Biochemistry Flashcards
Name the two carbohydrate chains that make up starch
Amylose and Amylopectin
Why can cellulose not be browk down by humans?
They dont have the enzyme cellulase to break it down
Give 2 functions of chitin
- Cells walls of fungi
- Outer skeletons of insects
Where is N-linked glycosylation added and modified?
Added in the endoplasmic reticulum and modified in the golgi complex
What is Aggrecan an example of?
A proteoglycan with extensive O-linked glycosylation on the core protein (link protein). Forms a bottlebrush shape.
What is the main enzyme involved in glycogen breakdown?
Glycogen phosphorylase
Why is an enlarged liver caused by a type 1 glycogen storage disease?
Excessive glycogen storage
Which hormone is released in response to an increase in blood glucose levels?
Insulin
Compare the 3 types of diabetes
Type 1 = very low insulin and no response to glucose loading
Type 2 = normal/high insulin and no response to glucose loading
Type 3 = normal insulin, delayed response to glucose loading
What is the result of hyperinsulinism?
Persistent hypoglycaemia
Which condition in sheep is characterised by hypoglycaemia?
Pregnancy toxaemia
Glycogen is primary stored in and used by which type of muscle fibres?
white glycolytic skeletal muscle fibres = fast fibres
How many enzymatic reactions are needed to convert glucose to pyruvate?
10
What types of tube are used for glucose collection and why?
Fluoride
- stop red blood cells from metabolising glucose other levels will be falsely reduced
Give 3 uses of ATP
- Muscle contraction
- Active transport
- Biosynthesis
- Cell signalling
What is the role of NAD+ and FAD as electron carriers?
Receive a pair of high energy electrons in chemical reactions
What is the role of acetyl-coenzyme A in biosynthesis?
Used to add 2 carbon units
What is gluconeogensis?
Biosynthesis of glucose in the liver (some in the kidney)
One molecule of NADH results in how many molecules of ATP in the ETC?
2.5
What are the 4 main processes in the nitrogen cycle?
- Nitrogen fixation
- Ammonification
- Nitrification
- Denitrification
Where does symbiotic nitrogen fixation occur?
In plants that harbour nitrogen fixing bacteria (Rhizobium) within their tissues
What is mutualism?
A symbiotic relationship in which both partners benefit
What are nitrates and nitrites taken up by plants reduced to?
Ammonia
What is the biological molecule that transmits signals across synapses and is the main excitatory neurotransmitter in the CNS?
Glutamate
What is transamination?
Chemical reaction between an amino acid and a keto acid, where groups are exchanged so the amino acid becomes a keto acid and the keto acid becomes an amino acid
Where is urea produced?
Liver by transamination and deamination reactions
Where is urea excreted?
In the kidneys, saliva and sweat
How is nitrogen excreted in aquatic animals?
Directly as ammonium as it is rapidly diluted - ammonotelic
How do birds and non-aquatic reptiles excrete nitrogen?
Uricotelic - as uric acid
Why are there no essential amino acids required by a ruminant?
Microbes in the rumen can synthesise all 20
What are the functions of protein?
- structural - collagen, keratin
- movement - actin and myosin
- immune system - antibodies
- endocrine - hormone and receptors
- transport - haemoglobin
- enzymes
Describe a protein’s primary structure
Chains of amino acids are joined by peptide bonds between COO groups and NH3 groups
Describe the quaternary structure of a protein
Interactions between different protein subunits held together by side chain interactions
Compare globular and fibrous proteins, giving examples
Globular = folded into compact structures, soluble, e.g. enzymes, antibodies Fibrous = multiple strands held by strong bonding, insoluble, e.g. collagen, keratin
What are prions?
Infectious proteins that cause a host’s normal proteins to switch to a conformation that readily aggregates, causing cell death
What is the main role of enzymes?
Increase the rate of a chemical reaction without being changed at the end - catalysts
Where on an enzyme performs the catalytic reaction?
Enzymes active site
Which weak forces are involved in binding of substrates to amino acid side chains?
- electrostatic attraction
- hydrogen bonds
- Van der Waals forces
- hydrophobic interactions
What is isosteric substrate binding?
Rate of reaction increases with substrate concentration until enzyme is saturated
What is allosteric substrate binding?
Substrate induces a conformational change in the enzyme that increases activity - S shaped saturation curve
What is the purpose of feedback inhibition?
Prevents the build up of intermediates and unnecessary use of energy
What is a competitive inhibitor?
Binds to the enzymes active site
What is a non-competitive inhibitor?
Bind to the enzymes allosteric site irrespective of whether a substrate is bound
What is an uncompetitive inhibitor?
Bind to the enzyme substrate complex
What 5 factors affect enzyme activity?
- substrate conc
- temperature
- pH
- post-translational modification
- coenzymes and cofactors
How does temperature affect enzyme activity?
Proportion of molecules with energy sufficient to overcome the activation energy increases
How does pH affect enzyme activity?
All enzymes have an optimum. small deviations lead to decreased activity, can lead to denaturation of the enzyme
What do many enzymes require to function?
Cofactors - small non-protein units
What are isoenzymes?
Different forms of an enzyme which catalyse the same reaction
Name the unsaturated fatty acid present in phospholipids
Arachidonic acid
What are the roles of lipids?
- Cell membranes
- Fuel
- Heat insulation
- Signalling molecules
- Vitaminas
- Nervous system
Breifly describe lipid digestion
- Bile salts emulsify fat droplets
- Absorbed by intestinal epithelia
- Fats are reassembled and added to chylomicrons
- Chylomicrons secreted to lymph and transported to the liver
How is fat storage altered by insulin?
Insulin promotes fat storage
What is hydrolysis?
Cleavage of chemical bonds by the addition of water
Name the catabolic process in which fatty acid molecules are broken down in the mitochondria?
B-Oxidation
What is generates from B-oxidation?
Acetyl-CoA
Where do the products of B-oxidation enter?
The TCA cycle
What is acetyl-CoA converted to if it doesn’t enter the TCA cycle?
Acetone, Acetoacetate and D-3-hydroxybutyrate
What is acetone used for?
It is exhaled as an emergency fuel source
How does a high level of ketone bodies affect the blood?
Makes it more acidic causing metabolic acidosis as pH buffer systems become exhausted
