When there is a negative delta G these reactions are exothermic. The opposite is called endothermic
which costs energy.
The metabolic network is regulated by hormones, the metabolite level and lifestyle.
ATP, GTP, NAD(P)H,FADH, delta mu are free energy carriers.
Oxidation is the flow of high energy electrons to low energy electrons
All excess fuel is stored as fat and between meals protein degradation for glucose synthesis takes
place in the brain. When the human body is in starvation, fatty acids are converted into ketone
bodies to spare the muscles.
Carbohydrate and glucose management
The brain cannot absorb long chain fatty acids, so it solely relies on glucose and ketone bodies.
Glucose have 3 different isoforms by opening and closing. The Dietary sources of glucose are starch,
plants, diary and of course sugar. Polymers like starch need several enzymes to be degraded.
Different enzymes have different amounts of affinities for different types of bondages. For example,
starch enters the body and is broken down in the stomach. Then, it turns into tri and
oligosaccharides in the small intestine. Then, at the epithelium there are enzymes that break down
the oligosaccharides into glucose, fructose, or galactose. These are the only ones that are taken up,
these are monosaccharides. Fibres cannot be digested by human enzymes but can be digested by
bacteria. Glucose is transported by facilitated diffusion by so called gluts. These are specific holes
that are driven by diffusion. Glucose or Galactose is going into the cells through the brush border by
active transport. This is done with sodium gradients. Fructose has only facilitated diffusion. Lactose
intolerance is when you lack the enzyme lactase. Bacteria eat the lactose and they start to make
lactic acid and attract water. This result into diarrhoea. There is also fructosemia which is a fruit
intolerance. These people lack the enzyme aldolase B and they start to accumulate fructose-1-
phosphate and this is toxic molecule. Galactosemia lack galactose 1-phosphate uridylyl transferase
and you get an accumulation of the intermediates.
Glycogen is a form of glucose that can be stored. It is branched. The liver stores glycogen during
periods between meals because it needs to maintain a glucose homeostasis. When there is no
glucose coming from the intestine, the liver releases glucose into the blood. The muscle stores
glycogen because it is the main local glucose source during exercise. Glucose turns into Glocose-6-P
and into Glucose-1-P and UTP is going in and creates UDP-G. Then drives a glucose onto an already
existing glycogen chain. Glycogen synthesis is a sort of on and off knob for the synthesis. Glycogen
phosphorylases puts a phosphor onto a glucose. Then you are back to Glucose-1-P. There are
branches, to increase the number of sites where you can chop of the glucose. In muscle the glycogen
is regulated by insulin and epinephrine and activity. In the liver the glycogen is regulated by fasting
and eating.
When you are starving, glucose is only made via gluconeogenesis. Insulin release increases glycogen
synthesis and this then can be stored. Glucagon is when you have a low blood sugar. The glucose
concentration should be around 5 mmol. Insulin inhibits glucagon release. Glucagon production is
stimulated by amino acids. Insulin is made inside of a beta cell trough a cascade of events. Km is at
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