Bio exam 2

14. The internal solute concentration of a plant cell is about 1.0M. To demonstrate lysis it would be necessary to suspend the cell in what solution?

**0.8M**

9. A cell contains 20 chromatids at the beginning of mitosis. How many chromosomes will it contain at the completion of cytokinesis?

**10**

23. Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein?

**A large polar molecule**

8. Why is energy required for active transport?

**Because it moves solutes against their concentration gradient.**

19. In animal cell mitosis the cleavage furrow forms during which stage of the cell cycle?,

**Cytokinesis**

27. Which of the following occurs in meiosis but not mitosis?

**Homologous chromosomes separate.**

12. __________ are membrane-bound metabolic compartments that specialize in the production of hydrogen peroxide (H2O2) and its conversion to water.

**Peroxisomes**

15. Which of the following phases of mitosis is essentially the opposite of prometaphase in terms of the nuclear envelope?

**Telophase**

17. What is a locus?

**The precise location of a gene on a chromosome.**

4. A cell is placed into a solution and the cell shrinks. Which of the following is true regarding the solution?

**The solution is hypertonic.**

2. Which of the following is correct regarding peripheral proteins?

**These proteins are found only on the surface of the plasma membrane.**

21. Which of the following statements about homologous chromosomes is correct?

**They have genes for the same traits at the same loci.**

28. Sickle-cell anemia is a disease that is caused by __________ in the __________ of the protein.

**a single amino acid change; primary structure**

16. Animal cells have unique organelles called __________ that are composed of structures called __________.

**centrosomes; centrioles**

30. The molecule with four fused rings that is found in animal membranes and is the precursor of vertebrate sex hormones is __________.

**cholesterol**

20. The complex of DNA and protein that makes up a eukaryotic chromosome is properly called __________.

**chromatin**

6. The type of bond that forms to join monomers (such as sugars and amino acids) into polymers (such as starch and proteins) is a(n) __________ bond.

**covalent**

26. Regardless of whether an organism is an animal a plant a fungus or an algal cell all zygotes are __________ and are formed during the __________ of two __________ gametes.

**diploid; fertilization; haploid*

22. Allelic variation is an important source of __________ in a population.

**genetic diversity**

13. Bacterial cells are prokaryotic. Unlike a typical eukaryotic cell they __________.

**have no membrane-bounded organelles in their cytoplasm**

5. The network of fibers that organizes structures and activities in a cell __________.

**is the cytoskeleton**

10. You would know a dividing cell was a plant cell rather than an animal cell if you saw that __________.

**it had formed a cell plate**

11. The endosymbiont theory explains the origins of __________.

**mitochondria and chloroplasts**

18. The lipids that form the main structural component of cell membranes are __________.

**phospholipids**

3. Dye injected into a plant cell might be able to enter an adjacent cell through __________.

**plasmodesmata**

25. Checkpoints in the cell cycle control system __________.

**regulate the cell cycle through a variety of stop-and-go signals**

24. The plasma membrane exhibits selective permeability. This means that __________.

**the plasma membrane allows some substances to flow through it more easily than others**

29. One characteristic shared by sucrose lactose and maltose is that __________.

**they are all disaccharides**

1. At the end of mitosis __________ daughter cells that are genetically __________ are formed while at the end of meiosis __________ daughter cells that are genetically __________ are formed.

**two; identical; four; distinct**

7. In a dehydration synthesis reaction __________ is always formed as a by-product of the reaction.

**water**

Carbohydrate

A biological molecule consisting of carbon, hydrogen, and oxygen atoms, typically in a ratio of 1:2:1. Example: Glucose.

Nucleic acid

A biopolymer composed of nucleotide monomers, essential for all known forms of life. Example: DNA.

Haploid

A cell that contains only one set of chromosomes. Example: Human gametes (sperm and egg cells).

Diploid

A cell that contains two sets of chromosomes, one from each parent. Example: Human somatic cells.

Hydrolysis reaction

A chemical reaction that involves the addition of a water molecule to break a bond within a molecule. Example: Breakdown of a disaccharide into monosaccharides.

Dehydration reaction

A chemical reaction that involves the loss of a water molecule from the reacting molecule. Example: Formation of a peptide bond between amino acids.

