Life at cellular Level 1-4 Flashcards
Why are cells so small?
SA:Volume ratio to allow easy absorption and secretion
Prokaryote
0.1-10 micrometres
Bacteria with no membrane bound structures or nuclear membrane
Eukaryote
10-100 micrometres
Human cells
Pluripotent
Capable of becoming all cell types in the body
Multipotent
Cells that can differentiate into many cell types
Cell differentiation
Cells pass through series of changes during development with changes in gene expression
Cell fusion
Cells in muscle divide as single cells then fuse together to form super cells which is a normal process for some cell types
Teratoma
Tumour with tissue or organ components representing normal derivatives of one or more germ layer eg hair, teeth, bone and is a stem cell derived cancer formation
Cancer cell
Divide without any control and fails to co-ordinate with normal cells or to differentiate
Apoptosis
Programmed cell death
Necrosis
Cell death due to disease
Amphipathic
Hydrophilic head and hydrophobic tail
Transport proteins
passive = concentration gradient and small uncharged molecules pass freely Facilitated = non specific (pore) or non specific (channel) transporter
Endocytosis - 2 parts
Phagocytosis - WBC engulfs and triggers phagosome formation
Pinocytosis - Constant removal of cell membrane by nervous system
Exocytosis
Protein produced by rough ER => Golgi apparatus for post transational modification then bud off in a vesicle eg beta cells produce insulin
Cell adhesion
Proteins allow cells to stick together to form tissue
Occluding/tight junction
Seals gap between epithelial cells and is a physical barrier preventing flow
Responsible for the blood brain barrier
Cell to cell anchoring
Link to cytoskeleton and includes adherens junction and desmosome
Adherens junction
Links actin filaments in 2 different cells
Desmosomes
Link keratin (intermediate) filaments in 2 different cells and keratin is not as ordered
Gap junction
Allows passage of small ions from cell to cell for collective communication
Connexins
6 subunit membrane spanning proteins allowing “1” cytoplasm
Cell matrix anchoring junctions
Stops epithelial cells ripping away and get actin linked cell matrix adhesion and hemidesmosomes
Paracrine
Signals to cells in local area