bioenergetics Flashcards
functions of fats
- protection of internal organs
- subcutaneous fat provides insulation
- insulation of nerve cells; the myelin sheath surrounding each nerve cell is composed of fat
- transportation of the fat soluble vitamins A,D,E and K, which require approx 20g of dietary fat per day
- an incredibly rich energy source, each gram of fat yields 9 kcal, more than twice that of carbs and protein
- help suppress hunger and provide the feeling of satiety and satisfaction
- stored body fat provides an almost unlimited energy reserve when the other nutrients aren’t available
- helps regulate female menstruation - low bodyfat = low oestrogen levels
functions of protein
- enzymes are made entirely from protein and control both the rate and pattern of all metabolic reactions throughout the body
- antibodies are proteins that are produced by white blood and released into the bloodstream
- production and transportation of oxygen (haemoglobin)
- in a fasted state, or when insufficient carbs are present, protein can be used as an energy source to form ATP. each g of protein contains 4 cals
- protein forms approx 20% of the weight of the heart, skeletal muscles, liver and glands and also makes up around 10% of brain’s weight
- many of the body’s hormones are formed from protein. these hormones act as chemical messengers, which dictate the body’s response to internal changes to its environment ~ 2 types = steroid hormones, protein hormones
steroid hormones
regulate growth and development of bodily tissues and are largely made from cholesterol
protein hormones
initiate immediate changes in the body and are largely made from amino acids
eg insulin, glucagon, growth hormones
complex carbs
take much longer to digest than a simple carb
usually provide prolonged supply of energy
once the carb has been digested, the end product of glucose is deposited into the bloodstream for immediate use as an energy source, or transported to and stored in the liver and skeletal muscles for storage as glycogen
glycogen
the form in which glucose is stored in the body
when blood glucose levels drop, glycogen stores are used to top up circulating blood glucose - makes sure brain and nervous system are still getting energy they need = process called glycogenolysis
liver glycogen store = supplies most to manage blood glucose
skeletal muscles glycogen store = supply to fuel contraction of muscle
muscles can only use glycogen stored in their own muscle cells
functions of carbohydrates
blood glucose in the only source of energy the brain and nervous system can use - bg = partially digested from of carb
contain large quantities of fibre = assist digestive system in transporting food along alimentary canal
helps preserve the body’s protein reserves, which helps maintain a healthy metabolism
serve as a ‘metabolic primer’ to ease the metabolism of fat = when carbs are insufficient, the body is unable to release energy from its fat stores efficiently
after strenuous exercise the body’s glycogen stores are depleted - carbs post exercise replenish stores and promote recovery
needed for water storage in the body
each g of glycogen stored is accompanied by 2.7ml water - without glycogen, water cannot be retained
triglycerides
most dietary fats consist of triglycerides
during digestion, each triglyceride is broken down into 3 fatty acids and one glycerol molecule in the duodenum of the small intestine
dietary fats take longer than other macros to digest because they do not dissolve in water and are not easily broken down by lipase (fat-digesting enzyme)
digested fatty acids and glycerol molecules
these are absorbed into lymphatic system, which deposits them into the bloodstream where they are transported to the membranes of adipose
the glycerol molecules are usually transported to the liver where they are converted to glucose through the process of glycogenesis
when additional ATP is required
esp at rest and lower intensity exercise, triglycerides are released from adipose tissue, which releases fatty acids back into the circulatory system
these fatty acids are transported by the cardiovascular system and diffused into the mitochondria, where they are metabolised aerobically to form ATP.
saturated fats
saturated with hydrogen = more toxic and harmful to health
usually found in animal and dairy products
unsaturated fats
generally liquid at room temperature and originate from plant sources
contain double bond, which connect adjoining carbon atoms which makes them more chemically reactive and available for metabolism.
one or more of hydrogen binding sites are vacant
amino acids in protein
20 amino acids make up structural component of protein
12 can be synthesised by body, 8 must be obtained through diet.
12 = non essential amino acids, 8 = essential amino acids
when there is insufficient protein
when there is insufficient protein or the protein lacks required amino acids, the body must generate or free them from existing protein tissues (namely muscle and organ tissues)
amino acids can be used from expired enzymes - once enzyme has performed role it can be degraded to meet the body’s protein needs at that time
when there is excessive protein intake
with excessive protein intake, the surplus aminos are transported to liver and converted into glucose through gluconeogenesis.
if blood glucose levels are normal and body’s glycogen levels are full, the new glucose molecules are converted into fatty acids and stored as adipose tissue = lipogenesis
protein and insufficient carbs
proteins are used as an energy source when insufficient carbohydrates are consumed. Carbs exert a muscle sparing effect. when carbs are deficient or low, the body uses a series of catabolic processes to breakdown and convert amino acids to glucose through gluconogenesis
metabolism
describes the sum of all chemical reactions that take place in the body; some of these reactions are concerned with releasing energy while others are associated with storing it
catabolic reactions
those that require the breakdown of larger molecules into smaller ones, like when glycogen is broken down into glucose and even further to release ATP
anabolic reactions
those that require the synthesis of larger molecules from smaller ones, as in hypertrophy, where additional amino acids are used to build new protein/muscle cells
chemical energy
stored in the foods we consume
not immediately metabolised to fuel work, but stored in a different form for use later
when the stored chemical energy is needed during exercise, it is metabolised to generate mechanical energy within skeletal muscles = movement
this changes again to become heat energy - which is released from cells
kilocalorie
energy is measured using kilogram calories (1000 calories) = kilocalories/kcal
1kcal = the volume of heat required to raise the temperature of 1 litre of water by 1 degrees
sometimes is measured in kilojoule/kj
1kcal = 4.186 kj
kj = the amount of work required to move a 1kg object a distance of 1 metre under standard force of gravity
two primary mechanisms in which energy can be generated (energy systems)
anaerobic energy production - achieved in absence of oxygen and includes 2 component energy systems by the name of ATP/CP system, and the lactic acid system
aerobic energy production - dependent on oxygen and takes place in mitochondria
the energy currency - ATP
only direct source of energy that cells can use
can be viewed as temporary reservoir of potential energy that can provide energy instantly.
stored in small quantities in the watery component of the cells (sarcoplasm)- therefore must be continually resynthesised
when ATP is required it is hydrolysed (reacts with water to breakdown) and releases its stored energy, water and free phosphate bond into cellular environment
catalyst of reaction is enzyme myosin ATPase
ATP becomes ADP and needs to be converted back - the body only stores small amounts of ATP so if biological system is to remain active; these biochemical processes are collectively referred to as energy systems
