Metabolic fuels and dietary components 10.10.22 Flashcards
What is metabolism?
the sum of the chemical reactions that take place within each cell of a living organism
How are dietary components metabolised?
- biosynthetic
- fuel storage
- oxidative processes
- waste disposal (detoxification)
What pathway are structural molecules e.g. proteins formed?
biosynthetic pathways occur and this includes the removal of those compounds which have no nutritional value (xenobiotics)
What are anabolic processes?
synthesise larger molecules from smaller components
What are catabolic processes?
break down larger into smaller
Which pathways are anabolic?
Biosynthetic and fuel storage and require energy as it results in the formation of macromolecules.
Which pathways are catabolic or either?
Oxidative - catabolic
waste disposal - either
Where does energy come from for cell processes? (ATP Cycle)
Comes from catabolic pathways. Fuel molecules like carbohydrates, lipids and proteins are broken down or catalysed and energy is released in the form of ATP.
Where does energy come from for cell processes? (Oxidative phosphorylation)
The oxidation of energy rich compounds e.g. carbohydrates yields ATP. Process requires oxygen and gives off carbon dioxide as a waste product. ATP is generated and when it is used it is converted to ADP and inorganic phosphate.
What are some specialisations of tissues?
- Adipose tissue - 85% fat, storage of energy-rich molecules
- Liver - metabolically active (e.g. gluconeogenesis: removal of toxins, usually urine) Carbohydrate
- muscle - activity, Protein
What is the Cori cycle?
Shows how different organs work together to maintain homeostasis.
If somebody has a spell of intense physical activity, the muscles rely only on any aerobic respiration , which means there is insufficient oxygen for the usual oxidative processes. This produces lactic acid. Liver can take up lactate and combine it with pyruvate and form glucose. Glucose release by liver into bloodstream, can be taken up or used by other organs
How is the concentration of glucose maintained?
By insulin. After a meal with lots of glucose, pancreas releases lots of insulin in response to increasing sugar levels.
How is adipose tissue affected by insulin?
To increase the uptake of glucose and to increase the production of storage compound, especially triglycerides
How is the liver and muscle cells affected by insulin?
- Increases the uptake of glucose as well as potassium and phosphate. It also stimulates biosynthesis. Increased synthesis of proteins and glycogen under the influence of insulin
- In the liver, also synthesis of fatty acids from carbohydrates, transported to adipose tissue for storage
- Insulin inhibits hydrolysis od triglycerides
- Actions of insulin are anabolic rather than catabolic.
What are the three main dietary sources of energy?
- carbohydrates
- lipids
- proteins
(in some people ethanol will too)
How much fuel do we need?
Can use the BMI as fuel is based on your weight and height
BMI of 18-25 is healthy
25-30 overweight
30 + morbidly obese
How has the prevalence of obesity in the England changed?
Upward trend since 1993 onwards. A lot of people overweight and some also obese
How are energy sources processed?
Energy rich molecules undergo oxidation and ATP released as energy as well as the release of CO2 and H20
What is gluconeogenesis and what does it use?
- Process that transforms non-carbohydrate substrates (such as lactate, amino acids, and glycerol) into glucose
- Uses lactate, amino acids and glycerol
What are triglycerides?
three fatty acids groups esterified to glycerol
Triglycerides are more reduced than other compounds such as carbohydrates.
What happens to excess energy intake?
Store as triglycerides in adipose. Liver can store 200 grams of glycogen and the muscle can store 150. Then after an overnight fast, the amount of glycogen decreases significantly
What is the energy compound of the different storage compunds?
-Carbohydrate: 4 kcal/g
-Protein: 4 kcal/g
-Alcohol: 7 kcal/g
-Lipid: 9 kcal/g
What is the Basal metabolic rate (BMR)?
A measure of the energy required to maintain non-exercise bodily functions such as: (just to stay alive)
- respiration
- contraction of heart muscles
- biosynthetic processes
- repairing and regenerating tissues
- ion gradients across cell membranes
What are the conditions for measuring BMR?
- post absorptive (12 hour fast)
- lying still at physical and mental rest
- thermo-neutral environment (27-29 degrees C)
- no tea/ coffee/ nicotine/ alcohol in previous 12 hours
- no heavy physical activity the previous day
If any of the above conditions are not met, we may refer to Resting Energy Expenditure (REE)
What are some factors affecting BMR?