Compare and contrast a dehydration reaction with a hydrolysis reaction.

A dehydration reaction involves the removal of a water molecule to join two molecules together, forming a larger molecule. In contrast, a hydrolysis reaction involves the addition of a water molecule to break a bond within a molecule, resulting in two smaller molecules.

What are the molecular differences between a fat molecule and a phospholipid molecule? Which are the basic building units of cell membranes?

A fat molecule, or triglyceride, consists of one glycerol molecule bonded to three fatty acid chains. A phospholipid molecule consists of a glycerol molecule bonded to two fatty acid chains and a phosphate group. Phospholipids are the basic building units of cell membranes due to their amphipathic nature, having both hydrophilic (water-attracting) and hydrophobic (water-repelling) properties.

Lipid

A group of naturally occurring molecules that include fats, waxes, sterols, and fat-soluble vitamins. Example: Triglycerides.

Phospholipid

A lipid containing a phosphate group in its molecule, a major component of cell membranes. Example: Phosphatidylcholine.

Ribosome

A molecular machine that synthesizes proteins. Example: Ribosomes on the rough ER.

Protein

A molecule composed of one or more polypeptides, each folded into a specific three-dimensional structure. Example: Hemoglobin.

Amphipathic

A molecule that has both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts. Example: Phospholipids.

Endoplasmic reticulum

A network of membranes involved in protein and lipid synthesis. Example: Rough ER and smooth ER.

Cytoskeleton

A network of protein fibers that provides structural support and facilitates cell movement. Example: Microtubules.

Extracellular matrix

A network of proteins and carbohydrates outside the cell membrane that provides structural support. Example: Collagen in connective tissue.

Hypertonic

A solution with a higher solute concentration than the cell, causing water to leave the cell. Example: Seawater.

Hypotonic

A solution with a lower solute concentration than the cell, causing water to enter the cell. Example: Distilled water.

Isotonic

A solution with the same solute concentration as the cell, resulting in no net movement of water. Example: Saline solution.

Vacuole

A storage organelle in cells, particularly large in plant cells. Example: Central vacuole in a plant cell.

Chromosome

A structure made of DNA and proteins that contains genetic information. Example: Human chromosome 1.

Nucleolus

A structure within the nucleus where ribosomal RNA is synthesized. Example: Nucleolus in a liver cell.

Triglyceride

A type of fat molecule consisting of one glycerol molecule bonded to three fatty acid chains. Example: Olive oil

Saturated

A type of fatty acid with no double bonds between carbon atoms, resulting in straight chains. Example: Butter.

Unsaturated

A type of fatty acid with one or more double bonds between carbon atoms, resulting in bent chains. Example: Olive oil.

Lysosome

An organelle containing digestive enzymes that break down waste materials. Example: Lysosomes in white blood cells.

Chloroplast

An organelle found in plant cells that conducts photosynthesis. Example: Chloroplasts in leaf cells.

Peroxisome

An organelle that contains enzymes to break down fatty acids and detoxify harmful substances. Example: Peroxisomes in liver cells.

Golgi complex

An organelle that modifies, sorts, and packages proteins and lipids for transport. Example: Golgi apparatus in gland cells.

Eukaryote

An organism whose cells contain a nucleus and other membrane-bound organelles. Example: Humans.

Prokaryote

An organism whose cells lack a nucleus and membrane-bound organelles. Example: Bacteria.

Provide several examples of how cancer cells differ from healthy cells.

Cancer cells differ from healthy cells in several ways: they divide uncontrollably, ignore signals to stop dividing, evade apoptosis (programmed cell death), can invade other tissues (metastasis), and often have abnormal shapes and sizes. Additionally, cancer cells can stimulate the growth of new blood vessels to supply the tumor with nutrients (angiogenesis).

Briefly describe the process of cell fractionation.

Cell fractionation is a laboratory technique used to separate cellular components while preserving their individual functions. It involves breaking cells apart using a blender or homogenizer, then using centrifugation to separate the different organelles based on their size and density.

Describe three reasons why cells go through division.

Cells divide for growth, to replace damaged or dead cells, and for reproduction. Growth involves increasing the number of cells to allow an organism to grow larger. Replacing damaged or dead cells helps maintain the health and function of tissues. Reproduction, particularly in single-celled organisms, allows for the creation of new individuals.

