Option B - Human biochemistry Flashcards

Question

How is chromatography used to analyse proteins?

Answer 1

1. A small sample of the amino acid mixture is spotted near the bottom of some chromatographic paper 2. This position (the origin) is clearly marked in pencil 3. The paper is put in a chromatographic tank containing a small volume of some solvent, ensuring that the spot is above the level of the solvent 4. The solvent rises by capillary action and passes over the spot 5. Amino acids in the spot will distribute themselves to different extents because they move up the paper in different speeds and become spread out 6. When the solvent reaches the top of the paper its final position is marked (solvent front) 7. The paper is removed and developed by sparying with ninhydrin 8. The ninhydrin makes the amino acids purple and visible and they can be distinguished as separate spots up the length of the paper - The position of each amino acid can be expressed as an R_f value (retention factor): (distance moved by amino acid)/(distance moved by solvent) - If some amino acids are not separated, the paper can be rotated 90° and the procedure can be repeated with another solvent, this way the rest will spread too

Answer 2

- Based on the movement of charged particles in an electric field - Amino acids carry different charges and can be separated by this means when placed in a buffered solution 1. A polyacrylamide gel is used and the amino acid mixture is placed in wells in the centre of the gel 2. An electric field is applied. 3. Depeding on the pH of the buffer used, different amino acids will move at different rates towards the oppositely charged electrodes 4. At their isoelectric point, amino acids will not move as they carry no net charge 5. When the separation is complete they can be detected by a stain or under UV light and identified from their position using data tables

Answer 3

1. Structural proteins 2. Enzymes 3. Hormones 4. Immunoproteins 5. Transport proteins 6. Energy source

Answer 4

1. Keratin - Protective covering in hair and finger nails 2. Collagen - Connective tissue in skin and tendons 3. Myosin - Contractile action in muscles to bring about movement

Answer 5

Casein - Fod substance in milk

Answer 6

Carbon, hydrogen, and oxygen (H and O are always in the same ratio, 2:1)

Answer 7

1. Energy source (glucose and fructose) 2. Energy reserves (glycogen) 3. Precursors for other biologically important molecules

Answer 8

- Contain a carbonyl group (C=O) - At least two –OH groups - Have the empirical formula CH₂O - Ring structures are either α or β

Answer 9

Glucose and fructose

Answer 10

In α the –OH group at C₁ is below the plane of the ring In β the –OH group at C₁ is above the plane of the ring

Answer 11

The link between monosaccharides. Lies between the C₁ and C₄ of the separate molecules

Answer 12

By acid hydrolysis or enzyme-catalysed reaction

Answer 13

Lactose = β-glucose + β-galactose Maltose = α-glucose + α-glucose Sucrose = α-glucose + β-fructose

Answer 14

Starch = α-glucose monomers condensed together Glycogen = α-glucose monomers Cellulose = β-glucose monomers

Answer 15

- A polymer of α-glucose, used as the main storage carbohydrate in plants - A mixture of two separate polysaccharides: amylose and amylopectin - Amylose is a straight-chain polymer with 1-4 α-glucose linkages - Amylopectin is a branched polymer with both 1-4 and 1-6 α-glucose linkages

Answer 16

- A polymer of α-glucose - The main storage carbohydrate in animals, found in the liver and muscles - Structure very similar to amylopectin - Much more 1-6 branches

Answer 17

- A polymer of β-glucose - Structural material in plant cell walls - A linear polymer with 1-4 links known as β-glycosidic links - The cellulose chain forms an uncoiled linear structure - This enables the hydroxyl groups to form hydrogen bonds with the hydroxyls of other cellulose molecules lying parallel - Forms cables, known as microfibrils, of parallel chains that give it its rigid structure

Answer 18

- Both are polymers of glucose units - Starch has two forms: amylose and amylopectin - Cellulose has one structure - Starch has α-1,4 and α-1,6 linkages - Cellulose has β-1,4 linkages

Answer 19

The β-1,4 linkages between the monomers can be hydrolysed by the enzyme cellulase, which is absent in most animals

Answer 20

Mainly plant material that is not hydrolysed by enzymes secreted by the human digestive tract but may be digested by microflora in the gut. e.g. cellulose, hemicellulose, lignin, and pectin

Answer 21

- Beneficial to the health of the large intestine - The cellulose fibrils abrade the wall of the digestive tract and stimulate the lining to produce mucus - This helps in the smooth passage of undigested food through the gut - Helps to reduce conditions such as constipation, hemorrhoids, and irritable bowel syndrome - May be helpful in preventing the development of colorectal cancer

