1.1 (Introduction to Cells) Flashcards
Calculate magnification formula
Scale bar label
What does the cell theory state?
- All living things are composed of cells (or cell products)
- The cell is the smallest unit of life
- Cells only arise from pre-existing cells
Cell theory exception: striated muscle
- Challenges idea that a cell has one nucleus
- Muscle cells have more than one nucleus per cell
- Muscle Cells called fibres can be very long (300mm)
- Surrounded by a single plasma membrane but they are multi-nucleated (many nuclei)
- Does not conform to the standard view of a small single nuclei within a cell
Cell theory exception: aseptate fungal hyphae
- Challenges the idea that a cell is a single unit.
- Very large with many nuclei and a continuous cytoplasm
- Tubular system of hyphae form dense networks called mycelium
- Multi-nucleated
- Cell walls composed of chitin
- Cytoplasm is continuous along the hyphae with no end cell wall or membrane
Cell theory exception: giant algae
- Single-celled organism challenges the idea that cells must be simple in structure and small in size
- Gigantic in size (5 – 100mm)
- Complex in form, consists of three anatomical parts:
Bottom rhizoid (that resembles a set of short roots)
Long stalk
Top umbrella of branches that may fuse into a cap - Single nucleus is located in the rhizoid
Functions of life.
- Metabolism - web of all the enzyme-catalysed reactions in a cell or organism, e.g. respiration
- Response - living things can respond to and interact with the environment
- Homeostasis - maintenance and regulation of internal cell conditions, e.g. water and pH
- Growth - living things can grow or change size / shape
- Excretion – the removal of metabolic waste
- Reproduction - living things produce offspring, either sexually or asexually
- Nutrition – feeding by either the synthesis of organic molecules (e.g. photosynthesis) or the absorption of organic matter
SA:Vol ratio
Larger SA;Vol ratio means the cell can act more efficiently: for every unit of volume that requires nutrients or produces waste, there is more membrane to serve it
How do organisms maximise SA:Vol ratio?
- Cells divide
- Cells compartilise
- Organelles are made of membranes
- Some organs fold up
- Alveoli in lungs
- Roots are long and branched with root hairs
What are emergent properties?
Emergent properties arise from the interaction of component parts. The whole is greater than the sum of its parts.
Specialised cells.
- In humans 220 distinct highly specialised cell types have been recognised
- All specialised cells and the organs constructed from them have developed as a result of differentiation
Stem cells.
Unspecialised cells that can:
- Continuously divide and replicate
- Have the capacity to differentiate into specialised cell types
Define totipotent, pluripotent, multipotent and unipotent.
- Totipotent:
Can differentiate into any type of cell. - Pluripotent:
Can differentiate into many types of cell. - Multipotent:
Can differentiate into a few closely-related types of cell. - Unipotent:
Can regenerate but can only differentiate into their associated cell type
Stargardt’s macular dystrophy
Problem:
- Affects one in 10 000 children
- Recessive genetic condition
- Mutation causes an active transport protein on photoreceptor cells to malfunction
- Photoreceptor cells degenerate
- Production of a dysfunctional protein that cannot perform energy transport
- Causes progressive, eventually total loss of sight
Treatment:
- Embryonic stem cells treated to differentiate and become retinal cells
- Retinal cells injected into retina, attach to retina and become functional
Leukemia
Problem:
Cancer of blood or bone marrow, resulting in abnormally high levels of poorly functioning white blood cells
Treatment:
- Hematopetic stem cells (HSCs) are harvested from bone marrow, peripheral blood or umbilical cord blood
- Chemotherapy and radiotherapy used to destroy diseased white blood cells
- New white blood cells need to be replaced with healthy cells
- HSCs transported back into the bone marrow
- HSCs differentiate to form new healthy white blood cells
