24.
which is not true of lipids?

they supply cells with energy.

they supply cells with nitrogen.

they form structural parts of cell membranes.

the carry fat-soluble vitamins to cells.

25.
paper is made from wood pulp. what carbohydrate makes up paper?

starch

cellulose

sucrose

glycogen

26.
which type of molecules does the body use to build and repair muscle tissue?

lipids

proteins

nucleic acids

carbohydrates

27.
why are enzymes important to cells?

they form the two layers of membranes.

they provide structural support.

they store large quantities of energy.

they bring about chemical reactions.

28.
what holds the two strands of a dna molecule to each other?

peptide bonds

hydrogen bonds

single carbon bonds

double carbon bonds

29.
what polysaccharide do plants store in plastids?

glycogen

lactose

starch

cellulose

30.
what is a complete protein?

it has at least three of the essential amino acids.

it has all nine of the essential amino acids.

it has all twenty of the essential amino acids.

it has all eleven of the amino acids produced in the body.

The correct options are as follows:
24. THEY SUPPLY CELL WITH NITROGEN.
Lipid is one of the classes of food that are very essential for humans' health. There are different types of lipids and they have a lot of vital roles which they play in the human system. The functions of lipids include the following: they form a structural part of the cell membranes, they provide cells with energy, they carry fat soluble vitamins to the body cells, they keep the body warm, they serve as shock absorber to some organs in the body, etc.
Lipids do not supply the body cells with nitrogen.

25. CELLULOSE.
There are different types of carbohydrate, some are found in animals only, some are found in plants only while some are found in both plants and animals. Cellulose is a type of carbohydrate that is found only in plants. Paper is usually made from wood pulp, which is derived from plants, thus the type of carbohydrate found in paper is cellulose.

26. PROTEINS.
Protein is one of the classes of food, which are very essential for human health. We have basically twenty different types of proteins and these proteins are formed from amino acids.Some of the proteins are described as non essential because we do not need to consume them in our food, they are already present in adequate amount in our bodies. Some are describe as essential because we need to eat them in our food. Proteins are the ones that are responsible for building new tissues and repairing injured ones. They also serves as enzymes, which speed up the rate of biochemical reactions in our bodies.

27. THEY HELP BRING ABOUT CHEMICAL REACTIONS
Enzymes are biological catalysts which speed up the rate of biochemical reactions in our body. Each biochemical reaction has its own specific enzymes. Without enzymes the body will not be able to digest eaten food in record time and this will lead to cell death and the eventual death of the concerned organism. 

28. HYDROGEN BOND
DNA belongs to the class of nucleic acids, nucleic acids are made up of many nucleotide which are joined together. A nucleotide is made up of phosphate, nitrogenous bases and a five carbon sugar molecule. A strand of DNA is made up of nucleotides that are joined together by phosphodiester bonds. A DNA molecule is made up of two strands of nucleotides that are twisted to form a double helix, it is the hydrogen bonds that hold the two strands together.

29. STARCH.
Plastids refers to the small organelles that are found inside the plant cytoplasm which contains food molecules. Plants typically store starch molecules inside the plastids. This is because, the food molecules that are manufactured by plants through photosynthesis are normally store in plants in form of starch. Animals and humans use this starch as food in order to produce energy for body use.

30. IT HAS ALL NINE OF THE ESSENTIAL AMINO ACIDS.
As I mentioned earlier, there are some amino acids which are considered to be essential proteins, we must consume these proteins in our foods because our bodies can not synthesize them. The protein are nine in number and they are: valine, tryptophan, phenylalanine, threonine, methionine, leucine, isoleucine, lysine and histidine. 
A complete protein is a protein that consist of all these nine proteins.

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