Diet and metabolism lecture Flashcards
What is gluconeogenesis?
Conversion of fatty acids/amino acids into energy source
What is glycogenolysis?
The breakdown of glycogen into glucose
What is glycogenesis?
The conversion of glucose to glycogen
What is glycolysis?
The breakdown of glucose into pyruvate
What is meant by nutrition?
The scientific study of processes concerned with repair, growth, and maintenace of hte body
What is nutrients?
The components of food which have recongisable function in the body
What is the difference between essential and conditionally essential nutrients?
Essential - cannot be made by the body e.g water
Conditionally essention - unable to synthesis enough to meet normal demand e.g during illness so is needed by diet
What is meant by glycaemic index?
How quickly a carbohydrate (food) causes an increase in blood glucose
High GI - rapid spike of short duration
Low GI - low spike of long duration
Compare the glycaemic index of basic sugars and carbohydrates
Simple carbohydrates - high GI
Complex carbohydrates - low GI
Glucose>Sucrose>Fructose
Gives some examples of a high glycaemix index food and some low glycaemic foods
High - potatoes, white bread and short-grain rice
Low - beans, fruit, pasta, milk
What factors influence how quickly glucose (from carbohydartes) is released into the blood stream from food?
Processed food - removes fibre so higher GI
Physical structure - surface area and vulnerability to enzymes
Cooking - al dente pasta has a higher GI
Higher fibre content already in stomach - lower GI
Higher fat or gastric acid content in stomach - delays gastric emptying so decreases the GI
What are some key factors why obesity is on the rise in the UK?
Lack of information about what constitutes a healthy diet
Motivation to adhere to healthy diets
Calorie rich food is cheap and easily available
Time, planning and finances needed to plan and prepare a healthy meal
What is the link between malnutrition and ill health?
Spiral of decline
Malnutrition, compromised immune system, unable to work, poverty, unable to imporve socio-economic status,
Government has reduced revenw so no change at the national or individual level
(not very important concept)
What is meant by catabolism and metabolism?
How do these processes relate to ATP (energy)?
Catabolism - breaks substances down - creates ATP (energy)
Anabolism - making larger substances - uses ATP
Think it is harder to put rips of paper together than it is to tear them apart in the first place.
What are the three key different metabolic fates of glucose?
Storage as glycogen in the liver or muscles
Broken down during glycolysis to produce ATP - converted to pyruvate (aerobic) can then enter the Krebs cycle (Aerobic)
Conversion - pyruvate can be converted to ribose 5-phosphate by pentose phosphate pathway. r5p is a nucleotide precursor
What is the deal with glucose 6-phosphate?
Is a metabolised form of glucose that is stored in the liver
Is common to all pahtways of glucose usage in the liver (glycolysis, glycogenesis and pentose phosphate pathway)
How is glucose 6-phosphate made?
In glyolysis (common to aerobic and anerobic respiration)
Glucose is phosphorylated by the glucokinase enzyme
What are the potential uses of glucose from the liver?
- released as blood glucose
- stored as glycogen
- aerobic energy production by the Krebs cycle
- conversion to nucleotides by the pentose phosphate pathway
- Conversion to triglycerides and phospholipids to be stored as fat (by pyruvate and acetyl CoA)
What is the use of cholesterol?
Steroid hormones, bile and fat soluble vitamin synthesis
What is the use of free fatty acids?
Alternative energy supply for the mitochondria
What is the role of triglycerides and phospholipids?
Fat = energy storage
What is the role of ribose-5-phosphate?
Produced by the pentose phosphate pathway from glucose
Used for DNA, RNA and creating ATP (from intermediates)
In regards to glucose metabolism in the liver
What energy sources enter the liver? How?
Glucose - by GLUT2 membrane transport protein
Lactate - by membrane transport protein
How would insulin, glucagon and adrenalin by classified as catabolic and anabolic?
Insulin - anabolic - creates glycogen from glucose
Adrenaline and glucagon - catabolic - break glucose down
In the liver what processes does insulin promote?
Glycogen synthesis
Glycolysis
Lipogenesis
Pyruvate entering the link reaction (conversion to acetyl-coa to enter oxidative phosphorylation)
In the liver what process does glucagon/adrenaline promote?
Gluconeogenesis
Glycogenolysis
What is lipogenesis?
The creation of fatty acids
Typically from glucose by glucose 6-phosphate to pyruvate (glycolysis) to Acetyl-CoA, then from Acetyl-CoA to fatty acids is lipogenesis.
