Flashcards in Nutrition, Body Weight and Homeostasis Deck (214):
The chemical process that occur within living organisms in order to maintain life.
What does metabolism consist of?
What do oxidative pathways do?
Convert food to energy
What do fuel storage and mobilisation pathways do?
Allow food to be mobilised when we are not eating or need to increase energy
How to fuel storage and mobilisation pathways allow fuel to be mobilised?
Through interconversion of glycogen and fat stores
What do biosynthetic pathways do?
Produce basic building blocks for cells
What do detoxification pathways do?
What are catabolic processes?
They break down molecules to release energy in form of reducing power
What are anabolic processes?
They use energy and raw materials to make larger molecules for growth and maintenance
The capacity to do work
What kind of energy to cells use?
Chemical bond energy
How do cells use chemical bond energy?
Through the utilisation of ATP
What kind of work do cells do?
What biosynthetic work do cells do?
Synthesis of cellular components
What transport work do cells do?
Movement of ions and nutrients across membranes
Why is the movement of ions across membranes important?
For neuronal communications
What mechanical work do cells do?
What electrical work do cells do?
Nervous conduction in the form of action potentials
Where does osmotic work occur?
In the kidney
Describe the structure of ATP
Adenine base linked to ribose sugar and 3 phosphates- alpha, beta and gamma.
How does ATP release energy?
Bond between beta and gamma phosphate breaks
Give the equation for ATP hydrolysis
ATP ↔ ADP + Pi
Give 5 examples something that pushes ATP hydrolysis in the forward direction
What pushes ATP hydrolysis in the backwards direction?
Energy production by oxidation
Give 4 examples of things oxidised for energy production
How is ATP generated?
By breaking down the chemical bonds in food
Give 3 processes that generate ATP
What is the official SI unit of energy?
How many kJ’s are there in 1 kcal (calorie)?
Give the 6 essential components of the diet
Which of the essential components of the diet can’t be digested?
What are carbohydrates required for?
Mostly supply energy
What are proteins required for?
Energy and amino acids
When are proteins utilised for energy?
What are fats required for?
Energy and essential fatty acids
What are minerals required for?
Cofactors of enzymes
What is water required for?
What is fibre required for?
Normal GI function
Why can’t fibre be digested?
Because humans can’t digest the 1,4-ß glycosidic bonds in cellulose, as they don’t have the enzyme
Give 4 examples of carbohydrates
What is starch
A glucose polymer that is the carbohydrate storage molecule in plants
What are the monomers of sucrose?
Glucose and fructose
What are the monomers of lactose?
Glucose and galactose
What is the purpose of digestion of carbohydrates
To break larger carbohydrates into monosaccharides
Why must larger carbohydrates be broken down into monosaccharides?
So they can be absorbed in the blood
What are proteins composed of?
Amino acids in linear chains
How are amino acids in proteins linked?
What effect does digestion have on proteins?
Breaks them down into constituent amino acids
What happens to the amino acid products of digestion?
They are absorbed into the blood
How many amino acids are used for protein synthesis in the body?
How do amino acids differ from one another?
They each have a different side chain
How many essential amino acids are there?
Why are essential amino acids so called?
They cannot be synthesised by the body
What is the result of the inability of the body to synthesise essential amino acids?
They must be obtained from diet
How must protein hormones enter the body
Why must protein hormones be injected?
Otherwise the body would break them down
What are the 9 essential amino acids?
What is meant by conditionally essential?
Some amino acids are only essential in extreme circumstances
When may amino acids be conditionally essential?
In children and pregnant women
Why might amino acids be conditionally essential in children and pregnant women?
High rate of protein synthesis as rapid growth rate
What 3 amino acids are conditionally essential in children and pregnant women?
What is the difference between protein of animal origin and plant origin?
Protein of animal origin ‘high quality’- contains all amino acids. Proteins of plant origin usually deficient in 1+ essential amino acids
What is the result of protein of plant origin being of lower quality?
Vegetarians need proteins from wide variety of sources
What are lipids composed of?
What are triacylglycerols composed of?
3 fatty acids esterified to 1 glycerol
What are the 2 types of lipids?
What is the result of a double bond in a lipid?
Allows more flexibility
How do fats differ from carbohydrates or protein?
They have much less oxygen
What is the result of fats having less oxygen than carbohydrates or protein?
They are more reduced, so yield more energy when oxidised
What are fats required for?
What are the 4 fat soluble vitamins?
What are the two essential fatty acids?
What kind of constituent are minerals in the diet?
What is the role of electrolytes in cells?
They establish ion gradients across membranes and maintain a water balance
Give an example of an electrolyte required in the body
Why is Cl - required in the diet?
It is an essential electrolyte for sodium potassium ATPase, needed to establish ion gradients
Give two examples of macrominerals
What are macrominerals essential for?
