Answer:
<u>d. Transport proteins within the membrane serve as a tunnel for molecules to enter the cell.
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Explanation:
Solutes are typically moved across the cell through either passive or active transport. The cells, surrounded by a bilipid layer or plasma membrane is amphiphlic- its polar, hydrophilic lipid heads face outwards, while their non-polar hydrophobic lipid tails face inwards towards each other.
While lipid-soluble molecules move across the layer easily, it is also difficult for charged and also large molecules to move across its surface, into the cell. Transmembrane channels, <u>embedded within the membrane</u>, help to maintain selective permeability as transport proteins, pores and gated channels. Simple diffusion happens as a method of passive transport in cells through plasma membranes.
The solutes travel through the plasma membrane in the process of diffusion from regions of high concentration to regions of low concentration; this occurs without the use of energy. <u>Molecules moving against their concentration require active transport mechanism to cross the membrane</u>.
Answer:
Sarcomere
Explanation:
The muscle fiber / myofibrils consist of 2 types of filaments - actin and myosin. The myosin filaments are thick filament whereas the actin filaments are the thin filament.
In addition to this, the muscles have A-band and I-bands. These bands give the muscles alternate light and dark colour band structure. In the A-band, myosin filaments are present, whereas in the I - band the actin filaments are found.
In I-band 2 Z-lines are located. The area between the Z-lines is called sarcomere. In this sarcomere region both actin and myosin filaments present.
When muscles get contracted the length of the sarcomere shorten. The actin and myosin filaments overlap in this area. A cross-bridge form between them, with the help of filamentous protein titin.
P<span>ituitary hormones:
1. Act on breasts to induce milk production.
2. Make you sweat.
3. Can cause weight gain.
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People who have leukemia, a cancer that affects white blood cells, are often given Cytrabine. This drug inhibits the synthesis of DNA.
S-phase of cell cycle is most affected by Cytrabine because cytrabine interfers with synthesis of DNA and we know that in S-phase of cell cycle synthesis of DNA takes place.
