7.2.2.3.2. Lactic fermentation

Lactic fermentation

In lactic fermentation, lactic acid is formed from pyruvic acid from glycolysis. This regenerates the NAD⁺, necessary to continue glycolysis.

In glycolysis, glucose is oxidized to two pyruvic acid molecules, generating NADH. The pyruvic acid then accepts the electrons from NADH, reducing itself to lactic acid. The energy yield is 2 ATP molecules, obtained by phosphorylation at the substrate level.

Among the bacteria that carry out lactic fermentation, it is worth highlighting the lactobacilli (Lactobacillus) and the Streptococcus, which are located in milk and in the intestine. Cheese, yogurt, kefir, are some of the products that are obtained by this type of fermentation.

This fermentation can also be used to preserve certain vegetable or meat products such as some sausages.

In muscle cells, during strenuous exercise in which there is not enough oxygen to oxidize glucose aerobically, pyruvic acid is reduced to lactic acid. The lactic acid is then transformed back into glucose (gluconeogenesis).

Lactic acid fermentation takes place in bacteria and in eukaryotic cells, such as muscle cells and erythrocytes (they lack mitochondria).

In lactic fermentation, cells anaerobically degrade glucose, obtaining two lactic acid molecules and only 2 ATP. This is very little energy compared to what would have been obtained with aerobic respiration, where the total oxidation of the six carbons of glucose to 6 CO₂takes place.

By Alejandro Porto (Own work) [CC BY-SA 3.0], via Wikimedia Commons

Gerty Cori and the Matilda effect

Gerty Cori, along with her husband Carl, received the Nobel Prize in Medicine in 1947. Despite having the same qualifications as her husband, she had much more trouble finding low-paying research jobs. Carl insisted on working collaboratively with Gerty, even though the institutions made it difficult for him.

Together they won the Nobel Prize for discovering how glycogen is transformed into lactic acid in muscle tissue and is then converted into glucose by gluconeogenesis in the liver (Cori cycle).

The Matilda effect is known as the prejudice against recognizing the achievements offemale scientists, whose work is often attributed to their male colleagues.

Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU)

Aragon, June 2019, option B, question 4 .

Answer the following questions: (2 marks)

a) Indicate an industrial application in which species of the genus Lactobacillus intervene, mentioning the type of reaction that they would carry out in said application. (0.5 points)

b) This same reaction can be carried out by the muscles. In what situation and in what compartment of the cell? (0.5 points)

c) In the case of winemaking, first, the grapes are squeezed to obtain the must, which is processed for a few months during which a series of anaerobic reactions take place. Why does the must stop being sweet over time? (0.5 points)

d) Why is it dangerous to enter a winery where the must is being processed? (0.5 points)

Aragon, September 2018, Option B, question 2

If you want to make homemade yogurt, we must mix a little yogurt with milk and keep the mixture at 35 or 40ºC for 8 hours so that the bacterial fermentation of the milk takes place. (2 points)

a) What would happen if the yogurt and milk mixture were kept in the refrigerator at 4ºC for 8 hours? (0.5 points)

b) What would happen if the milk used was sterilized? (0.5 points)

c) What would happen if the yogurt was sterilized before adding it to the milk? (0.75 points)

d) What type of bacteria are used in this fermentation? (0.25 points)

Valencian Community, June 2017, option B, block 4, question 3 .

To prepare homemade yogurt, a certain amount of milk is mixed with a little yogurt and kept at 35-40ºC for 48 hours. Answer the following questions justifying the answer (3 points).

a) What would happen if by mistake the mixture was kept for 8 hours at 1ºC?

b) Would we obtain yogurt if previously sterilized milk is used?

c) What if what is sterilized is the yogurt before adding it to the milk?

