Nutrition and Metabolism Flashcards
1
Q
What is nutrition?
A
The provision of the necessary materials to support life to cells
2
Q
What are macronutrients?
A
Nutrients that are requires in large amounts. Carbohydrates, fats, protein and water. They provide the material for organelles such as amino acids for proteins and lipids for membranes
3
Q
Why is water required in the diet?
A
It is the universal solvent for bodily chemical reactions
4
Q
What are micronutrients?
A
Nutrients that are needed in smaller quantities. Minerals and vitamins
5
Q
What influences whether a carbohydrate is a monosaccharide, disaccharide or polysaccharide?
A
The number of sugar units they contain
6
Q
What do carbohydrates provide?
A
Energy, glucose
7
Q
What is cellulosse?
A
A large carbohydrate polymer that makes up most dietary fibre. It is indigestible
8
Q
What does fibre help to reduce?
A
Constipation and diarrhoea
9
Q
What is the recommended daily intake for fibre in adults?
A
25-30g
10
Q
What foods contain insoluble fibre?
A
Whole-wheat, nuts and vegetables
11
Q
What does insoluble fibre do in the intestines?
A
Helps with muscular contractions of the intestines that move food along
12
Q
What foods contain soluble fibre?
A
Oats, peas, beans and fruit
13
Q
What does soluble fibre so in the intestines?
A
Dissolves in water to produce a gel that slows the movement of food and so can help to lower blood glucose since it slows the rate of absorption
14
Q
What does a molecule of fat consist of?
A
3 fatty acids bonded to a molecule of glycerol
15
Q
What are the 2 classifications of unsaturated fatty acids and what determines their class?
A
Omega-3 and omega-6
Depends on the location of the first double bond in the chain
16
Q
What are the full names for the fatty acids that cannot be synthesised and so must be included in the diet?
A
Omega-3 alpha-linolenic acid from fish oil
omega-6 linoleic acid from vegetable oils
17
Q
What are omega-3 and omega-6 converted to in the body?
A
Omega-3 eicosapentanoic acid (EPA)
Omega-6 arachidonic acid (AA)
18
Q
What type of fatty acids are a risk for high cholesterol if consumed in excess?
A
Saturated fatty acids
19
Q
What is EPA and AA (derived from omega-3 and omega-6) precursors for?
A
Inflammatory hormones called prostaglandins (PG)
20
Q
Do prostaglandins produced from AA or EPA have a greater inflammatory response?
A
AA
21
Q
Why are patients encouraged to eat fish oil to help prevent inflammation in conditions such as arthritis
A
Fish oil is omega-3 which forms EPA which has a much lower inflammatory response than AA from omega-6
22
Q
What are the 2 proinflammatory mediators derived from AA? (cause inflammation)
A
Prostaglandin E2 and Leukotriene B4
23
Q
What are the 2 less potent inflammatory mediators produced by EPA?
A
Prostaglandin E3 and Leukotriene B5
24
Q
Why must amino acids be present in the diet?
A
There is no storage for amino acids
25
How many amino acids out of the 20 found in humans cannot be synthesised?
10
26
What can excess amino acids from the diet be used for?
They can be oxidised for energy or converted into glucose
27
Why can reduced consumption of protein increase the risk of diabetes? Linked to skeletal muscle
Proteins help to build skeletal muscle. Skeletal muscle is a major consumption of glucose. Less skeletal muscle can lead to excess glucose stored as fat
28
What is the overall idea of protein supplements?
They provide high levels of protein which help give muscles more amino acid substrates required to recover and grow more quickly
29
What is the recommended daily intake of protein for an adult male and female?
```
Male = 55.5g
Female = 45g
```
30
What are dietary minerals?
The chemical elements required by living organisms
31
What are macrominerals?
Minerals that are required in high quantities. E.g Calcium
32
What are the 2 calcium containing complexes in bone and what are their roles?
Calcium phosphate: Helps maintain blood levels and can be used to make hydroxyapatite in bones and teeth
Hydroxyapatite: Help with the strength of collagen with hardness and rigidity
33
What are trace minerals?
Minerals required in trace amounts and are involved in a catalytic role in enzymes
34
What is the role of copper in the body?
It is a component of many redox enzymes
35
What is the role of iodine in the body?
It is involved in the biosynthesis of thyroxine
36
What is thyroxine?
A hormone that is secreted into the bloodstream by the thyroid gland and is involved in digestion, heart muscle function and brain development
37
What is the role of iron in the body?
