3. CHEMISTRY & BIOCHEMISTRY 1 Flashcards
This module covers: • Key concepts in chemistry and biochemistry, including water, pH and buffers. • Structure and functions of carbohydrates. • Structure and functions of lipids.
State THREE functions of triglycerides
- Fats provide a source of energy, but the process of energy released from fats is less efficient than when carbohydrates are used.
- Fats 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).
What is Chemistry?
The science that deals with the composition and properties of substances and various elementary forms of matter (gas, liquid, solid).
What is Biochemistry?
The science concerned with the chemical and physicochemical processes and substances that occur within living organisms.
What is matter?
Everything around us that has mass and occupies space
What are atoms?
Atoms are small particles that make up matter
What are atoms made up of?
Electrons, protons and neutrons
What is an element?
A element is a substance made up of one type of atom so it cannot be split up into simpler substances
Where are all known elements recorded?
Periodic table
List the chemical symbol for the following:
* Hydrogen
* Carbon
* Calcium
* Magnesium
- H+
- C
- Ca
- Mg
Where are all known elements recorded?
Periodic table
How many elements are there in the human body?
26
Name 4 major elements that make up 96% of the human body?
Carbon, hydrogen, oxygen and nitrogen
Describe:
When a chemical reactions occurs, what happens to the bonds?
Chemical reactions occur when new bonds are formed or old bonds are broken between different molecules.
In which TWO ways does energy transfer change in every chemical reation?
Energy changes from either potential energy (stored) or kinetic energy (heat).
In chemical reactions what are the STARTING and END materials called respectively?
- Reactants
- Products
In what way are chemical reactions written?
Reactions are written in a formula. They must always balance in electrons from one side to the other.
What is needed for a chemical reactions to occur?
Collision. There needs to be the opportunity for two molecules to collide to strart with.
What happens when when the molecules posses higher energy?
The molecules move faster and they have a greater chance of reacting.
What is the minimum energy that is required for a reaction known as?
It is known as the ENERGY OF ACTIVATION
What do chemical reactions rely on?
They rely on the correct temperature and enough reactants.
What can change the speed of reactions apart from temperature and reactants.
Changes in Pressure: Increasing pressure forces molecules closer together.
What do catalysts do in a chemical reaction?
Catalysts speeds up reactions by lowering the activation energy required. It means that the reaction if faster or can occur at a lower temperature.
What is the name of the catalysts that the body produces and give one example.
Enzymes, HMG-CoA reductase in the production of cholesterol and CoQ10
What do inhibitors do in relationship to catalysts?
They act antagonistically. They stop the catalysts from being so effective by making the activation energy higher and hence slow down the reaction time.
Name the HMG-CoA reductase inhibitor?
STATINS
Define anabolic reactions and give an example?
Anabolic reactions are synthesis (building) reactions. E.g Taking amino acids and building a protein. This requires energy.
Define catabolism and provide an example.
Catabolism describes reactions where ‘breaking down’ occurs. E.g. When breaking down food, releasing energy from them. We trap that energy as ‘ATP’.
Define ‘Hydrolysis reaction’
when water is the medium that breaks down the molecule into smaller pieces, it is known as a hydrolysis reaction.
Explain what is dehydration synthesis and give an example.
When water is formed as the waste product of a reaction. This is normally when larger molecules are being made, e.g. when making carbohydrates.
What are ‘reversible reactions’?
They 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
How do you control the direction of reversable reactions in the body?
This is done using enzymes and having mechanism in place that allow us to remove starting materials and prodcuts.
What is the function of buffers?
Buffers 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.
Name the buffer system that mops up excess acidity.
The most important buffer system in the blood stream is the bicarbonate (HCO3)- buffer system.
What forms when carbon dioxide from cellular respiration reacts with water in the blood?
Carbon dioxide, catalysed by carbonic anhydrase form carbonic acid which rapidly dissociates to form a bicarbonate and hydrogen ion.
Give the formula for carbon dioxide, water, carbonic acid, hydrogen and a buffer in the blood.
CO2+H2O ↔ H2CO3 ↔ HCO3- + H+
Describe the workings of the lungs as a buffer system.
When extra hydrogen ions accumulate in the blood, for example after strenous excercise ( ↑ lactic acid), the reaction is able to adjust to mop up the extra H+ ions, making more carbon dioxide and water.
This then accounted for by increasing the breathing rate and hence the exhalation of carbon dioxide through the lungs.
Describe how the kidneys function as a buffer system.
