Chemistry and biochemistry I; the study of the chemical compounds and reactions in living systems

Question 1

Learning outcomes:

Answer 1

• Key concepts in chemistry and biochemistry, including water, pH buffers
• Structure and functions of carbohydrates
• Structural and functions of lipids

Question 2

Chemistry

Answer 2

The science that deals with the composition and properties of substances and various elementary forms of matter (gas, liquid, solid)

Question 3

Biochemistry

Answer 3

This science concerned with the chemical and physicochemical processes and substances that occur within living organisms
Bio = life

Question 4

Matter, what is it and what is it made from?

Answer 4

Everything around us that has mass and occupies space
* Atoms are small particles that make up matter – the ‘Lego bricks’ that make up everything in our universe
* Atoms are made up of electrons, protons and neutrons

Question 5

Chemical elements

Answer 5

An element is a substance made up of just one type of atom so it cannot be split up into simpler substances.
* As with Lego, there is a finite number of different types of atoms from which we can build things
* The elements we know of are in the periodic table
* In chemistry, each element is given a chemical symbol for its long name, for example:
o Hydrogen = H
o Carbon = C
o Calcium = Ca
o Magnesium = Mg

Question 6

Elements in the human body

Answer 6

26 different elements are normally present in the human body.
* 4 major elements – carbon, hydrogen, oxygen and nitrogen, which account for 96% of the human body
* It is useful to know some element of abbreviations, for example, in clinic notes (i.e. ‘FE deficiency’) and because it is common in medical texts

Question 7

Subatomic particles

Answer 7

Every element is made up of atoms. Each atom is made up of subatomic particles called protons, neutrons and electrons.
* Protons and neutrons together form the nucleus of an atom
* Protons have a positive charge and a mass of approximately 1 atomic unit
* Neutrons have no charge and a mass of approximately 1 atomic unit
* Electrons are negatively charged particles that ‘buzz’ around the outside of the nucleus, creating an electron cloud. They have virtually no mass at all.

Question 8

Electrons

Answer 8

An atom will have an equal number of electrons and protons giving an overall neutral charge to the atom. Recall that electrons carry a negative charge.
* Electrons move in groups around the nucleus, known as ‘electron shells’.
* Within my shells of electrons ‘pair up’.
* An atom becomes reactive if its outer shell isn’t full or if it loses an electron
* This happens in ‘free radicals’, where an electron becomes unpaired

Question 9

Atoms analogy

Answer 9

“Atoms are Like the families”

• Each proton is an adult with one child (an electron)
• Each neutron is an adult with no children
• The adults hang out together in the centre (nucleus) – each weigh 1.
• The children (electrons) buzz around the adults like an excited cloud and weigh (virtually) nothing
• Each parent (proton) has a positive charge and each child (electron) has a negative charge
• The opposite charges attract each other, keeping the family together!
• All the chemical properties of an atom are down to its number of protons and electrons. The neutrons just add weight to the atom; they don’t significantly change how it chemically reacts.

Question 10

The Periodic Table

Answer 10

The periodic table is a list of all the currently known elements, arranged in columns and rows that show us which elements share similar reactivity and physical properties
* The number that is assigned to each element tells us how many protons and, therefore, how many electrons each atom has
* The larger number is always the mass number (the weight in atomic units). It tells us how much the atom weighs so it can be used to work out the number of neutrons (remembering that electrons weigh nothing)
Each column contains elements that react in a similar way.
* All of the elements in column one react with water. The lower down the column indicate a more vigourous reaction

Question 11

The Periodic Table: Halogens

Answer 11

A specific column of elements in the periodic table is collectively known as the ‘halogens’.
* Like with any column in the periodic table, the halogens share very similar chemical and physical properties
* In nutrition, this is highly relevant when considering the role of iodine in thyroid health. Recall that iodine is required for the synthesis of thyroid hormones (T3 and T4)
o If present in the body, the other halogens (e.g. fluoride and chlorine ) can enter the thyroid, preventing the formation of T3 and T4 (inducing hypothyroidism)
o Fluoride is in toothpaste, tap water and mouth washes, whilst chlorine is in swimming pools and chlorinated washed vegetables

Question 12

Counting subatomic particles

Answer 12

• Atomic number = Number of protons
• Mass number = Number of protons + Number of neutrons
• Number of neutrons = mass number number (always bigger) – atomic number
  e.g. Potassium (K):
• Atomic number = 19
• Mass number = 39.0983
  So;
• Protons = 19
• Neutrons = 20
• Electrons = 19

Question 13

Isotopes

Answer 13

Isotopes = atoms of the same element which have a different number of neutrons in the nucleus
* In nature there are often different versions of the same atom called isotopes
* This does not affect the chemical activity of the atom as neutrons have no charge, but it does change the mass
Iso = equal, -topos =- place

