1. Biochemistry of Life (Part I) Flashcards
(122 cards)
1
Q
What nutrients are necessary during cell division?
A
- Energy
- Proteins to create new structures and motors
- Lipids to create cell membranes
2
Q
Define nutrigenetics.
A
Genes control the metabolism of nutrients
3
Q
Define nutrigenomics.
A
Nutrients influence the expression of genes
4
Q
Explain what happens on a molecular level to the lac operon when there is a lack of lactose.
A
- lacI encodes the repressor protein
- The repressor protein binds to the lac operator, present in the promoter region of the lac operon
- This ultimately shuts down the transcription of the operon
5
Q
Explain what happens on a molecular level to the lac operon when there is lactose.
A
- Lactose binds to the repressor protein, which causes a conformation change
- The changed repressor is unable to bind to the lac operator region
- RNA polymerase can see the promoter, and make RNA for the lacZ, lacY, and lacA regions (genes known for their role in lactose metabolism)
6
Q
What are the three genes that are known to be involved in the metabolism of lactose?
A
- B-Galactosidase
- Permease
- Transacetylase
7
Q
What is a responsive gene?
A
- Either be induced or repressed by a dietary constituent
- If it does not do either, it is not a responsive gene
8
Q
What do secondary mediators have an impact on in nutrient-gene interactions? What are they affected by?
A
- They have an impact on their own responsive genes
- They are indirectly affected by dietary constituents
9
Q
What are the five ways dietary constituents can interact with genes, either directly or indirectly?
A
- Responsive genes (direct)
- Physiological modulation (indirect)
- Regulation of transcription
- Regulation of translation
- Modification of proteins
10
Q
Explain how amino acids and fatty acids regulate gene expression indirectly.
A
- Interact with a protein embedded on a cell membrane, which will initiate a signal transduction pathway (e.g. phosphorylation-chain)
- When the signal reaches the nucleus, the protein interacts with a promoter region of a gene to induce or repress RNA transcription
11
Q
Concerted Regulation of Protein and Lipid Biosynthesis occurs by which pathway?
A
The Akt/mTORC1 pathway
12
Q
What are the four proteins involved in the Akt/mTORC1 pathway?
A
- AMPK
- Akt
- mTORC1
- SREBP
13
Q
AMPK and Akt are components of a signalling pathway. What are their functions?
A
- AMPK: responds to cellular energy status
- Akt: responds to growth factors, including insulin
14
Q
What is the role of mTORC1?
A
- Integratesthe information related to the kind:
- Nutrients available
- Cellular energy status,
- Growth factors interacting with the cell receptor
15
Q
What does the Akt/mTORC1 pathway affect?
A
Regulates protein and lipid biosynthesis
16
Q
True or False: if you increase your mass of cells, you increase your lipid content. Why or why not?
A
- True
- Due to the Akt/mTORC1 pathway, which regulates cell growth through protein AND lipid biosynthesis
17
Q
Why is glucose uptake necessary for the Akt/mTORC1 pathway?
A
Since the production of protein and lipid biosynthesis is an energetically expensive process, which requires the production of ATP through glycolysis and the TCA cycle
18
Q
What is SREBP responsive to?
A
To the status of cholesterol in the environment
19
Q
Explain what happens to SREBP when you have low sterol concentrations.
A
- SREBP, interacting with SCAP and COPII, migrates from the ER towards the Golgi
- At the Golgi, the SREBP protein is processed by specific proteases of the Golgi
- The proteases liberate a portion of SREBP, which migrates to the nucleus and binds to the Sterol Response Element (SRE)
- SRE stimulates the target genes involved in cholesterol and fatty acid biosynthesis
20
Q
Explain what happens to SREBP when you have high sterol concentrations.
A
- SREBP remains bound to SCAP, which is bound by INSIG, and remains in the ER
21
Q
Give examples of abundant elements.
A
Carbon, hydrogen, nitrogen, oxygen, phosphorus
22
Q
Give examples of trace elements.
A
Calcium, chlorine, cobalt, copper, iodine, iron, manganese, magnesium, potassium, sodium, sulphur, selenium, zinc
23
Q
What raw materials are necessary for life?
A
- Carbon source
- Nitrogen source (protein and DNA)
- Water
- Oxygen
- Salts
24
Q
Which terminal of an amino acid corresponds to the 5’-end of the gene that encodes it? What about the 3’-end?
A
- N-terminal (+) = 5’
- C-terminal (-) = 3’
25
What is hydrolyzed protein used for?
