Respiration

Chemical C 6 H 12 O 6 + O 2  CO 2 + ATP + H 2 O *Balanced C 6 H 12 O 6 + 6O 2  6CO 2 + ATP + 6H 2 O

Purpose? Provide energy for other processes – Chemical reactions / metabolic processes eg protein synthesis – Active transport of material into cells – Movement eg muscle contractions, to operate flagella – MRS GREN… – …to ultimately stay alive!

Why ATP?

Structure…Chemists only..

Recycling of ATP + Phosphorylation Energy released in cells (eg muscle) when last bond in ATP broken. Makes ADP + Pi Energy needed to turn ADP + Pi back to ATP. Provided by respiration

Parts of a Mitochondrion Cristae (folds of inner membrane) Inner membrane Outer membrane

Key Steps & Locations = “sugar splitting” Cytoplasm Mitochondria (in matrix = fluid filled interior) Mitochondria (on inner membrane)

Key Steps *Other names… Krebs cycle = citric acid cycle Electron transport chain = respiratory chain, oxidative phosphorylation

*Detailed Steps

Respiration Glycolysis Glycolysis literally means "sugar- splitting." In glycolysis, the six-carbon sugar glucose is split into two molecules of pyruvate, also called pyruvic acid. This process produces a net gain of two ATP molecules. The resulting molecules of pyruvate each have three carbon atoms. Glycolysis takes place in the cell's cytoplasm. The remainder of cellular respiration takes place in organelles called mitochondria. AnaerobicAerobic

The Krebs Cycle The Krebs Cycle takes place in the fluid- filled area inside the inner membrane of the mitochondria known as the matrix. Some ATP (2ATP) and other energy carrying molecules are produced here. The gas carbon dioxide is a byproduct of this process.

The Electron Transport Chain Most of the ATP is produced in this last step of cellular respiration. Electron transport takes place in the infoldings of the inner-membrane of the mitochondria. These infoldings are called cristae. At the end of electron transport, oxygen combines with hydrogen ions and electrons (e - ) to form water. ½O 2 + 2H + + 2e - → H 2 O

Overall Process glucose + oxygen → carbon dioxide + water + 38 atp Fermentation In the absence of oxygen, the cell resorts to anaerobic metabolism. In animal cells, pyruvate is converted to lactic acid. In yeast and bacteria, the pyruvate is often converted to ethanol. In both cases, no new ATP is produced, so the net production of the energy-carrying molecule is only the two molecules of ATP produced in glycolysis.

Glycolysis Glycolysis literally means "sugar-splitting." In glycolysis, the six-carbon sugar glucose is split into two molecules of pyruvate, also called pyruvic acid. This process produces a net gain of two ATP molecules. The resulting molecules of pyruvate each have three carbon atoms. Glycolysis takes place in the cell's cytoplasm. The remainder of cellular respiration takes place in organelles called mitochondria. The Krebs Cycle The Krebs Cycle takes place in the fluid-filled area inside the inner membrane of the mitochondria known as the matrix. Some ATP and other energy carrying molecules are produced here. The gas carbon dioxide is a byproduct of this process. The Electron Transport Chain Most of the ATP is produced in this last step of cellular respiration. Electron transport takes place in the infoldings of the inner-membrane of the mitochondria. These infoldings are called cristae. At the end of electron transport, oxygen combines with hydrogen ions and electrons (e - ) to form water. ½O 2 + 2H + + 2e - → H 2 O Overall Process glucose + oxygen → carbon dioxide + water + 38 atp Fermentation In the absence of oxygen, the cell resorts to anaerobic metabolism. In animal cells, pyruvate is converted to lactic acid. In yeast and bacteria, the pyruvate is often converted to ethanol. In both cases, no new ATP is produced, so the net production of the energy-carrying molecule is only the two molecules of ATP produced in glycolysis.

Structure & Function #1 Cristae (folds of inner membrane) Inner membrane Outer membrane

Structure & Function #2 Outer membrane – regulates passage of materials into and out of the mitochondria Inner membrane – compartmentalised into numerous infoldings called cristae, which expand its surface area thereby enhancing the ability to produce ATP Inter-membrane space Matrix – fluid filled space enclosed by inner membrane, contains enzymes which function on the large surface area created by the cristae Cristae

Reasons for varying numbers… Low #s mitochondria = low respiration rate – Plants (compared to animals): low metabolic rate so less respiration required (producing unnecessary mitochondria would be a waste and lead to lower ‘fitness’ – Bone cells require little ATP. Why? High #s mitochondria = high respiration rate – Muscle cells: ATP needed for contraction, more mitochondria = more respiration = more ATP = more movement = better able to carry out other MRS GREN functions (catch food…) – Sperm: ATP needed to make flagella move, so that… – Glands: make lots of hormones, hormones are proteins and this requires protein synthesis (requires ATP)…why are hormones needed? – Liver: lots of enzymes to break down toxins (requires protein synthesis), why? – Cells lining small intestine: Take up glucose against concentration gradient so need ATP… Variation in mitochondria number is related to energy requirement of the particular cell. The higher the energy demand the greater the number of mitochondria.