Kidneys produce HCO3 which acts as a buffer. They can also excrete excess H+ ions. But this is a fairly slow and strenuous process, so it is important to avoid an acidic diet to reduce the strain on this system.
What is meant by ‘oxidation’?
It is the loss of electrons from an atom or a molecule.
How does most oxidation generally occur?
Most oxidation occurs by removing electrons with the help of hydrogen.
What happens to the energy in a compound by oxidation?
Reduction of the potential energy in the compound.
Name the reaction when hydrogen is lost?
It is called a Dehydration reaction
What happens when something is ‘reduced’ in a chemical reaction?
When something is ‘reduced’, it gains electrons, resulting in the increase of energy in that molecule. A gain of hydrogen is normally indicative of something being reduced.
What are ‘free radicals’?
Free radicals are molecules or compounds that have an unpaired electron in their outer shell.
What do free radicals do?
Free radicals want to stabilise their outer shell, so they try and ‘steal’ electrons from other stable molecules. By doing so, they become destructive, causing ‘oixidation’.
What happens to a molecule with an unpaired electron?
A chain reaction of oxidative damage occurs. Free radicals can even take electrons from DNA, which can damage genes and can ultimately result in cancerous changes.
Give 4 examples of conditions linked to ‘oxidative damage’?
It is linked to cancer, atherosclerosis (endothelial damage), fibromyalgia and neurodegenerative diseases.
From which processes within our bodies and from the environment can free radical damage occur?
Within our bodies it can result from aerobic respiration, metabolic processes and inflammation.
From the environment e.g. pollution, sunlight, strenuous exercise, X-rays, smoking and alcohol.
How do antioxidants work?
Antioxidants donate electrons to free radicals to convert them to harmless molecules, without being damaged themselves.
What is the key to a good antioxidant?
The key to a good antioxidant is that it must be stable once it has given away its electron(s).
Name 5 antioxidants
Beta carotene
Vitamin C
Vitamin E
Quercetin
Glutathione peroxidase (antioxidant enzyme).
In which way do antioxidants work best?
Antioxidants work best as a collection, where they can recycle each other. They do not work in isolation.
What is a key characteristic of living things?
Living things are characterised by molecules made from carbon.
Characterise functional groups
Any other groups of atoms that are attached to the carbon skeleton are known as ‘functional groups’.
What is the purpose of the functional group in a molecule?
Functional groups contribute to the structure and function of that molecule.
Explain what does ‘R’ group in chemical reaction stand for?
The ‘R’ group is an abbreviation for the unreactive part of the molecule that is just made up of carbon and hydrogen bonds.
What are some characteristics of Sulfhydril groups and where are they found?
They are polar and hydrophilic. They are common in some protein channels. Found in the sulphur-containing amino acid cysteine.
What are some characteristic signs of a Carboxyl group?
Found in amino acids. They are hydrophilic and can interact as weak acids or as negative particles.
Where can Amine groups be found?
Found in amino acids. The - NH2 group can act as a weak base if necessary (mopping up H+).
Where do you find Esters?
Predominate bond in triglycerides.
What are some characteristic of Phosphate groups and where are they found?
Found in ATP. Phosphate groups are very hydrophilic (dissolve easily in water), as they can form a double negative charge.
What are all carbohydrates made of and what types do they include?
Carbohydrates are made of C-H-O and they include starches (bread, pasta etc.), cellulose (plants) and sugars.
What groups do carbohydrates have in their structure?
O-H groups - hydroxyl groups so they can form hydrogen bonds. This means the smaller carbohydrates such as simple sugars can dissolve easily in water.
Which 3 classes are carbohydrates grouped into?
Monosaccharides, disaccharides and polysaccharides.
Name 5 monosaccharides
Glucose, Fructose, Galactose, Deoxyribose, Ribose.
Name 3 disaccharides and how they break down into monosaccharides
- Sucrose = glucose + fructose
- Lactose = glucose + galactose
- Maltose = glucose + glucose
Name 3 Polysaccharides
Glycogen - glucose chain
Starch - glucose chain
Cellulose - glucose chain
What are monosaccharides?
Monosaccharides are simple sugars that can exist as single molecules, e.g., glucose and fructose.
How are monosaccharides grouped and what is their ending?
Monosaccharides are grouped into families named after the number of carbon atoms. The names end in -OSE. e.g. triose (3 carbons), Pentose (5 carbons), Hexoses (6 carbons) e.g. glucose/fructose
What is the characteristic of Isomers? Give the formula for the isomers fructose, glucose, galactose and mannose.
