Biological molecules Flashcards
What percentage of cells are made up of water, and how do most ionic substances behave in this environment?
Cells are 60-70% water, so most ionic substances are separated into their constituent oppositely charged ions.
What are the important functions of Na+ (sodium ions) in the body?
Helps conduct nerve impulses
Influences muscle contraction and relaxation
Balances fluid and electrolytes, regulates blood pressure
Osmotic effect helps cells take up water
Most important for fluid regulation
What happens in the body during hypernatremia and how is it treated?
Hypernatremia causes water to be drawn out of brain cells, leading to dehydration and shrinkage. It is caused by inadequate water intake or excessive water loss (regulated by vasopressin, ADH). Treatment: hypotonic fluids.
How does hyponatremia manifest and how is it treated?
Hyponatremia causes edema and neurologic symptoms. In hypovolemic hyponatremia (caused by vomiting), it is treated with isotonic solutions. In hypervolemic hyponatremia, it is treated with diuresis.
Why are premenopausal women more susceptible to acute hyponatremia?
Oestrogen and progesterone increase vasopressin levels, causing kidneys to retain more water and inhibit the Na-K pump, which prevents the excitation of brain cells.
What role does Na+ play in glucose and amino acid transport?
Na+ co-transports glucose and amino acids into cells by being actively transported out of epithelial cells in the small intestine. This creates a concentration gradient, allowing Na+ to re-enter cells through co-transport proteins along with glucose and amino acids.
What are the functions of K+ (potassium ions) in the body?
Regulates intracellular osmolarity and acid-base balance
Maintains normal cardiac rhythm
Helps transport insulin into cells
Influences muscular activity and nerve function
Allows water reabsorbption in kidneys
What is the role of K+ in nerve cell repolarization?
Potassium ions move out of the axon through voltage-gated channels, returning the axon’s membrane potential to normal (about -70mV), a process called repolarization.
What is the function of Ca2+ (calcium ions) in the body?
Keeps bones and teeth strong
Supports blood circulation
Aids in muscle contraction by facilitating actin-myosin cross-bridge formation
Helps in neurotransmission and activates transcription factors
Helps release hormones in clotting process
Regulates protein channels affecting permeability of membranes
How does Ca2+ play a role in muscle contraction?
When an impulse reaches a muscle fiber, Ca2+ is released from the sarcoplasmic reticulum, binding to troponin C. This removes tropomyosin from myosin-binding sites on actin, allowing muscle contraction.
What is the role of Mg2+ (magnesium ions) in the body?
Can reduce blood pressure and lower the likelihood of arrhythmias
Counteracts calcium in muscle contraction and reduces muscle cramps by inhibiting over excitation of nerves
Important in protein synthesis and energy metabolism
What are the functions of Cl- (chloride ions) in the body?
Regulates fluid and electrolyte balance and pH by moving out of RBCs
Forms HCl in stomach acid
Assists in transmission of nerve impulses
Helps in CO2 transport in blood
Used by WBCs to kill bacteria
What is the role of OH- ions in biological systems?
OH- ions are essential for hydrogen bonding.
What is the function of PO4^3- (phosphate ions) in the body?
Involved in cell growth, energy generation, and ATP storage
Forms bones and teeth
Acts as a buffer
Helps deliver oxygen to the body
The bond between phosphate groups stores energy in ATP, which is released when broken
Why is maintaining pH at 7.4 important in the body?
pH 7.4 is the optimum for enzyme function. Small changes in pH, especially in the acidic range, can lead to large changes in the number of H+ ions, affecting secondary and tertiary protein structure by binding of H+ ions and enzyme activity.
How do buffers maintain pH stability in the body?
Buffers take up or release H+ ions in reversible reactions, preventing rapid changes in pH. HCO3- (bicarbonate) acts as a weak acid/base, providing a mechanism to stabilize pH.
What is the function of Fe2+ (iron ions) in the body?
Fe2+ is part of hemoglobin and myoglobin, crucial for oxygen transport
Involved in electron transfer during respiration as part of cytochromes in the electron transport chain (switches between oxidation states)
What is the role of Folic Acid (Vitamin B9) in the body?
Required to generate red blood cells
Helps in the development of the brain, skull, and spinal cord in embryos, preventing birth defects like spina bifida
Improves DNA replication and transcription by increasing cell division and DNA replication rates
Needed for methylation and DNA base synthesis
How does Methotrexate affect folic acid metabolism?
Methotrexate is an anti-folate drug that inhibits folate metabolism, preventing cancer cell proliferation.
What are the key properties of water in biological systems?
High melting and boiling points
Polar solvent for most cellular reactions and transport medium for dissolved metabolites
Maximum density at 4°C (ice insulates water below)
High specific heat capacity (important for temperature regulation of blood and heat transfer around body via blood and tissue fluid)
High latent heat of vaporization (important for sweating)
Non-compressible, important in hydraulic mechanisms
Cohesive and adhesive properties (important in blood circulation)
High surface tension (surfactant in lungs)
What are the important uses of water in the body?
Sweating and temperature regulation
Transport of substances in blood, tissue fluid, and urine
Electrolyte balance
Solvent for cell reactions
Reactant in hydrolysis reactions
Lubrication and providing surface tension in alveoli preventing collapse
What are the main compartments of body fluids?
Intracellular fluid: ⅔ of body fluid, inside cells
Extracellular fluid: includes plasma (intravascular) which uses capillary membrane to separate from tissue fluid (interstitial), and transcellular fluid (e.g., spinal fluid, joint fluid, pericardial and peritoneal)
How do you measure Total Body Water (TBW)?
TBW can be measured by using substances that pass through the cell membrane.
How do you measure extracellular fluid (ECF) and plasma volume?
ECF: Measured by substances that pass through the capillary membrane but not the cell membrane.
Plasma volume: Measured by substances that do not pass through either the capillary or cell membrane.
What is the general formula for carbohydrates?
Cx(H2O)y
What are monosaccharides?
Simple sugars, such as triose sugars (e.g., pyruvate in respiration), pentose sugars (e.g., DNA, RNA), and hexose sugars (e.g., glucose (can cross the blood brain barrier to nourish brain cells, sucrose, galactose).