Answer 22

1. Triglycerides (fats and oils) 2. Phospholipids (lecithin) 3. Steroids (cholesterol)

Answer 23

- Considered as bad cholesterol and good cholesterol, respectively - LDL (low density lipoprotein) gets stuck on the walls of the arteries HDL (high density lipoprotein) protects against heart attach by carrying cholesterol away from the arteries - LDL main sources are saturated fats and trans fats - HDL main source is unsaturated fats

Answer 24

- Contain a mixture of saturated, mono-unsaturated, and poly-unsaturated fatty acids - Are classified according to the predominant type of unsaturation present

Answer 25

- Saturated fatty acids contain all single carbon–carbon bonds - Unsaturated fatty acids contain one or more double carbon–carbon bond in the hydrocarbon chain

Answer 26

An ester formed by condensation reaction between a glycerol and three fatty acids

Answer 27

A molecule of three carbon atoms, each of which bears an alcohol group

Answer 28

A long chain carboxylic acid, R–COOH

Answer 29

1. The length of their hydrocarbon chain - Usually an even number between 14 and 22 carbons 2. The number and position of carbon–carbon double bonds (affects its melting point) - No double bonds → saturated - One double bond → mono-unsaturated - Several double bonds → polyunsaturated

Answer 30

- All carbon–carbon bonds are single, 109.5° bond angles in between - This allows the molecules to pack closely together - This leads to strong van der Waals' between them - As a result, they have high melting points and are solids at room temperature - Known as fats and are derived mostly from animals - E.g. butter and lard

Answer 31

- Contain one or more carbon–carbon double bonds with 120° angles - The angles cause kinks in the chains that make it harder for the molecules to pack closely together - Weaker intermolecular forces - Lower melting points, liquids at room temperature - Known as oils and are found mostly in plants and fish - E.g. corn oil and cod liver oil

Answer 32

Fatty acids that the body is unable to produce and must be obtained in the diet: 1. linoleic acid (omega-6-fatty acid) 2. linoleic acid (omega-3-fatty acid)

Answer 33

- Omega-3 → green leaves - Omega-6 → seeds and vegetable oils

Answer 34

- They are involved in lowering blood pressure - Play a role in lowering LDL cholesterol - Essential in many other metabolic processes

Answer 35

The number of moles of I₂ reacting with one mole of fat/oil indicates the number of double bonds present in the fat/oil molecule (the unsaturated bonds undergo addition reactions)

Answer 36

- Fats produced industrially by adding hydrogen to decerase the degreee of unsaturation - As a result has a higher melting point and solids at room temperature - Have a longer shelf life - e.g. margarines and fatty acids

Answer 37

- Raise the level of LDL cholesterol - Reduce the blood levels of HDL cholesterol

Answer 38

- Insoluble molecules so cannot be transported in the blood - Broken down to fatty acids and glycerol - Hydrolysis with the help of lipases (enzymes) - The slowest molecules to be broken down (takes hours)

Answer 39

- Lipids are less oxidised than carbohydrates and so can effectively undergo more oxidation, thus release more energy per unit mass - A gram of lipid releases almost twice as much energy as a gram of carbohydrate

Answer 40

- Derived from fatty acids and glycerol (two fatty acids and one glycerol) - Also one phosphate group condensed - e.g. lecithin - Hydrophilic head and two hydrophobic tails - Spontaenously form a phospholipid bilayer → maximises the interactions between polar groups and water, while creating a non-polar, interior - Basis of membrane structure

Answer 41

- Lipids with a structure consisting of four fused rings (backbone) - e.g. cholesterol

Answer 42

1. Energy storage 2. Insulation and protection of organs 3. Steroid hormones 4. Structural component of cell membrane 5. Omega-3 poly-unsaturated fatty acids reduce the risk of heart disease 6. Poly-unsaturated fats may lower levels of LDL cholesterol

Answer 43

- Increased risk of heart disease from LDL and trans fatty acids - Obesity

Answer 44

Micronutrients are substances required in very small amounts (mg or µg) and that mainly function as a co-factor of enzymes (\<0.005% of body weight) Examples include vitamins and (FADEKCB) and trace minerals (Fe, Cu, F, Zn, I, Se, Mn, Mo, Cr, Co, B) Macronutrients are chemical substances that are required in relatively large amounts (\>0.005% body weight) Examples include proteins, fats, carbohydrates, and minerals (Na, Mg, K, Ca, P, S, Cl)