Question 14

Isotopes and Radiation

Answer 14

Some (but not all) isotopes have such an imbalance of protons (parents) and neutrons in their nucleus that it causes the atom (Family) to become unstable.
* This is the cause of radioactivity. The unstable atom needs to get rid of energy to become stable.
E.g. A ‘PET Scan’ is an imaging technique used in allopathic medicine. Radioactive isotopes are introduced (often injected) into the body

Question 15

Isotopes in medicine

Answer 15

Some diagnostic techniques in medicine use radioactive tracers with emit gamma rays from within the body
* Radiotherapy uses the gamma rays from radioactive isotopes to target rapidly dividing cells. However, this is also highly damaging to healthy tissues
* The breath test for H.pylori uses urea labeled with either radioactive carbon– 14 or nonradioactive carbon– 13. In the subsequent 10 to 30 minutes, the detection of isotype labeled carbon dioxide in exhaled breath indicates that the urea is split; this indicates that urease (the enzyme that H.pylori uses to metabolise urea) is present in the stomach, and hence that H.pylori bacteria are present.

Question 16

Electrons shells

Answer 16

Electrons like to ‘hang out’ in certain numbers (2, 8, 8, 8) so the optimum number of electrons in a shell is a known number

• This means that the first electron shell has 2 electrons, whilst the second 8 and so on
• Electrons always want to be in pairs
• All of the reactions that happen in chemistry are driven by atoms trying to end up with a stable and full outer shell either by stealing, giving away (donating) or sharing electrons

Question 17

Hydrogen: The simplest atom of all

Answer 17

Hydrogen contains: one proton, one electron, no neutrons.
* We often refer to hydrogen, when it is in its H+ form (hydrogen minus the electron), as being a ‘proton’. This is why we talk about acidity in terms of protons.
* Because hydrogen has only one electron in its outer shell, it will often go looking for another atom that needs one electron to fill its shell. This means that hydrogen easily reacts with other atoms
* Some elements do not easily react as they have their outer shell filled with the perfect number, so they are rarely involved in chemical reactions. We call these elements ‘inert’.

Question 18

Bonding

Answer 18

Atoms that are trying to become stable by bonding with other atoms so that they can get just the right number of electrons in their outer shell.

The two main types of bonding are:
1. Ionic bonding – atoms transfer electrons (1 donates, 1 receives)
2. Covalent bonding – occurs when atoms share electrons

Question 19

Ionic Bonding

Answer 19

Ionic bonds occur when one atom donates some of its electrons to another
* This usually only occurs when there are 1, 2 or occasionally 3 electrons to donate
* Moving any more electrons than this isn’t energetically favourable
* Consider the regular appearance of table salt (NaCl), and Sea /Himalayan salt (which contains various other minerals too) in

Question 20

Ions

Answer 20

If an atom gives up or gains electrons to fill its outer shell, it becomes an ion
* Ionisation is the process of giving or gaining electrons
* Ions are written with their corresponding – or + charge
For example:
* CA2+ has donated two electrons to another element and now has a positive charge
* Cl- has gained an electron so has taken on a negative charge
* In both cases are calcium and chlorine have ended up with a full outer shell

Question 21

Sodium ion

Answer 21

Sodium has one electron in its outer shell
* Energetically its is far easier to give that one electron away than to gain or share 7
* So sodium always gives its one electron away to become Na+

Question 22

Covalent bonds

Answer 22

Covalent bonds occur when two elements share electrons so that they both have the ‘magic number’ they are looking for.

• This kind of bonding tends to happen when the two atoms are similar or when there are a lot of spaces to be filled to reach a full outer shell

Question 23

Polar bonds

Answer 23

Polar convalent bonds form where electrons are shared and unequally. This happens because some atoms have a lot of ‘electron pulling power’.

• Some elements have lots of protons compare to the number of electrons shells i.e. a strong positive centre. These elements referred to ‘electronegative’ because they tend to pull the shared electrons towards themselves.
• These very electronegative atoms are able to pull the electrons in a bond towards them, leading to an uneven distribution of charge.
• F, Cl, O and N are the most electronegative elements

Question 24

Hydrogen bonding

Answer 24

One of the most important examples of a polar bond are the bonds between oxygen and hydrogen in water.
* The oxygen pulls the electrons towards itself, resulting in a negatively-charged area over the oxygen and a positively-charged area over each hydrogen
* The positive hydrogens on one water molecule are attracted to the negatively-charged oxygens on the next molecule
* These loving interactions are called hydrogen bonds and are what give water many of its special properties such as surface tension and the ability to dissolve so many different things