Murcia, July 2020, question 4.6

In relation to microorganisms in the food industry:

a) Indicate a microorganism used in the preparation of bread and briefly describe the characteristics of the process in which it participates. (0.5 points)
b) What microorganisms are used in the manufacture of dairy products (cheese, yogurt)? Briefly describe the process in which they participate. (0.5 points)

Basque Country, July 2020, option 4B

Applications of microorganisms in biotechnology on an industrial scale:

a) (0.5 points) What microorganisms are used to produce yogurt, bread and beer?

b) (0.5 points) What type of organisms are in each case, prokaryotic or eukaryotic?

c) (1 point) What type of metabolism (aerobic or anaerobic) do these organisms carry out to obtain these products? Reason for the answer.

d) (0.5 points) Indicates what energy benefit the organisms that carry out these transformations obtain, indicating which substrate they use and which chemical product appears at the end.

Extremadura, June 2021, question 3

3.- In relation to fermentation:

A. Concept of alcoholic fermentation and lactic fermentation. Global equation of each process. (1 point)
B. Cite an industrial process that requires lactic fermentation and the type of microorganism that performs it and another industrial process that requires alcoholic fermentation and the type of microorganisms that performs it. (1 point)

Murcia, June 2021, question 2.4

2.4. After glycolysis, the pyruvate obtained can have two different destinations:

1. Pyruvate + NADH + H + → lactate + NAD +
2. Pyruvate + CoA + NAD + → acetyl-CoA + CO2 + NADH

a) Explain under what conditions each of them occurs. (0.75 points)
b) Indicate whether the lactate and acetyl-CoA obtained could continue to be oxidized. If so, indicate which metabolic path each of them should enter and whether both processes would ultimately provide the same energy. (0.75 points)

Murcia, July 2021, question 4.6

Both bread and yogurt are obtained by a fermentation process, carried out by different yeasts and bacteria.

a) Why does yogurt have a marked acid taste and the same does not happen with bread? Reason for it by helping yourself to the reactions that are carried out in each case. (0.5 points)
b) To make homemade yogurt, simply distribute milk in several glasses and add a little commercial yogurt to each one. They are then left overnight at 35-40ºC. What would happen if, before making the mixture, we sterilized the commercial yogurt? What if we sterilize the milk? Reason for the answers. (0.5 points)

Fundamental insights on lactic fermentation

Lactic fermentation

In glycolysis, glucose is oxidized to two pyruvic acid molecules, generating NADH. Afterwards, pyruvic acid accepts the electrons from NADH, reducing itself to lactic acid and the NAD⁺, necessary to continue glycolysis , is regenerated .
Energy yield: 2 ATP molecules.
Bacteria that carry out lactic fermentation: lactobacilli (Lactobacillus) and Streptococcus, which are located in milk and in the intestine.
It is used for the production of cheese, yogurt, kefir, ...
It is also carried out in some eukaryotic cells, such as muscle cells and erythrocytes.

Licensed under the Creative Commons Attribution Share Alike License 4.0

BIOLOGÍA - GEOLOGÍA . COM
1st ESO	3rd ESO	4th ESO	Biology 2nd Baccalaureate
Index by courses	Forums	Geología 2º Bach.

