What are the features of catabolic pathways in metabolism?
Break down of molecules (large to small)
Releases energy (some conserved as ATP)
Produces reducing power (release of H+)
Produces intermediary metabolites
What are the features of anabolic pathways in metabolism?
Builds smaller molecules into larger ones
Reductive (uses H+ ions)
Uses intermediary metabolites and energy as ATP to synthesise new cell components
What is the daily energy expenditure of a 70kg male?
What is the daily energy expenditure of a 58kg woman?
Daily energy expenditure is comprised of what 3 basic components?
Energy to support base metabolism (basal metabolic rate)
Energy for voluntary physical exercise
Energy to process food we eat (diet induced thermogenesis)
List the essential components of the diet
Minerals and vitamins
Why are fats essential to diet?
Necessary to absorb fat soluble vitamins (ADEK)
Contain essential fatty acids (eg linoleic and linolenic acids)
What is the energy yield of fats compared to carbohydrates?
2.2 times greater
What are the fatty acids linolenic acid and linoleic acid used for?
Structural components of cell membrane
Precursors of important regulatory molecules (eicosanoids)
Why are proteins essential components of the diet?
Amino acids used in synthesis of N containing compounds (eg. Creatine, nucleotides, haem)
Maintain nitrogen balance
Contain essential amino acids that can't be synthesised by the body.
What is the nitrogen balance?
Intake of N2 = N2 loss daily
How much protein is degraded and excreted per day and hence what is the daily protein requirement in the diet?
Average 35g degrades
35g intake required to maintain nitrogen balance
Why are carbohydrates and essential dietary requirement?
Main source of energy in diet
What is the energy content of carbohydrates per gram?
Are fats necessary for energy production?
Why is water an essential dietary component?
Water lost by the body each day, must be replaced by drinking
What proportion of the body weight is water?
How much water is lost to the body a day and how is it lost?
2.5L lost total
0.4L expired air
How is water gained by the body?
Cellular metabolism (0.35L)
Why is fibre necessary in the diet?
Normal bowel function
Why are minerals and vitamins necessary in the diet?
Deficiency/absence/excess of these associated with disease.
In adults what can starvation lead to?
Muscle and subcutaneous fat wasting as fat and protein reserves used for energy.
What are the common complaints of starvation?
Cold, muscle weakness, GI tract and lung infections common
What is marasmus?
Protein-energy deficiency most commonly seen in children under 5
What are symptoms of marasmus?
Emaciated appearance (muscle and fat wasting)
Hair is thin/dry
Diarrhoea/anemia commonly present
What is kwashiorkor?
Form of malnutrition typically found in young children that stop breast feeding to early and are fed a low protein diet with some carbohydrate.
What are the common complaints in a child with kwashiorkor?
Why is the abdomen distended and generalised oedema seen in children with kwashiorkor?
Distended abdomen due to hepatomegaly (enlarged liver) and/or ascites (fluid in peritoneal cavity)
Generalised oedema due to low serum albumin (low blood osmotic pressure)
How is BMI calculated?
Weight (kg) / (height (m) squared)
How is BMI interpreted?
Underweight = <18.5
Desirable range = 18.5 - 24.9
Overweight = 25 - 29.9
Obese = 30 - 34.9
Severely obese = >35
Excess body fat accumulation that may have adverse effect on health leading to reduced life expectancy and/or increased health problems
What leads to changes in body weight?
Differences between input of substances and output of substances and energy will lead to increase or decrease in body weight
Define homeostasis then explain its importance and what it controls.
The maintenance of a stable internal environment.
A dynamic equilibrium that acts to counteract changes in the internal environment
Occurs at all levels from cellular to organ/system to whole body
Controls supply of nutrients, oxygen, blood flow, temperature, removal of waste and pH
Failure of homeostasis leads to disease
What are the 2 major communication pathways of the body?
Nervous and endocrine
What is paracrine control?
Local release of hormones (via ducts/exocrine)
What is autocrine control?
Release of agent which affects the releasing cell.
What two categories can the peripheral nervous system be sorted into?
Efferent - motor output
Afferent - sensory input
What are the major features of the bodies control system?
What are the functions of the control centre of the body's control system
Establishes reference set points
Analyses afferent input and determines response
Where is the hypothalamus and what does it control?
Found in the diencephalon
Involved in control of the endocrine system
Where is the medulla oblongata and what functions is it involved in?
Found in brainstem
Involved in control of ventilation and cardiovascular system.
What are receptors in the PNS of the body involved in?
Detect stimuli with specialised nerve endings and communicate this to the CNS via afferent nerves
What is the function of effectors?
Cause change when prompted by efferent nerve stimulation
Are set points of control by the CNS fixed?
Give an example of set point control
No, they can vary over time
Eg. Cortisol peaks around 7am and troughs around 7pm this is known a circadian rhythm.
The menstrual cycle is a good example of what?
A biological rhythm, a woman's core body temperature varies throughout the cycle. (Sharp increase indicates ovulation).
Define cell metabolism
Highly integrated network do chemical reactions comprised of a series of metabolic pathways (some specific to specialised cells, some general).
What are the functions of cell metabolism?
Metabolise nutrients to produce a variety of products.
What is produced by cell metabolism and what are the products used for?
Energy for cell function - produces ATP
Building block molecules - used in the synthesis of cell components needed for growth, repair and division of the cell
Organic precursor molecules - used to interconvert building block molecules (eg. AcetylCoA)
Biosynthetic reducing power - used in the synthesis of cell components (eg NADPH)
Where do cell nutrients in the blood come from?
Synthesis in other tissues
Release from storage in other tissues
What are cell nutrients used for?
Degradation for energy release
Synthesis of cell components
Storage - (only in liver, adipose tissue, skeletal muscle)
Why do cells need a continuous supply of energy?
To maintain function
Explain the concept of energy coupling and how it's performed.
Transferring energy released in exergonic reactions to endergonic reactions. This is performed by intermediary molecules of the ADP/ATP cycle.
Name three high energy phosphorylated compounds and give the energy released by their hydrolysis
Phosphoenolpyruvate = -62kJ.mol-1
Creatine phosphate = -43kJ.mol-1
ATP = -31kJ.mol-1
What is the equation for hydrolysis of ATP or ADP ans how much energy is released?
ATP + H2O ADP + Pi
ADP + H2O --> AMP + Pi
What is Creatine phosphate used for?
To provide a store of high energy molecules that can be used immediately for metabolism in high activity tissues eg. muscle
What is the reaction for the phosphorylation of Creatine, what enzyme is involved and how is it controlled?
Creatine + ATP Creatine phosphate + ADP
When ATP is high forward reaction favoured
Catalysed by Creatine kinase
How is ATP involved in regulation of metabolism?
High ATP concentration leads to activation of anabolic pathways
Low ATP concentration leads to activation of catabolic pathways
What signals a cell has adequate energy?
High levels of ATP as well as reducing agents such as FADH/NADHH/NADPH are high energy signals
What signals a cell has low energy?
High levels of ADP and NAD+/FAD/NADPH+
Carrier molecules such as NAD+ are derived from what type of molecule?
What can be said about the total amount of H+ carrier molecules in the body?
Total amount is constant