Question 25

Water: the universal solvent

Answer 25

Water serves as the medium for most chemical reactions in the body.
* As water contains polar bonds, it is an ideal solvent for dissolving chemicals into separate ions. In addition, the different electrical charges in water can allow water molecules to become attracted to other molecules (hence water dissolved salts)
* Hydrophilic molecules are molecules which have polar bonds. They dissolve easily in water (e.g. alcohol)
* Hydrophobic molecules contain non-polar covalent bonds, so they do not dissociate easily in water (e.g. fats)
Hydro = water, -phillic = loving, -phobic = hating

Question 26

Electrolytes

Answer 26

An electrolyte is formed when an ionic compound (e.g. salt) dissolves in water.
* Electrolytes can conduct electricity
* The key electrolytes in the body include sodium, potassium, chloride, magnesium, phosphate, bicarbonate
* Electrolytes are important body constituents because:
o Conduction of electricity is essential for nerve/muscle function
o They exert osmotic pressure important for water balance
o Some play an important role in acid base balance
Electro = Electric, lyte = from ‘lutos’ meaning released

Question 27

Acids and bases

Answer 27

• An acid is a substance that releases a high amount of H+ ions when dissolved in water
• A base is a substance which binds to hydrogen irons in solution. This creates lots of OH-
• Water is a neutral solution because that every H+ released and OH- is also created. Although, if you steal H+ from a water molecule (H2O), you are left with lots of OH-
• The pH scale was developed using water as a standard. The pH of water is 7. Anything with a pH lower than 7 is an acid and anything higher than 7 is considered a base (alkali)
• The blood closely monitors and maintains an optimal pH of 7.35-7.45 for chemical reactions to occur, whilst the stomach has an optimal pH of 2-3
  pH = ‘potential of hydrogen’

Question 28

Acids and bases: alkaline foods

Answer 28

In a healthy digestive system, the following is the case;
* Fruit and vegetables contain organic acids and hence may have a low pH when measured as foods before consumption. Yet these organic acids can be metabolised by the body and intestinal bacteria to become alkaline.
* These foods are also high in alkaline minerals e.g. potassium, magnesium and calcium, which contribute to their net alkaline effect

Question 29

Acids and bases: acidic foods

Answer 29

• Before consumption, dairy is not very acidic and is also high in calcium, an alkaline mineral. Yet dairy is considered more ‘acidic’ because of the higher proteins/sulphur amino acid content. The sulphur amino acids increase sulphuric acid formation, which and then disrupts blood pH drawing more calcium from bones and increasing calcium lost in urine.
• For this reason meat, also high in sulphur amino acids, will have a net acid effect regardless of whether or not it is organic, since amino acid ratios are identical in both
• Other acidic foods are those rich in refined sugars and processed foods. It is also worth noting that stress and being sedentary also create an acidic environment

Question 30

Testing pH in the body

Answer 30

Cancer lives in an acidic environment. It is thought that a tissue pH of 8 of above would start to kill cancer cells
* It is vital to consider tissue acidity when considering the ‘terrain’ of the body, i.e. What is the environment
* Given the significant link between body acidity and the effect this has an optimising the environment for various diseases such as cancer, it is vital practitioners are able to measure pH
* Ideally we would measure ‘ tissue pH’ directly, although this is very difficult. The blood will always work hard to maintain its own pH (through breathing, the kidneys and buffer systems) between 7.35–7.45. Therefore, urine and saliva are the good ‘outputs’ of the body to assess.
Using a strip of pH (litmus) paper instructions:
* Urine: urinate onto a strip on your second urine output in the morning (about an hour after your first urine output upon waking). Measure the pH midstream
* Saliva: wash your mouth upon waking with plain water. Wait for about 10 minutes and then spit onto the pH paper.
Remember this gives you information about the terrain/environment. You’re aiming for a slightly alkaline or neutral pH. Many cancer patients do in fact have pH results of 4.5-6. pH is a close reflection of what an individual has eaten.

Question 31

Chemical Reactions

Answer 31

Chemical reactions occur when new bonds are formed or old bonds are broken between different molecules.
* Every reaction involves the transfer of energy to either potential (stored) energy, kinetic energy or heat
* The starting materials are known as the reactants and the end molecules are known as the products
* Reactions are written in formula and they must always balance electrons from one side to the other
* E.g. A + B =AB
For a chemical reaction to occur, there needs to be the opportunity for two molecules to collide (‘collision theory’).
* The higher the energy of the molecules, the faster they move and the greater chance they have of reacting
* The minimum energy that is required for a reaction is known as the energy of activation
* Chemical reactions are reliant on the correct temperature and enough reactants
* Changes in pressure can also change the speed of reactions, with increasing pressure forcing molecules closer together

