Ch. 2. Physiological chemistry and processes Flashcards
Control mechanisms
Nearly all are controlled by negative feedback mechanisms Some use positive feedback mechanism - control of uterine contractions during childbirth and blood clotting
Movement of substances within body fluids
In liquids or gases, molecules distribute from an area of high concentration to one of low (if there is no barrier) until the molecules are evenly spread throughout (equilibrium is reached). No energy is required (passive)
two main fluid compartments of the body
Most body water is intracellular (70%), the remaining 30% is extracellular (mostly in the interstitial fluid bathing the tissues, with the remainder found in plasma)
Diffusion
Movement of molecules from area of high concentration to area of low concentration and occurs mostly in gases, liquids, and solutions
Nucleic acids
largest molecules in the body, built from nucleotides, include deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
Homeostasis
fairy constant state, tightly controlled internal environment (unchanging)
Strong acids and bases
dissociate more extensively than weak acids. Same goes for bases.
Catabolic reaction
involve breakdown of substrate into smaller products (digestion)
The pH scale
Scale from 0 to 14, with 7 as midpoint (neutral)
Enzyme action
If conditions are unsuitable, enzyme action is reduced or stopped (temperature, pH)
pH most body fluids
Most of bodily fluids (except gastric juices) are close to neutral
Rings around nucleus
electrons orbit them, they represent different energy levels of atom’s electron
Body’s reactions release energy
breakdown of sugars in presence of O2
When atoms are joined together…
they form a chemical bond, generally one of two types: covalent or ionic
Enzymes in mitochondria …
capture the released energy, using it to make ATP from adenosine diphosphate (ADP)
Cation
with positive charge Na+
Osmotic pressure
Force with which osmosis occurs
Element
contains only one atom (carbon, hydrogen) There are 92 elements
Steroids
including important hormones produced by gonads (ovaries and testes) and adrenal glands.
Peptide bond
when two amino acids join up to form a bond, the reaction expels a molecule of water
Plasma (osmosis) hypertonic
The other way, plasma water concentration falls so plasma becomes more concentrated then intracellular fluid within red blood cells (plasma becomes hypertonic), water passively moves by osmosis from blood cells into plasma and blood cells shrink
Electrons
negatively charged, super small
interstitial fluid or tissue fluid
Cells are bathed in fluid called interstitial fluid or tissue fluid – they absorb oxygen and nutrients from the surrounding interstitial fluid, which absorbed these from the circulation blood (opposite happens for excretion)
Carbohydrates
Sugars and starches Contain carbon, oxygen, and hydrogen, usually in ratio 1:1:2
Phospholipids
Integral to cell membrane structure Form a double layer, providing a water-repellent barrier separating cell contents form its environment
Extracellular fluid (ECF)
Mainly blood, plasma, lymph, cerebrospinal fluid, and fluid in the interstitial spaces of the body Other fluids mainly lubricate joint (synovial) fluid, pericardial fluid (around the heart), pleural fluid (around the lungs)
Functions of sugars:
Ready source of energy to fuel cell metabolism Form of energy storage (glycogen) Integral part of structure of DNA and RNA Acting as receptors on the cell surface, allowing cell to recognise other molecules and cells
Lipids
Substances with common property of inability to mix with water (hydrophobic) Made up mainly of carbon, hydrogen, and oxygen atoms (some also contain nitrogen or phosphorus)
When NaCl is dissolved in water…
the ionic bond breaks and two atoms separate. The atoms are charged (since they traded electrons) so are no longer called atoms, but ions
Hydrogen ions
disrupt these internal stabilizing forces and change the shape of protein, leaving it unable to function
Atomic number
number of protons in the nuclei of its atoms, each element has its own atomic number
Internal environment
water-based medium in which body cells exist
Carbon atoms
are usually arranged in a ring with the oxygen and hydrogen atoms linked to them
Total body water (men and women)
Lower in women than men due to higher amount of adipose tissue then muscle tissue (adipose tissue is 10% water, and muscle tissue is 75%)
Monosaccharide
can be linked together to form bigger sugars – disaccharides (2 sugar units) sucrose
Positive feedback mechanism (labour)
During labour – contractions are stimulated by hormone oxytocin, forcing baby’s head into the uterine cervix, stimulating stretch receptors there. In response, more oxytocin is released further strengthening the contractions and maintaining labour. After baby is born, the stimulus (stretching of cervix) is no longer present and so release of oxytocin stops
internal bonds between amino acids
protein chains are stabilised by them Function of the protein will depend on the 3D shape into which it has been twisted
Atomic weight
of an element, sum of the protons and neutrons in the atomic nucleus, average atomic weight using all its atoms
Exert osmotic pressure
keeping body fluids in their own compartments
Anabolic reaction
when enzyme catalyses the combination of two or more substrates into a larger product
Substrate
the molecule(s) entering the reaction, binds to specific site on enzyme (the active site) and the reaction proceeds Once it is complete the product(s) of reaction breaks away from the enzyme
Lungs (buffers)
regulators of blood pH – excrete CO2 which increases H+ in bodily fluids (it combines with water to form carbonic acid which then dissociates into bicarbonate ion and hydrogen ion) Brain detects rising H+ in the blood and stimulated breathing, causing increased CO2 loss and fall in H+ (works the other way around)
Atoms
contain equal number of protons and electrons (no net charge)
Covalent bonds
when atoms share their electrons with each other, a strong and stable link (H20)
cofactor
Some enzymes require presence of cofactor (ion or small molecule) Can catalyse both synthetic and breakdown reactions
pH
measuring system to express the concentration of hydrogen ions H+ in a fluid, it is an indicator of its acidity or alkalinity
Negative feedback mechanism (body temperature)
E.g. body temperature (hypothalamus of the brain – where body’s temperature control centre is located), mechanisms that raise body temperature(effectors): Stimulation of skeletal muscles (shivering) Narrowing of blood vessels (reducing blood flow and heat loss from the peripheries Behavioural changes (put on more clothes or curl up)
Compound
substances containing two or more types of atom (H20)
Saliva (pH)
has pH between 5.4 and 7.5, the optimum value for the action of salivary amylase - enzyme in saliva that initiates the digestion of carbs, it is then destroyed by gastric acid when it reaches the stomach
mitochondria
Cells synthesise ATP in specialised organelles
Control centre
determines limits within variable factor, receives input from detector or sensor, and integrates the incoming information. When an incoming signal indicates that an adjustment is needed, control system responds and its output to the effector is changed.