- We have a decreasing BMR with age, especially during the first two decades of life. There is a small gender difference, where males are higher
- Also dieting/ starvation will affect it
- hypothyroidism (thyroid gland, secretes thyroid hormones which regulate metabolic rate. Can have a condition with reduced thyroid hormone secretion so can have a reduced BMR)
- Decreased muscle mass( higher muscle to fat ratio tends to have higher BMR)
What equations do we use for estimating BMR?
- Harris Benedict equations
- Schofield equations
- Henry equations
Rough estimate: 1 kcal/kg body mass/hour
How many kCal/kg/day should patients who are not severely ill have?
25-35
What effect does starvation have on the body?
- insulin levels decrease
- Glycogenolysis (biochemical pathway in which glycogen breaks down into glucose-1-phosphate and glucose)
- During a long period of fasting/starvation, glucose must be formed from non-carbohydrate sources - gluconeogenesis
What happens after 4 days of starvation?
Liver: Ketones produced from fatty acids
Brain adapts to using ketones instead of glucose as a fuel
Decreased BMR = accommodation
What is malnutrition?
A state of nutrition with a deficiency, excess or imbalance of energy, protein or other nutrients, causing measurable adverse effects. These adverse effects are on tissue/body form (shape, size, composition), body function and clinical outcome
What are the dangers of re-feeding too quickly?
Re-distribution of phosphate, potassium, magnesium etc due to insulin
Switch back to carbohydrates as the main fuel which requires phosphate and thiamine. If these are not met we can get thiamine deficiency.
What are micronutrients?
Include trace elements and vitamins and are required for:
- co-factors in metabolism
- gene expression
- structural components
- antioxidants
What does Vitamin C do?
- ascorbic acid
- fruit and veg
- collagen synthesis
- improve iron absorption
- antioxidant
What does B12 do?
- protein synthesis
- DNA synthesis
- Regenerate folate (and thus cell division)
- fatty acid synthesis
- energy production
Vitamin B1 (thiamine)
Helps with energy production in your body
Vitamin B2 (riboflavin)
Helps with energy production in your body
Helps your body use other B vitamins
Vitamin B3 (niacin)
Helps your body to use protein, fat and carbohydrate to make energy
Helps enzymes work properly in your body
Biotin
Allows your body to use protein, fat and carbohydrate from food
Vitamin B6 (pyridoxin)
Helps your body to make and use protein and glycogen which is then stored energy in your muscles and liver
Helps form haemoglobin which carries oxygen in your blood
Vitamin B12 (cobalamin)
Works with the vitamin folate to make DNA
Helps to make healthy blood cells. Low B12 can cause a type of anaemia
Keeps nerves working properly
Folate (also known as folic acid)
Helps to produce and maintain DNA and cells
Helps to make red blood cells and prevent anaemia
Getting enough folic acid lowers the risk of having a baby with birth defects like spina bifida (type of neural tube defect)
Vitamin C
Prevent cell damage and reduce risk for certain cancers and heart disease
Collagen synthesis - heals cuts, keeps gums healthy
Protects from infections by keeping immune system healthy
Increases amount of iron we can absorb
Vitamin A
Helps you to see in the day and at night.
Protects you from infections by keeping skin and other body parts healthy.
Promotes normal growth and development.
Carotenoids
Carotenoids are not vitamins but some types can turn into vitamin A in the body.
Act as antioxidants which protect your body from damage caused by harmful molecules called free radicals.
Vitamin D
Increases the amount of calcium and phosphorus your body absorbs from foods.
Deposits calcium and phosphorus in bones and teeth, making them stronger and healthier.
Vitamin E
Helps to maintain a healthy immune system and other body processes.
Acts as an antioxidant and protects cells from damage.
Vitamin K
Makes proteins that cause our blood to clot, when you are bleeding.
Involved in making body proteins for your blood, bones and kidneys
What is a prudent diet?
- 5+ fruit and veg
- base meals around starchy carbohydrate foods
- no more than 5% of the energy we consume should come from free sugars
- 0.8g/kg/day protein
- man no more than 30g, woman no more than 20g of saturated fat a day
-no more than 6g salt
-no more than 14 units alcohol a week
