Biology Unit 1: Water and Molecules

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Questions and Answers

Explain how hydrogen bonds form (explanation must include polar covalent bonds)

Hydrogen bonds form when a slightly positive hydrogen atom in one molecule is attracted to a slightly negative atom (usually oxygen or nitrogen) in another molecule. These attractions are weaker than covalent bonds, but they are crucial for many biological processes, such as holding DNA strands together and stabilizing the structure of proteins.

Define/provide examples of the following properties of water:

Water is a universal solvent. An example is that it has the ability to dissolve a wide variety of substances (correct)
Cohesion is the attraction between 2 of the same substances. An example would be water molecules sticking together. (correct)
The amount of heat needed to raise the temperature of 1 gram of water by 1°C. An example is why water takes a relatively long time to boil. (correct)
This is the attraction of water to a smaller diameter tube. An example is water moving up a plant's stem. (correct)
Water is less dense as a solid than a liquid. An example is ice floating on water. (correct)
Adhesion is the attraction between 2 different substances. An example would be water being attracted to the glass in a graduated cylinder. (correct)

Include an image of the following functional groups:

There is no image provided.

Explain the difference between a dehydration and hydrolysis reactions (be able to recognize an image of each)

Dehydration reactions involve the removal of a water molecule, creating a new bond between monomers. Hydrolysis reactions involve the addition of a water molecule, breaking a bond between monomers. Signup and view all the answers

How does saturation affect fatty acid structure/function?

Saturated fatty acids have no double bonds between carbon atoms, making them straight and tightly packed together. They are generally solid at room temperature and provide more energy per gram. Unsaturated fatty acids have one or more double bonds, making them have kinks and a less packed structure. They are usually liquid at room temperature and are associated with better cardiovascular health. Signup and view all the answers

What determines the primary structure of a protein?

The linear sequence of amino acids in a polypeptide chain determines the primary structure of a protein. Signup and view all the answers

Would the function of a protein change if the amino acid sequence changed? Why or why not?

True (A) Signup and view all the answers

What interactions occur in the (select all that apply):

Quaternary structure occurs when multiple polypeptide chains interact with one another. (A), Tertiary structure occurs due to interactions between R groups. (C), Secondary structure occurs due to hydrogen bonding between amino acids. (D) Signup and view all the answers

What three components make up a nucleotide?

A nucleotide is composed of a phosphate group, a sugar (deoxyribose in DNA or ribose in RNA), and a nitrogenous base. Signup and view all the answers

List the 5 possible nitrogen bases

Cytosine (A), Guanine (B), Thymine (C), Uracil (D), Adenine (E) Signup and view all the answers

What is the difference in how A bonds to T versus C to G?

Adenine (A) forms two hydrogen bonds with thymine (T), while cytosine (C) forms three hydrogen bonds with guanine (G). Signup and view all the answers

Compare and contrast DNA and RNA. 2 comparisons and 4 contrasts

Both DNA and RNA are nucleic acids that carry genetic information. They both consist of nucleotides made up of a phosphate group, a sugar, and a nitrogenous base. However, DNA is double-stranded, while RNA is single-stranded. DNA contains deoxyribose sugar, while RNA contains ribose sugar. DNA uses the nitrogenous base thymine, while RNA uses uracil. DNA stores genetic information, while RNA is involved in protein synthesis. Signup and view all the answers

Identify the main differences between prokaryotic and eukaryotic cells.

Prokaryotic cells lack a nucleus and other membrane-bound organelles, while eukaryotic cells have both. Prokaryotic cells are generally smaller than eukaryotic cells. Prokaryotes have a single circular chromosome, while eukaryotes have multiple linear chromosomes. Prokaryotes reproduce by binary fission, while eukaryotes reproduce by mitosis and meiosis. Signup and view all the answers

Trace the path of a protein, from production to final product

A protein's journey begins at a ribosome, where it is synthesized based on genetic instructions from DNA. From there, it may be transported to the endoplasmic reticulum (ER), where it can be folded and modified. The protein then travels to the Golgi apparatus, where it undergoes further processing, packaging, and sorting. Finally, it is transported to its final destination within the cell or secreted outside the cell. Signup and view all the answers

Identify the function of the following organelles:

Ribosome = Site of protein synthesis Rough ER = Modifies and folds proteins, synthesizes lipids, and detoxifies harmful substances Smooth ER = Synthesizes lipids and steroids; detoxifies harmful substances Golgi = Packages, sorts, and modifies proteins and lipids for export or delivery to other organelles Lysosome = Digests cellular waste and debris Vacuole = Stores water, nutrients, and waste; maintains cell shape and turgor pressure Mitochondria = Powerhouse of the cell; responsible for ATP production through cellular respiration Chloroplast = Site of photosynthesis; converts light energy into chemical energy Signup and view all the answers

Why would an organelle have a highly folded inner membrane (chloroplasts and mitochondria)

A highly folded inner membrane increases the surface area of the organelle, maximizing the efficiency of its function. In chloroplasts, this allows for more efficient light absorption and energy conversion during photosynthesis. In mitochondria, it facilitates a greater surface area for the electron transport chain, maximizing ATP production during cellular respiration. Signup and view all the answers

What happens to the surface area to volume ratio as a cell grows?

As a cell grows, its volume increases at a faster rate than its surface area. Therefore, the surface area to volume ratio decreases. Signup and view all the answers

Do you want a large or small surface area to volume ratio? Why?

A large surface area to volume ratio is preferable because it allows for more efficient exchange of materials between the cell and its surroundings. This is essential for nutrient uptake, waste removal, and maintaining a stable internal environment. Signup and view all the answers

What adaptations do cells have to increase their ratio?