Skip navigation Biology 2nd Baccalaureate Biology 2nd Bac. 1. Bioelements and biomolecules. Water and mineral salts 1.1. Chemical bonds in biology 1.1.1. Intramolecular bonds 1.1.1.1. Covalent bond 1.1.1.2. Ionic bond 1.1.2. Intermolecular bonds 1.1.2.1. Van der Waals forces 1.1.2.2. Hydrogen bonds 1.2. The chemical basis of life: inorganic and organic components 1.2.1. Primary bioelements 1.2.2. Secondary bioelements 1.2.3. Trace elements 1.3. The immediate principles or biomolecules 1.3.1. Water 1.3.1.1. Chemical structure of water 1.3.1.2. Properties and functions of water 1.3.2. Mineral salts 1.3.2.1. Functions of salts in solution 1.3.2.2. Colloidal solutions and dispersions 1.3.2.3. Properties of colloidal dispersions 1.3.2.4. Diffusion, osmosis and dialysis 1.3.2.4.1. Diffusion 1.3.2.4.2. Osmosis 1.3.2.4.3. Dialysis 1.4. Bibliography 2. Glucides 2.1. Glucid concept 2.2. Classification of carbohydrates 2.3. Monosaccharides 2.3.1. Trioses 2.3.1.1. Spatial isomerism or stereoisomerism 2.3.2. Tetroses 2.3.3. Pentoses 2.3.3.1. Monosaccharide cyclization 2.3.4. Hexoses 2.4. The N-glucosidic and O-glucosidic bonds 2.4.1. Substances derived from monosaccharides 2.5. Disaccharides 2.6. Polysaccharides 2.6.1. Homopolysaccharides 2.6.1.1. Reserve homopolysaccharides 2.6.1.2. Structural homopolysaccharides 2.6.2. Heteropolysaccharides 2.6.3. Heterosides 2.7. General functions of glucides 2.8. Bibliography 3. Lipids 3.1. Lipid concept 3.2. Classification of lipids 3.2.1. Fatty acids 3.2.1.1. Saturated and unsaturated fatty acids 3.2.1.2. Chemical properties of fatty acids 3.2.1.3. Physical properties of fatty acids 3.2.1.4. Fatty Acid Functions 3.2.2. Saponifiable lipids or with fatty acids 3.2.2.1. Simple lipids 3.2.2.1.1. Acylglycerides 3.2.2.1.2. Cerides 3.2.2.2. Complex lipids 3.2.2.2.1. Phospholipids 3.2.2.2.2. Glycolipids 3.2.3. Unsaponifiable lipids or without fatty acids 3.3. Lipid functions 3.4. Bibliography 4. Proteins 4.1. Introduction to proteins 4.2. Amino acids 4.2.1. Classification of amino acids 4.2.2. Properties of amino acids 4.3. The peptide bond 4.4. Protein 4.4.1. Protein structure 4.4.1.1. Primary structure of proteins 4.4.1.2. Secondary structure of proteins 4.4.1.3. Tertiary structure of proteins 4.4.1.4. Quaternary structure of proteins 4.4.2. Protein properties 4.4.3. Classification of proteins 4.4.3.1. Holoproteins 4.4.3.2. Heteroproteins 4.4.4. Protein functions 4.5. Enzymes 4.5.1. Structure of enzymes 4.5.2. The active center of enzymes 4.5.3. General Mechanism of Enzyme Catalysis 4.5.4. Regulation of enzyme activity 4.5.5. Allosteric enzymes 4.5.6. Nomenclature and classification of enzymes 4.6. The vitamins 4.6.1. Fat-soluble vitamins 4.6.2. Water soluble vitamins 4.7. Bibliography 5. Nucleotides and nucleic acids 5.1. The chemical composition of nucleic acids 5.1.1. Components of nucleic acids 5.1.2. Concept, types and functions of nucleic acids 5.1.3. Nucleosides 5.1.4. Nucleotides 5.1.4.1. Nucleotide functions 5.1.5. Nucleic acids 5.2. Deoxyribonucleic acid (DNA) 5.2.1. DNA structure 5.2.1.1. Primary structure of DNA 5.2.1.2. Secondary structure of DNA 5.2.1.3. Tertiary structure of DNA 5.2.1.3.1. Tertiary structure of DNA in prokaryotes 5.2.1.3.2. Tertiary structure of DNA in eukaryotes 5.2.1.4. Quaternary structure of DNA 5.2.2. DNA types 5.2.3. Genetic material: chromatin and chromosomes 5.2.3.1. Karyotype and karyogram 5.3. Ribonucleic acid (RNA) 5.3.1. RNA types 5.3.1.1. Transfer RNA 5.3.1.2. Messenger RNA 5.3.1.3. Ribosomal RNA 5.3.1.4. Nucleolar RNA 5.3.1.5. Small nuclear RNA 