Cells, like humans, cannot generate energy without locating a source in their environment. However, whereas humans search for substances like fossil fuels to power their homes and businesses, cells seek their energy in the form of food molecules or sunlight. In fact, the Sun is the ultimate source of energy for almost all cells, because photosynthetic prokaryotes, algae, and plant cells harness solar energy and use it to make the complex organic food molecules that other cells rely on for the energy required to sustain growth, metabolism, and reproduction (Figure 1).
Cellular nutrients come in many forms, including sugars and fats. In order to provide a cell with energy, these molecules have to pass across the cell membrane, which functions as a barrier — but not an impassable one. Like the exterior walls of a house, the plasma membrane is semi-permeable. In much the same way that doors and windows allow necessities to enter the house, various proteins that span the cell membrane permit specific molecules into the cell, although they may require some energy input to accomplish this task (Figure 2).
Answer:
Scientists were unsure about the last common ancestor between apes and humans because fossils are so scarce, researchers do not know what the last common ancestors of living apes and humans looked like or where they originated.
Explanation:
Answer:
6 moles
Explanation:
Take a look at the balanced chemical equation for this synthesis reaction
N
2(g]
+
3
H
2(g]
→
2
NH
3(g]
Notice that you have a
1
:
3
mole ratio between nitrogen gas and hydrogen gas. This means that, regardless of how many moles of nitrogen gas you have, the reaction will always consume twice as many moles of hydrogen gas.
So, if you have
2
moles of nitrogen taking part in the reaction, you will need
2
moles N
2
⋅
3
moles H
2
1
mole N
2
=
6 moles H
2
Answer:
I believe they deserve to be here.
Explanation:
Answer:
The hydroxyl groups in alcohol molecules are responsible for hydrogen bonding between the alcohol molecules. As greater energy is required to overcome these strong intermolecular forces, the melting points and boiling points of alcohols are higher than those of alkanes with a corresponding chain length