Question 32

Catalyst and inhibitors

Answer 32

A catalyst speeds up reactions by lowering the activation energy required
* This means the reaction is faster or can occur at a lower temperature
* Catalysts that the body produces are called ‘enzymes’. For example, consider the enzyme ‘HMG-CoA reductase’ in the production of cholesterol and CoQ10
* Inhibitors act antagonistically to catalysts. They stop the catalyst from being so effective by making the activation energy higher and hence slow down the reaction time. Many drugs are inhibitors e.g. ‘statins’ are HMG-CoA reductase inhibitors

Question 33

Types of Chemical Reactions

Answer 33

Anabolic reactions are synthesis (building) reactions
* This occurs when the body is making new substances and building bonds
* For example, taking amino acids and building a protein. This requires energy
* A + B = AB
Catabolism (catabolic reactions) describes reactions where ‘breaking down’ occurs
* For example, when breaking down food, releasing energy from them. We trap that energy as ‘ATP’.
* AB = A + B

Question 34

Chemical Reactions: Water

Answer 34

• When water is the medium that breaks down the molecule into smaller pieces, it is known as a hydrolysis reaction.
• When water is formed as the waste product of a reaction, it is known as a dehydration synthesis; this is normally when larger molecules are being made, e.g. when making carbohydrates.
  Hydro = water, lysis = split

Question 35

Reversible Reactions

Answer 35

Reversible reactions describe chemical reactions whereby the products of the reaction can react together to produce the original reactants (meaning it can go back the other way).
A + B = AB / AB = A + B
Represented by: A + B

• These kind of reactions establish an equilibrium where there are always some starting materials and some product present.
• Controlling the direction of reversible reactions is very important in the body. This is done using enzymes and having mechanisms in place that allow us to remove starting materials and products.

Question 36

Buffer Systems

Answer 36

Buffers are substances that maintain the H+ concentration in the body within normal limits. They can bind to H+ ions and OH- to ensure the blood pH remains between 7.35–7.45
* The most important buffer system in the blood stream is the bicarbonate (HC03-) buffer system, which ‘mops up’ excess acidity
* Catalysed by carbonic anhydrase, carbon dioxide from cellular respiration reacts with water in the blood to form carbonic acid, which rapidly dissociates to form a bicarbonate and hydrogen ion.
* These reactions are reversible – at any given time there’s a balance of carbon dioxide, water, carbonic acid, H+ & HCO3- in the blood
CO2 + H2O H2CO3  HCO3- + H+

• When extra hydrogen ions accumulate in the blood, for example, after strenuous exercise (increased lactic acid), the reaction is able to adjust to mop up the extra H+ ions, making more carbon dioxide and water.
• This is then accounted for by increasing breathing rate and hence the exhalation of carbon dioxide through the lungs
• The kidneys also play a key role in the buffer system, as they can produce the HCO3- buffer. They can also excrete excess H+ ions
• The kidneys are fairly slow in this system and their production of HCO3- is fairly strenuous upon the organ. Therefore, it is important to avoid an acidic diet, so as to reduce the stress placed on this system.

Question 37

Oxidation and Reductase Reactions

Answer 37

The removal of electrons from an atom or molecule is called ‘oxidation’.
* Oxidation reduces the potential energy in a compound. Generally most oxidation occurs by removing electrons with the help of hydrogen.
* Because hydrogen is lost, this is often called a dehydration reaction
When something is ‘reduced’, it gains electrons, resulting in the increase of energy in the molecule
* A gain of hydrogen
Acronym: OIL RIG = oxidation is loss, reduction is gain

Question 38

Free Radicals

Answer 38

Free radicals are molecules or compounds that have an unpaired electron in their outer shell
* Free radicals want to stabilize that outer shell, so they try and ‘steal’ electrons from other stable molecules. By doing so, they become destructive, causing ‘oxidation’.
* This leaves the attacked molecule with an unpaired electron, so a chain reaction of oxidative damage occurs. Free radicals can even take electrons from DNA, which can damage genes and can ultimately results in cancerous changes.

Question 39

Oxidative Damage

Answer 39

• Free radicals can cause ‘oxidative damage’ to tissues in the body.
  Oxidative damage is linked to cancer, atherosclerosis (endothelial damage), fibromyalgia and neurodegenerative diseases
• Free radicals develop from processes within our bodies such as aerobic respiration, metabolism and inflammation
• They can also come from the environment e.g. Pollution, sunlight, strenuous exercise, x-rays, smoking, alcohol
• In a healthy body there are mechanisms in place to mop up excess free radicals, but if exposure is high these can become overwhelmed
• We need to reduce the exposure of our clients to excess sources of free radicals, whilst also optimizing their antioxidants status in an effort to protect them from free radical change

Question 40

Antioxidants

Answer 40

Antioxidants work by donating an electron to the free radicals to convert them to harmless molecules, without being damaged themselves.
* Antioxidants consist off a group of vitamins, phytochemicals and enzymes that work to neutralize free radicals before they harm bodies
* The key to a good antioxidant is that it must be stable once it has given away its electron
* Examples of antioxidants: vitamins C, beta-carotene, vitamin E, quercetin, glutathione peroxidase

Question 41

Antioxidant recycling

Answer 41

Antioxidants (AO) work best as a collection, where they can recycle each other. They do not work in isolation.