What is a key molecule to remember in glycogenolysis, glycolysis and gluconeogenesis?
Glucose 6-phosphate is the molecule just before/after glucose
What is important to remember about the brain and energy supply?
In fast most glucose in utilised for the brain
Brain is unable to switch to alternative energy supplies
Is an essential organ so has obligatory glucose metabolism
What are the main sources of energy to the liver?
Amino acid or fatty acid oxidation
Describe the pattern of glucose metabolism during a fast e.g overnight?
Low blood glucose - reduces insulin, increased glucagon/adrenaline
Gluconeogenesis occurs in the liver and kidney - most glucose is directed to the brain
Tissue utilization of glucose decreases
Glycogenolysis also occurs in the liver
In the presence of low insulin how will the energy source in muscle and adipose tissue change?
Energy will be sourced from mainly non-glucose substrates such as fatty acids and ketones
What are the different substrates for gluconeogenesis and where do they come from?
Alanine - from breakdown of muscle and protein
Lactate - from breakdown of rbc
Glycerol - from fat
Explain what glucose metabolism is like in the fed state e.g just after a meal?
High blood glucose - increased insulin, decreased glucagon/adrenaline
Promotes glycogenesis in liver and muscle
Brain has plentiful glucose
Higher levels of insulin in the muscles and adipose tissue increase glucose utilisation
Excess glucose is stored as fat.
What is the role of lactate in glucose/energy metabolism?
Lactate is taken up from food or is produced by anaerobic respiration
Lactate can be converted and stored as glycogen in the liver
Lactate can also be converted to glucose, via a pyruvate intermediate
What are the key processes in fat metabolism in the liver?
Common starting point is fatty acids in the liver
1. liver lipids stored as fat in adipose tissue (transprted as LDLP)
2. Energy production
3. Converted to cholesterol or ketones in the blood by Acetyl-CoA intermediate
4. Released as plasma lipoproteins or fatty acids
How do fatty acids in the liver get converted into energy?
Undergoe beta oxidation to form acetyl CoA
Can then enter the Krebs cycle to undergoe oxidative phospharylation in the mitochondria
What is an alternative name for the krebs cycle?
The citric acid cycle
What glucose metabolic process are ketones a byproduct in?
Gluconeogenesis
What processes does insulin promote in relation to fatty acids in the liver?
Conversion of glucose into Acetyl-CoA to malonyl-CoA to fatty acids
fatty acids may then be further converted to triacylglycerol
Excess glucose is stored as fat
What processes does glucagon promote in the liver in relation to fat metabolsim?
Breaks down fatty acids by beta oxidation
Broken into ketone bodies which enter the blood stream
What is diabetic ketoAcidosis?
Insulin resistant or lack of insulin
High glucagon levels
Promotes fatty acids beta oxidation into ketones
Produces CO2 as a side product this is released into blood and decreases the blood pH. Can be fatal for diabetics
What types of food is cholesterol found in?
Eggs fatty foods and cheese
How does cholesterol travel through the blood?
How does this link to the difference between good and bad cholesterol?
Travels bound to lipoproteins
Good cholesterol - high density of lipoprotein, cholesterol is secure and unlikely to detach and stick to arterial walls, in some cases can pick up additional cholesterol
Bad cholesterol - low density of lipoprotein, cholesterol can escape and stick to blood vessel walls
What is meant by the imposter cholesterol?
Triglycerides
Many strategies that reduce cholesterol also reduce triglycerides
In a fasted state what are the key features of fat metabolism?
High glucagon and low insulin
Lipolysis occurs
Adipose tissue is broken down into 2 components
. NEFA a non-essential amino-acid used for energy by muscle/liver and kidney
Glycerol - used in the liver for glycolysis and gluconeogenesis
Ketones and glucose will be released from fat metabolism in the liver
What are the key parts of fat metabolism in the fed state?
High insulin and low glucagon
Fat is absorbed from small intestine (micelles and chylomicrones via lymphatics)
Insulin causes adipose tissue to store fat as triglycerides.
Also stored as triglycerides in the muscles.
What are the key stages of protein metabolism in the liver?
- is converted to liver and plasma proteins/AA
- Is converted to urea for excretion by the kidney
- Enters the krebs cycle as acetyl CoA by a pyruvate intermediate
- Is convreted to nucleotides, hormones and Hb
How do amino acids in muscle get utilised to create ATP?
Converted to pyruvate
Converted to acetyl-CoA
Enters the krebs cycle then undergoes oxidative phosphorylation.