Isomers have the same chemical formula but different structures. C6H12O6
How are disaccharides formed?
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’.
Explain Hydrolysis
If we were to ingest a disaccharide, we can break it apart by putting water back into the bond - this is known as hydrolysis.
When is maltose formed?
During the hydrolysis of STARCH.
How many monosaccharides are in polysaccharide bonds?
10s - 100s of monosaccharides are in glycosidic bonds in polysaccharides.
What is one important characteristic of Polysaccharides?
They are normally INSOLUBLE in water (because they have given up many - OH groups) and hence starch (e.g. pasta) just doesn’t dissolve in water.
Polysaccharides do not taste sweet. Their digestion begins in the oral cavity. The most common type in the body is glycogen.
In which foods can we find starch and where does it first start being digested?
Found in bread, rice and pasta. Starch begins to be digested in the oral cavity.
Which two polysaccharides is starch made up of?
20-25% Amylose - a single chain of a glucose units
78-80% Amylopectin - glucose chains with a branch-like structure.
What is special about Amylopectin?
Amylopectin is highly branched, leaving more surface area available for digestion. It is broken down quickly, which means it produces higher rise in blood sugar (glucose) and subsequently, a higher rise in insulin.
What is special about Amylose?
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.
Some resistant starch end up in the large intestine where it can act as a food source for the bacteria there.
What is glycogen?
Glycogen is a polysaccharide of glucose which functions as the primary short-term energy store in the body.
How many glucose molecules make up each glycogen molecule?
60,000 glucose molecules make up each glycogen molecule, which has even more branches than amylopectin.
Where is glycogen primarily stored and made?
In the liver and the muscles.
What is the function of glycogen in the liver?
Glycogen in the liver can be used to help maintain blood sugar levels.
What is the job of glycogen in the muscles?
Glycogen in the muscles can only be used for energy by that particular muscle.
What is cellulose?
Cellulose is the structural material of plants - found in plant cell walls.
Can humans break down cellulose and what does it do in our body?
Humans lack the correct enzymes to break the ‘unique’ bonds between glucose molecules in cellulose, so we can’t digest it. Instead, cellulose acts as fibre which assists with the movement of materials through the intestines.
Explain the Function of carbohydrates
Energy: Carbohydrates are a primary fuel for energy production and also provide a limited storage form of energy, glycogen (i.e. fasting).
What are the functions of fibre?
Fibre is needed for proper bowel function and protects against cardiovascular disease, diabetes and colorectal cancer. It increases satiety and aids weight loss.
What is the function of glucose?
Glucose can be used for a number of processes, including ATP production, glycogen synthesis, triglyceride synthesis (if excess in quantity) and amino acid synthesis.
How are carbohydrates digested?
Salivary amylase starts working on the end of the long glucose chains in starches (hence if you chew starch for a long period, you will start to taste sweetness).
Salivary amylase works well at a fairly neutral pH, but is deactivated by stomach acid. In the small intestine, the pancreas releases pancreatic amylase which continues carbohydrate digestion.
The last stage involves digestion by the brush border enzymes.
[Remember in Celiac disease the brush border can be damaged leading to poor carbohydrate digestion.]
What is the current daily recommendation for fibre intake?
30g fibre per day
Which elements do lipids contain?
Carbon, hydrogen and oxygen
Just like carbohydrates, but in different ratios.
What are the characteristics of lipids?
Lipids have fewer polar -OH groups and 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’.
What are triglycerides?
The main form of dietary fat.
Contain a single glycerol molecule and three fatty acid chains that has undergone dehydration synthesis
Triglycerides contain a single glycerol molecule and how many fatty acid chains?
Three
Triglycerides can be either ……………or…………….., this depending on it being in a solid or liquid state at room temperature.
Saturated or unsaturated
How are fatty acids attached to glycerol? and what type of bonds are formed?
Which reaction breaks them down?
By a dehydration synthesis
Ester
Hydrolysis
Name four functions of triglycerides?
- A source of energy
- Store excess calorific intake
- Insulation
- Protection of body parts and organs
Which type of fats contain single covalent bonds between each of the fatty acid carbon atoms?
Saturated
Saturated fatty acids are very straight which means they are …….. at room temperature. Give one example.
Solid
Coconut oil
Describe monounsaturated fats and give one example.
How would it look on paper?
Typically they are……at room temp.
Monounsaturated fats contain fatty acids with one double covalent bond between two carbons. An example is olive oil.