Question 42

Biochemical molecules

Answer 42

Living things are characterised by molecules made from carbon
* Any other groups of atoms that are attached to the carbon skeleton known as ‘functional groups’.
* Functional groups contribute to the structure and function of that molecule
Biochemical molecules are important when considering the living nature of biochemistry
* Ultimately cells require energy to function, which comes from breaking chemical bonds from what we have absorbed from our foods

Question 43

Functional groups: Hydroxide group

Answer 43

N/B: the ‘R’ is an abbreviation for the unreactive part of the molecule that is just made up of carbon and hydrogen bonds

Hydroxyl group: R – O
H

• Alcohols – they are polar and hydrophilic
• Dissolve easily in water
  (hydro = hydrogen, -oxy = oxygen)

Question 44

Functional groups:
Sulfhydryl group

Answer 44

Sulfhydryl group: R - S
H

• Common in some protein chains. Founded in sulphur–containing amino acids cysteine.
• Polar and hydrophilic
  (sulf = sulphur -oxy = oxygen)

Question 45

Carboxyl groups:

Answer 45

Carboxyl group: O

                             C
                  R                   OH

• Found in amino acids
• They are hydrophilic and can interact as a weak acid or as negative particle
  (carbo = carbon, -oxy = oxygen)

Question 46

Amine groups:

Answer 46

Amine group: H H
N

                                    R

• Found in amino acids
• The –NH2 Group can act as a weak base if necessary (mopping up H+)
  (amine =amino (acid))

Question 47

Esters groups:

Answer 47

Esters: O

                     C

            R                 OR

• Predominant bond in triglycerides
  (ester – meaning ‘vinegar’)

Question 48

Phosphate

Answer 48

Phosphates: O

       R           O          P          OH

                                OH

• Found in ATP
• Phosphate groups are very hydraulic (dissolve easily in water), as they can form a double negative charge

Question 49

Carbohydrates

Answer 49

Carbohydrate include starches (bread, Pasta etc), cellulose (plants) and sugars.
* All carbohydrates are made of C-H-O
* The carbon atoms are normally arranged in a ring with oxygen and hydrogen atoms attached.
* Carbohydrates have many –OH groups so they can form hydrogen bonds. This means the smaller carbohydrates such a simple sugars can dissolve easily in water.
* Carbohydrates are grouped into 3 classes, depending on their size: monosaccharides, disaccharides and polysaccharides
Carbo/hydrate = meaning the carbon is ‘hydrated’

Question 50

Monosaccharides

Answer 50

Monosaccharides (3-7 atoms): Single sugars;
* Glucose
* Fructose
* Galactose
* Deoxyribose
* Ribose
Glucose = from ‘glukus’ meaning is sweet, fructose = from ‘fructus’ meaning fruit, lactose = from ‘lac’ meaning milk

Question 51

Major Carbohydrate groups: Disaccharides

Answer 51

Disaccharides: Two monosaccharides joined together by dehydration reaction;
* Sucrose = glucose + fructose
* Lactose = glucose + galactose
* Maltose = glucose + glucose

Question 52

Major Carbohydrate groups: polysaccharides

Answer 52

Polysaccharides:
10s – 100s of monosaccharides joined together by dehydration reaction:
* Glycogen – glucose chain
* Starch – glucose chain
* Cellulose – glucose chain

Question 53

Monosaccharides

Answer 53

Monosaccharides are simple sugars that exist as single molecules, e.g. glucose and fructose
* Most monosaccharides have a sweet taste – fructose is the sweetest
* Monosaccarides are grouped into families named after the number of carbon atoms
* The name of monosaccharides all end in –ose
o Triose (3 carbons)
o Pentose (5 carbons)
o Hexoses (6 carbons) e.g. glucose / fructose
o Heptose (7 carbons)
Mono = one, saccharide = sugar

Question 54

Isomer

Answer 54

Isomers have the same chemical formula but different structures.
* Anaology: Each atom is a Lego brick. The same number of Lego bricks can be used to create different structures, e.g. a house or a car.
* E.g. C6H12O6 is the formula for fructose, glucose, galactose and mannose
* Honey is an example of something that contains a combination of these isomers i.e. it is formed from a combination of fructose and glucose (almost 1:1)
Iso = equal/same

