3. Energy and carbohydrates 1 Flashcards
Define metabolism
Metabolism is the set of processes which derive
energy and raw materials from food stuffs and use
them to support repair, growth and activity of the
tissues of the body to sustain life
Describe an overview of metabolism
- Food comes in through the GI tract
- Broken down to smaller molecules
- Absorbed into the blood where they are transported to tissues that require them
- In the tissues either used directly to release energy within them or interconverted into synthetic pathways to make larger molecules perhaps for storage, eg to make other proteins from the proteins that were digested.
What are the two metabolic pathways?
- Catabolic pathways
2. Anabolic pathways
Describe catabolic pathways
1.Break down larger molecules into smaller ones
(intermediary metabolites)
2.Release large amounts of free energy
3. Oxidative – release H atoms –‘ reducing power’
Describe anabolic pathways
- Synthesis larger important cellular components fro intermediary metabolites
- Use energy released from catabolism (ATP)
- Reductive(ie use H released in catabolism)
Do all metabolic pathways occur in all cells?
No
- Some metabolic pathways occur in all cells
- Others are restricted to some cell types
- Some may be further restricted t compartments within cells
In catabolic metabolism, what are the fuel molecules metabolised to supply?
- Building block material
- Organic precursors
- Biosynthetic reducing power
- Energy for cell function
Give 3 examples of building block material
- Sugars
- Amino acids
- Fatty acids
What are the building block materials produced in catabolic metabolism used for?
- Dynamic state of cell components (turnover)
- Cell growth and division
- Repair
Give an example of an organic precursor?
Acetyl CoA
Give two examples of biosynthetic reducing power
- NADH
2. NADPH
Define energy
Capacity to do work
What sort of work is energy needed for?
- Biosynthetic work (anabolism) - synthesis of cellular components
- Transport work - membranes
- Specialised functions
Give two examples of transport work
- maintenance of ion gradients (Na+,K)
2. Nutrient uptake
Give 3 samples of specialised functions
- mechanical work- muscle contraction
- Electrical work - nervous impulse contraction
- Osmotic work - kidney
What is the standard international unit for energy content for food?
Joule
What does a calorie generally mean?
1 kcal
What is basal metabolic rate?
Energy required by an awake individual during physical, digestive and emotional rest at 18oC
Sum of energy used by all of the tissues in the body
When energy intake (FOOD) > energy required, then what is the excess energy used for?
- Growth - synthesis of new tissue
2. Stored - production of adipose tissue
Which form f energy is predominantly used to drive energy requiring activities?
Chemical bond
Define exergonic
A chemical reaction which releases energy
Define Endergonic
Chemical reactions which require energy
Which reactions occur spontaneously?
Exergonic reactions
In which reactions are deltaG negative?
Exergonic
In which reactions are deltaG positive ?
Endergonic
Define oxidation
Removal of electrons or removal of H atoms
Define reduction
Gain of electrons or H atoms
When fuel molecules are oxidised, the electrons and protons are transferred to what?
Carrier molecules eg NAD, NADP
Carrier molecules act as carriers of reducing power for which processes?
- ATP production(NADH)
2. Biosynthesis(NADPH)
How many H atoms are added to the carrier molecules?
2 and 1 dissociates into solution
How can energy released as reducing equivalents be used to drive energy requiring activities?
1.Directly, e.g. use of NADPH in biosynthesis 2.Indirectly, e.g. mitochondrial system to couple NADH to the production of ATP
What is the energy released during exergonic reactions used to drive?
ATP production -Part of the free energy conserved as the chemical bond energy of the terminal phosphate group (PO
44-) of ATP
Can ATP be used as a store of energy
NO - only a carrier, not a store
What feature of ATP makes it very good as a carrier molecule
It is stable -does not break down
When ATP is high, which pathways are activated
Anabolic
When ATP levels are low and ADP and AMP levels are high which pathways are activated?
Catabolic