Answer:
b. a semi-permeable double layer of phospholipids that have hydrophilic heads and hydrophobic tails
Explanation:
B is correct as the cell membrane is selectively semi-permeable. It is selectively semi-permeable because this quality allows it to control what can and can't enter the cell, and how it does so.
The cell membrane also has a phospholipid bi-layer comprised of a double layer of phospholipids which have hydrophilic head and hydrophobic tails. This is because the heads are made of phosphate and are polar and are therefore attracted to water (hydrophilic), while the tails are made of lipids (i.e. fats, oils) which do not mix with water and are therefore hydrophobic.
The properties of each phospholipid is also why they form the double layer structure, the hydrophilic heads naturally face outwards into the water and protect the hydrophobic tails on the inside.
Hope this helped!
Answer:
any of numerous complex proteins that are produced by living cells and catalyze specific biochemical reactions at body temperatures
Answer:
STEM CELLS
They serve as a repair system for the body.
Answer:
in the S phase of the cell cycle
Explanation:
<em>Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have 1.5 times more DNA than G1 phase cells. The cells of this group are _____.</em>
The cell cycle has two main stages which is the interphase and the M phase.
While the M phase is characterized by active division, the interphase consists of G0 phase which is entirely a resting phase for cells that do not need to divide ordinarily, G1 phase which is a phase for cell drowth and development, S phase which is a phase for DNA synthesis or replication and G2 phase which is a phase for protein synthesis.
Hence, cells in the S phase and G2 phase of the cell cycle are expected to have more DNA than cells in the G0 and G1 phase.
<em>Essentially, the amount of DNA is doubled in the S phase. Therefore, if the cell group have 1.5 times more DNA than G1 phase cells, it means the cells are still in S phase.</em>
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