What are cilia and flagella? Where would you find examples of each in your body?

Cilia are short, hair-like structures that move fluid or mucus over the surface of a cell. Flagella are longer, whip-like structures that propel a cell through its environment. In the human body, cilia can be found in the respiratory tract, while flagella are found on sperm cells.

Discuss the primary physical and molecular differences between the nucleotide polymers DNA and RNA.

DNA (deoxyribonucleic acid) is a double-stranded molecule with a long-term storage role for genetic information, consisting of deoxyribose sugar, phosphate groups, and four nitrogenous bases (adenine, thymine, cytosine, and guanine). RNA (ribonucleic acid) is typically single-stranded and plays various roles in gene expression, consisting of ribose sugar, phosphate groups, and four nitrogenous bases (adenine, uracil, cytosine, and guanine).

What are genomics and bioinformatics?

Genomics is the study of the complete set of DNA (the genome) in an organism, including its structure, function, evolution, and mapping. Bioinformatics is the application of computational tools and techniques to analyze and interpret biological data, particularly large datasets generated by genomic studies.

Explain in detail the mechanism and process that will cause red blood cells to lyse in a hypotonic solution.

In a hypotonic solution, the concentration of solutes outside the red blood cells is lower than inside the cells. Water moves into the cells by osmosis to balance the solute concentrations. As water enters, the cells swell and may eventually burst, or lyse, due to the increased internal pressure.

How does interphase of the cell cycle differ from the mitotic stage?

Interphase is the phase of the cell cycle where the cell grows, replicates its DNA, and prepares for division. It consists of three stages: G1 (cell growth), S (DNA synthesis), and G2 (preparation for mitosis). The mitotic stage, on the other hand, is when the cell actually divides, consisting of mitosis (division of the nucleus) and cytokinesis (division of the cytoplasm).

What are the characteristics of molecules that pass easily through a cell's lipid bilayer and those that do not? What is it that makes the bilayer "selective" in permeability?

Molecules that pass easily through the lipid bilayer are typically small, nonpolar, and hydrophobic, such as oxygen and carbon dioxide. Molecules that do not pass easily are usually large, polar, or charged, such as ions and glucose. The bilayer is "selective" in permeability due to the hydrophobic interior of the phospholipid bilayer, which repels polar and charged molecules while allowing nonpolar molecules to pass through.

How do monosaccharides disaccharides and polysaccharides differ? Give an example of each.

Monosaccharides are the simplest form of carbohydrates, consisting of a single sugar molecule, such as glucose. Disaccharides are composed of two monosaccharide molecules bonded together, such as sucrose (table sugar). Polysaccharides are complex carbohydrates made up of many monosaccharide units linked together, such as starch.

Chromatid

One of two identical halves of a replicated chromosome. Example: Sister chromatids during metaphase.

Mitochondria

Organelles that produce energy through cellular respiration. Example: Mitochondria in muscle cells.

What primarily differentiates passive and active transport in cells?

Passive transport does not require energy and involves the movement of molecules down their concentration gradient, such as diffusion and osmosis. Active transport requires energy, usually in the form of ATP, and involves the movement of molecules against their concentration gradient, such as the sodium-potassium pump.

Compare and contrast phagocytosis pinocytosis and receptor-mediated endocytosis.

Phagocytosis is the process by which a cell engulfs large particles or cells, forming a phagosome. Pinocytosis is the process by which a cell engulfs extracellular fluid and its dissolved solutes, forming a vesicle. Receptor-mediated endocytosis is a selective process where specific molecules bind to receptors on the cell surface, triggering the formation of a vesicle to bring the molecules into the cell.

How do the extracellular (exterior to the cell membrane) components of plant and animal cells differ?

Plant cells have a rigid cell wall made of cellulose that provides structural support. Animal cells lack a cell wall but have an extracellular matrix composed of proteins and carbohydrates that provides support and facilitates cell communication.

Tonicity

The ability of a solution to cause a cell to gain or lose water. Example: Hypertonic, hypotonic, and isotonic solutions.

Chromatin

The complex of DNA and proteins that make up chromosomes in the nucleus of a cell. Example: Chromatin in the nucleus during interphase.