Homeostatic imbalance
If the change in a system is excessive (rapid), it may not be able to adapt and the system may shift outside the normal range. This can lead to disruption or disease if not corrected
Acid substance …
releases hydrogen ions in solution
Important physiological variables maintained by homeostatic mechanisms:
Core temperature Water and electrolyte concentration pH of bodily fluids blood glucose levels blood and tissue oxygen and carbon dioxide levels blood pressure
Osmosis
Equal concentrations of molecules on both sides of the membrane (often diffusion of water)
Three forms of hydrogen atom
1 proton + 1 electron (deuterium) 1 proton + 1 neutron + 1 electron (tritium) 1 proton + 2 neutrons + 1 electron Each is an isotope of hydrogen
Biochemistry
chemistry of life
Buffers
Body pH is kept stable by systems of buffering chemicals in body fluids and tissues Important homeostatic mechanisms temporarily neutralise pH fluctuations Requires means by which excess acid or bases can be excreted form the body (lungs, kidneys) In extreme cases, the buffers can be exhausted
Adenosine triphosphate (ATP)
Nucleotide built from ribose (sugar unit), adenine (base), and 3 phosphate groups attached to ribose Called energy currency of the body Body has to synthesise it before it can spend it
Isotopes
Atoms of an element in which there is different number of neutrons in the nucleus (doesn’t affect electrical charge, affects atomic weight)
Nucleotides
Made up of a sugar, a base and a phosphate group
Fats (triglycerides)
stored in adipose tissue as energy source insulated the body and protects internal organs molecule of fat contains 3 fatty acids attached to a molecule of glycerol when broken down, more energy is released than when glucose is broken down Saturated (solid) or unsaturated (fluid – oils)
Anion
with negative charge Cl-
Other buffer systems:
body proteins (haemoglobin in red blood cells absorbs excess H+ and phosphate – important for intracellular pH)
Acids in water
Not all acids ionise completely when dissolved in water
Cholesterol
stabilises cell membranes and is precursors of steroid hormones mentioned above, used to make bile salts for digestion
Certain vitamins
fat-soluble vitamins are A, D, E, and K
Radioisotopes
some isotopes are unstable because of extra neutrons in the nucleus, and achieve more stable state by emitting radiation (detected by Geiger counter) which can be used to kill cancer cells, and as tracer material
Polysaccharides
complex carbohydrates containing, e.g. many thousands of monosaccharides (starch)
Glucose
cell’s preferred fuel molecule, a monosaccharide (mono=one, saccharide = sugar) can be broken down with or without oxygen (much more efficient with O2)
Ionic bonds
weaker than covalent, formed when electrons are transferred from one atom to another (NaCl – sodium chloride), stick together because they are carrying opposite, mutually attractive charges
mEq
Milliequivalent (mEq) per litre
Blood (pH)
is between 7.35 and 7.45
Chemical buffers
can reversibly bind hydrogen ions, responsible for keeping body pH stable
Energy from ATP breakdown …
fuels muscle contraction, motility of spermatozoa, anabolic reactions, transport of materials across membranes
Neutrons
carry no electrical charge, 1 atomic mass
Weight (measurement units)
milligrams, micrograms, nanograms
Control systems
Homeostasis is maintained by control systems that detect and respond to changes Have 3 basic components: detector, control centre, effector
Enzymes
Proteins that act as catalysts for biochemical reactions – they speed up the reaction up but are not themselves changed by it, can be used repeatedly Very selective, usually catalyse only one specific reaction
When atoms’ outer electron shell does not contain a stable number of electrons…
the atom is reactive and can donate, receive or share electrons with other atoms to achieve stability
ECF and ICF
ICF composition is very different to ECF Sodium levels are nearly 10 times higher in ECF then in the ICF. That’s because sodium diffuses down the concentration gradient, there is a pump in the membrane (the Na+/K+ pump) that selectively pumps it back out again. This is essential for excitable cells (nerve and muscle). Many substances are found inside the cell in higher amounts than outside: ATP, protein, and potassium
Amino acids in human protein synthesis…
have common structures: amino group (NH2), a carboxyl group (COOH), hydrogen atom
When cells need chemical energy …
to fuel metabolic activities, ATP is broken down again into ADP, releasing water, a phosphate group, and energy from the splitting of the high-energy phosphate bond
Atomic structure
Central nucleus containing protons and neutrons, surrounded by clouds of orbiting electrons
Alkaline substance …
accepts hydrogen ions, often with release of hydroxyl OH- ions
