1. Biochemistry of Life (Part I) Flashcards
What is human nutrition?
Making sure that our composition (from a molecular to an organismal level) is functioning properly
Why do cells require ATP for maintenance?
Resting cells still require ATP to maintain their cellular structures through cell division, which utilizes energy and, thus, needs nutrients
What nutrients are necessary during cell division?
- Energy
- Proteins to create new structures and motors
- Lipids to create cell membranes
Define nutrigenetics.
Genes control the metabolism of nutrients
Define nutrigenomics.
Nutrients influence the expression of genes
What happens if lactose is present in the culture media of E. coli?
Induction of the gene (lac operon) involved in lactose metabolism
Explain how the nutrient-gene interaction between lactose and the lac operon gene is a homeostatic mechanism.
You don’t want to waste your energy to produce enzymes for metabolizing lactose, if there is no lactose to metabolize in the first place
Explain what happens on a molecular level to the lac operon when there is a lack of lactose.
- 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
Explain what happens on a molecular level to the lac operon when there is lactose.
- 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)
What are the three genes that are known to be involved in the metabolism of lactose?
- B-Galactosidase
- Permease
- Transacetylase
Lactose is an example of a ______________, while the lac operon is an example of a _____________.
dietary constituent
responsive gene
What is a responsive gene?
- Either be induced or repressed by a dietary constituent
- If it does not do either, it is not a responsive gene
What do secondary mediators have an impact on in nutrient-gene interactions? What are they affected by?
- They have an impact on their own responsive genes
- They are indirectly affected by dietary constituents
What are the five ways dietary constituents can interact with genes, either directly or indirectly?
- Responsive genes (direct)
- Physiological modulation (indirect)
- Regulation of transcription
- Regulation of translation
- Modification of proteins
Where do responsive genes reside in Eukaryotic cells? What about in Prokaryotic cells?
- Eukaryotic: nucleus
- Prokaryotic: nucleoid body
Explain how amino acids and fatty acids regulate gene expression indirectly.
- 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
Explain how fat-soluble vitamins, trace elements, fatty acids, phytochemicals, and sterolsregulate gene expression.
- Find their way inside the cell through nutrient transporters
- Interact with specific transcription factors
- Nuclear receptors act on target genes, affecting transcription
Explain how folic acid, vitamin B12, and methionine regulate gene expression.
- Affect DNA methylation
- Impacts the ability of the cell to utilize genetic information
- Renders it unaccessible for transcription
Explain how cofactors and vitamins regulate gene expression.
Translation cannot occur if they are not present
Explain how nutrients can affect proteins directly.
- Certain proteins find their way inside the cell and interact directly with proteins and enzymes
- This affects their conformation, their binding capacity, and their interactions
- These influence metabolism by either increasing or decreasing efficiency
Concerted Regulation of Protein and Lipid Biosynthesis occurs by which pathway?
The Akt/mTORC1 pathway
What are the four proteins involved in the Akt/mTORC1 pathway?
- AMPK
- Akt
- mTORC1
- SREBP
AMPK and Akt are components of a signalling pathway. What are their functions?
- AMPK: responds to cellular energy status
- Akt: responds to growth factors, including insulin
What is the role of mTORC1?
- Integratesthe information related to the kind:
- Nutrients available
- Cellular energy status,
- Growth factors interacting with the cell receptor
What does the Akt/mTORC1 pathway affect?
Regulates protein and lipid biosynthesis
True or False: if you increase your mass of cells, you increase your lipid content. Why or why not?
- True
- Due to the Akt/mTORC1 pathway, which regulates cell growth through protein AND lipid biosynthesis
Why is glucose uptake necessary for the Akt/mTORC1 pathway?
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
What is SREBP responsive to?
To the status of cholesterol in the environment
Explain what happens to SREBP when you have low sterol concentrations.
- 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
Explain what happens to SREBP when you have high sterol concentrations.
- SREBP remains bound to SCAP, which is bound by INSIG, and remains in the ER
Give examples of abundant elements.
Carbon, hydrogen, nitrogen, oxygen, phosphorus
Give examples of trace elements.
Calcium, chlorine, cobalt, copper, iodine, iron, manganese, magnesium, potassium, sodium, sulphur, selenium, zinc
Are there few or many functional groups?
Few (12) functional groups composed of reorganized elements exist
Describe the 6 levels of organization of life.
- Macromolecule
- Supramolecular Assembly
- Organelle
- Cell
- Tissue
- Organ
- Organism
What are the two requirements for life?
- Energy: light, heat, chemical
- Raw materials
What raw materials are necessary for life?
- Carbon source
- Nitrogen source (protein and DNA)
- Water
- Oxygen
- Salts
Which terminal of an amino acid corresponds to the 5’-end of the gene that encodes it? What about the 3’-end?
- N-terminal (+) = 5’
- C-terminal (-) = 3’
What is hydrolyzed protein used for?
- Common in some large scale food manufacturing
- Texturizer, flavour enhancer
Explain how hydrolyzed proteins may be hypoallergenic.
If you break up a protein, our immune system might not recognize its different three-dimensional structure
What is the function of glutamic acid as a neurotransmitter?
Involved in long-term potentiation (learning and memory)
What symptoms has MSG been suggested to cause?
- Headaches
- Numbness
- Tingling sensations
- Obesity
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)
How does L-glutamate made by chemical synthesis differ from L-glutamate made by fermentation?
They are the same despite chemical synthesis being synthetic
Which foods contain MSG?
- Anything that contains “protein hydrolysate” (prepared foods, protein supplements)
- Fermented food products (soy sauce, Worcestershire sauce, vegemite)
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
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.
Is RNA or DNA easier to degrade?
RNA is easier to degrade; DNA is sequestered in the nucleus anyways
Explain how high uric acid concentration leads to the irritation and inflammation of joints.
Leads to the formation of uric crystals
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
What is uric acid synthesized from in humans?
Adenine and guanine
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
What are the two sections of fatty acids?
- Carboxyl-end (hydrophilic)
- Methyl-end (hydrophobic)
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)
How does palmitic acid compare to stearic acid?
Palmitic (16:0) is bad, stearic acid (18:0) is better
What is olive oil rich in?
Oleic acid (C18:1)
What is safflower oil rich in?
Linoleic acid (C18:2)
What is lard and beef tallow rich in?
Palmitic (C16:0) and stearic (C18:0) acids
What are the dangers of trans fatty acids?
- Mimic the structure of saturated fatty acids
- Body does not know how to metabolize these structures, so they are unknown to the body
- Their shape is different, thus, they do not fit the proper configuration in the enzymes
What are the three different uses of fatty acids?
- Energy source
- Structural component
- Substrate for the synthesis of signalling molecules
Describe myristillation.
- Covalent modification of proteins
- Attach myristic acid to a portion of a protein residue, which renders it hydrophobic
- It will tend to insert its hydrophobic residue in a membrane, along with the attached protein