Biochemistry Flashcards
What are the classes of nucleic acids?
- RNA (ribonucleic acid)
- DNA (deoxyribonucleic acid)
What is the structure of DNA?
- double-stranded, double helix with a sugar phosphate backbone
- bases are joined by H bonds
What are the functions of nucleic acids (DNA, mRNA, tRNA, rRNA)?
- DNA: storage of genetic info
- mRNA: carriers of genetic info (directs translation of genetic info into proteins)
- tRNA: translator of genetic info (delivers amino acids during protein synthesis)
- rRNA: components of ribosomes (have structural and functional roles)
General structure of nucleic acids (and what is the bond that joins nucleic acids together)
- nucleic acids joined by phosphodiester bonds
- sugars: ribose (RNA), deoxyribose (DNA)
Purine bases…
Pyrimidine bases…
Bases, nucleosides, nucleotides…
Structure of tRNA…
- tRNA has a clover-leaf secondary structure
- note: RNA molecules are single-stranded
- note: Uracil instead of Thymine
What are the minimum daily intake requirements for calcium (female, male, growing skeleton, osteoporosis, and maximum)?
- female: 350mg
- male: 450mg
- growing skeleton: 750mg
- osteoporosis: 1500mg
- maximum: 3000mg
Define ‘adjusted calcium’ (laboratory test) and it’s use.
- in the blood half of the calcium is ionised and half is bound to albumin
- adjusted calcium adjusts for the amount of albumin and gives a better indication of ionised levels
- note: only ionised calcium is physiologically important
How is calcium stored in bone (what form?)? (and what is bound in bone with Ca)
- hydroxyapetite
- note: phosphate bound in bone with Ca and will also be released when bone is broken down
What effects does acidosis and alkalosis have on calcium binding to proteins?
- acidosis decreases binding
- alkalosis increases binding
What is the response to decreased circulating calcium and how does PTH act?
- caclium-sensing receptors respond and increase PTH synthesis and release from Chief cells
PTH acts in 3 ways:
- promotes Ca reabsorption via kidney
- stimulates osteoclast resorption of bone releasing Ca
- drives 1,25 vit D production in kidney which results in increased Ca absorption via the gut
What is the most common and important calcium-sensing receptor defect?
- Familial Benign Hypocalciuric Hypercalcaemia (FBHH)
- circulating calcium is elevated
What are the clinical symptoms of hypercalcaemia and what is the most common cause?
- most common cause: primary hyperparathyroidism (54%)
- stones, bones, abdominal moans, and psychic groans
What are the clinical symptoms of hypocalcaemia and what are some causes?
Symptoms:
- paraesthesia, muscle spasm, tetany, seizures, coma, Chvostek’s sign (hypersensitivty of facial nerve), Trousseau’s sign (involuntary contractions of muscles in hand/wrist), cardiac problems
Causes:
- renal failure, hypoparathyroidism, vit D deficiency/malabsorption
Trabecular (or cancellous or spongy) bone…
Cortical or compact bone…
What type of collagen is the bone matrix made out of and what are the 2 patterns in which collagen can be laid down?
- type I collagen
Can be laid down as…
- woven bone: immature form with random fibre orientation, laid down during rapid growth and fracture repair
- lamellar bone: composed of successive layers of collagen fibres with distinct orientation
Lamellar bone…
Woven bone in Paget disease…
Structure of bones…
- a shell of compact bone surrounds the medullary (or marrow cavity)
- the medullary (or marrow cavity) is the site of production of blood cells in immature animals (red marrow), but becomes progressively replaced by inactive yellow marrow, composed mainly of adipose tissue (body fat)
Structure of a child’s bone…
What is the function of osteoblasts, osteocytes, and osteoclasts?
- Osteoblasts: bone matrix synthesis (bone formation)
- Osteocytes (most abundant cells within bone): osteoblasts engulfed in bone matrix
- Osteoclasts: resorption of bone