- Common in some large scale food manufacturing
| - Texturizer, flavour enhancer
26
Explain how hydrolyzed proteins may be hypoallergenic.
If you break up a protein, our immune system might not recognize its different three-dimensional structure
27
What is the function of glutamic acid as a neurotransmitter?
Involved in long-term potentiation (learning and memory)
28
What symptoms has MSG been suggested to cause?
- Headaches
- Numbness
- Tingling sensations
- Obesity
29
What are the three kinds of MSG manufacturing? Are they L or D amino acids?
- Hydrolysis of proteins (L-amino acids)
- Chemical synthesis (DL-glutamate; synthetic)
- Fermentation (L-glutamate)
30
How does L-glutamate made by chemical synthesis differ from L-glutamate made by fermentation?
They are the same despite chemical synthesis being synthetic
31
Which foods contain MSG?
- Anything that contains "protein hydrolysate" (prepared foods, protein supplements)
- Fermented food products (soy sauce, Worcestershire sauce, vegemite)
32
Define homeostasis.
- Homeostasis occurs when the rate of input is equal to the rate of output
- Disease states occur when there is dysregulation in homeostasis
33
What is gout? What is the cause?
- A painful genetically-predisposed disorder characterized by joint inflammation.
- Caused by high uric acid concentration in the body due to high production or inefficient disposal of uric acid.
34
Is RNA or DNA easier to degrade?
RNA is easier to degrade; DNA is sequestered in the nucleus anyways
35
Explain how high uric acid concentration leads to the irritation and inflammation of joints.
Leads to the formation of uric crystals
36
Why is gout aggravated by an animal-based diet?
- They contain a higher proportion of purines (nucleic acids) than plant-based diets
- By unit-mass, there is more DNA compared to plant-based diets
37
What is uric acid synthesized from in humans?
Adenine and guanine
38
How do lipids differ from other macromolecules?
- They are not defined as polymers, but detain a functional classification
- Lipids are all hydrophobic molecules (fatty acids, cholesterol) and do not have a common subunit
39
What are the two sections of fatty acids?
- Carboxyl-end (hydrophilic)
| - Methyl-end (hydrophobic)
40
Describe the varying lengths of fatty acid chains.
- Short-chain (2-6 carbons)
- Medium-chain (8-10 carbons)
- Long-chain (12-20 carbons)
- Very long-chain (>20 carbons)
41
How does palmitic acid compare to stearic acid?
Palmitic (16:0) is bad, stearic acid (18:0) is better
42
What are the three different uses of fatty acids?
- Energy source
- Structural component
- Substrate for the synthesis of signalling molecules
43
How are fatty acids stored?
In triacylglycerols
44
Is cholesterol a fat?
No, because solid fats and liquid oils are made of triacylglycerols
It's a lipid
45
Give examples of interactions occurring within the lipid bilayer.
- Integral membrane proteins
- Peripheral membrane proteins
- Glycoproteins
- Carbohydrate side chains of glycoproteins
46
What is the role of phospholipases?
- Release fatty acids
| - Leaves you with a lysophospholipid (missing a fatty acid)
47
Give examples of acquired metabolic syndromes.
- Obesity
- Atherosclerosis
- Fatty liver disease
- Gallstones
- Hypertension
- IBD
- Diabetes
48
What does the sentence "food components are bioactive" mean?
- Nutrients are not solely needed to build muscle, bone and energy
- Nutrients are a part of what makes cells work, regulate their activity, and are the components of what they are made of
49
Do plant-based foods have cholesterol?
No, they have sterols
50
What is particular about plant-based sterols?
They are poorly absorbed because transporters are configured to solely recognize cholesterol
51
What is needed to synthesize cholesterol?
- HMG-CoA reductase
| - The quantity of HMG-CoA reductase is a rate-limiting enzyme, which dictates the efficiency of the pathway
52
What is the function of statins?
Inhibit HMG-CoA reductase, and blocks cholesterol synthesis
53
________ is a lipid that is a precursor of highly bioactive molecules.
Cholesterol
54
Can cholesterol be oxidized to produce energy?
No, ATP spent synthesizing this molecule cannot be recovered
55
Cholesterol is a substrate for the synthesis of what?
- Steroid hormones
- Vitamin D
- Bile acids
56
What is cholesterol required for?