It is required for the haem group which carried oxygen in the blood.
38
Which vitamin is synthesised in the skin from cholesterol?
Vitamin D
39
Give 3 functions of vitamins
Co-factors in enzyme activity
Antioxidants
Pro-hormone (only D)
40
What are the 2 classifications of vitamins?
Fat-soluble
| Water-soluble
41
How are free radicals formed?
Oxygen spits into single atoms with unpaired electrons in redox reactions
42
Why are free radicals damaging in the body?
The lone electrons are seeking to find other lone electrons in order to become a pair. They can react very strongly with membranes and proteins causing ell and tissue damage
43
What molecules neutralise radicals and oxidative stress?
Antioxidants
44
Give an example of an antioxidant in the body?
Vitamin C
45
What causes scurvy?
Vitamin C deficiency causes less collagen to be made which is important in wound healing and preventing bleeding from capillaries
46
Describe the symptoms of scurvy
Formation of brown spots on the skin and bleeding from all mucous membranes
47
What foods contain vitamin C?
Fruits and veg
48
What is carnitine important for?
Fat oxidation
49
What type of vitamin is vitamin B1/ thiamine?
Water-soluble
50
What is TPP and what is its role?
Thiamine pyrophosphate, a form of vitamin B which is a coenzyme of Pyruvate Dehydrogenase for the production of ATP and acetylcholine
51
What causes beriberi?
Vitamin V deficiency and affects the nervous system and the cardiovascular system
52
What are the symptoms of dry beriberi?
Symmetric impairment of sensory, motor and reflex functions affecting distal limb segments and causing calf muscle tenderness
53
What are the symptoms of wet beriberi?
Mental confusion, muscular atrophy, oedema and congestive heart failure
54
What is muscle atrophy?
When muscles waste away
55
Give a function oh phytochemicals
Antioxidant
56
What are phytochemicals?
Compounds that are produced by plants
57
What foods is the phytochemical zeaxanthin found in and what disease does it help to prevent?
It is found in the yellow pigment of yellow and orange fruits and vegetables. It helps to lower the risk of eye disease and cataracts.
58
What does beta-cryptoxanthin found in fruits and vegetables help to protect against?
Chronic joint inflammatory diseases
59
What does the phytochemical lycopene help to prevent and what foods is it found in
Tomatoes, it helps to prevent prostate cancer and atherosclerosis (high blood pressure)
60
What is a nutraceutical and give an example?
A product isolated or purified from foods that is sold in medicinal forms not usually associated with food and provides protection against a disease. E.g supplements or foods with added supplements
61
How many forms of vitamin B are there?
8
62
What is the main role of vitamin B?
Help with cell metabolism
63
What is a dietary supplement?
A product that contains nutrients derived from food products that are concentrated in liquid or capsule form
64
What are autotrophs?
Organisms that can derive their energy from sunlight e.g plants
65
What are heterotrophs?
Organisms that rely on degradation of chemical sources of fuel for energy
66
What are the 3 main classes of food macronutrients that supply energy or materials for biosynthesis?
Carbohydrates, fats and proteins
67
What are proteins, carbohydrates and fats converted to during hydrolysis reactions?
```
Proteins = amino acids
Carbohydrates = monosaccharides (glucose)
Fats = fatty acids and monoacylglycerols
```
68
What is ingestion?
The collection of food into the digestive tract, it involves smelling, thinking and involuntary release of saliva to prepare for food entry
69
What is digestion?
The mechanical an chemical breakdown of food into nutrients
70
What is the enzyme in the mouth that begins to breakdown complex carbohydrates?
Amylase
71
What is the mechanical breakdown of food in the mouth?
Chewing
72
What is the chemical breakdown of food in the mouth caused by?
Saliva
73
What is a bolus?
The slippery mass of partially broken-down food
74
What happens to the bolus after you swallow?
It travels from the mouth through the pharynx into a muscular tube called the oesophagus.
75
What helps to prevent choking after swallowing?
After the bolus travels through the pharynx, a small flap called the epiglottis closes so that food doesn't go into the trachea
76
What type of contractions propel the food from the oesophagus to the stomach?
Peristaltic contractions
77
What must happen in order for the food bolus to be transferred from the oesophagus to the stomach?
The sphincter relaxes and opens to allows the food to pass through
78
How long does solid food and liquids take to travel down the oesophagus?
