Cell theory is the historic scientific theory, now universally accepted, that living organisms are made up of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pre-existing cells. Cells are the basic unit of structure in all organisms and also the basic unit of reproduction. With continual improvements made to microscopes over time, magnification technology advanced enough to discover cells in the 17th century. This discovery is largely attributed to Robert Hooke, and began the scientific study of cells, also known as cell biology. Over a century later, many debates about cells began amongst scientists. Most of these debates involved the nature of cellular regeneration, and the idea of cells as a fundamental unit of life. Cell theory was eventually formulated in 1839. This is usually credited to Matthias Schleiden and Theodor Schwann. However, many other scientists like Rudolf Virchowcontributed to the theory. It was an important step in the movement away from spontaneous generation.
The three tenets to the cell theory are as described below:
All living organisms are composed of one or more cells.
The cell is the basic unit of structure and organization in organisms.
Cells arise from pre-existing cells.
The first of these tenets is disputed, as non-cellular entities such as viruses are sometimes considered life-forms.
All living things are made of cells. Answer
Answer:
A. Only L-amino acids (except for glycine) are used in proteins.
B. The partial double bond character of the α-C-N bond in the peptide group limits the conformations of the peptide group.
C. Hydrogen bonding within elements of secondary structure stabilize certain atomic geometries.
D. Although any one of 20 amino acids is possible at each position, only one is used.
Explanation:
Proteins are biomolecules composed of one or more chains of amino acid residues which are joined together by peptide bonds (this sequence represents the primary structure of the protein). Proteins are made up of 20 types of amino acids which have diverse properties. The secondary structure of a protein refers to the local structure of the protein backbone, which is stabilized by hydrogen bonding between amino groups (—NH2) and carboxyl groups (—COOH) in neighboring areas of the protein. The most common secondary structures in proteins include alpha helices, beta sheets, and random turns. Moreover, the tertiary structure in proteins describes the packing of these secondary structures. The peptide bond (CO–NH) is a stable covalent bond that has a rigid planar structure and acquires partial double-bond properties, thereby peptide bonds undergo very little rotation (i.e., rotation around peptide bonds is restricted). With the exception of glycine, all amino acids are stereoisomers, i.e., there exist mirror images of their structures which are labeled as L (left-handed) and D (right-handed) in order to differentiate between mirror images. All amino acids in proteins have the L-configuration.
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Answer: (A) a membrane‑bound organelle with stacks of thylakoid discs called grana.
(E) the main site of photosynthesis in a plant cell.
Explanation:
The plant chloroplast is a large organelle, it is bounded by a double membrane like structure that is chloroplast envelop.
The chloroplast consists of chlorophyll pigment which traps the light energy from sun and converts it into chemical energy in the form of ATP. Thus the chloroplast is the main site for photosynthesis. Including the inner and outer membrane structure it also posses the third internal membrane structure which is called as the thylakoid membrane. The thylakoid membrane forms the network of flat discs which are called as thylakoids, the thylakoids are arranged in stacks which are called as grana.
The thylakoid membrane is the center point for the synthesis of ATP through a chemiosmotic process.
50% Not sure how you would draw the punnett square, however heterozygous means different so it would be Ab and homozygous dominant means the same but one is upper case and one is lower case Aa.
AA AA
Aa Aa
