Question

Selectively permeable membranes allow

• A.ANY substance to enter but nothing can leave
• B.ANY substance to leave but nothing can enter
• C.some substances to move in/out and others are prohibited from entering/leaving
• D.nothing to enter or leave

Plasma membranes are made ONLY of a bilayer of phospholipid molecules with no other moecules embedded in it or attached to it.

true or false

Each substance diffuses along its own concentration gradient.

true or false

Active transport requires an input of energy

true or false

Which type of organism conducts photosynthesis?

• A.photosynthetic autotrophs
• B.heterotrophs
• C.both A and B

Answer 1

1. C

Selectively permeable membrane the one which regulate the entry and exit of molecules across the surface of the cell. It allows and prohibits the entry and exit of the molecules. The entry and exit of molecules depends upon their requirement on both the sides of the membrane.

2. False

Plasma membrane is made up of phospholipids and proteins. One molecule of phospholipid is made up of one phosphate group, glycerol and fatty acids. There are two types of proteins, integral membrane proteins and peripheral membrane proteins.

Integral membrane protein are embedded inside the membrane and span both the surfaces of the membrane Where are peripheral membrane proteins are present at one side of the membrane.

3. A

Photosynthesis is performed only by organisms called as autotrophs. They contain special pigment molecules and in the presence of Sunlight they fix atmospheric carbon dioxide into glucose.

Heterotrophic organisms are those which cannot prepare their own food and depend upon autotrophs and other organisms.

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