Nucleus

The control center of a cell containing DNA. Example: Nucleus in a neuron.

Osmosis

The diffusion of water across a selectively permeable membrane. Example: Water moving into a plant cell.

Cytokinesis

The division of the cytoplasm to form two separate daughter cells after mitosis. Example: Cytokinesis in plant cells involves the formation of a cell plate.

Explain the endosymbiont theory. What evidence supports this theory?

The endosymbiont theory suggests that mitochondria and chloroplasts originated from free-living prokaryotes that were engulfed by an ancestral eukaryotic cell. Evidence supporting this theory includes the fact that mitochondria and chloroplasts have their own DNA, similar to bacterial DNA, and they replicate independently of the cell.

Explain the fluid mosaic model used to describe the structure of cell membranes.

The fluid mosaic model describes the cell membrane as a flexible layer made of lipid molecules interspersed with large protein molecules that act as channels through which other molecules enter and leave the cell. The "fluid" part refers to the phospholipid bilayer, which is flexible and allows the movement of proteins within it, while the "mosaic" part refers to the pattern produced by the scattered protein molecules when viewed from above.

Plasma membrane

The lipid bilayer that surrounds a cell, controlling the movement of substances in and out. Example: Plasma membrane of a red blood cell.

Secondary structure

The local folded structures that form within a polypeptide due to hydrogen bonding. Example: Alpha helices in keratin.

Active transport

The movement of molecules across a cell membrane using energy, typically against their concentration gradient. Example: Sodium-potassium pump.

Share some key facts about the nucleus.

The nucleus is the control center of the cell, containing most of the cell's genetic material in the form of DNA. It is surrounded by a double membrane called the nuclear envelope, which has pores to allow the exchange of materials between the nucleus and the cytoplasm.

Tertiary structure

The overall three-dimensional shape of a single polypeptide chain. Example: The globular structure of myoglobin.

Diffusion

The passive movement of molecules from an area of high concentration to an area of low concentration. Example: Oxygen diffusing into cells.

Describe each of the four levels of protein structure. Be sure to include a description of the molecular interactions that stabilize each level of structure.

The primary structure of a protein is its unique sequence of amino acids. The secondary structure refers to local folded structures that form within a polypeptide due to hydrogen bonding, such as alpha helices and beta sheets. The tertiary structure is the overall three-dimensional shape of a single polypeptide chain, stabilized by various interactions including hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges. The quaternary structure is the arrangement of multiple polypeptide chains into a functional protein complex, stabilized by similar interactions as the tertiary structure.

Exocytosis

The process by which a cell expels materials by fusing a vesicle with the plasma membrane. Example: Secretion of neurotransmitters.

Endocytosis

The process by which a cell takes in materials by engulfing them in a vesicle. Example: Phagocytosis.

Compare and contrast the structures and functions of rough and smooth ER.

The rough endoplasmic reticulum (ER) has ribosomes on its surface, making it appear "rough," and is involved in protein synthesis and modification. The smooth ER lacks ribosomes, appears "smooth," and is involved in lipid synthesis, detoxification, and calcium storage.

Primary structure

The sequence of amino acids in a protein. Example: The amino acid sequence of insulin.

What ultimately limits the size of cells? Explain.

The size of cells is ultimately limited by the surface area-to-volume ratio. As a cell grows, its volume increases faster than its surface area, making it difficult for the cell to efficiently exchange materials with its environment.

Metaphase

The stage of mitosis where chromosomes line up in the middle of the cell. Example: Metaphase in a dividing cell.

Anaphase

The stage of mitosis where sister chromatids are pulled apart to opposite ends of the cell. Example: Anaphase in a dividing animal cell.

Quaternary structure

The structure formed by the assembly of multiple polypeptide chains into a functional protein complex. Example: Hemoglobin.

Endosymbiont Theory

The theory that mitochondria and chloroplasts originated from free-living prokaryotes. Example: Mitochondria in animal cells.

The textbook states that a "cell is a living unit greater than the sum of its parts." What does that mean?

This means that a cell's functionality and life processes arise from the complex interactions of its various components, which work together in a coordinated manner to sustain life, making the cell more than just a collection of individual parts.