Answer 45

Organic micronutrients

Answer 46

- Water-solubles are transported directly in the blood and excesses are filtered out by the kidney and excreted (C and B) - Fat-solubles are slower to be absorbed and excesses tend to be stored in fat tissues where they can produce side-effects (F,A,D,E,K) - Differences in their structure determine the solubility differences - Water-solubles have polar bonds and the ability to form hydrogen bonds with water - Fat-solubles are mostly non-polar molecules with long hydrocarbon chains or rings

Answer 47

- A fat soluble vitamin - Hydrocarbon chain and ring are non-polar and influence the solubility more than the one polar –OH group - Involved in the visual cycle in the eye and particularly important for vision in the dark

Answer 48

- A water soluble vitamin - Several –OH groups enable hydrogen bonds with water - Cofactor in some enzymic reactions - Important in tissue regeneration following injuries - Helps give resistance to some diseases

Answer 49

- A fat soluble vitamin - Predominantly a hydrocarbon molecule with four non-polar rings and only one –OH group - Chemically similar to cholesterol - Stimulates the uptake of calcium ions by cells and so is important in the health of bones and teeth

Answer 50

1. Iron → anemia 2. Iodine → goitre 3. Vitamin A → xerophtalmia, night blindness 4. Vitamin B₃ → pellagra 5. Vitamin B₁ → beriberi 6. Vitamin C → scurvy 7. Vitamin D → rickets

Answer 51

1. Proteins → marasmus and kwashiorkor

Answer 52

1. Lack of distribution of global resources 2. Depletion of nutrients in the soil and water cultures through soil erosion 3. Lack of education about, or understanding of, the importance of a balanced diet 4. Over-processing of food for transport and storage 5. The use of chemical treatments such as herbicides in food production

Answer 53

1. Providing food rations that are composed of fresh and vitamin- and mineral-rich foods 2. Adding nutrients missing in commonly consumed food 3. Genetic modification of food 4. Providing nutritional supplements 5. Providing selenium supplements to people eating foord grown in selenium-poor soil

Answer 54

Chemical messengers that stimulate different actions around the body

Answer 55

They are secreted directly into the blood by the endocrine system (endocrine glands)

Answer 56

- A short peptide - Produced in the pituitary gland - Target cells are kidney tubules - Increases uptake of water, so raises the concentration of urine; important in the control of osmotic potential of the blood

Answer 57

- A modified amino acid containing iodine - Secreted by thyroid gland - Target cells include all cells - Regulate the basal metabolic rate, growth, and development

Answer 58

- A steroid - Produced in the adrenal cortex - Target cells are kidney cells - Increases uptake of Na⁺ by the kidneys and is important in the control of Na⁺ and K⁺ ratios in fluids; raises blood pressure

Answer 59

- A modified amino acid - Produced in the adrenal medulla - Target cells are many parts of the body including muscles, brain, circulatory, and digestive systems - Raises blood glucose level, increases rate and force of heartbeat, and increases blood supply to heart and skeletal muscles

Answer 60

- A protein - Produced by the pancreas - Target cells are all cells, especially liver cells - Decreases blood glucose level by increasing uptake and utilisation by cells; increases glucose to glycogen conversion in the liver

Answer 61

- Steroids - Produced in the ovaries - Target cells are many parts of the body; especially the uterus lining during pregnancy - Develop secondary female characteristics, control mestrual cycle, growth and development of the placenta and fetus

Answer 62

- A steroid - Produced in the testes - Targets many parts of the body - Develop male secondary sexual characteristics

Answer 63

- Common steroid backbone - The different side chains and functional groups give the different properties - Progesterone differs from testosterone only by having a ketone group instead of an alcohol - Estrogen has an aromatic ring (benzene) and two alcohol groups

Answer 64

- Work by preventing ovulation - Contain a mixture of progesterone and estrogen - Act to suppress the secretion of FSH and LH - Stimulate the hormonal conditions of pregnancy - Taken every day for three weeks and then stopped for one week - Also morning after pills, which contain higher concentrations to prevent fertilisation from occurring after unprotected intercourse

Answer 65

- Female hormones used in medications prescribed to women at menopause to alleviate some of the unpleasant symptoms → HRT (hormone replacement therapy) - Male hormones used in treatment of disorders of the testes and breast cancer or medically help to gain weight after debilitating diseases

Answer 66

- Anabolic steroids have been used by athletes to build up muscle and increase endurance - Can cause many changes in secondary sexual characteristics: changes in hair distribution, sexual desire, and fertility - Hormones are toxic to the liver - Increased risk of liver cancer

