Cellular Biochemistry overview

Dr. Samah KotbLecturer of Biochemistry

2015

Cellular Biochemistry and

Metabolism(CLS 331)

Roadmap of metabolic pathways

metabolism

CatabolismAnabolism

breaking down

building up

Carbohydrates

Glucose

Pyruvate

Acetyl CoA

TCA cycle

Protein Fats

Glycerol +

fatty acids

Amino acids

muscle and lean tissue

Amine group

urine

High energy carriers

ATPenergy

ETC

Adipose tissue

O2

CO2 +H2O

Glucagon, epinephrine, Glucocorticoids, Thyroxine,GH Insulin ,Sex

steroids ,Thyroxine,GH

O2

CO2

H2O

• Let’s talk about metabolism• Metabolism is the sum of all of the chemical reactions

in the human body and defined as the balance in the body between the reactions that build things up, and another way of saying that is anabolism , on the other side of the scale, the reactions that break things down, the medical way of saying that is catabolism.

• So metabolism is kind of the balance between building things up or repairing or storing inside the body and breaking things down, usually for energy needs.

Metabolism

• How are the things that we eat broken down for energy or stored within the body?

Let’s start by carbohydrates

We eat our carbohydrates in the form of starches or sugars that could get broken down into their kind of components parts.

Metabolism and biochemical pathways

• The major component , or the major single unit currency of carbohydrates is called glucose.

• That glucose is very big picture that can get broken down further into acompound called pyruvate .

• The pyruvate then gets broken down into avery important molecule that’s kind of the center of making energy in the body, and that molecule is called acetyl-CoA that enters tricarboxylic acid cycle or krebs cycle TCA cycle.

Metabolism and biochemical pathways

• Essentially , what do you need to know about TCA cycle ?

• You need to know that acetyl-CoA moves around the cycle to form all of different compounds, things are bounced off and the things that are bounced off are these high- energy carriers which enter the electron transport chain that yield ATP, ATP is the same as energy in the human body.

Metabolism and biochemical pathways

• In order for TCA cycle to move around , Oxygen O2 is required and carbon dioxide CO2 and water H2O are given off.

Metabolism and biochemical pathways

• Those are the breaking down reactions that aside of the equation of metabolism, but what about the building up reactions???

Metabolism and biochemical pathways

• The amino acids that come from protein in our diet,• 1. can be used to make things like muscle and other

lean tissue in our bodies.

• 2. can be used for repair.

• 3. can be used as protein carriers in our blood.

Metabolism and biochemical pathways

• The glucose in our body can also be stored as something called glycogen which is the storage form of carbohydrates in our bodies

Metabolism and biochemical pathways

• The fats that we’ve eaten, if there are too many of those in our diet, they can also be stored as adipose tissue , so they’re put back together and stored in our body

Metabolism and biochemical pathways

• The balance between the breaking down reactions or the catabolic reactions and the building up reactions , the balance is controlled by hormones in our body.

Metabolism and biochemical pathways

• There are several hormones that lead to breaking down of tissues like glucagon that leads to the breakdown of the stores of glycogen in our body. Other hormones like epinephrine and glucocorticoids.

• There are sort of the stress hormones in our body favor the breaking down or catabolism. Thyroxin and growth hormone (GH) are also included that favor the breaking down of our fat and carbohydrates stores .

Metabolism and biochemical pathways

• The hormones that lead to the building up or the anabolism in our bodies , the sex hormones or sex steroids, and then there are some hormones that are anabolic or favor the building up of proteins , and those are the hormones thyroxin and growth hormone (GH).

Metabolism and biochemical pathways

• The last thing I want to add is that some of these reactions are reversible so glucose that converted to pyruvate can be reversed , It can go back up in the other direction and that’s how we can make glycogen form, but there is one –way reaction that is an irreversible ( pyruvate to acetyl coA) that meant that fatty acids can never go up to make pyruvate and be used as glucose for the brain , or they can never be used to replenish glycogen stores in the body .

Metabolism and biochemical pathways

• Let’s say , some amino acids make pyruvate, this kind of amino acids can be used to make glycogen.

• The backbone of the fatty acids called glycerol could be used to make glycogen or to make glucose to feed the brain

Metabolism and biochemical pathways

• Another important thing that we have to understand is that TCA cycle only go around.

• If ATP is needed by the body, if we’re using energy , we’re doing exercise , we’re demanding ATP and energy from our system then this cycle will continue going around, but if we don’t, let’s say we’re sedentary and we don’t use energy then acetyl CoA is going to build up and favor the return in this towards adipose tissue direction.

Metabolism and biochemical pathways

• This is how excess carbohydrates , if it’s taken in the diet can lead to excess adipose tissue .

• Excess fat, If we eat too much fat in our diet that can lead to adipose tissue and even if we eat too much protein, it’ll just be deaminated and converted to acetyl-coA, which can be converted to adipose tissue.

Metabolism and biochemical pathways

Biochemistry