5.3.2. Functions of ribonucleic acids 5.4. Bibliography 6. Cell morphology 6.1. Cell concept 6.1.1. Cell history 6.1.2. Cell theory 6.2. Levels of cellular organization 6.2.1. General characteristics of cells 6.2.2. Prokaryotic cells 6.2.2.1. Prokaryotic cell morphology 6.2.2.2. Structure of prokaryotes 6.2.2.2.1. Bacterial capsule 6.2.2.2.2. Bacterial wall 6.2.2.2.3. Plasma membrane 6.2.2.2.4. Cytoplasm-Ribosomes-Inclusions 6.2.2.2.5. Bacterial DNA 6.2.2.2.6. Bacterial appendages 6.2.2.3. Bacteria Physiology 6.2.3. Eukaryotic cells 6.2.3.1. Animal and plant cell 6.2.3.1.1. Animal eukaryotic cell 6.2.3.1.2. Plant eukaryotic cell 6.2.3.2. Cell Evolution: Endosymbiont Theory 6.3. Size, shape and quantity 6.4. The plasma membrane 6.4.1. Chemical composition of the membrane 6.4.2. The structure of the membrane. The fluid mosaic model 6.4.3. Functions of the plasma membrane 6.4.4. Transport across the membrane 6.4.4.1. Small molecule transport 6.4.4.2. Macromolecule transport 6.4.5. Plasma membrane differentiations 6.5. The cell wall of plant cells 6.5.1. Chemical composition of the cell wall 6.5.2. Cell wall structure 6.5.3. Cell wall differentiations 6.5.4. Cell wall functions 6.6. Extracellular matrix or glucocalyx 6.7. Cytosol or hyaloplasm 6.8. The cytoskeleton 6.8.1. Microfilaments or actin filaments 6.8.2. Intermediate filaments 6.8.3. Microtubules 6.9. Cell membrane and organelle systems 6.9.1. Membrane systems 6.9.1.1. The endoplasmic reticulum 6.9.1.2. Golgi apparatus 6.9.2. Cell organelles 6.9.2.1. Lysosomes 6.9.2.2. Peroxisomes 6.9.2.3. Vacuoles 6.9.2.4. Mitochondria 6.9.2.4.1. Functions of the mitochondria 6.9.2.5. Plastids 6.9.2.5.1. Chloroplasts 6.9.2.6. Ribosomes 6.9.2.7. Centrosome 6.9.2.8. Cilia and flagella 6.10. Cell motility 6.11. The cell nucleus 6.11.1. Characteristics of the cell nucleus 6.11.2. The interphase nucleus 6.11.3. The mitotic nucleus or nucleus in division 6.12. Bibliography 7. Metabolism 7.1. Metabolism 7.1.1. Energetic Aspects of Cellular Chemical Reactions 7.2. Catabolism 7.2.1. Catabolism and obtaining energy 7.2.2. Carbohydrate catabolism 7.2.2.1. Glycolysis 7.2.2.2. Cellular respiration 7.2.2.2.1. Oxidative decarboxylation 7.2.2.2.2. Krebs cycle 7.2.2.2.3. Electron transport chain 7.2.2.2.4. Energy balance of cellular respiration 7.2.2.3. Fermentations 7.2.2.3.1. Alcoholic or ethyl fermentation 7.2.2.3.2. Lactic fermentation 7.2.2.3.3. Other types of fermentations 7.3. Anabolism 7.3.1. Autotrophic anabolism 7.3.2. Photosynthesis 7.3.2.1. Photochemical or light phase 7.3.2.1.1. Photosystems 7.3.2.1.2. Photophosphorylation 7.3.2.1.2.1. Non cyclic photophosphorylation 7.3.2.1.2.2. Cyclic photophosphorylation 7.3.2.2. Biosynthetic or dark phase 7.3.2.3. Factors influencing photosynthesis 7.3.2.4. Products of photosynthesis 7.3.3. Chemosynthesis 7.4. Bibliography 8. Cell reproduction 8.1. The cell cycle 8.1.1. Interphase 8.1.2. Cellular division 8.2. Cellular division 8.2.1. Mitosis 8.2.1.1. Prophase 8.2.1.2. Metaphase 8.2.1.3. Anaphase 8.2.1.4. Telophase 8.2.1.5. Cytokinesis 8.2.1.6. More on mitosis 8.2.2. Meiosis 8.2.2.1. Meiosis I 8.2.2.2. Meiosis II 8.2.3. Meiosis and sexual reproduction 8.2.4. Meiosis and life cycle 8.2.5. Biological importance of meiosis 8.3. Differences and similarities between mitosis and meiosis 8.4. Bibliography 9. Classical genetics 9.1. Genetics basics 9.2. Mendelian genetics 9.2.1. The method 9.2.2. Mendel's Laws 9.2.2.1. Mendel's first law or principle of uniformity in the first generation 9.2.2.2. Mendel's second law or principle of segregation 