Question 55

Disaccharides

Answer 55

Two monosaccharides can join together in a dehydration synthesis to form a disaccharide.
* This dehydration reaction occurs by ‘removing water’ to create a ‘glycosidic bond’.
* If we were to ingest a disaccharide, we can break it apart by putting water back into the bond – this is known as ‘hydrolysis’.
* Lactose constitutes 5% of cows milk and 7% of human milk
* Maltose is formed during the hydrolysis of starch
* Sucrose is table sugar (glucose and fructose)
Di = two, saccharide = sugar, sucrase = from ‘sucre’ meaning sugar

Question 56

Polysaccharides

Answer 56

Polysaccharides contain 10s – 100s of monosaccharides in glycosidic bonds.
* Typically long chains of glucose molecules joined together e.g. starch, glycogen and cellulose
* They are normally insoluble in water (because they have given up many
–OH groups) and hence starch (e.g. Pasta) doesn’t just dissolve in water.
* Polysaccharides do not taste sweet
* Their digestion begins in the oral cavity
* The most common type in the body is glycogen
Poly = many, saccharide = sugar, cellulose = from ‘cellule’ meaning small cell,
glyco = sweet, -gen = to become

Question 57

Starch: Amylose and Amylopectin

Answer 57

Starch is the major dietary source of carbohydrate.
* Starch is found in foods such as bread, rice and pasta. Is digestions begins in oral cavity
* Starch is made up of two different polysaccharide components
o 20 – 25% = amylose
o 75 - 80% = amylopectin
* Amylose is a single chain of glucose units
* Amylopectin is also made from glucose chains, but it has a branch-like structure
Amylopectin is highly branched, leaving more surface area available for digestion.
* It’s broken down quickly, which means it produces a high rise in blood sugar (glucose) and subsequently a high rise in insulin
Amylose is a straight-chain, which limits the amount of surface area exposed for digestion
* Foods high in amylose are sometimes referred to as sources of resistant starch as they are digested more slowly
* Due to its slower digestion, some resistant starch ends up in the large intestine where it can act as a food source for the bacteria there.
From ‘amylum’ meaning starch, -ose = sugar, -pectin = meaning ‘make solid’

Question 58

Glycogen

Answer 58

Glycogen is a polysaccharide of glucose which functions as the primary short-term energy storage
* Each glycogen molecule is made up of about 60,000 glucose molecules and has even more branches than amylopectin
* It is made and stored primarily by the liver and the muscles
* Glycogen in the liver can be used to help maintain blood sugar levels
* Whereas the glycogen in the muscles can only be used by that particular muscle

Question 59

Cellulose

Answer 59

Cellulose is the structural material of plants – found it in plant cell walls
* It is also a glucose polymer but the units are linked in a different way using different bonds, giving a flat ribbon-like strand, with an overall rigid structure
* Humans lacked the correct enzymes to break the ‘unique’ bonds between glucose molecules in cellulose, so we cannot digest it
* Instead, cellulose acts as fibre which assists with the movement of materials through the intestines
* Cellulose is the single most abundant organic compound on earth

Question 60

Functions of carbohydrates

Answer 60

Energy: carbohydrates are a primary fuel for energy production and also provide a limited storage form of energy, glycogen (are you fasting).
* Fibre (cellulose):
o Needed for proper bowel function
o Protects against cardiovascular disease (14 g per 1000 kcal)
o Protects against diabetes (15 g per day)
o Increase satiety (14 - 24 g per day) and aids weight loss (14 g per day)
o Protects against colorectal cancer
* Glucose can be used for a number of processes, including ATP production, glycogen synthesis, triglyceride synthesis (if excess in quantity) and amino acid synthesis

Question 61

Carbohydrate digestion

Answer 61

• Salivary amylase starts working on the end of the long glucose chains in starches (hence if you choose starch are a long period, you start taste sweetness)
• Salivary amylase works well at a fairly neutral pH, but is deactivated by stomach acid
• In the small intestines, the pancreas releases pancreatic amylase which continues carbohydrate digestion, but this time into disaccharide units
• The last stage of carbohydrate digestion involves brush border enzymes in the small intestine (lactase, maltase and sucrase)
  N/B: remember that in pathologies such as coeliac disease, the brush border can be damaged leading to poor carbohydrate digestion

Question 62

Lipids

Answer 62

Lipids contain the elements carbon, hydrogen and oxygen, just like carbohydrates, but in a different ratio.
* Lipids have fewer polar –OH groups, so they are hydrophobic
* To move around the body they are often bonded to a protein to make them more soluble (proteins act like ‘taxis’). They are then called ‘lipoproteins’.