Structure, e.g. bones and teeth
Other than structure, what is calcium important for?
Important signalling molecule
Give 7 examples of enzyme cofactors
Give an example of a process that requires an enzyme cofactor
Glutathione peroxidase, required to combat oxidative stress, requires selenium
What is iron essential for?
Component of haemoglobin
From high to low amount, how much of a mineral is needed?
Electrolytes → minerals → trace minerals → ultratrace
In what quantity are vitamins required?
Are vitamins fat or water soluble?
Can be either
What happens if someone has incorrect vitamin intake?
If too little, can get deficiency diseases
Can also have vitamin excess
Give an example of a vitamin excess disease, and it’s effects
Give 4 examples of fat soluble vitamins
Give 10 examples of water soluble vitamins
- B1 (Thiamine)
- Pantothenic acid
What disease is caused by a deficiency in vitamin A?
What disease is caused by a deficiency in vitamin D?
What is caused by a deficiency in vitamin E?
What is caused by a deficiency in vitamin K?
Defective blood clotting
What disease is caused by a deficiency in vitamin B1?
What disease is caused by a deficiency in vitamin B12?
What diseases are caused by a deficiency in vitamin B6?
What is caused by a deficiency in biotin?
Alopecia, scaly skin, CNS defects
What disease is caused by a deficiency in vitamin C?
What is caused by a deficiency in choline?
What is caused by a deficiency in folate?
Neural tube defects, anaemia
What disease is caused by a deficiency in niacin?
What is caused by a deficiency in pantothenic acid?
What disease is caused by a deficiency in riboflavin?
What vitamins have an antioxidant role?
A and C
What antioxidant role do vitamins A and C have?
They are free radical scroungers
Give 4 examples of dietary fibres
What is dietary fibre essential for?
Normal GI function
Can dietary fibres be broken down by human digestive enzymes?
What is the recommended intake of dietary fibre?
What is the consequence of low dietary fibre?
What is the result of high dietary fibre intake?
Why does a high dietary fibre intake reduce cholesterol?
Bile salts are secreted into the stomach, which requires cholesterol. Fibre absorbs bile salts, so if there is high fibre intake, more bile salts are absorbed, so less bile salts reabsorbed into liver. This means that more bile salts must be made, so more cholesterol used.
What is the advantage of lower cholesterol?
Lower risk of diabetes
Who publishes dietary reference values (DRV’s)?
What are DRVs?
A series of estimates of amount of energy and nutrients needed by different groups of the UK population
What is the reference nutrient intake (RNI)?
The level of protein, vitamins and minerals that would meet the needs of 97.5% of the population
When is the estimated average requirement (EAR) used?
What is the EAR?
The energy requirement for 50% of the group
What is the lower reference nutrient value (LRNI)?
The level that would be enough for 2.5% of the population- the majority need more
When is safe intake used?
When there is insufficient data
What do nutrient requirements depend on?
How are nutrient requirements established?
By review of scientific evidence and frequency distribution for groups
Are nutrient requirements applicable to individuals?
Give 4 things that daily energy requirements depend upon
- Body composition
- Physical activity
What is daily energy expenditure equal too?
Basal metabolic rate + diet induced thermogenesis + physical activity level
What is the basal metabolic rate?
The energy used to keep the body going, e.g. for liver function, brain etc.
What is diet induced thermogenesis?
Energy required to process food
Give two examples of things required for the maintenance of cells
- Ion transport across membrane
- Biochemical reactions
What percentage of the BMR is accounted for by the skeletal muscle?
What percentage of the BMR is accounted for by the brain?
What percentage of the BMR is accounted for by the heart?
What percentage of the BMR is accounted for by other organs?
Give 5 factors that affect BMR
How does body size affect BMR?
Depends on surface area
How does gender affect BMR?
It is higher in males
How does environmental temperature affect BMR?
It increases when it’s cold
How does endocrine status affect BMR?
It is increased in hyperthyroidism
How does body temperature affect BMR?
It increases by 12% per degree
What does energy required for voluntary physical activity depend on?
What systems does voluntary physical activity increase energy demand for?
What happens to the heart and breathing rate with physical activity?
What does an increase in energy demand with activity reflect?
An increase in demand on skeletal muscle
Why does skeletal muscle require more energy with activity?
Skeletal muscle hydrolyses ATP to form cross bridges that underlie skeletal muscle contraction.
How does skeletal muscle contraction work?
Muscle contraction is determined by myosin in the thick filament and actin in the thin filament. Myosin head binds to thin filament, hydrolyses ATP (chops off gamma phosphate). Energy released used to change the myosin head, which draws the filaments over each other.
What is the very short term energy store?
Where is creatine phosphate found?
