Topic 1: Biochemistry of Life (Nutrients and Nutrition) Flashcards
Why are nutrients so important from a cellular perspective?
Cells continuously regenerate/repair/produce and they need building blocks (nutrients) to do so
Give an exemple of a nutrient influencing gene expression. How does it work?
Lactose and the lac Operon;
Absence of lactose –> repressor (normally produced) binds to promoter region => LacO cannot be transcribed
Presence of lactose –> induction (turns on) a gene that produces an inducer. It will bind to repressor preventing the repressor to bind to lacO –> lac Operon can now be transcribed
How can a dietary constituent regulate transcription (scheme) and how do we ensure a permanent change?
by interacting with genes which will then by
a) Direct regulation: Inc. or Dec. in the transcription of genes –> change in mRNAs –> change in Proteins (will induce an incease or decreases in specific cellular activity)
b) Indirect regulation (fast change, but temporary): produce a Physiological Modulation (insulin –> signaling cascade) which will produce a Secondary Mediator who will then interact again with genes to then Regulate transcription –>…
To ensure a permanent change, need to change genes (regulate transcription)
How can nutrients specifically regulate gene expression in a cell (4)
- Bind to receptor on membrane which will produce a signal, affecting gene expression
- Are transported in the cell and bind to transcription factors (Nuclear receptors), affecting gene expression
- Induce DNA methylation, affecting gene expression
- Bind directly to produced protein and modifies it’s activity (activate/deactivate)
What are functional groups?
Reorganized elements that have specific properties
What else to cells need to grow (bulk up) other than proteins? What specific protein is central to this process; what does it do? By what (3) ways is this central protein influenced?
1) Lipids: need to increase membrane to have a bigger volume
2) mTORC1: it basically controls the synthesis of proteins and lipids (through SREBP1). mTROC1 is influenced by nutrients (amino acids and glucose intake), cellular energy status (AMPK) and growth factor (Akt)
How is SREBP activity regulated?
- In low [sterol], SREBP (found on the ER) is transported into the Golgi to be transformed into a nuclear factor which will target genes responsible for cholesterol and fatty acid biosynthesis
- In high [sterol], cholesterol binds to SREBP, preventing it to leave ER => no inc. in sterol production
Name three carbohydrates and where we can find them
Glycogen (liver of animals)
Cellulose (cell wall of plant cells)
Starch (in plant cells)
When it come to digestion, what influences changes in blood sugar for carbohydrates?
A difference in their complexity (glycemic index)
What is important for proteins to function?
They need to retain their shape; A change in shape can induces a loss in function
Why is water important?
It is the medium in which chemical reactions occur
How can protein become hypoallergenic? What is their use (2)?
By changing their shape or cutting them (hydrolyzing) to smaller pieces. They are used in infant formula; Gives glutamic acid (flavor enhancer, responsible for umami taste, neurotransmitter)
What is PKU? What are it’s effects?
Phenylketonuria: gene variation that alters phenylalanine enzyme or Phe enzyme activity. Results in increase [Phe] in blood –> high [Phe] in brain =>
decreases: synaptic transmission, protein synthesis, neurotransmitter synthesis
damages myelin
What should not be eaten if have PKU?
If have PKU, want to watch Phe consumption; Aspartame should not be consumed since it is composed of aspartic acid and phenylalanine.
What are the 4 types of fatty acids whose name depends on their length?
Short chain (2-6C) Medium chain (8-10C) Long chain (12-20C) Very long chain (>20C)
What is gout (what, how) and what should be eaten in moderation?
Gout is a genetic disorder associated with painful joint inflammation. People with gout cannot successfully dispose of uric acid (synthesized from adenine and guanine). High [uric acid] leads to uric crystal precipitation which irritates and inflames the joints. Adenine and Guanine are present in DNA. DNA is present in cells. Since animal based products contain more cells than plant based products, they should be eaten less.
Explain hydrogenation
Process by which an unsaturated FA (like oil) is transformed to trans FA. It allows this new “saturated” FA to be solid a room temperature
What happens with trans FA in the body?
NOTHING! they are not metabolized; they accumulate
What are FA stored as?
Triacylglycerol (1 glycerol + 3 FA)
What are phospholipids? How can they organize and how (2)?
Glycerol with a posphate group, and 1 or 2 FA;
If has 1 FA –> forms micelle
If has 2 FA –> forms lipid bilayer
What is characteristic of sterols?
a 4 ring structure
How can sterols be devided (2 types). Name 1 of each.
Partially absorbable: cholesterol
Poorly absorbable: stigmasterol (plant cholesterol)
What is special about cholesterol (4)
- Is highly bioactive
- To store, needs be “inactivated”. Do so by binding it with a FA
- Controls membrane fluidity
- Precursor of steroid hormones and Vit D
What are the general causes of the Global Obesity Problem (3)?
Energy dense food is cheap
Low nutrient diversity (fruits & veg are expensive)
Why is it cheaper to use High Fructose Corn Syrup (HFCS)?
Easy to manufacture: add enzyme: starch decomposes intro glucose + glucose isomers –> can make fructose
Easy to use: do not need to heat to dissolve crystallized sugar since HFCS is in liquid form
What are the three main uses (purpuse/function) of nutrients
Energy source
Build structures
Provide support functions
Define essential nutrients
In the absence of a nutrient, have signs of a deficiency disease and these signs disappear when the nutrient (or a precursor) is added back to the diet
What are the 10 essential amino acids? What is specific about two of them?
Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine Histidine Arginine
Why are some fatty acids essential? Which one are they?
Humans cannot make double bonds at position 8 or less from the methyl end. Linoleic acid (C18:2 n-6,9) Linolenic acid (C18:3 n-3,6,9 or n-6,9,12)
What is choline and what is it used for?
It is a water-soluble essential vitamin. Is a substrate for phosphotidylcholine …
