentiate into specialised cell types
