Week 5 Flashcards
Two main types of glucose anabolism
Glycogenesis - formation of glycogen- polysaccharides
Gluconeogenesis -synthesis of new glucose molecules
Process of glycogenesis
Glucose Uptake:
Glucose enters cells through transport proteins in the cell membrane, such as GLUT4 in muscle cells and GLUT2 in liver cells.
Phosphorylation of Glucose:
Inside the cell, glucose is phosphorylated to glucose-6-phosphate (G6P) by the enzyme hexokinase (in muscle cells) or glucokinase (in liver cells). This step consumes one ATP molecule and traps glucose within the cell, as G6P cannot easily cross the cell membrane.
Conversion to Glucose-1-Phosphate:
G6P is then converted to glucose-1-phosphate (G1P) by the enzyme phosphoglucomutase.
Activation of Glucose:
G1P is activated to UDP-glucose (uridine diphosphate glucose) by the enzyme UDP-glucose pyrophosphorylase. This step involves the coupling of G1P with uridine triphosphate (UTP), producing UDP-glucose and pyrophosphate (PPi).
Glycogen Synthesis:
UDP-glucose is then used by the enzyme glycogen synthase to add glucose units to a growing glycogen chain. Glycogen synthase catalyzes the addition of glucose from UDP-glucose to the non-reducing end of a glycogen molecule, forming α-1,4-glycosidic bonds.
Branching of Glycogen:
To create the highly branched structure of glycogen, the enzyme branching enzyme (or amylo-(1,4→1,6)-transglycosylase) introduces α-1,6-glycosidic branches into the glycogen molecule. This branching increases the solubility and allows for more rapid synthesis and mobilization of glycogen.
Glycogen Storage:
The resulting glycogen is stored in the liver and muscle tissues. In the liver, glycogen helps regulate blood glucose levels, while in muscle tissue, it serves as a local energy reserve for muscle contraction.
Glyconeogenesis
Lactic acid +amino acids (alanine and glutamine) + pyruvic acid = glyceraldehyde 3 phosphate
GA3P + glycerol = glucose 6 phosphate
glucose-6-phosphate is converted to glucose by the enzyme glucose-6-phosphatase which then releases the new glucose molecule into the bloodstream
What hormones initiate gluconeogenesis
Cortisol and glucagon
Why are lipids the primary energy storage molecules?
Over twice as energy dense per gram compared to carbs or proteins
Hydrophobic- cells do not exert osmotic pressure
What is the purpose of lipolysis
lipolysis is crucial for converting stored fat into usable energy, maintaining blood glucose levels, and adapting to changes in energy requirements.
What happens in the process of lipolysis
The fatty acids from triglycerides can be oxidised and used to produce ATP. First, the fatty acids must be removed from the glycerol molecule.
What is the process of Beta oxidation
A catabolic process occurring in the mitochondrial matrix. It removes two carbon atoms at a time from a fatty acid (long carbon chain. The carbons are then attached to coenzyme A to create acetyl coenzyme A and therefore put into the Krebs cycle to produce ATP
Fatty acid classifications
Saturated or unsaturated
Length of hydrocarbon chain
Short chain fatty acids
<5 carbons
Medium fatty acids
6-12 carbons
Long fatty acids
13-21
Very long fatty acids
22>
Lipogenesis
Takes place in liver and adipocytes
Initiated by insulin
Requires +ve energy balance
Carbs, proteins, fats all converted into triglycerides to be stored
Lipid transportation lipoproteins
Chylomicrons - Formed in intestines, highly dense, for dietary lipid transportation
Very low density and low density lipoproteins - liver (no good for you, they drop the triglycerides)
High density lipoproteins - intestines and liver (very good for you, they pick up waste)
Why does Protein catabolism occur?
So that the proteins can be broken down into amino acids so they can be:
- converted into different amino acids
- Used to construct new proteins
- Converted to fatty acids, ketone bodies or glucose
- Oxidised to make ATP
Why does deamination occur?
Involves the removal of amino group from the amino acid in the liver or kidney to maintain an internal environment (ie. nitrogen is toxic in excess or the amino acids need to have amino group removed to be processed into ATP)
Involves NADH, deaminase, and water
What is transamination
It transfers an amino group into a keto group. It recycles nitrogen to produce non-essential amino acids and prevent ammonia production and excretion of nitrogen from kidneys.
What 6 processes is the digestive system broken down into
Ingestion
Secretion
Mixing and propulsion
Digestion
Absorption
Defacation
What four layers is the GI tract made of
Mucosa
Submucosa
Muscularis
Serosa
Mucosa
Innermost layer
Divided into surface epithelium and lamina propria
Submucosa
Connective tissue
Extensive vascularisation, nervous supply and lymphatics
Muscularis
Muscle layer divided into circular and longitudinal tissue
Moves food and fluid through tract by peristalsis
Serosa
Outermost layer
Thin connective tissue surrounds tract and extends to form mesentery that anchors tract to abdominal wall.