- The control of membrane fluidity
- Required for proteins to move and undergo conformational changes, respond to temperature changes, and allow substances to pass through
57
Cholesterol is a highly bioactive molecule that needs to be regulated to be kept within an optimal range. What homeostatic mechanism occurs when there is too much cholesterol?
- Cholesteryl esters (inactive) are synthesized and stored in an oil droplet
- Choleseteryl esters can't be used to make steroid hormones or bile acids
- They need to be converted to cholesterol to become bioactive again
58
Define a nutrient.
A nutrient is either a chemical element or compound that is used in the metabolic processes of, or forms an integral component of the physiology of an organism
59
What are macronutrients?
- Needed in large quantities
- Carbohydrates, proteins, fat
- Nucleic acids are not a source of energy
60
What are micronutrients?
- Small quantities
| - Vitamins and minerals
61
What is the criteria for nutrient essentiality?
That absence of the nutrient from the diet results in characteristic signs of a deficiency disease and these signs are prevented only by the nutrient itself, or a specific precursor of it
62
What are the essential amino acids?
- Phenylalanine
- Valine
- Tryptophan
- Threonine
- Isoleucine
- Methionine
- Histidine
- Arginine (in children and special cases; preterm infants are unable to synthesize or create Arginine internally)
- Lysine
- Leucine
63
What are the essential fatty acids?
- Fatty acids with double bonds located at positions 8 or less (counting from the methyl end)
- Linoleic acid
- Linolenic acid
64
What are the essential fat-soluble vitamins?
- A
- D
- E
- K
65
What are the essential water-soluble vitamins?
- B1, B2, B3, B5, B6, B7, B9, B12
- C
- Choline
66
What is vitamin A?
Retinol
67
What is vitamin D?
Ergocalciferol, cholecalciferol
68
What is vitamin E?
Tocopherol
69
What is vitamin K?
Naphthoquinoids
70
What is vitamin B1?
Thiamine
71
What is vitamin B2?
Riboflavin
72
What is vitamin B3?
Niacin
73
What is vitamin B6?
Pyridoxine
74
What is vitamin B5?
Pantothenic acid
75
What is vitamin B9?
Folic acid
76
What is vitamin B12?
Cobalamin
77
What is vitamin B7?
Biotin
78
What are the four functions of choline?
- Susbtrate for phosphatidylcholine biosynthesis
- Ensures the structural integrity and signaling functions of cell membranes
- Source of methyl groups
- Used to make a variety of very important metabolites (e.g. acetylcholine, platelet-activating factor, betaine)
79
What is the mechanism that spares choline when it is deficient?
The body will recover and reabsorb all the choline it secretes in the bile
80
Describe the de novo synthesis of choline.
- Three successive methylations (recovers methyl groups) of the phosphatidylethanolamine headgroup generates phosphatidylcholine
- Choline can be released from phosphatidylcholine
81
What are the essential macrominerals? What is their function?
- Calcium
- Chloride ion
- Phosphorus
- Important in forming active enzymes needed to support metabolism
82
What are phytochemicals?
- A broad and diverse group of plant-derived compounds
| - Compound that you can't find anywhere else other than plants
83
Which phytochemicals are thought to have beneficial effects on health? Are all phytochemicals good?
- Flavonoids
| - No, some are very toxic
84
Define malnutrition.
- Refers to improper to insufficient diet
| - Nutrient deficiency and nutrient excess
85
What are essential fatty acids substrates for?
A class of molecules called eicosanoids
86
Give examples of eicosanoids.
- Prostaglandins
- Leukotrienes
- Thromboxanes
87
What are the functions of essential fatty acids?
- Immune function
- Inflammatory response
- Blood clotting
- Vasodilation
- Kidney function
- Cognitive function
88
What are the consequences of essential fatty acid deficiency?
- Growth retardation
- Sparse hair growth, dry skin and scaling (excema)
- General weakness
- Depression
- Poor wound healing, increased susceptibility to infection
- Edema
- Vision problems
- Neurological problems (particularly in severe cases).
89
What are the consequences of essential fatty acid excess?
- Currently, does not appear to cause severe problems.
| - May cause excessive bleeding (slow blood clotting)
90
What is the essential function of vitamin A?
Maintenance of epithelial cells
91
Vitamin A and other retinoids are ________. What does this mean?
- Teratogenic
| - Disturbs the development of the embryo or fetus
92
Vitamin A is the ligand for which receptors? What happens if you supply too much vitamin A?
- Retinoic acid receptor (RAR) and retinoid x receptor (RXR)
| - If you supply too much vitamin A, you inappropriately induce the expression of genes, which may cause damage
93
Where is vitamin A found? How does overdose usually occur?