In the muscles
How much creatine phosphate do the muscle contain?
A few seconds worth
What energy store is used for immediate use?
What form are the carbohydrate stores in?
What is the time scale for glycogen utilisation?
Minutes to hours
Where is glycogen stored?
Muscles and liver
Where are the long term energy stores?
How much energy is stored in adipose?
About 40 days worth
Where does energy come from in emergency situations?
Muscle protein converted to carbohydrate
Why is muscle protein only used as an energy source in emergency situations?
The body wants to conserve muscle mass
What is the main difference in body composition between men and women?
What happens to body composition in obesity?
Not everything in body increases, just adipose tissue
What happens if energy intake = expenditure?
The body weight is stable
What happens if energy intake > expenditure?
Energy stores increase
What happens if energy intake
Body components, e.g. protein, utilised to provide energy
What is obesity?
Excessive fat accumulation in adipose tissues
What is the result of obesity?
It impairs health
How is obesity usually measured?
What BMI would be considered obese?
What is the problem with obesity?
It is the major preventable cause of death in developed countries, with an increasing prevalence
What health issues is obesity associated with?
- Increased risk of some cancers
- Cardiovascular disease
- Type 2 diabetes
What is the unit for BMI?
How is BMI calculated?
Weight (kg) / Height 2 (m 2 )
What is BMI used for?
To clinically evaluate a patients weight
What BMI is considered underweight?
What BMI is considered normal?
18.5 - 24.9
What BMI is considered overweight?
25 - 29.9
What BMI is considered severely obese?
Under what conditions is BMI measured?
What is the advantage of a BMI measurement?
Good correlation with body fat measurement
What is the disadvantage of a BMI measurement?
Very muscular individuals may be classified as obese
What is an alternative to BMI?
What has been evidenced to be clinically important?
Distribution of body fat
Why is distribution of body fat clinically important?
Greater proportion of fat in upper body (especially abdomen) compared with hips is associated with increased risk of-
- insulin resistance
- type 2 diabetes
- premature death
What is a major preventable cause of death in developing countries?
What are the two main types of malnutrition?
What is kwashiorkor?
What is marasmus?
Why does malnutrition cause death?
Due to damage from low energy intake and deficiency diseases of other nutrients
What can low protein intake result in?
Insufficient blood protein synthesis
Why does low protein synthesis result in insufficient blood protein synthesis?
Inhibition of the liver to create proteins such as albumin
What is the result of insufficient blood protein production?
A decrease in plasma osmotic pressure and oedema
What is Starlings Law of the Capillary?
Flow net = (P c - P i ) - (π c - π i )
- P x = hydrostatic pressure
- π x = oncotic pressure
- X c = of capillary
- X i = of interstitial fluid
Using Starling’s Law of Capillary, what causes oedema?
π c decreases because of decrease in plasma protein, therefore increased net flow of fluid into interstitial fluid
What does fluid oedema lead to?
Give 6 functions of blood
- Immune functions
- Regulation of body pH
- Regulation of core body temperature
- Hydraulic functions
What are the transport functions of blood?
- O 2 and nutrient supply
- Removal of waste products
What are the nutrients supplied by the blood used for?
Give 3 waste products removed by the blood
- CO 2
- Lactic acid
How is the blood used for signalling?
By transporting hormones
Why is metabolite measurement in the blood used rather than using actual tissue samples?
Difficult to examine actual tissues with metabolic problem, as could be dangerous or expensive to biopsy
What are the advantages of using blood to measure metabolite concentrations?
- Blood readily obtainable
- Tests inexpensive
What could an increase or decrease in concentrations of substances found in blood mean?
Could be used as diagnostic tool to help indicate nature of problem
Give an example of where a change in concentration of substances in blood could be used as a diagnostic tool
An increase in ketone bodies could be indicative of diabetes
Are normal ranges of substances found in blood absolute or typical?
Typical - they vary within a range
What does the concentration of substances in the blood depend on?
What can happen when the skeletal muscle, liver and adipose tissue release the substances they store?
Can change the concentrations of nutrients in the blood plasma
Which organs can interconvert substances?
Which tissues can utilise nutrients?
What do homeostatic mechanisms do?
Act to counteract changes in the internal enviroment
Are body systems in a steady state?
No, in a dynamic equilibrium
What is the result of homeostatic failure?
What levels do homeostatic mechanisms exist on?
All- cell, tissue, organ, organism
Are homeostatic mechanisms independent or interdependent for the variable being regulated?
What are the 4 main aspects of a homeostatic mechanism?
What does the receptor do?
Monitors and responds to changes in environment
What does the control centre do?
- Sets range where variable is maintained
- Determines appropriate response
- Sends signal to effector
What does the effector do?
Brings about desired changes