Cell Structure and Function

2. Fat Cells (adipose tissue cells) and other cells look similar 

FALSE

3. What is the reagent used to detect sugar?

Benedict’s Solution

5. What is the difference between glucose and starch? Explain.

      While glucose is a monosaccharide, starch is a polysaccharide. Monosaccharides are simple carbohydrates that act as building blocks for larger carbohydrates. Glucose is the most important carbohydrate fuel in the human body with its molecules metabolized during respiration. Its molecular formula is C6H12O6. The condensation polymerization of monosaccharides leads to the formation of polysaccharides. Starch is made from α-glucose. Starch exists in two forms, amylose and amylopectin, and is usually produced in plants as an energy reserve.           

7. Proteins are made of amino acids. How are they joined and what is the name of the bond? Amino acids in a polypeptide chain are joined to each other by peptide bonds. The bonds are formed through a condensation reaction. The carboxyl group of an amino acid at the end of a polypeptide chain reacts with the amino group of an incoming amino acid. The reaction releases a water molecule resulting in the formation of a peptide bond between the two amino acids.

8. Who has starch, potatoes or onions?

 Potatoes have starch but onions don’t. Onions are primarily made of water with the only form of carbohydrates being simple sugars. This is unlike the case in potatoes which have both simple sugars and complex sugars such as starch.

9. How do fats and oils differ?

Fats and oils are both lipids whose building blocks are fatty acids. The fatty acids join together to form base molecules known as triglyceride. Fatty acids can either be saturated or unsaturated with the latter category being further broken down to mono and polyunsaturated. A triglyceride is called a fat it is a solid at 25ºC. If it is a liquid at that temperature, it is called an oil. The degree of unsaturation and the number of carbon atoms in constituent fatty acids is responsible for the differences in melting points. Triglycerides of plant origin are generally oils while those obtained from animal sources are usually solids.

10. What is the difference between fats and phospholipids? Which one is used to produce energy (ATP)?

Fats are generally composed of glycerol and three fatty acids. Phospholipids, on the other hand, have one of the fatty acids replaced by a phosphate group. As such, they are not regarded as “true fats.” One of the core functions of fats is to store energy. When the body needs extra energy, lipases can break down triglycerides to produce more ATP.

12. What are the 4 major macromolecules present in cells?

Carbohydrates

Lipids

Proteins

Nucleic acids

13. What is the difference between maltose and sucrose? What type of saccharide are they called generally?

Maltose and sucrose are both disaccharides which are the result of the combination of two monosaccharide molecules. Maltose is the result of the combination of two glucose molecules. On the other hand, sucrose is the result of the combination of glucose and fructose. Maltose is also a reducing sugar, with its reactivity leveraged in processes such as the brewing of beer. Sucrose, however, is a non-reducing sugar unlike other disaccharides.

13. Which type of lipid has four fused rings of carbon atoms?

Steroids.

14. When does cytokinesis occur during mitosis?

Cytokinesis is the physical process during which the cytoplasm of the parent cell is divided into two daughter cells. It begins towards the end of the anaphase stage and completes shortly after telophase. The result of the process is two genetically identical daughter cells.

15. Describe interphase. How many steps constitute interphase, describe each step.

The interphase is the first stage of the cell cycle that is responsible for preparing the cell for mitosis. Most of a cell’s time in the cell cycle is spent in this stage. The preparation for division typically happens in three distinct stages: G1 phase, S phase, and G2 phase. The G1 phase, which is also referred to as the first gap phase, is characterized by an increase in mass as the cell prepares for division. As such, besides growing physically larger, the cell also copies organelles and makes molecular building blocks to be used in later steps. The S phase (synthesis phase), on the other hand, is all about the synthesis of DNA. DNA molecules of each chromosome are copied. At the end of the stage, chromosomes have two chromatids. The last stage of interphase is the G2 phase. In this stage the cell grows more and makes proteins and organelles. Cell contents are also reorganized in preparation for mitosis.    

17. Cell division in animals and plants differs only at the last step. Is it true, how?

This is true. Cytokinesis differs essentially due to the different rigidities of the plant and animal cell. In the case of animal cells, which are relatively flexible, a cleavage furrow forms separating the two daughter cells. However, for the rigid plant cell, a cell plate is formed to serve the purpose of separating daughter cells. Another difference is the presence of centrioles in animal cells. They are absent in plant cells.

18. What are centrioles and what is their function?

Centrioles are tube-shaped cell structures that are present in all eukaryotic cells except of plant and fungal cells. They are contained within a structure called the centrosome which is located near the nucleus. Centrioles play an instrumental role in cell division. They replicate during interphase and migrate to opposite poles during prophase. They are the site of the formation of spindle fibers. The centrioles determine the correct orientation of spindle fibers and influence the attachment of chromosomes to spindle fibers. The spindle fibers are responsible for the segregation of chromosomes into the two daughter cells formed by mitosis. After segregation, centrioles determine the position of the cell’s nucleus. In addition, they influence the overall cellular organization.