- Coloured fruits and vegetables
- Difficult to overdose on fruits and veggies
- Overdose usually occurs with supplements and drugs (e.g. Acutane)
94
How does vitamin A deficiency lead to xerosis? What is xerosis?
- Abnormal dryness
| - Causes mucus-secreting cells to be replaced by keratin producing cells
95
What is the consequence of vitamin A deficiency?
- Primarily affects eye function
- Eye blindness
- Eye xerosis causes ulcerations and leads to blindness
96
People with diseases involving the absorption of lipids are at risk for which deficiency?
Vitamin A
97
What are the consequences of vitamin A excess?
- Birth defects
- Reduced bone mineral density
- Weight loss, headache, vision problems, dry itchy skin, hair loss, anemia, teeth discolouration, enlarged liver and spleen
98
Is iron a macromineral or a micromineral?
- Transition metal
| - Micromineral
99
What is iron's main function?
- Used by a prosthetic group by many biologically important proteins (ex: heme groups of hemoglobin, myoglobin)
- Generally found in enzymes involved in carrying or metabolizing oxygen
100
How much iron does the average person contain? Where is it largely found
- 3-4 grams of iron
| - 60% in the blood
101
What is the average intake of iron? What is the average absorption?
- 15 mg
| - 2 mg
102
What % of the world is deficient in iron?
80
103
What individuals are at risk for iron deficiency anemia?
- Alcoholics
| - Patients with infectious, inflammatory, or neoplastic diseases
104
What are the symptoms of iron deficiency anemia?
- Pale skin
- Tired and weakness
- Difficulty maintaining body temperature
- Shortness of breath
- Inflamed tongue
- Diminished cognitive function
- Decreased immune function
105
How does iron loss occur?
- Shedding of epithelial surfaces
- Through occult blood loss in the intestine
- Menstruation
- Lactation
106
What is the cause of secondary hemochromatosis?
- Excessive alcohol consumption
| - Excessive use of dietary iron supplements
107
What other disorders can iron excess lead to?
- Arthritis
- Liver disease leading to liver failure
- Damage to the pancreas causing diabetes
- Cardiac function abnormalities
- Impotence
- Abnormal skin pigmentation (making it look grey or bronze)
- Thyroid deficiency
- Damage to the adrenal glands
108
Is iodine a macromineral or a micromineral?
- Halogen
| - Micromineral
109
What are the major functions of iodine?
- Necessary for normal thyroid function
| - Essential substrate for the synthesis of thyroid hormones
110
What are the functions of thyroid hormones?
- Control many aspects of energy (carbohydrate and fat) metabolism
- Ligands of TR receptor (transcription factor belonging to the nuclear receptor superfamily of transcription factors)
111
What are sources of iodine?
- Seafood (cod, sea bass, haddock, perch)
- Kelp
- Dairy products
- Iodized table salt
112
What are the consequences of iodine deficiency?
- Increased fetal and infant mortality
- Neurological defects
- Mental retardation (cretinism)
- Decreased reproductive fitness
- Hypothyroidism
- Goiter (hypertrophy of the thyroid gland)
113
What are secondary thyroid related disorders?
- Anemia
- Arthritis
- Eye enlargement and inflammation
- Hair loss and premature graying of hair
- Inflammatory bowel diseases
- Depression
114
What is the cause of goiter?
- Iodine deficiency; impaired by thyroid hormone synthesis
| - Also caused by excessive iodine, which results in the inhibition of thyroid hormone production
115
Does an excess of iodine develop more or less problems than iodine deficiency?
Excess iodine develops less problems than iodine deficiency
116
What are the consequences of an excess of iodine?
- Skin ulceration ("kelp acne", high incidence in Japan where kelp is consumed in large quantities)
- Impairs thyroid hormone production and causes goiter in response to decreased thyroid hormone concentration
117
What is the lacZ region associated with?
B-galactosidase
118
What is the lacY region associated with?
Permease
119
What is the lacA region associated with?
Transacetylase
120
What does the inhibitor protein of the lac operon bind to in order to shut down transcription?
lacO
121
How do statins function?
- By competitively inhibiting to HMG-CoA reductase
| - Competitive binding to the active site of HMG-CoA reductase prevents HMG-CoA from binding to produce mevalonate
122
What binds to HMG-CoA reductase? What is produced?
- HMG-CoA binds
| - Mevalonate is produced
