The cell membrane is also called selectively permeable membrane for the sole reason being it is selective in nature.
It forms a physical barrier and as a barrier between the cell and the external environment as it allows only selected necessary molecules to pass through it and at the same time prevents entry of unwanted / unnecessary substances.
It also regulates the entry and exit of molecules into and out of the cell.
The cell membrane permits the entry of vital molecules like
<span>water, oxygen, amino acids and glucose into the cell as they are crucial for various life processes and at the same time metabolic waste products are expelled through the cell membrane.</span>
It may be c, if not you can punch me in the face.
Answer:Mass of bullet, m=20g= 0.02kg
Velocity of bullet, v=100m/s
Mass of gun, M=5kg
Let recoil velocity of gun =V
Before firing, the system (gun+bullet) is at rest, therefore, initial momentum of the system =0
Final momentum of the system = momentum of bullet + momentum of gun
=mv+MV=
=2+5v
we know Final momentum = Initial momentum
i.e., 2+5v=0
5V=−2
v=-0.4m/s
Negative sign shows that the direction of recoil velocity of the gun is opposite to the direction of the velocity of the bullet.
Answer:
an object that goes boing boing
Explanation:
because I said so
Answer:
b. Small stagnant pools do not provide enough water to dilute ammonia, which is toxic.
Explanation:
Amongst urinary waste products which are ammonia, urea and uric acid, ammonia is the most toxic, then comes urea which is mildly toxic while uric acid is the least toxic. Various organisms excrete these urinary wastes as per their habitat/adaptations. These waste products have some advantages and some disadvantages over each other. For example, ammonia is extremely toxic so it cannot be retained in the body for a longer time but it requires very less energy to produce ammonia than to produce urea that is why most of the aquatic animals excrete ammonia as urinary waste to save their energy and keep on urinating frequently because they live in water all the time. In a large water pool, excreting this ammonia does not cause toxicity because it gets diluted in the surrounding easily.
In contrast to this, land inhabiting animals like mammals prefer to excrete urea as urinary waste even if they have to spend more energy/ATP to convert ammonia into urea with the help of urea cycle. Land animals have to retain urinary waste products in their body for a longer time as compared to aquatic animals and this is the reason why they urinate less frequently because urea being less toxic can be retained in the body for a longer time.
But african lungfish is an exception to other aquatic animals when it comes to producing urinary waste because they live in small stagnant pools of fresh water and if they will excrete ammonia as waste it will make the habitat toxic leading to their death.
