Answer:
the right atrium.
Explanation:
Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium.
A carbohydrate composed of two covalently bonded simple sugars is called a <u>disaccharide</u>.
Carbohydrates or sugars are one of the four main categories of the macromolecules that make up living things (the other three being nucleic acids, proteins and lipids). It can either be a simple sugar (sugar monomer or monosaccharide) or a polymer of simple sugars.
Carbohydrates are composed entirely of carbon, oxygen and hydrogen atoms. Simple sugars or monosaccharides contain six carbon atoms, twelve hydrogen atoms and six oxygen atoms. When two monosaccharides bond covalently, they form a disaccharide.
Some examples of disaccharides include:
- Sucrose or table sugar - It is made up of one glucose molecule and one fructose molecule
- Lactose or milk sugar - It is made up of one glucose and one galactose molecule
- Maltose or malt sugar - It is made up of two glucose molecules.
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Watson and Crick's model explained mutability because bases pairs can suffer changes (mutations) during DNA replication. Moreover, this model also explained stability because DNA strands are held together by hydrogen bonds.
Deoxyribonucleic acid (DNA) is a double helix molecule composed of two long chains of four types of nucleotides, each containing one different nitrogenous base, i.e., Adenine, Guanine, Cytosine and Thymine.
In Watson and Crick's model, both DNA strands are held together by hydrogen bonds between nitrogenous bases on opposite DNA strands, thereby providing stability to the DNA molecule.
In DNA, Guanine always pairs with Cytosine by three hydrogen bonds, while Adenine always pairs with Thymine by two hydrogen bonds.
Moreover, Watson and Crick suggested that mutations could occur as a consequence of a base occurring very infrequently in one of the less likely tautomeric forms during DNA replication, thereby also explaining the mutability of life.
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Every cell has a cytoplasm
Answer:
Pericardial sac has protective tole
Explanation:
Pericardial sac or pericardium is a fibrous tissue that surrounds the heart. It has two coats:
- the outter coat-parietal pericardium
- the inner coat-visceral pericardium or epicardium which is double-layered and contains pericardial fluid between those two layers (pericardial fluid is necessary as a lubricant for the heart movement).
Besides lubrication, percardium also protects heart from infections, fixes it and limits its movements.