```
Food = 4-8 seconds
Liquids = 1 second
```
79
What is chyme and how is it formed?
A semiliquid mass of partially digested food that contains gastric juiced secreted by cells in the stomach. It is made by peristaltic contractions in the stomach churning the food.
80
What is the function of hydrochloric acid and pepsin in the stomach?
To chemically break down protein into smaller peptides and amino acids
81
What protects the stomach from digesting itself?
A thick mucus coat
82
What are the 3 main tasks of the stomach?
Store food
Mechanically and chemically break down food
Empty partially broken-down food into the small intestine
83
What macronutrient is digested the fastest?
Carbohydrates
84
Which sphincter allows chyme to pass into the small intetsine?
Pyloric sphincter
85
What are the 3 sections that the small intestine is split into?
Duodenum, jejunum and ileum
86
What happens when the chyme enters the dueodenum?
The accessory organs (liver, pancreas and gallbladder) are stimulated to release juices to aid digestion
87
How much fluid does the pancreas release into the duodenum per day?
1.5 litres
88
What is in the fluid that the pancreas secretes and what do they do to the chyme?
Mostly water
Bicarbonate ions neutralise the acid in the stomach
Enzymes that breakdown proteins, carbohydrates and lipids
89
What does the gallbladder secrete into the duodenum?
Bile to help with digestion of fats
90
Describe bile
A liquid that is made in the liver and stored in the gallbladder. The salts act like detergent by surrounding fats and emulsifying them into smaller droplets which lipases can act on
91
What are the 2 types of muscle contraction that move and mix food in the small intestine?
Peristalsis and segmentation
92
Describe peristalsis and segmentation
Peristalsis: Circular waves of smooth muscle contraction that move food forward
Segmentation: Forward and backward movement of food that promotes further mixing of chyme
93
Describe the breakdown of proteins to amino acids
In the stomach, acid denatures the proteins. Pepsin is released which starts to break down the protein into polypeptides. In the small intestine, trypsin and other proteases complete this breakdown
94
Describe the breakdown of carbohydrates to monosaccharides
In the mouth, amylase digests starch into glucose. This continues in the small intestine with pancreatic amylase and other enzymes
95
Give the name of a polysaccharide
Starch
96
Give 3 disaccharides
Maltose, sucrose, lactose
97
Give 3 monosaccharides
Glucose, fructose, galactose
98
Describe the breakdown of fats to fatty acids and monoacylglycerols
Fats are emulsified by bile acids in the small intestine to form small droplets. Lipases then break these droplets down more into fatty acids and glycerol
99
What is found on the surface of the small intestine that increases its surface area?
Villi which are also covered in microvilli
100
Which molecules are able to be directly transported from the intestines into the capillaries?
Amino acids, minerals, alcohol, water soluble vitamins and monosaccharides
101
What vessels do larger fatty acids, lipids and fat-soluble vitamins have to pass through before reaching the blood vessels?
Lymphatic vessels
102
How are amino acids and carbohydrates transported to the liver?
They are taken up by the epithelial cells by carrier processes and enter the blood capillaries into the hepatic portal system (portal vein)
103
How do fatty acids reach the lymphatic system?
They enter the intestinal brush border cells and resynthesized into triacylglycerols. These then come together with cholesterol to form chylomicrons which are passed into the lymphatic system
104
What food moves from the small intestine to the large intestine?
Incompletely broken down food as the food's indigestible fibre
105
What is the connecting valve between the small intestine and the large intestine called?
Ileoceceal sphincter
106
What is the main function of the large intestine?
To reabsorb water
107
Why is it important for the body to reabsorb water?
During digestion, the stomach releases a few 100mLs of gastric juice as well as the pancreas releasing 500mLs. This water needs to be conserved
108
What is the only organism responsible for digestion in the large intestine?
Bacteria
109
What is the role of bacteria in the large intestine?
To synthesise vitamin K, minerals and short chain fatty acids from the undigested fibre
110
What is the difference between pre and pro biotics?
Probiotics provide health benefits e.g lactic acid which is added to yoghurt
Prebiotics are indigestible foods, e.g fibre, that stimulate growth of certain bacteria
111
Approximately how long does food stay in the stomach?
A few hours
112
Approximately how long does food stay in the small intestine?
3-6 hours
113
Approximately how long does food stay in the large intestine?
16 hours
114
What does the faeces contain?