Question 63

Triglycerides

Answer 63

Triglycerides are the main form of dietary fat.
* Contain a single glycerol molecule and three fatty acid chains (these can be saturated or unsaturated– this combination will determine whether it solid or liquid at room temperature)
* Fatty acids are attracted to glycerol by a dehydration synthesis reaction and the bond formed is known as an ‘ester’ (different from the glycosidic bond seen in carbohydrates)
* They are broken down by hydrolysis reaction (like with carbohydrates)

Question 64

Functions of triglycerides

Answer 64

• Fats provide a source of energy, but the process of energy released from fat is less efficient than when carbohydrates are used
• Fax provide a convenient form in which to store excess calorific intake (extra glucose is also turned into triglycerides)
• Insulation
• Protection of body parts and organs (e.g. kidneys)

Question 65

Saturated fats

Answer 65

Saturated fats contain single covalent bonds between each of the fatty acid carbon atoms.
* Each carbon atom is saturated with hydrogen atoms
* Saturated fatty acids are very straight, meaning they can line up close to each other and hence are more likely to be solid. Saturated fats are generally solid at room temperature, e.g. coconut oil
Saturated = full Monounsaturated fats

Question 66

Monounsaturated fats

Answer 66

Monounsaturated fats contain fatty acids with one double covalent bond between two carbons.
* The double bond forces the molecule into a bent configuration
* Mono unsaturated fats are generally liquids at room temperature because the molecules can’t pack very closely together e.g. olive oil
Mono = one (meaning one double bond)

Question 67

Polyunsaturated fats

Answer 67

Polyunsaturated fats contain more than one double bond in the carbon chain
* These molecules are ‘kinked’ so they too, are liquids at room temperature, e.g. Sunflower oil, rapeseed oils, vegetable oils

Question 68

Naming fatty acids

Answer 68

• Fatty acids are named according to the closest double bond to the end of the chain
• The end of the chain is always the end without oxygen’s
  o Omega-3 – the double bond is three carbons up from the end
  o Omega-6 – the double bond is six carbon from the end
• Omega-3 and omega-6 our essential in our diet

Question 69

Cis and trans configurations

Answer 69

The presence of a double bond means that two different molecular configurations are possible
o A cis configuration is when the H atoms are on the same side of the double bonds
o A trans configuration is when the H atoms are on separate sides of the double bond

• In nature, nearly all fats have a cis structure. Our body recognizes these and can use them
• When we try to create these fats in laboratories/industry, they position the H atoms on opposite sides where they have more space
• Consider eating sunflower seeds (i.e. from nature) vs. eating something cooked in sunflower oil

Question 70

Cis and Trans

Answer 70

A cis fatty acid is bent, whereas a trans fatty acid is more linear
* Cis and Trans have different properties, especially when incorporated into biological structures such as cell membranes. Cis fats make cell membranes more flexible. Trans fats ‘stiffen’ cell membranes and are prone to oxidative damage and making cell membranes leaky
* Cis fats can be turned into Trans fats by heating to high temperature or heating oil repeatedly (the hydrogen spins around)
* They are also formed during hydrogenated reactions used to make process foods and margarine (trans fat)
* Consider how an oil that keeps being heated becomes thicker as the fatty acids become more linear and hence more solid.

Question 71

Essential fatty acids

Answer 71

Essential fatty acids (or EFAs) are polyunsaturated fatty acids that cannot be constructed within the body from the other components and therefore, must be obtained from the diet
* There are two families of EFAs: Omega-3 and Omega-6
* The body can convert one omega-3 to another omega-3, for example, but cannot create an omega-3 from scratch

Question 72

Omega-3 Fatty Acids

Answer 72

Omega-3 fatty acids:
* a-linolenic acid (ALA) – essential in the diet
* Eicosapentaenoic acid (EPA)
* Docosahexaenoic acid (DHA)

Question 73

Omega-6 Fatty Acids

Answer 73

Omega-6 fatty acids:
* Linoleic acid (LA) – essential in the day
* Gamma linoleic acid (GLA)
* Arachidonic acid (AA)

Question 74

Omega-3 and Omega-6 fatty acids; Word derivations

Answer 74

Lino = Greek for flax (linseed)
-oleic = relating to olive oil (oleic acid)
docosa = Greek for 22 (meaning 22 carbons)
eicosa = Greek for 20 (meaning 20 carbons)
penta = from pentagon / 5 (meaning 5 double bonds)
hexa = from hexagon / 6 (meaning 6 double bonds)
-enoic acid = a carboxyl group (-COOH)
arachidonic = from arachidic = of the groundnut (the Greek for peanut is arachis), which has a similar fatty acid structure

