Biochemistry Flashcards
What are the functions of enzymes, are they anabolic or catabolic? How do they lower activation energy?
Biological catalysts, diagnostic tests
Both
Bring molecules closer together, reduce repulsion
What do active sites do? What are multi-enzyme complexes?
Bind with substrate, make/break chemical bonds
Aggregation of several co/enzymes
What are isoteric enzymes?
Enzymes which rate of reaction increases with substrate concentration (until saturation)
What are allosteric enzymes?
Enzymes which bind with an allosteric site, induces a change in the enzyme and allows easier binding (sigmoidal shape curve)
What is cooperativity?
The binding of an enzyme which changes the structure of the active site, which triggers the same in other active sites
What are the 3 types of inhibitors? Where do they bind to?
Competitive - active site
Non-competitive/allosteric - binds to allosteric site
Uncompetitive - binds to ES complex
What factors affect enzyme activity?
Temperature, concentration, pH, post-translational modification, coenzymes, cofactors
What are post-translation modifications?
Changes in the structure of an enzyme
Can be proteolytic activation (activates other enzymes) or phosphorylation
What are proteinase?
Enzymes which cleave proteins, can cause proteolytic activations
What are isoenzymes?
Different forms of an enzyme which catalyse the same reaction
What are the 4 stages of the nitrogen cycle? What happens in each stage?
Nitrogen fixation - nitrogen fixing bacteria convert N gas
Ammonification - conversion to ammonia by saprobionts
Nitrification - conversion to nitrates by nitrifying bacteria
Denitrification - conversion to gas in anaerobic conditions by bacteria
How many amino acids are there?
21
1 is rare
How do animals obtain essential and non-essential amino acids?
Essential - diet
Non-essential - biosynthesis
What are the functions of amino acids?
Build protein
Energy
Neurotransmitters
Amino acids can be ketogenic or glucogenic. What do these 2 terms mean? What happens after this?
Converted to ketones or glucose
Broken down to intermediates of acetyl CoA
Enter Krebs cycle
What are ureotelic animals?
Animals which produce urea
Where is urea excreted?
Kidneys, saliva, sweat
GI in ruminants - used to synthesise AAs as no protein in diet
What are urioctelic animals? Give examples?
Animals which excrete uric acid
Birds/reptiles
What are ammonotelic animals? Give examples
Animals which can directly excrete ammonia Aquatic animals (cartilaginous fish are both ammonetlic and ureotelic)
What are the stages of protein synthesis?
DNA transcribed to mRNA, then translated to a protein
What are the functions of proteins?
Structural - collagen, keratin, fibroin (silk/webs)
Movement - actin/myosin
Immune system - antibodies
Endocrine system - hormones/receptprs
Transport - haemoglobin, transferrin (glycoproteins in blood plasma)
Biocatalysts - enzymes
Zwitterions are which type of isomer? What 2 forms can they be in?
Enantiomer
D or L - (L only in the body)
What are the 4 protein structures?
1 - sequence of AAs held by peptide bonds
2 - H bonding between peptide bonds - alpha helix and beta pleated sheets
3 - H, disulfide, ionic bonds. 3D structures, metal ions between chains. Hydrophobic interactions
4 - interactions between subunits/polypeptide chains
Proteins are mainly globular but can be fibrous or membranous. Give examples of each
Globular - enzymes/antibodies. Soluble, fold into compact molecules
Fibrous - multiple strands held by bonds, e.g. fibroin. 2 rows = protofilaments, dimerise to protofibrils, to microfibrils, then macrofibri;s
Membranous - channel/receptor proteins
What is pregnancy toxaemia in sheep? What is a risk factor?
Blood poisoning from hypoglycaemia - high metabolic demand in last trimester of pregnancy
Excessive fat
How do ruminants obtain glucose?
Gluconeogenesis
Which carbohydrates are monosaccharides? Which are disaccharides?
Glucose, galactose, fructose
Maltose, lactose, sucrose
Name 4 polysaccharides
Starch - amylopectin (branched) or amylose (coiled) chains of glucose in plants
Glycogen - like amylopectin, but in animals
Cellulose - straight chains of B glucose in plants
Chitin - chains of N-amide in fungi walls
Which organ primarily controls blood glucose levels?
Liver
Some glycogen storage disease are Van Gierkes, Pompe’s, Cori’s. What do these result in?
Hypoglycaemia
Hepatomegaly (liver enlargement due to glycogen)
Which hormones do islets of Langerhans secrete?
Insulin - lower blood glucose. Promotes fat storage, B islets. Work by second messenger
Glucagon - increase blood glucose, a islets.
What are the 3 types of diabetes?
Type 1- autoimmune, destroy islets. Symptoms emerge when most cells destroyed
Type 2 - obesity. Low insulin levels/ unresponsive.
Type 3 - Alzheimer’s disease due to insulin resistance in the brain
What is hyperinsulinism? Why may this occur?
Abnormally high levels of insulin, results in hypoglycaemia.
Pancreatic tumours
Why do many neonates get hypoglycaemia at birth? What induces enzymes which synthesise glucose?
Inadequate synthesis
Cold
Feeding
What are the roles of lipids?
phospholipid bilayer Fuel Insulation Signalling molecules Vit a/d/e/k Nervous system
What is arachidonic acid?
Fatty acid present in phospholipid bilayer
What is cholesterol?
Precursor for lipid soluble hormones
Describe the digestion and transport of lipids
Bile salts emulsify fats Degraded by intestinal lipases Taken up by intestinal mucosa FAs enter cells Chylomicrons enter blood stream
What are chylomicrons?
Fat droplets that have been digested
Where are lipids stored and released? What is the purpose of brown fat?
Adipose tissue
Thermogenesis
Which multi enzyme complex is responsible for the biosynthesis of fatty acids?
Fatty acid synthase
what is beta oxidation?
The breakdown of fatty acids to acetyl coA, which then enters the Krebs cycle.
Where does beta oxidation take place? Is it anabolic or catabolic?
Mitochondria
Catabolic
What is ketosis? What does it lead to? When might it be present?
Abnormally high levels of ketone bodies in the blood
Metabolic acidosis
Starvation, pregnancy toxaemia, acetonemia
How many ATP are used and gained in glycolysis?
2 used
4 gained
How are monosaccharides transported?
Na/Glucose transporters in intestinal epithelial cells
In aerobic glycolysis, what is pyruvate converted to?
Acetyl coenzyme A
In anaerobic glycolysis, what is pyruvate converted to? What happens to this after?
Lactate
Leaves muscles and travels to liver via blood
Converts lactate to glucose by gluconeogenesis
What is gluconeogenesis?
The synthesis of glucose from non-carbohydrates e.g. lactate, glucogenic AAs
(Ruminants, starvation, intense exercise)
What are the 2 types of muscles? What are their properties?
- Slow twitch, red, high myoglobin, little glycogen, oxidative
- Fast twitch, white, low myoglobin, high glycogen, glycolytic