Indigestible food and gut bacteria
115
Where is the faeces stored before leaving the body?
In the rectum
116
What is lipaemia?
A milky blood plasma as a result of a fatty meal
117
How long does it take for an average person's blood glucose levels to revert back to normal after a meal?
2 hours
118
How and where is glucose stored?
As glycogen in the liver and muscle
119
What does the liver do with glycogen?
Stores it and supplies other tissues with glucose when needed
120
How and where is fat stored in the body?
Triacylglycerols in adipose tissues
121
What happens to excess amino acids?
They are broken down and the nitrogen is converted to urea for excretion, the carbon skeleton is oxidised for energy or converted into glucose or fats
122
What 2 processes does metabolism consist of?
Catabolism (breakdown) and anabolism (synthesis)
123
What is the major role of catabolism?
Oxidise food to provide energy as ATP
124
What is a by product of metabolism?
Heat
125
What are the 4 stages involved in catabolism of glucose?
Glycolysis
Link reaction
TCA cycle
Electron transport chain and ATP synthesis (oxidative phosphorylation)
126
What happens in glycolysis?
In the cytoplasm, glucose is converted into pyruvate
127
What happens in the link reaction?
In the mitochondria, pyruvate is converted into acetyl-CoA, this can also be done through fatty acid oxidation
128
What happens in the TCA cycle
C-C bonds are broken, CO2 is produced as waste, energy is transferred to electron carriers: NADH and FADH
129
What happens in oxidative phosphorylation?
Electrons are accepted from the mitochondria and ATP is generated
130
What does ATP stand for?
Adenosine Triphosphate, the energy carrier
131
Where does the energy ultimately come from for the formation of ATP?
Breaking C-C bonds in the oxidation of carbohydrates, lipids and proteins
132
Give 3 uses of ATP in which ATP is hydrolysed
Metabolic reactions, active transport and changes in protein conformation (actomyosin)
133
How many Kcal per mole is yielded from the hydrolysis of ATP?
7.3
134
Describe the structure of ATP
An adenine molecule bonded to a ribose which is bonded to a triphosphate group
135
What are the 3 names of phosphate that make up triphosphate?
Alpha, beta and gamma
136
Which bond in ATP is broken when it is hydrolysed?
Beta-gamma phosphate bond since it is broken more readily
137
Why does ATP hydrolyse more readily compared to other phosphorylated compounds?
The 3 phosphate groups are large and negatively charged, when this bond breaks, the repulsion is reduced.
The free phosphate group that is released is able to stabilise through resonance
138
What is phosphate group transfer potential?
The potential yielded when a phosphate group is removed during hydrolysis of a compound
139
What is used for longer term energy storage in muscles and why?
Phosphocreatine, it has a higher phosphate group transfer potential so can be used to make ATP when required
140
What is the role of kinases?
To catalyse the reactions where ATP donates a phosphate group
141
Which vitamins are components of coenzymes, making them essential for metabolism?
Vitamin Bs
142
What is the role of coenzymes?
To aid an enzyme by carrying certain functional groups that can be transferred to the enzyme
143
What does the coenzyme NAD carry?
Electrons
144
What are the electrons released by metabolism carried by to the electron transport chain?
NADH
145
What carries the reducing power for biosynthesis reactions and how?
NADP, the phosphate group directs the coenzyme to the anabolic enzymes instead of the electron transport chain
146
Where does oxidative phosphorylation occur?
In the mitochondria
147
What are the 2 types of nucleotides that are reduced in the oxidation of fuel molecule?
NAD to NADH and FAD to FADH
148
Where does the reduction of NAD and FAD occur?
In the mitochondria matrix
149
Where does the electron transport chain occur?
In the inner mitochondrial membrane
150
What are the large protein complexes used in the ETC?
Complex I, II, III and IV
151
What type of reactions occur in the ETC?
Redox, each time, energy is released
152
What is different about each of the complexes in the ETC?
Each one is a little better at accepting electrons, it has a higher reduction value
153
What is the energy released from complex I, III and IV, by reduction used for in the ETC?
Pumping H+ of the matrix across the inner mitochondrial membrane and into the intermembrane space
154
What is the value for the free energy released by the complete oxidation of NADH to NAD and FADH to FAD?
-52.6 kcal/mol
155
Why is the energy released from complex II not used for pumping H+?
The complex doesn't cross the entire inner mitochondrial membrane
156
What is the overall outcome of the ETC?