9.2.2.2.1. Backcross and test crossover 9.2.2.3. Mendel's third law or principle of independent combination 9.3. Gene interaction 9.3.1. Gene interaction between allelic genes 9.3.2. Gene interaction between non-allelic genes that influence for the same trait 9.4. Chromosomal theory of heredity 9.5. Ligation and recombination 9.6. Complex mendelism 9.6.1. Multiple allelism 9.6.1.1. Lethal genes 9.6.2. Pleiotropy 9.6.3. Expressiveness and genetic penetrance 9.7. Sex-linked inheritance 9.7.1. Y-linked inheritance 9.7.2. X-linked inheritance 9.8. Heredity influenced by sex 9.9. Bibliography 10. Molecular genetics 10.1. DNA as hereditary material 10.2. DNA replication 10.2.1. The need for DNA replication 10.2.2. First hypotheses about DNA duplication 10.2.3. Meselson and Stahl experiment 10.2.4. The sense of growth of the new strands 10.2.5. Mechanism of DNA replication 10.2.5.1. Replication in prokaryotes 10.2.5.2. Replication in eukaryotes 10.2.6. Error correction 10.2.7. Enzymes involved in replication 10.3. Gene concept 10.4. "One gene-one enzyme" theory 10.5. Transcription 10.5.1. Mechanism of transcription 10.5.1.1. Transcription in prokaryotes 10.5.1.2. Eukaryotic transcription 10.6. Translation or protein biosynthesis 10.6.1. The genetic code 10.6.2. Mechanism of translation of RNA to proteins 10.6.2.1. Translation in eukaryotes 10.7. Regulation of gene expression 10.8. Bibliography 11. Genetics and evolution 11.1. Mutations 11.2. Types of mutations 11.2.1. Gene or point mutation 11.2.2. Chromosomal or structural mutation 11.2.3. Mutation at the genomic level 11.3. Causes of mutations 11.4. Evolutionary implications of mutations 11.5. Metabolic implications of mutations 11.6. Bibliography 12. Microbiology and biotechnology 12.1. Microbiology 12.2. Viruses 12.2.1. Viral morphology 12.2.2. Viral physiology 12.2.2.1. Lytic cycle 12.2.2.2. Lysogenic cycle 12.2.2.3. Cycles of viruses of special interest 12.2.2.3.1. Flu virus life cycle 12.2.2.3.2. Life cycle of the AIDS virus 12.3. Other acellular forms 12.3.1. Viroids 12.3.2. Prions 12.4. Biotechnology 12.5. Bibliography 13. Immunology 13.1. Infection concept 13.2. Defense mechanisms against infections 13.2.1. Nonspecific mechanisms 13.2.1.1. Primary barriers: external defenses 13.2.1.2. Secondary barriers: internal defenses 13.2.2. Specific mechanisms 13.3. Immunity and immune system 13.3.1. Components of the immune system 13.3.2. Concept and nature of antigens 13.4. The immune response 13.4.1. Humoral immune response: the antibodies 13.4.1.1. Antibody-producing cells: B lymphocytes 13.4.1.2. Antibodies 13.4.1.2.1. Types of antibodies 13.4.1.2.2. Antigen-antibody reaction 13.4.1.3. Immune memory: primary and secondary responses 13.4.2. Cellular immune response: T lymphocytes 13.5. Types of immunity 13.5.1. Natural immunity 13.5.2. Artificial immunity 13.6. Immune system disorders 13.6.1. Autoimmunity 13.6.2. Hypersensitivity 13.6.3. Immunodeficiency 13.6.4. Transplants and the phenomenon of rejections 13.7. Bibliography « Previous \| Next » 7.2.2.3.2. Lactic fermentation Lactic fermentation In lactic fermentation, lactic acid is formed from pyruvic acid from glycolysis. This regenerates the NAD⁺, necessary to continue glycolysis. In glycolysis, glucose is oxidized to two pyruvic acid molecules, generating NADH. The pyruvic acid then accepts the electrons from NADH, reducing itself to lactic acid. The energy yield is 2 ATP molecules, obtained by phosphorylation at the substrate level. Among the bacteria that carry out lactic fermentation, it is worth highlighting