Answer 67

Male hormones that promote tissue growth of especially of muscles

Answer 68

- Proteins, typically containing several hundred amino acids - Well-defined tertiary structure → globular proteins - Soluble in water - Structure determined by the interactions between all its R groups and is essential for its function - Some enzymes are made of more than one polypeptide and so have a quaternary structure - Some require the binding of non-protein molecules (co-factors) for activity

Answer 69

Organic or inorganic molecules that aid enzymes in their action e.g. vitamins, metal ions

Answer 70

- Increase the rate of a chemical reaction without undergoing chemical change itself - The enzyme lowers the activation energy of the reaction → enables the reaction to occur more quickly at the same temperature - Forms a temporary binding to the substrate (enzyme substrate complex) that occurs at the active site - Interactions such as hydrophobic interactions, dipole-dipole attractions, hydrogen bonds, and ionic attractions form between the active site and the substrate - The binding puts a strain on the substrate molecule and its bonds - The enzyme facilitates the breaking and the forming of bonds - Once the substrate has reacted, the product no longer fits in the active site and so detaches - The enzyme is released unchanged and is able to catalyse further reactions

Answer 71

- Instead of being a rigid active site, the site changes it shape when a substrate binds to it - The active site undergoes conformational changes, shaping itself to allow a better fit - Think of a hand and glove

Answer 72

1. At low substrate concentration, the rate of the reaction is proportional to the substrate concentration; enzyme is available to bind to the substrate 2. As the substrate concentration is increased, the rate decreases and is no longer proportional; some of the enzyme has its active sites occupied by substrate and is not available 3. At high substrate concentration, the rate is constant and independent of the substrate concentration; the enzyme is saturated with the substrate and is working at full speed

Answer 73

- The maximum velocity of the enzyme under the conditions of the experiment - Varies greatly between enzymes - Affected by pH and temperature

Answer 74

- The substrate concentration at which the reaction rate is equal to one half of its maximum value - The substrate concentration when the rate is V_max/2 - Varies with pH and temperature - The value gives information about the affinity of the enzyme for its substrate - A low value of K_m means that the reaction is going quickly even at low substrate concentration - A high value means that the enzyme has a lower affinity for its substrate

Answer 75

Conditions that affect the enzyme's shape and binding ability 1. Temperature 2. pH 3. Presence of heavy-metal ions

Answer 76

- Rate of a reaction is increased y a rise in temperature due to the increase in the average kinetic energy of the particles (more collisions) - Only true up to a certain temperature (≈40°C) - After this the enzyme becomes denatured - Lowering temperature deactivates an enzyme but it is reversible as it does not change the tertiary structure

Answer 77

- Represents changes in the hydrogen ion concentration - Alters the ionic charge in the amino acids - Alters the attractive forces stabilising the molecule, hence its shape and ability to bind a substrate - The specific effect depends on the pK_a and pK_b of the R groups - Different for each enzyme - Usually there is a clear optimum value - Changing pH is one way of controlling enzymatic activity

Answer 78

- When metals are present as positive ions they react with sulfydryl groups (–SH) - Form a covalent bond with the sulfur atom displacing a hydrogen ion - Disrupts the folding of the protein, which may change the shape of the active site and its ability to bind susbtrates - A form of non-competitive inhibition - This is why lead, copper, mercury, and silver are poisonous

Answer 79

1. Competitive inhibitors (bind to the active site) 2. Non-competitive inhibitors (bind away from the active site)

Answer 80

- Chemicals chemically similar to the substrate that compete with the substrate for the binding position - Block the active site and make it unavailable to the substrate - Increasing concentration of substrate reduces the effect of inhibition - V_max is not altered as there is a substrate concentration where full activity of the enzyme can be achieved - K_mis increased

Answer 81

- Chemicals that bind reversibly away from the active site - Cause a conformational change in the protein change that alters the active site, inhibiting its ability to bind to substrates - Increasing the substrate concentration will not reduce the effect of inhibition - V_max is reduced and cannot be restored - K_m is unchanged because the uninhibited enzymes are perfectly functional

Answer 82

Enzyme VS inorganic catalyst **1. Structure:** All are proteins VS varied structure **2. Mode of action:** Both lower the activation energy **3. Effect on equilibrium constant:** No effect on either one **4. Specifity:** Highly specific VS much less specific **5. Saturation:** Reach a maximum reaction rate VS do not show reactant saturation **6. Phase:** Homogenous catalysts VS homo- and heterogenous **7. Speed:** Very fast VS pretty slow **8. Regulation by chemicals:** Regulated by inhibitors and activators VS not regulated **9. Sensitivity to temperature and pH:** Sensitive VS not sensitive