The conversion of energy from electrons into potential energy (ATP)
157
What creates the pH gradient across the inner mitochondrial membrane?
The pumping of H+ from the matrix to the inner space
158
What happens at complex I?
NADH approaches the complex, it is reduced to NAD+ and the 2 electrons are passed into the membrane. The energy released is used to pump H+ across the membrane
159
What happens are complex II?
FADH approaches and is reduced to FAD+, 2 electrons are passed into the membrane, however, no H+ is pumped through
160
What happens are complex III?
The electrons built up from complex I and II are used to pump H+ across the membrane
161
What happens at complex IV?
The electrons build up are used to pump H+ across the membrane, oxygen is oxidised to water using the electrons
162
What happens if oxygen is not available for the ETC?
The ETC process stops and no ATP can be made
163
How is ATP synthesised at the end of the ETC?
The H+ in the inter-membrane space diffuses through ATP synthase into the inner mitochondrial matrix, as this happens, ATP synthase spins, generating energy used for phosphorylation of ADP to ATP
164
What is proton motive force?
The movement of protons back into the mitochondrial matrix due to the concentration gradient
165
Describe the quaternary structure of ATP synthase
4 subunits make up the proton channel (F0), 3 subunits make up FA which is the neck, and F1 is the headpiece made up of 6 subunits which contains the active site for ATP synthesis
166
What are the 6 subunits that make up F1 of ATPsynthase?
3 alpha and 3 beta
167
What is redox potential?
How easily a compound gives up or donates an electron, positive = accepts (reduction)
168
What is the P:O ratio?
Amount of ATP made per atom of oxygen consumed in the ETC
169
How can the amount of oxygen consumed in the ETC be measured?
Using an oxygen electrode, the concentration of oxygen in solution can be measured
170
How do you work out the P:O using an oxygen electrode?
Calculate the change in O2 concentration from when a known amount of ADP is added to when is has all be converted. Multiple the change in [O2] by 2 to account for 2 atoms. Divide mol of ATP formed by atoms of O used
171
What is the P:O for FADH in the ETC and why?
2, electrons are fed through complex II, III and IV but 2H+ is pumped = 2 ATP used but only one O is hydrolysed to water
172
What is the P:O for NADH in the ETC?
3, the electrons are fed through complex I,III and IV, 3 H+ are pumped in = 3 ATP made for every 1 oxygen oxidised
173
Describe the oxygen electrode
The mitochondria bugger with O2 is kept in suspension using a magnet and stirrer. A plastic film is on top and separates the buffer and the electrodes. When a voltage is applied, the anode is oxidised and the electrons produced flow to the cathode where oxygen is reduced. When mitochondria are respiring, this uses oxygen and lowers the current of the electrode
174
What is an inhibitor of Complex I and what process does it stop?
Rotenone, this stops the electron transfer of NADH
175
What is rotenone use for?
Insecticide and control of lice and ticks on pets
176
Why does rotenone not fully stop the ETC?
FADH can still feed electrons into complex II
177
What blocks complex III?
Antimycin A, it stops the acceptance of electrons into complex III
178
How is antimycin A overcome?
Ascorbate can feed electrons into cytochrome C, just after complex III
179
What blocks complex IV?
Cyanide
180
Why is cyanide so toxic?
It blocks complex IV, preventing any electrons being fed through the ETC, it cannot be overcome resulting in ATP not being made
181
What blocks the channel in ATPase in the ETC?
Oligomycin
182
How does oligomycin stop the production of ATP?
It blocks the channel in ATPase stopping the proton motive force.
183
How is the total inhibition of the ETC reversed?
By using an uncoupler
184
What are chemical uncouplers such as 2,4-dinitrophenol also known as?
Proton ionophores
185
What is the role of proton ionophores (uncouplers)
To provide an alternative pathway for H+ to pass back across the membrane and into the matrix
186
Why do uncouplers result in ATP not being synthesised?
The H+ pass through as alternative route and so no proton motive force is made in ATP synthase.
187
What happens in terms of energy when uncouplers are used?
The ETC speeds up in an attempt to restore the proton motive force however, the energy produced is not used to make ATP, but is wasted and dissipated as heat
188
Describe the new path for H+ when the uncoupler DN{ is used
In the membrane, DNP has an acid group and becomes protonated when at the intermembrane space (lots of H+), when it reaches the matrix, it is deprotonated due to changes in pH