the *lactobacilli (Lactobacillus)* and the *Streptococcus, which are located in milk and in the intestine. Cheese, yogurt, kefir, are some of the products that are obtained by this type of fermentation. This fermentation can also be used to preserve certain vegetable or meat products such as some sausages. In muscle cells, during strenuous exercise in which there is not enough oxygen to oxidize glucose aerobically, pyruvic acid is reduced to lactic acid. The lactic acid is then transformed back into glucose (gluconeogenesis). Lactic acid fermentation takes place in bacteria and in eukaryotic cells, such as muscle cells and erythrocytes (they lack mitochondria). In lactic fermentation, cells anaerobically degrade glucose, obtaining two lactic acid molecules and only 2 ATP. This is very little energy compared to what would have been obtained with aerobic respiration, where the total oxidation of the six carbons of glucose to 6 CO₂takes place. By Alejandro Porto (Own work) [CC BY-SA 3.0], via Wikimedia Commons* Gerty Cori and the Matilda effect Gerty Cori, along with her husband Carl, received the Nobel Prize in Medicine in 1947. Despite having the same qualifications as her husband, she had much more trouble finding low-paying research jobs. Carl insisted on working collaboratively with Gerty, even though the institutions made it difficult for him. Together they won the Nobel Prize for discovering how glycogen is transformed into lactic acid in muscle tissue and is then converted into glucose by gluconeogenesis in the liver (Cori cycle). The Matilda effect is known as the prejudice against recognizing the achievements offemale scientists, whose work is often attributed to their male colleagues. Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU) Aragon, June 2019, option B, question 4 . Answer the following questions: (2 marks) a) Indicate an industrial application in which species of the genus Lactobacillus intervene, mentioning the type of reaction that they would carry out in said application. (0.5 points) b) This same reaction can be carried out by the muscles. In what situation and in what compartment of the cell? (0.5 points) c) In the case of winemaking, first, the grapes are squeezed to obtain the must, which is processed for a few months during which a series of anaerobic reactions take place. Why does the must stop being sweet over time? (0.5 points) d) Why is it dangerous to enter a winery where the must is being processed? (0.5 points) Aragon, September 2018, Option B, question 2 If you want to make homemade yogurt, we must mix a little yogurt with milk and keep the mixture at 35 or 40ºC for 8 hours so that the bacterial fermentation of the milk takes place. (2 points) a) What would happen if the yogurt and milk mixture were kept in the refrigerator at 4ºC for 8 hours? (0.5 points) b) What would happen if the milk used was sterilized? (0.5 points) c) What would happen if the yogurt was sterilized before adding it to the milk? (0.75 points) d) What type of bacteria are used in this fermentation? (0.25 points) Valencian Community, June 2017, option B, block 4, question 3 . To prepare homemade yogurt, a certain amount of milk is mixed with a little yogurt and kept at 35-40ºC for 48 hours. Answer the following questions justifying the answer (3 points). a) What would happen if by mistake the mixture was kept for 8 hours at 1ºC? b) Would we obtain yogurt if previously sterilized milk is used? c) What if what is sterilized is the yogurt before adding it to the milk? Murcia, July 2020, question 4.6 In