Bent configuration
Liquid
What type of fats contain more than one double bond in the carbon chain?
What shape are they?
Give examples?
polyunsaturated
kinked
Sunflower oil, rapeseed oil, vegetable oils
Explain how the Omega 3 and Omega 6 EFA are named?
The first double bond is three and six carbons away from the end respectively
Name two Fatty Acids that are essential in our diet?
Omega 3 and Omega 6
Which configuration is when H atoms are on the same side as the double bond?
Cis
Which configuration is when H atoms are on separate sides of the double bond?
Trans
Which fats does our body recognise and are found in nearly all fats in nature?
Cis
What is the difference in shape between cis and trans?
Cis are bent and trans more linear
When incorporated into cell membranes, how do cis and trans fats differently affect it?
Cis fats makes the membrane more flexible and trans fats stiffen cell membranes
How can cis fats be turned into trans fats?
At high temperatures or repeatedly heating the oil.
What are Essential fatty acids?
EFA’s are Polyunsaturated fats and cannot be constructed within the body from other components, only from the diet.
Name the two families of essential family acids?
Omega 3 and Omega 6
Name the acids in Omega 3 fatty acids essential in the diet.
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
Name the Omega 6 fatty acids.
Linoleic acid (LA) essential in the diet. Gamma linolenic acid (GLA) Arachidonic acid (AA)
Give examples of food sources containing Omega 3 ALA?
ALA - flax seeds, walnuts, green leafy vegetables
What kind of food is a good source of Omega 3 EPA & DHA
oily fish
Give examples of food rich in Omega 6 LA?
vegetable oils, most nuts/seeds
Name two sources of Omega 6 GLA
- Borage oil
- evening primrose oil
Give examples of Omega 6 AA food sources.
Meat, dairy and eggs
Why do we need a healthy balance of Omega 3 and Omega 6 fats?
For healthy cells, and healthy cell to cell communication
What is the % efficiency of conversion of ALA to EPA?
10%
What does the conversion for LA and ALA depend on?
The same enzymes which usually favours the EFA that is in abundance. Usually Omega 6
Which enzymes are involved in adding double bonds for the conversion of EFAs?
Desaturase enzymes
Which Omega is (and in particular which acid) is pro-inflammatory?
Omega 6 - arachidonic acid
Name 5 functions of EFA’s?
- Fluidity and structure of cell membranes.
- Synthesis of prostaglandins.
- Regulate oxygen use, electron transport and energy production
- Help form haemoglobin, supports the production of digestive enzymes. Makes lubrication for joints.
- Helps transport cholesterol in the blood.
- Generates electric currents and keeps the heart rate regular.
- Needed by the tissues of the brain, retina, adrenal glands, testes
- Balances the immune system and prevents allergies.
- Ensures proper nerve transmission, especially in the brain.
What happens to polyunsaturated fat that is heated?
Electrons are lost and it becomes a free radical.
Which groups between double bonds now become vulnerable?
CH2
What happens to the damaged fats?
They are incorporated into cell membranes
Name three ways in which free radical formation can be accelerated?
- Light
- Oxygen
- Heat
Which fats should you never cook with and how should they be stored?
Polyunsaturated fats.
Store them in dark glass bottles in the fridge
Which saturated fat is the preferred option for cooking?
organic coconut oil
Which cooking method is Olive oil suitable for?
Lower temperatures for olive oil, extra virgin can be used at higher temperatures due to the higher level of antioxidants.
What does VLDL stand for and what is its function?
Very low-density lipoprotein carries newly synthesised triglycerides from the liver to the adipose tissue.
What’s the difference between LDL and HDL?
LDL carry cholesterol from the liver to the cells and HDL transports it back to the liver
What are the functions of LDL?
- Repair cells
- Support cell membrane
- Synthesise sex and adrenal hormones
Describe a phospholipid
Phospholipds contain a glycerol part and two fatty acid chains.
The phosphate head contains many OH- molecules which makes it hydrophilic, polar and water-soluble.
Which type of fats is contained in the fatty acid tails of phospholipids?
Saturated and unsaturated (ie mono- and poly-)
Cells need a balance of both
How do steroids differ from triglycerides?
They differ in shape. Triglycerides are formed from four rings of carbon atoms joined at their base.
What are steroids?
Steroids are lipids that are formed from
cholesterol.
Different from triglycerides,
where they are formed of four rings of
carbon atoms joined together at their base.
• Sterols are steroid bases 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.
What is the main function of steroids?
Creation of hormones eg oestrogen, testosterone, cortisol
