Cells Flashcards
Give the structure of collagen.
3 collagen protein chains in a triple helix
Give the structure of collagen proteins.
Many repeating Gly-Pro-X units
How does a vitamin C deficiency cause sore gums, loose teeth, sores, swollen joints and rough coats?
Vitamin C is a cofactor of hydroxylase enzymes.
- Prolines are converted to hydroxyprolines by prolyl hydroxylase
- Lysines are converted to hyroxylysines by lysyl hydroxylase
Hydroxyproline interactions strengthen links between collagen chains, so deficiency causes weakened collagen structure.
Why is vitamin C not an essential vitamin in most animals?
Most animals can make their own vitamin C. Only humans, certain birds and guinea pigs cannot.
What is dermatosparaxis and its effects?
Defect in collagen peptidase gene, which impairs fibril formation. Causes weak collagen, ECM and skin.
Selective breeding may be used to eradicate the disease but cannot be treated so animals with the disease are euthanised.
What is Ehlers-Danlos syndrome and its effects?
A defect in fibre formation . Causes elastic skin and lax joints that can have hyperflexibility. Animals may have fine white scars and develop unhealable splits in skin.
Break the cell cycle down into stages.
G1 - daughter cell grows and prepares for mitosis straight away
S - at sufficient cell size, DNA replication occurs
G2 - prepares for cell division
M - mitotic phase to produce 2 daughter cells
G0 - optional phase where cells are proliferating or are stationary. Most cells are in this phase. Growth factors and signals can trigger return to G1.
What happens at each check point of the cell cycle?
G1 - ensures all cells have all external and internal resources to enter S phase
G2 - checks if DNA is replicated, if DNA is in good condition, and if the cell has all the resources for M phase
M - checks if chromosomes are lined up nicely and ready for separation before cytokinesis
Why are checkpoints important?
Prevention of cancerous cells
What are pluripotent stem cells?
Stem cells are able to exist in all tissues and can make copies of themselves for a very long time. Terminally differentiated cells arise from stem cells.
How does gene expression affect cell differentiation?
Gene expression changed by histone acetylation and methylation. Genes can be turned on and off, meaning phenotype will include proteins for genes for cell specialisation or not.
What is the hormonal pathway for control of growth in development?
Hypothalamus releases Growth Hormone Releasing Hormone > GHRH acts on pituitary gland to release GH > GH stimulates liver to make Insulin-like Growth Factor-1 > IGF-1 acts on muscle, bone and fat to stimulate growth
Define hypertrophy and hyperplasia.
Hypertrophy - increased cell size
Hyperplasia - increased cell number
How do amino acids control cell growth?
Amino acids activate mTORC1, the major controller of cell growth.
What is the function of apoptosis - controlled cell death?
In development, some cells need to be removed to sculpt tissues and organs: webbing between digits, removal of tadpole tails and unnecessary retina vessels in mice. Also kills faulty and cancerous cells.