relation to microorganisms in the food industry: a) Indicate a microorganism used in the preparation of bread and briefly describe the characteristics of the process in which it participates. (0.5 points) b) What microorganisms are used in the manufacture of dairy products (cheese, yogurt)? Briefly describe the process in which they participate. (0.5 points) Basque Country, July 2020, option 4B Applications of microorganisms in biotechnology on an industrial scale: a) (0.5 points) What microorganisms are used to produce yogurt, bread and beer? b) (0.5 points) What type of organisms are in each case, prokaryotic or eukaryotic? c) (1 point) What type of metabolism (aerobic or anaerobic) do these organisms carry out to obtain these products? Reason for the answer. d) (0.5 points) Indicates what energy benefit the organisms that carry out these transformations obtain, indicating which substrate they use and which chemical product appears at the end. Extremadura, June 2021, question 3 3.- In relation to fermentation: A. Concept of alcoholic fermentation and lactic fermentation. Global equation of each process. (1 point) B. Cite an industrial process that requires lactic fermentation and the type of microorganism that performs it and another industrial process that requires alcoholic fermentation and the type of microorganisms that performs it. (1 point) Murcia, June 2021, question 2.4 2.4. After glycolysis, the pyruvate obtained can have two different destinations: 1. Pyruvate + NADH + H + → lactate + NAD + 2. Pyruvate + CoA + NAD + → acetyl-CoA + CO2 + NADH a) Explain under what conditions each of them occurs. (0.75 points) b) Indicate whether the lactate and acetyl-CoA obtained could continue to be oxidized. If so, indicate which metabolic path each of them should enter and whether both processes would ultimately provide the same energy. (0.75 points) Murcia, July 2021, question 4.6 Both bread and yogurt are obtained by a fermentation process, carried out by different yeasts and bacteria. a) Why does yogurt have a marked acid taste and the same does not happen with bread? Reason for it by helping yourself to the reactions that are carried out in each case. (0.5 points) b) To make homemade yogurt, simply distribute milk in several glasses and add a little commercial yogurt to each one. They are then left overnight at 35-40ºC. What would happen if, before making the mixture, we sterilized the commercial yogurt? What if we sterilize the milk? Reason for the answers. (0.5 points) Fundamental insights on lactic fermentation Lactic fermentation In glycolysis, glucose is oxidized to two pyruvic acid molecules, generating NADH. Afterwards, pyruvic acid accepts the electrons from NADH, reducing itself to lactic acid and the NAD⁺, necessary to continue glycolysis , is regenerated . Energy yield: 2 ATP molecules. Bacteria that carry out lactic fermentation: *lactobacilli (Lactobacillus*) and Streptococcus**, which are located in milk and in the intestine. It is used for the production of cheese, yogurt, kefir, ... It is also carried out in some eukaryotic cells, such as muscle cells and erythrocytes. Licensed under the Creative Commons Attribution Share Alike License 4.0 « Previous \| Next » These pages are semi-automatically translated from the web Biology 2nd Baccalaureate. Biología de 2º de Bachillerato (biologia-geologia.com). You can make any suggestion, question, comment, ..., in our forum 2º Bachillerato Biología - Foro de biologia-geologia.com
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Lactic fermentation