Molecules and energy and body
Body is dependent on the breaking down of various molecules (sugars, fat) to release energy for cellular activities)
First Rings around nucleus Second Rings around nucleus
First level – can hold 2 electrons Second level – can hold 8 electrons
Acidosis
when pH falls below 7.35 (more common) – may follow respiratory problems if lungs are not excreting CO2 as efficiently or if the body is producing excess acids (diabetic ketoacidosis) or in kidney disease if renal H+ excretion is reduced
Concentration (measurement units)
(if molecular weight is known) moles, millimoles, nanomoles per litre
Alkalosis
when pH rises above 7.45 – loss of acidic substances through vomiting, diarrhoea, endocrine disorders or diuretic therapy (increased renal excretion), may follow increased respiratory effort (acute anxiety attack, hyperventilation)
Proteins
are made from amino acids joined together can be used as alternative energy source in starvation (muscle tissue)
Diffusion (oxygen)
Oxygen diffuses through walls of the alveoli where oxygen concentrations are high, into bloodstream, where oxygen concentrations are low
When two sugar molecules combine
to form a bigger sugar molecule, a water molecule is expelled and the bond formed is called a glyosidic linkage
Total body water
In adults on average is 40 litres, 60% body weight Higher in babies and young people, and people with low weight Lower in the elderly and in obesity
Intracellular fluid (ICF)
Composition is largely controlled by cell itself because there are selective uptake and discharge mechanisms present in the cell membrane.
Electrolytes
When an ionic compound (NaCl) is dissolved in water it is called an electrolyte because it conducts electricity. Act as buffer to resist pH changes in body fluids Sodium Na+, chloride Cl-, potassium K+, calcium Ca2+, bicarbonate HCO3-, phosphate PO43-
Negative feedback mechanisms
Any movement away from its normal set point is negated (reversed) Response to a stimulus reverses the effect of stimulus, keeping the system in a steady state and maintaining homeostasis
The gastric juice (pH)
is maintained by hydrochloric acid secreted by parietal cells in the walls of gastric glands
Inert or chemically unreactive
element which has the max number of electrons or a stable proportion of this fraction in outer shell, and it will not easily combine with other atoms (helium, neon, argon, krypton, xenon, radon)
Kidneys (buffers)
regulate blood pH by adjusting the excretion of hydrogen and bicarbonate ions. If pH falls, hydrogen ion excretion is increased and bicarbonate conserved (and reverse). The kidneys generate bicarbonate ions as by-product of amino acid breakdown in the renal tubules, this process also generates ammonium ions.
Prostaglandins
chemicals derived from fatty acids, involved in inflammation
Important proteins:
Carrier molecules (haemoglobin) Enzymes Hormones (insulin) Antibodies
Diffusion through walls
Can also occur across a semipermeable membrane (cell membrane, capillary wall). Only molecules small enough or soluble enough to cross the membrane can diffuse through
Organic
Compounds containing carbon and hydrogen, all other compounds are classed as inorganic
Electricity conduction
essential for muscle and nerve function
Proteins chains
can vary in size form few amino acids long to many thousands. They may exist as simple, single strands of protein (hormones), but more commonly are twisted and folded into complex 3D structures
What makes one amino acid different form the next
is a variable side chain
Amino acids
always contain carbon, hydrogen, oxygen, and nitrogen (many carry sulphur, magnesium, phosphate, iron, and other) 20 amino acids are used as the principal building blocks of protein
Plasma (osmosis) hypotonic
if the plasma water concentration rises, plasma becomes more dilute than the intracellular fluid within the red blood cells, then water will move down the concentration gradient into red blood cells. This may cause them to swell and burst. Here plasma is hypotonic.
Salts
A salt releases other anions and cations when dissolved, sodium chloride is therefore a salt
substances moving against the concentration gradient
in such cases energy is required (breakdown of ATP) (active)
Protons
positively charged, 1 atomic mass
Molecules
2 or more atoms that are chemically combined (could be the same element – O2)
Changes in pH
A change of 1 number of pH scale indicated 10-fold change in H+
Small amounts (4%) of other compounds
sodium, potassium, calcium, phosphorus
Compounds making up living tissues composed mostly of
carbon, hydrogen, oxygen, nitrogen
The hydrogen ion concentration
is a measure of the amount of dissociated acid (ionised acid)
Interstitial or intercellular fluid (tissue fluid) bathes
all cells of the body except the outer layers of the skin