Cells have adaptations like microvilli (finger-like projections) and folds in their membrane to increase their surface area, without significantly increasing their volume. This allows them to maintain a favorable surface area to volume ratio even as they grow. Signup and view all the answers

Calculate the surface area to volume ratio of the following: a) A spherical with a radius of 5 µm b) A cuboidal cell with a side length of 7 µm

a) Surface area of a sphere = 4πr² = 4 * 3.14 * (5 µm)² = 314 µm² Volume of a sphere = (4/3)πr³ = (4/3) * 3.14 * (5 µm)³ = 523.3 µm³ Surface area to volume ratio = 314 µm² / 523.3 µm³ = 0.6 b) Surface area of a cube = 6s² = 6 * (7 µm)² = 294 µm² Volume of a cube = s³ = (7 µm)³ = 343 µm³ Surface area to volume ratio = 294 µm² / 343 µm³ = 0.86 Signup and view all the answers

Identify each letter in the image below (not H-I):

A = Cytoplasm B = Phospholipid bilayer C = Integral Protein D = Peripheral Protein E = Glycoprotein F = Cholesterol G = Hydrophilic head Signup and view all the answers

What molecule embeds itself within the membrane and affects fluidity? How does it affect fluidity?

Cholesterol embeds itself within the phospholipid bilayer, decreasing fluidity at high temperatures by restricting the movement of phospholipids. However, at low temperatures, cholesterol acts as a buffer, preventing the membrane from becoming too rigid by keeping phospholipids loosely packed. Signup and view all the answers

What type of molecules are able to pass through the membrane and why?

Small, nonpolar molecules, such as oxygen and carbon dioxide, can easily pass through the phospholipid bilayer because they are compatible with the hydrophobic interior. However, large, charged molecules, such as ions, require the assistance of transport proteins to cross the membrane because they are repelled by the hydrophobic interior. Signup and view all the answers

Identify the molecules as polar or nonpolar:

Oxygen (D), Carbon dioxide (E) Signup and view all the answers

What are the main differences between passive and active transport?

Passive transport does not require energy and relies on the concentration gradient of molecules to move substances across the membrane. Active transport, on the other hand, requires energy to move substances against their concentration gradient. Signup and view all the answers

Is facilitated diffusion a type of active or passive transport?

False (B) Signup and view all the answers

What molecule is necessary for active transport?

ATP is the molecule that provides the energy needed for active transport processes. Signup and view all the answers

Define the following and explain what would happen to a cell placed in those solutions:

Isotonic solution has the same concentration of solutes inside and outside the cell. There is no net movement of water across the membrane. (A), Hypotonic solution has a lower concentration of solutes outside the cell than inside. A cell placed in a hypotonic solution will gain water and swell, possibly bursting. (B), Hypertonic solution has a higher concentration of solutes outside the cell than inside. A cell placed in a hypertonic solution will lose water and shrink. (C) Signup and view all the answers

If the concentration of NaCl inside a plant cell is 0.45M, which way will water diffuse if the cell is placed in a 0.25M NaCl solution?

Water will diffuse from the 0.25M NaCl solution into the plant cell because the concentration of solutes is higher inside the cell. Signup and view all the answers

The concentration of an NaCl solution is 0.5 M. This solution is in a beaker sitting on your desk in the open air. Calculate the solute potential at 22°C.

The solute potential (ψs) can be calculated using the formula ψs = -iCRT, where i is the ionization constant (2 for NaCl), C is the molar concentration (0.5 M), R is the ideal gas constant (0.0831 L bar/mol K), and T is the temperature in Kelvin (22°C + 273 = 295 K). Therefore, ψs = -2 * 0.5 M * 0.0831 L bar/mol K * 295 K = -24.5 bar. Signup and view all the answers

The molar concentration of a sugar solution is 0.2M. This beaker is sitting on your desk in the open air. Calculate the water potential at 27°C.

The water potential (ψw) can be calculated using the formula ψw = ψs + ψp, where ψs is the solute potential and ψp is the pressure potential. Since the beaker is open to the air, the pressure potential is 0. The solute potential can be calculated using the formula ψs = -iCRT, where i is the ionization constant (1 for sugar), C is the molar concentration (0.2 M), R is the ideal gas constant (0.0831 L bar/mol K), and T is the temperature in Kelvin (27°C + 273 = 300 K). Therefore, ψs = -1 * 0.2 M * 0.0831 L bar/mol K * 300 K = -4.99 bar. The water potential is therefore ψw = -4.99 bar + 0 = -4.99 bar. Signup and view all the answers

Describe the endosymbiotic theory in your own words

The endosymbiotic theory proposes that eukaryotic cells evolved from a symbiotic relationship between ancestral prokaryotic cells. It suggests that mitochondria and chloroplasts, organelles within eukaryotic cells, were once free-living bacteria that were engulfed by larger prokaryotic cells. Over time, these engulfed bacteria became integrated into the host cell, eventually evolving into the organelles we see today. Signup and view all the answers

What evidence is there that supports the endosymbiotic theory?

Several lines of evidence support the endosymbiotic theory, including the fact that mitochondria and chloroplasts have their own DNA and ribosomes, which resemble those found in bacteria. These organelles also undergo independent replication, similar to how bacteria reproduce. Moreover, their size and structure are similar to bacteria, further suggesting their prokaryotic origin. Signup and view all the answers

Flashcards

Hydrogen bond

A type of weak chemical bond formed between a slightly positive hydrogen atom and a slightly negative atom, often oxygen or nitrogen.

Cohesion

The tendency of water molecules to stick together due to hydrogen bonding.

Adhesion

The tendency of water molecules to stick to other surfaces due to hydrogen bonding.

Capillary action

The upward movement of water in narrow tubes or spaces due to the combined forces of cohesion and adhesion.