1. Biochemistry of Life (Part II) Flashcards
Give an example of how an optimal level exists for each nutrient.
- Goiter appears when there is iodine deficiency as well as excess
- The pathways that lead to goiter are different in terms of deficiency and excess
How do fatty acids impact signal transduction pathways?
If the composition of membranes is changed, the protein signalling in the membrane might be restricted
Give an example of how vitamin A influences gene expression.
- Is internalized and influences transcription factors
- Deficiency: blindness
- Excess: birth defects
What is the true cause of obesity?
- While increased macronutrient intake is one true cause, the opinions vary based on the source
- Singling on one type of food or nutrient might cause important discoveries (ex: vitamin A), but it does not give the whole picture when it comes to obesity
What did the “Patterns of Sedentary Behavior and Mortality in US Middle-Aged and Older Adults” demonstrate?
- 8000 adults (prospective cohort study)
- Analyzed excessive sedentary time and how this impacts quality of life
- Associated with a high-risk of OVERALL mortality, not just obesity
What causes an increase in energy input?
- High fat, energy dense foods
- Palatable, low-cost, easily available foods
- Large portion sizes
What causes a decrease in energy output?
- Decrease in work-related physical activity
- Decrease in activity of daily living
- Increase in sedentary behaviour
Why isn’t there a single factor that causes obesity?
- Because we have different genes that alter our susceptibility
- Because we are free to intake as many calories as we want
- Because we are free to dictate our rate of expenditure
How can obesity be caused socially?
- People that are overweight tend to hang out with other people who are overweight; perhaps, worsening their habits
- Also, commensal bacteria can be passed on socially
- When we alter the proportion of microorganisms that we live with, we tip off the beneficial balance, which may render it pathogenic
What study demonstrates that commensal bacteria (gut microbiota) may influence metabolic status and the state of adiposity?
- Microbiota transplant from an obese twin renders the recipient mouse obese
- Microbiota transplant from a lean twin renders a mouse lean
How many adipocytes are we born with? What happens to them?
- We are born with few white adipocytes
- The body makes more from stem cells when energy needs to be stored
What are the functions of white adipocytes?
- Take up excess fatty acids
- Synthesize fats
- Store them within the adipocytes’ cytoplasm
Why is a long-term lifestyle change necessary to get rid of white adipocytes?
- We can burn stored energy and shrink these adipocytes
- But, they have a 2-year half-life (long-lived)
What is atherosclerosis?
- Lipid, mostly (if not exclusively) cholesterol, deposition within the arteries
- Decreases the opening of the arteries
- Leads to a heart attack or stroke
What is one of the biggest risk factors for atherosclerosis?
High concentration of (LDL)-cholesterol in the blood
What is cholesterol produced by? What products contain cholesterol?
- By the liver
- Meat and dairy products
Does the intake of cholesterol affect your blood cholesterol?
- Well, cholesterol is usually only partially absorbable
- It is easier to intake cholesterol with fat, as they dissolve and travel with them
- Thus, individuals with high-fat diets absorb more cholesterol
Why is the cholesterol from food “extra” cholesterol?
Every single cell in the body has the capacity to make their own cholesterol
What does the “Red meat + wrong bacteria = bad news for the heart” study demonstrate?
- L-carnitine, present in meat, negatively influences cholesterol metabolism and increases the risk of atherosclerosis
- A regular diet of meat encourages the growth of bacteria that turns L-carnitine into TMAO (compound responsible for alteration in cholesterol metabolism)
What do variations in bitter taste receptors determine?
- How an individual perceives bitter taste
- Dictates (past acquired cultural tastes), an individual’s taste
Describe how the bitter taste bud receptor works.
- Taste receptor protein (TAS2R) interacts with a bitter taste molecule
- Causes a conformational change in TAS2R
- Interacts with a G-Protein (hydrolysis of cGMP)
- Calcium flows from the inside to the outside of the cell in an ion channel
- Signal transduction to the brain signals bitter taste
Explain why an individual would find a certain food more bitter than another.
If an individual’s TAS2R protein receptor has a higher affinity to bitter ligands, they will bind at much lower concentrations, thereby increasing their sensitivity
Why are we able to detect sweetness from aspartame?
Because the structure of the protein can interact with the structure of the sweet receptor
What gene encodes lactase? What is special about it?
- LCT gene
- It normally shuts down after weaning
What allows the LCT to not be shut off in certain cases?
- Polymorphism
- Lactate continues to be produced
- These individuals have access to the nutrients of dairy products
What can gene variations influence?
- Can determine whether specific classes of nutrients will have a change in regulating metabolic function
- Can provide individuals’ use of nutrients that are normally only accessible during specific periods of the life cycle
Where do the polymorphisms that cause lactase to be produced in adults occur?
- Not in the LCT gene itself
- In a neighbouring gene (MCM6 gene)
What are SNPs? What are they associated with in lactase?
- Single-nucleotide polymorphism are point mutations
- Associated with lactase persistence
