Why are penicilins often more effective against gram-positive bacteria than gram-negative bacteria?

Because Gram negative bacteria have an extra protective layer of lipopolysaccharide surrounding their cell wall!

Explanation:

Mechanism of action of penicillin is:

Effect on gram negative :

As you can see in the image, the gram negative bacteria has an extra layer of protection on its cell wall by lipopolysaccharide. Penicillin can't reach the cell wall to bind to the D-D Transpeptidase, so it is more effective on gram positive bacteria than gram negative bacteria.

x = -6.5

explanation:

with this editor, you should be careful to put what you mean. 5/(2x - 7) = 3/(4x +14) is the way i will interpret it. cross multiply

5*(4x + 14) = 3*(2x - 7)       remove the brackets

20x + 70 = 6x - 21             add 21 to both sides

20x+ 70+21= 6x                 combine

20x + 91 = 6x                     subtract 20x

20x-20x+91=6x-20x           combine

91 = - 14x

x = - 91/14

x = - 6.5

answer: the answer is d.

explanation: this is because when you exercise you make your muscle produce a certain liquid, that does not evaporate it.   also when you exercise you do not reduce muscle fiber.   and it does not really control your twitch that much.