Cell Metabolism

Cell Respiration (Metabolism)• Cellular Respiration- is a metabolic process

used to obtain energy from organic compounds or food

• can run under aerobic and anaerobic conditions.

• catabolic pathway. • occurs in the cytoplasm and mitochondria • 3 main steps: Glycolysis and the Kreb Cycle,

also known as the citric acid cycle and tricarboxylic acid cycle, and the ETC (electron transport chain)

Cellular Metabolism

Metabolism – all chemical reactions that occur in the body

Two types of metabolic reactions

Anabolic Catabolic

Goal of Cell Respiration-Make ATP

Anabolic

Anabolism provides the substances needed for cellular growth and repair

Dehydration synthesis • type of anabolic process• used to make polysaccharides, triglycerides, and proteins- produces water

CatabolicCatabolism breaks down larger molecules into smaller ones

Hydrolysis• used to decompose carbohydrates, lipids, and proteins• water is used• reverse of dehydration synthesis

Control of Metabolic Reactions

Enzymes- all are proteins

lower activation energy•not consumed in chemical reactions•substrate specific•Controlled through feedback inhibition

Do not make anything happen that could not happen on its own

Enzymes can be reused over and over

Same enzymes catalyses the forward and reverse reactions.

They are very specific

Control of Metabolic ReactionsMetabolic pathways

• series of enzyme-controlled reactions leading to formation of a product•

Enzyme names commonly• reflect the substrate• have the suffix – ase• sucrase, lactase, protease, lipase

Control of Metabolic Reactions

Cofactors • make some enzymes active• ions or coenzymes

Coenzymes• organic molecules that act as cofactors• vitamins

Factors that alter enzymes• heat• radiation• electricity• chemicals• changes in pH

Energy for Metabolic Reactions

Energy• ability to do work or change something• heat, light, sound, electricity, mechanical energy, chemical energy•involved in all metabolic reactions

Cellular RespirationOccurs in three series of reactions

1. Glycolysis2. Citric acid cycle3. Electron transport chainProduces

• carbon dioxide• water• ATP (chemical energy)• heat

Includes• anaerobic reactions (without O2) - produce little ATP• aerobic reactions (requires O2) - produce most ATP

Glycolysis

• There are 10 steps and all require specific enzymes to catalyze them

• Goal- Produce pyruvate for use in the Krebs Cycle

• NADH used in ETC

Citric Acid Cycle• begins when acetyl CoA combines with oxaloacetic acid to produce citric acid

• citric acid is changed into oxaloacetic acid through a series of reactions

• cycle repeats as long as pyruvic acid and oxygen are available

•Makes 2 ATP 6 NADH and 2 FADH2

•BP- 4 CO2

The Goal is the production of NADH and FADH2 for use in the ETC—they are electron carriers

ETC• So far only 4 of the 38 ATP that will be produced have

been, all by substrate level phosphorylation. • The remaining will be produced by the ETC. • The majority of the ATP produced comes from the

energy carried in the electrons of NADH (and FADH2) that were produced by the Krebs Cycle. 6 NADH and 2 FADH2

• The energy in these electrons is used in the ETC to power the synthesis of ATP.

• There are thousands of ETC’s found in each mitochondria, which can number in the 100’s depending on the cell type.

Oxygen if the Final Electron AcceptorWhy do we Breath??

Summary of Catabolism of

Proteins, Carbohydrates,

and Fats

4-21

Carbohydrate StorageExcess glucose stored as

• glycogen (primarily by liver and muscle cells)• fat• converted to amino acids

Regulation of Metabolic Pathways

Turned off when their product is in

strong supply

Works by supply and demand

4-23

Nucleic Acids and Protein Synthesis

Gene – segment of DNA that codes for one protein

Genome – complete set of genes

The Central Dogma• It is all about Proteins!!!

• DNA contains the information needed to build these life giving proteins in a code on segments called genes.

• One gene can code for more than one protein?

Structure of DNA

• two polynucleotide chains• hydrogen bonds hold nitrogenous bases together• bases pair specifically (A-T and C-G)• forms a helix• DNA wrapped about histones forms chromosomes

RNA Molecules

mRNA

rRNA

tRNA

Protein Synthesis (Transcription and Translation)

• 1st the DNA strand is used as a template to build a molecule of RNA called mRNA that can leave the nucleus taking the instructions for the protein to ribosome for assembly.

• 2nd during translation the information contained in the RNA molecule is used to determine the sequence of amino acids needed to build a protein.

• Order: DNA - RNA – protein - trait.

Translation

Overview: Protein

Synthesis

DNA Replication

Mutations

Mutations – change in genetic information

Result when • extra bases are added or deleted• bases are changed

May or may not change the protein

Some good some bad

Clinical Application

PhenylketonuriaPKU

• enzyme that breaks down the amino acid phenylalanine is missing• build up of phenylalanine causes mental retardation• treated by diets very low in phenylalanine