Consider the following statements
(A) Plant cells have centrioles which are absent in almost all animal cells
(B) Ribosomes are the site of protein synthesis
(C) The middle lamella is a layer made of calcium carbonate which holds the different neighbouring cells together
(D) In animal cell, steroidal hormones are synthesised by smooth endoplasmic reticulum
Of the above statements
Answers
Explanation:
a)Centrioles are absent from the cells of higher plants. When animal cells undergo mitosis they are considered by some to benefit from the presence of centrioles which appear to control spindle fibre formation and which later has an effect on chromosome separation.
B )Ribosomes are the sites in a cell in which protein synthesis takes place. ... Within the ribosome, the rRNA molecules direct the catalytic steps of protein synthesis — the stitching together of amino acids to make a protein molecule. In fact, rRNA is sometimes called a ribozyme or catalytic RNA to reflect this function
c) The middle lamella is a pectin layer which cements the cell walls of two adjoining plant cells together. It is the first formed layer which is deposited at the time of cytokinesis. The cell plate that is formed during cell division itself develops into middle lamella or lamellum.
d). Ribosomes are naked ribonucleoprotein particles found in both pro- and eukaryotic cells. They are involved in protein synthesis. Smooth endoplasmic reticulum (SER) lack ribosomes. SER occurs in adipose cells, muscle cells, glycogen metabolising liver cells, steroid synthesizing cells, retinal cells etc.
Middle lamella is a cementing layer between two plant cells. Pectin is the main component. Middle lamella is chiefly composed of calcium and magnesium pectate (not calcium carbonate).
Centrioles are a characteristic