Question 75

Omega-3 and Omega-6 fatty acids

Answer 75

The Omega-3 family:
* Alpha linoleic acid (ALA); your body converts some ALA into =
* Eicosapentaenoic acid (EPA); your body converts EPA into =
* Docosahexaenoic acid (DHA)
Omega-3 fats include:
ALA = flaxseeds, walnuts, green leafy vegetables.
EPA & DHA = oily fish

The Omega-6 family:
* Linoleic acid (LA); your body converts some LA into =
* Gamma linoleic acid (GLA); your body converts GLA into =
* Arachidonic acid (AA)
Omega-6 fats include:
LA = vegetable oils, most nuts/seeds
GLA = borage oil, evening Primrose oil
AA = meat, dairy and eggs

For healthy cells and healthy cell-to-cell communication, a diet would ideally contain a well sourced variety of Omega-3 and Omega-6 fats

Question 76

Omega-3 and 6 fatty acids conversion

Answer 76

The conversion of ALA to EPA and DHA is only about 10% efficient, and even lower for LA to and AA
* This conversion for LA and ALA is dependent upon the same enzymes. It will ultimately favour the EFA that is in abundance (often Omega-6)
* The conversion between them involves adding in double bonds. This involves ‘desaturase’ enzymes
* Most western diets are rich in Omega-6; especially arachidonic acid. This is pro inflammatory

Question 77

Functions of EFAs

Answer 77

• Fluidity and structure of cell membranes
• Synthesis of prostaglandins – hormone like substances responsible for many functions at cellular level and regulating body processes
• Regulating oxygen use, electron transportation and energy production
• Help to form haemoglobin
• Support the production of digestive enzymes
• Help make the lubricants for joints
• Help transport cholesterol in the blood
• Help generate electric currents and keep the heart rate regular
• Needed by the tissues of the brain, retina, adrenal glands and testes
• Help balance the immune system and prevent allergies
• Ensure proper nerve transmission especially in the brain

Question 78

Oxidation and fatty acid

Answer 78

Polyunsaturated fats such as EFAs are very prone to becoming free radicals
* When these fats are heated, electrons can be lost. This means that a fat is formed that becomes a free radical. This then further reacts with the oxygen in the air over the cooking pan which becomes even more damaging
* The CH2 groups between the double bonds are especially vulnerable because radicals formed at these points in the molecules are very stable
* The damaged fats formed will be incorporated into cell membranes
Radical formation is accelerated by light, oxygen and heat
* Keep polyunsaturated fats in dark glass bottles in fridge – never use for cooking!
* To cook with, you should use saturated fats (where there are no vulnerable points for elections to be stolen), e.g. organic coconut oil (for higher temperatures)
* It is thought that olive oil can be used to cook at lower temperatures because it only has one double bond
* However, it has been shown that extra virgin olive oil remains stable when cooked at higher temperatures. This exception is thought to be due to its higher antioxidant content

Question 79

Lipoproteins

Answer 79

A lipoprotein is a fat molecule that has been joined to a protein molecule, enabling the lipid to move around the bloodstream
* Lipoproteins contain triglyceride and cholesterol internally
* Remember that fats are hydrophobic
* Lipoproteins are synthesised by the liver
* Note: Chylomicrons carry triglycerides from the intestines to the liver, skeletal muscle and adipose tissue

Question 80

Types of Lipoprotein

Answer 80

• Very low-density Lipoproteins (VLDL)
  o Carry newly synthesised triglycerides from the liver to adipose tissue (if high: a sign of a over-eating)
• Low-density Lipoproteins (LDL)
  o Carry cholesterol from liver to cells of the body. Needed to repair cells, support cell membranes and synthesise sex and adrenal hormones
• High-density Lipoproteins (HDL)
  o Collect cholesterol from the body’s tissues, bringing it back to liver
  The balance between LDL and HDL is ultimately important

Question 81

Phospholipids

Answer 81

Phospholipids contain a phosphate part and two fatty acid chains
* The phosphate head contains lots of –OH molecules, which make it hydrophilic. It is therefore, polar and water-soluble.
* The fatty acid tails are non-polar and interact only with other lipids. They are hydrophobic and fat-soluble
* The fatty acid tails can contain saturated and unsaturated fats (i.e. mono / poly). Cells should contain a balance of these to support a healthy cell membrane structure that is not excessively rigid or fluid
* As they are soluble on one side and insoluble on the other, they are known as ‘amphiphatic’.

Question 82

Steroids

Answer 82

Steroids are lipids that formed from cholesterol.
* They differentiate in shape from triglycerides where they are formed of four rings of carbon atoms joined together at their base
* Sterols are steroid basis that contain an –OH group
* Steroids are used to create hormones, e.g. oestrogen, testosterone, cortisol, etc.
* We do not need to eat/ingest cholesterol because the liver can produce it