Cell Biology and Structure

Dermatogen is also known as protoderm which further divides to form the three dermal layer which is epidermis, endodermis and hypodermis. These form the protective layer of the plant. Epidermis is the outer layer which mainly bears small opening known as stomata.
Therefore, the correct answer is option B.

• Scab is a collection of dried blood cells and serum and sits on top of the skin surface.
• The outermost layer of our skin is composed of epithelial cells. As wounds heal, epithelial cells regenerate across the wound surface from the edges to close the wound. 
  
• The Epidermal growth factor induces the epithelial cells below the scab to undergo mitosis and facilitates closure of the wound.
• So, the correct answer is 'Epidermal growth factor'.

Bacteria perform respiration via the cytoplasmic membrane, while cyanobacteria use specialized extensions of the plasma membrane called mesosomes. Eukaryotic cells utilize mitochondria for cellular respiration.

• Sarcoplasm is the cytoplasm of a myocyte (muscle fibre, muscle cell).
•  It is comparable to the cytoplasm of other cells, but it contains unusually large amounts of glycosomes (granules of stored glycogen) and significant amounts of myoglobin, an oxygen-binding protein. Hence, the Cytoplasm of a muscle cell is sarcoplasm.

Mitochondria and the nucleus are both organelles enclosed by a double membrane system. Golgi bodies and endoplasmic reticulum are single-membrane bound.

Both prokaryotic cells (like bacteria) and plant cells possess a cell wall, although the chemical composition differs (peptidoglycan vs cellulose).

RBC (red blood cell) of the human is the best material for the study of structure of cell membrane. Chemical studies on the RBC cell membrane enabled the scientists to infer the possible structure of plasma membrane.

A typical cell is composed of the plasma membrane (boundary), the cytosol (fluid matrix), and various organelles (functional structures).

Yellow cells (chloragogen cells) in oligochaetes and polychaetes are specialized cells found in the coelomic fluid that accumulate waste products, functioning similarly to a liver.

Plants are autotrophic organisms which manufacture their own food. Plant cells have chlorophyll containing chloroplasts which are involved in the process of photosynthesis. A plant cell is surrounded by cellulosic cell wall which is dead at maturity. Chloroplasts and cellulosic cell wall are characteristics of plant cells only.

Most of the energy is produced in the mitochondria through the process of oxidative phosphorylation during aerobic respiration. Hence, mitochondria is called powerhouse of cell. Energy is also produced through glycolysis and anaerobic fermentation in cytoplasm but major energy production occurs in mitochondria through aerobic respiration. Chloroplasts have green pigment chlorophyll and carry out the process of photosynthesis which results in production of sugars. This sugar forms food for plant themselves and all the heterotrophic organism. Hence, chloroplast are called 'Kitchen of cell'.

Mitochondria and chloroplasts are unique cell organelles in a eukaryotic cell. Both are double membraned, contain DNA, have their own ribosomes and protein synthesizing machinery. They are semi-autonomous entities. The ribosomes of these organelles resemble prokaryotic ribosomes. These characteristics are seen as an evidences supporting the endosymbiotic theory. The theory of endosymbiosis  postulates that chloroplasts and mitochondria are the result of evolution initiated by the endocytosis of bacteria and blue - green algae. According to this theory, blue green algae and bacteria were not digested; they became symbiotic instead. This concept has been expressed by the phrase, 'A Cell within a cell'. 

In a eukaryotic cell, energy transformation reactions majorly occur in cytoplasm, mitochondria and chloroplast. In cytoplasm, the energy is captured and used to produce ATP by substrate level phosphorylation during glycolysis. In mitochondria, the energy is captured and used to produce ATP by oxidative phosphorylation. In chloroplasts, the energy is captured and used to produce ATP by photophosphorylation. Thus, two cell organelles involved in energy transformation reactions are chloroplast and mitochondria.

Both chloroplast and mitochondria were once independent free living organisms and later on became lodged in eukaryotic cells as endosymbionts. This hypothesis is supported by many evidences example both of these organelles are surrounded by double membranes, have their own DNA which is circular like prokaryotic chromosome, have their own ribosomes which are 70S type like prokaryotic ribosomes and are not dependent on nucleus for their multiplication but can increase in number by fission like bacteria.

Chloroplasts have internal membranes called thylakoids suspended in ground substance called stroma. The thylakoids are of two types : appressed and non-appressed. The appressed membranes are stacked like a pile of coins called grana. The thylakoid membranes enclose small chambers. This thylakoid membrane system is absent in mitochondria. In mitochondria, the inner mitochondrial membrane is folded into cristae.