Unit 11 - Cells & Their Social Networks Flashcards
Similarities of the ECM & Cell Wall
- cross-linked network of filaments
- semi-solid gelatinous matrix of polysaccharides/proteins
Plant Cell Walls (in general)
- sedentary
- tissues fairly rigid
- extracellular matrix secreted by plant cell
Protoplasts
- name given to plant cells when separated from their walls
- weak & fragile
Primary Cell Wall
- secreted as cells are growing
- relatively thin
- pectins made in the rough ER are processed in the Golgi and secreted
- cellulose is made at the plasma membrane by proteins with cellulose synthase enzymes
Middle Lamella
-gelatinous pectins that ‘glue’ cells together
Secondary Cell Wall
- in certain types of mature cells
- much thicker than the primary cell wall, cells become rigid once they have the secondary wal
- composition depends on whether they are structural, waterproofing, or protecting against pathogens & droughts
How are plant cells able to grow?
- driving force of growth is turgor pressure
- orientation of cellulose microfibrils determines the direction of growth
This forms the template for cellulose synthesis
Microtubules
Animal Tissue
- cells held together by cell-cell junctions & ECM
- strong, capable of rapid movement, & quick changes in shape
Connective Tissue
- large amount of ECM which provides mechanical support
- examples: tendons, bone, adipose
- tensile strength is provided by a protein
Collagen
- fibrous component of animal ECM
- cable-like protein
- several different types in body
- most abundant protein in mammals
Proteoglycans
- gel ‘filler’ in animal ECM
- proteins which are heavily glycoslyated
- core proteins attached to chains of GAGs
- very hydrophillic, attracts water
- provides a porous, hydrated gel
Functions of Proteoglycans
- resists compression
- forms pores of varying sizes for passage of molecules through ECM
- can block, encourage or guide cell migration through ECM
ECM is connected to the cytoskeleton via…
integrins - humans have at least 24 types
Types of Epithelial Cells
- Simple
- Stratified
- Columnar
- Cuboidal
- Squamous
Adherens Junctions
- via actin filaments
- form ‘belts’ around epithelial cells
- tightening of the ‘belt’ at certain sections of the epithelium causes the formation of an epithelial tube
Gap Junctions
- like a subway
- allows passage of very small molecules (ions, secondary messengers)
- connecting via gap junctions allows cells to coordinate activities and work as a team
Tight Junctions
- forms barrier forcing material to go through, rather than between cells
- ‘fence’
- helps to maintain polarity of cells
- defines epithelium as tight
Desmosomes
-joins intermediate filaments in one cell to those in a neighbour
Hemidesmosomes
-anchors intermediate filaments in cell to basal lamina
Plasmodesmata
- channels between plant cells
- proteins that expand/contract their cytoplasmic space to allow/restrict transport
- lined with plasma membrane
Stem Cells
- undifferentiated cells found throughout body which divide to supply terminally differentiated cells
- replenish dying cells and repair damaged tissues
- properties:
1. self-renewal
2. multipotency
Embryonic Stem Cells
- original egg cell divides repeatedly, all contain same genome, specialized in different ways
- properties:
1. pluripotent
Cancer Cells
- usually somatic mutations - acquired in mature body
- usually involve defects in DNA rep. and repair, cell cycle checkpoints, pathways that drive cell cycle, mitosis –> aneuploidy
- not dependent on signals for growth/survival/division
- less likely to kill themselves
- ‘immortal’ - can divide indefinitely
- invasive –> loss of cell adhesion molecules
Carcinoma
cancer in epithelial
Sarcoma
cancer in bone, cartilage, muscle, fat
Hematopoietic
leukemia, lymphoma
