Ingredients of Life Flashcards
What is hypokalemia?
Low plasma potassium ion level
Hypo: below normal
Physical examination of hypokalemia
Dry tongue and mucous membrane (possible dehydration)
Acute onset of muscle weakness (generalized, more prominent in the lower limb)
Composition of blood
Formed elements (cell and cell fragments) suspended in plasma, which is mostly water
Plasma
- 55-60% of blood volume (can flucuate from time to time due to dehydration and overhydration)
Formed elements (40-45% of blood volume)
- Erythrocytes (red blood cells): 99%
- Leukocytes (white blood cells): < 1%
- Platelets: < 1%
Spin down whole blood using a centrifuge
- Plasma
- Buffy coat: leucocytes and platelets
- Packed cells and solids: erythrocytes (red blood cells)
Composition of plasma
Water, proteins, nutrients, metabolic wastes, hormones and inorganic electrolytes (K+ and Na+ ions)
Hematocrit
Percentage of blood volume that is red blood cells
Average size adult
70kg
Serum
- Clearer than plasma
- Can be obtained by setting the blood sample at room temperature for 30 mins before centrifuging it
- This is because the blood clotted and the fibrinogen and other clotting proteins are removed
Important electrolyte
Nerve impulse (action potential): Ca2+, K+, Na+
Major extracellular anion: Cl-
Major intracellular cation: K+
Major extracellular cation: Na+
Acid and base balance: H+
0.9% sodium chloride (NaCl)
- Normal saline
- Sterile: X micro-organism
- Non-pyrogenic: X fever-causing substances
- for fluid and electrolyte replenishment
- isotonic volume expander (increase blood volume) and electrolyte replacement for intravenous infusion (dip)
Hypernatremia
Plasma Na+ ion level is higher than normal in the plasma
Ions (Na+ and Cl-) attract and retain water, Na+ affects water balance (i.e. blood volume), then indirectly affects blood pressure called mean arterial pressure (MAP), may trigger stroke
Isomers
e.g. glucose, fructose, and galactose
In ileum, fructose and galactose are subsequently converted into glucose as only glucose can be digested and used as a source of energy
Normal physiological concentrations of important ions in plasma
Key to their ability to produce physiological functions
Na+ ion: 135-145 mmol/L
K+ ion: 3.5-5.0 mmol/L
Water
- Most abundant substance in human body (60% of total body weight)
- Provides an optimal medium in which cells can function
- Major transport component of the body
- Aids in thermoregulation
- Provides cushioning
- Acts as lubricant
- Breaks down food particles into smaller components in the digestive system
- I srequired for a variety of metabollic processes that are necessary for survival
- Is a good physiological solvent for electrolytes and non-electrolytes
Surface tension
Cohesion: forces of attraction between like molecules
Adhesion: forces of attraction between dissimilar molecules
Both of them lead to the formation of meniscus (bending of the liquid surface)
Meniscus
Water forms bowl-shaped (concave) meniscus: adhesive forces > cohesive forces
* measure the center bottom
Mercury forms dome-shaped (convex) meniscus: cohesive forces > adhesive forces
* measure the center top
Manometers
to measure the pressure by means of a vertical coumn of fluid
Mercury sphygmomanometer: measurement of arterial blood pressure
Saline manometer: measurement of central venous pressure (CVP)
Lack of surfactants in the lungs
Insufficient surfactant leads to reduced pulmonary compliance and increased surface tension. This increases risk of alveoli collapse at end-expiration followed by reduction in total surface area for gaseous exchange. Lung may undergo collapse and cause the patient to have difficulty breathing.
Pulmonary surfactant
Acts as a film to keep alveoli open by reducing the cohesive forces between water molecules
- Lubricates the alveoli and allow them to expand without overstretching and get smaller without collapsing
- Produced by type II alveolar cells
Newborn Respiratory Distress Syndrome (NRDS)
- Life-threatening breathing disorder of premature newborns which commences at or soon after birth (mostly before 28th week)
- Surfactants are normally produced between 34th and 36th wee of pregnancy
- Management: breathing support and artificial surfactant
Organic molecules
- Accounts for 18% of body weight
Dehydration (Condensation)
Removes the equivalent of a water molecule to link molecular units so that macromolecules can be built
Hydrolysis
Adds the equivalent of a water molecule to break apart macromolecules
Carbohydrates
The most abundant monosaccharide in human: glucose, stored in cells in the form of polysaccharide glycogen
Oligosaccharide
* Sucrose: glucose + fructose
* Maltose: glucose + glucose
* Lactose: glucose + galactose
Proteins
Haemoglobin (found in rbc): contains heme (Fe) pigment, carries oxygen in blood
Myoglobin: contains heme pigment, store oxygen in striated muscles (skeletal and cardiac muscles)
4 levels of structure of protein
Primary
* Chain of amino acids
* Alightest change of sequence affects the protein’s ability to function
Secondary
* Coiling (alpha helix) and folding (pleated sheet) of polypeptide are resulted from hydrogen bonding
Tertiary (Polypeptide, a single subunit of transthyretin/thyroxine)
* Three dimensional shape
* Results from interactions between the R groups of various amino acids
* Disulphide bridges (between two sulphur molecules) are covalent bonds that further strengthen the protein’s shape
* Hydrophobic interactions between two non-polar side chains
Quaternary (thyroxine)
* Two or more polypeptide chains associated together
Gobular protein
- Ball-shaped
- Functional protein
- E.g. enzymes, plasma proteins (low level of albumin caused swelling), erythrocyte pigment haemoglobin
Fibrous protein
- Rope-like
- Structural protein
- E.g. keratin (provides impermeability on the epidermis), collagen (toughness of the skin), elastin (elasticity of the skin), fibrinogen (protein precursor of fibrin)