Answer 83

Polymers made up of nucleotides

Answer 84

1. A phosphate group PO₄^-3 2. A pentose sugar C₅H₁₀O₅ 3. An organic nitrogenous base (A,G,C,T,U)

Answer 85

1. Must be a very stable molecule, able to retain its precise chemical structure in cell conditions 2. It must contain some code that stores genetic information 3. It must be able to replicate

Answer 86

- Large bases that contain two fused rings - Adenine and guanine

Answer 87

- Smaller bases that contain a single ring - Cytosine, thymine, and uracil

Answer 88

- The pentose, phosphate, and base are condensed together - The base always condenses to the C₁ of the sugar - The phosphate condenses to the C₅ of the sugar

Answer 89

- RNA has ribose as its pentose sugar; DNA has deoxyribose - Deoxyribose lacks an oxygen atom on C₂ - RNA has uracil instead of thymine as one of its bases - RNA is a single-strand nucleic acid; DNA is a double-strand acid

Answer 90

- The phosphates and sugars condense forming covalent bonds (phosphodiester links) - The phosphate links to either the C₅ or to the –OH group at the C₃ of the sugar

Answer 91

By two hydrogen bonds:

Answer 92

By three hydrogen bonds:

Answer 93

- Double helical structure - Two strands held together by hydrgen bonds - Sugar-phosphates are on the outside and bases on the inside - Anti-parallel, run in opposite directions (3' → 5' and 5' → 3')

Answer 94

Achieved by the fact that it maximises hydrophobic interaction between the stacked bases in the middle of the molecule, while allowing polar and charged groups in the sugar-phosphate backbone to interact with the aqueous solution

Answer 95

The sequence of bases in the polynucleotide strand (infinite variety is possible)

Answer 96

1. Contains the inherited genetic material 2. Directs mRNA synthesis (transcription) 3. Directs protein synthesis (translation) through mRNA using codons

Answer 97

1. DNA is extracted from the source (blood, semen, hair, saliva) 2. The DNA is cut into small pieces using restriction enzymes 3. Short tandem repeats (STRs) are produced from the pieces of DNA. STRs are unique for every individual 4. Polymerase chain reaction (PCR) is used to amplify the unique regions of DNA by making multiple copies 5. The DNA fragments are separated and detected using gel electrophoresis. Due to its phosphate groups, DNA carries a negative charge and moves to the positive terminal. 6. The distance travelled depends on the size of the DNA fragments: shorter fragments move further than longer fragments 7. The sheet used is treated with radiation (³²P) and exposed using X-ray film 8. An autoradiogram is produced, showing the positions of the fragments as dark bands. The pattern of these bands is the DNA profile

Answer 98

1. To identify victims whose bodies are not recovered from the scene of an accident or crime. 2. In forensic cases to identify the suspect. 3. To confirm biological relationships between individuals. (determining paternity or family relationships) 4. To determine relationships between populations (evolution, migration, ecology)

Answer 99

The process of chemical breakdown of energy-rich molecules in cells with the release of energy. Takes place in all living cells all the time

Answer 100

In aerobic respiration, glucose is converted into pyruvate, which, in the presence of oxygen, changes to carbon dioxide and water. Glucose undergoes oxidation and oxygen undergoes reduction. Lots of energy released In anaerobic respiration, pyruvate is converted to lactate in humans, and to ethanol and carbon dioxide in yeast. Little energy released

Answer 101

- Electron transport carriers - Proteins that are embedded in a membrane - Become successively reduced and then re-oxidised as they accept and pass on the electrons - Are organised in sequence correspoinding to their electrode potentials - Electrons flow down an electrochemical gradient - Contain a non-protein component called a prosthetic group (a ring containing Fe) - The iron changes its oxidation state from +2 to +3 when oxidised

Answer 102

- It acts at the end of the electron transport chain - Inhibits the enzyme cytochrome oxidase and blocks the whole chain - Prevents aerobic respiration from occurring

Answer 103

- Uptake of oxygen is not accompanied by a change in the oxidation number - The oxygen is bound in molecular form, O₂, in the structure in a complex way that involves a conformational shift of the protein - Molecules are called oxygenated - Each oxygenated haemoglobin carries four molecules of oxygen

Option B - Human biochemistry Flashcards

(130 cards)