Unit 2 Cells Bite Size

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Cell Theory

All Living things are made of cells

Evidence: living things observed under a microscope look like they are composed of cells, except: muscle cells (multi-nucleated), fungal cells (continuous cytoplasm)

Cells are the smallest units of life

Evidence: organelles, though smaller need the presence of other organelles to function properly

Existing cells have come from other cells

Evidence: Mitosis, binary fission

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Stem cells

Therapeutic use of stem cells

Bone marrow transplant, cells in the bone marrow produce blood cells, people with Leukemia can receive a transplant with healthy bone marrow which may cure their disease. Cells need to become part of the body to function 

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Extracellular component roles

-       plant cell wall:

    found around all plant cells, composed of cellulose, maintains shape, structural support, prevents excessive uptake of water

-       animal extracellular matrix:

      basement membrane, secretion formed from collagen and glycoproteins, support for organ/tissue, filter, vascular niche. 

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Fluidity of membrane allows it to...

.....change shape, break and reform during endocytosis and exocytosis 

Endocytosis: process which cells take up a substance by surrounding it with it’s membrane. It requires energy, and cells use this to take in things that are too large or very polar ie. White blood cells take up bacteria

Exocytosis: materials being removed from cells (requires energy) reversal of endocytosis. ATP is consumed by energy requiring processes (endothermic) and generated by process that release energy (exothermic) ATP – main source of energy for cellular functions. 

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Prokaryotic cells and Eukaryotic Cells

nucleus     nucleoid.

Membrane bound organelles    none.

Mitochondria    mesosomes

Mitosis     binary fission

80s ribosomes     70s

Larger     smaller. 

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Plants vs Animal cells

both are Eukaryotic

Chlroplast      none

large vacuole     small or none

cell wall       no cell wall

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Phases of mitosis

·         In prophase the mitotic spindle forms.

·         In prometaphase the chromosomes attach to the mitotic spindle at the centromere

·         In metaphase, the condensed chromosomes align in a plane across the equator of the mitotic spindle.

·         Anaphase follows as the separated chromatids move abruptly toward opposite spindle poles.

·         Finally, in telophase a new nuclear envelope forms around each set of unraveling chromatids.

·         The mitotic spindle is composed of microtubules, each of which is a tubular assembly of molecules of the protein tubulin.

·         Microtubules can grow or shrink by the addition or removal of tubulin molecules. This change in length propels attached chromatids to the spindle poles, where they unravel to form new nuclei.

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