13 other than using a catalyst, how can a reaction be sped up?
14 which of the following is a carbohydrate? (circle the carbohydrate(s))
a nh₃ b co₂ c c₂h₄o d c₆h₁₂o₆ e c₃h₆o₃
15 what kind of reaction is used for building disaccharides, polysaccharides, fats, and proteins? what kind of reaction can break these substances down?
16 which of the following is an acid? (circle the acid(s))
a. chemical structure b. chemical structure c. chemical structure
17 describe the ph scale and what it measures.
18 what are steroids? how do they differ from fats? describe two functions they have in cells.
19 what are the basic building blocks of proteins, lipids, and polysaccharides?

Question

13 other than using a catalyst, how can a reaction be sped up?
14 which of the following is a carbohydrate? (circle the carbohydrate(s))
a nh₃  b co₂  c c₂h₄o  d c₆h₁₂o₆  e c₃h₆o₃
15 what kind of reaction is used for building disaccharides, polysaccharides, fats, and proteins? what kind of reaction can break these substances down?
16 which of the following is an acid? (circle the acid(s))
a. chemical structure  b. chemical structure  c. chemical structure
17 describe the ph scale and what it measures.
18 what are steroids? how do they differ from fats? describe two functions they have in cells.
19 what are the basic building blocks of proteins, lipids, and polysaccharides?

Accepted Answer

### Question 14: Which of the following is a carbohydrate?
# Brief Explanations:
Carbohydrates have the general formula $ C_n(H_2O)_m $, or can be represented as having a ratio of carbon, hydrogen, and oxygen where hydrogen to oxygen is approximately 2:1 (like in monosaccharides, disaccharides, polysaccharides). Let's analyze each option:
- Option a: $ NH_3 $ is ammonia, not a carbohydrate (no C, H, O in the carbohydrate - typical ratio).
- Option b: $ CO_2 $ is carbon dioxide, not a carbohydrate (no hydrogen in the 2:1 ratio with oxygen).
- Option c: $ C_2H_4O $ - the ratio of H:O is 4:1, not 2:1, so not a typical carbohydrate.
- Option d: $ C_6H_{10}O_5 $ - The ratio of H:O is $ 10:5 = 2:1 $, which fits the carbohydrate formula (polysaccharides like cellulose or starch can have this formula).
- Option e: $ C_3H_8O_3 $ - The ratio of H:O is $ 8:3\approx2.67:1 $, not 2:1, so not a typical carbohydrate.
# Answer: d. $ C_6H_{10}O_5 $

### Question 15: Reaction for building and breaking substances
# Brief Explanations:
- **Building (Synthesis) Reaction**: For building disaccharides (from monosaccharides), polysaccharides (from monosaccharides), fats (from fatty acids and glycerol), and proteins (from amino acids), a dehydration synthesis (or condensation) reaction is used. In this reaction, a water molecule is removed as two smaller molecules are joined together.
- **Breaking (Decomposition) Reaction**: To break these substances down, a hydrolysis reaction is used. In hydrolysis, a water molecule is added to break the bond between the subunits (e.g., breaking a disaccharide into two monosaccharides by adding a water molecule to the glycosidic bond).
# Answer: Building: Dehydration synthesis (condensation) reaction; Breaking: Hydrolysis reaction

### Question 16: Which of the following is an acid?
# Brief Explanations:
An acid is a substance that can donate a proton ($ H^+ $) or has a carboxyl group ($ -COOH $) which can ionize to release $ H^+ $. Let's analyze the structures:
- Option a: The structure is ethanol ($ C_2H_5OH $), it has a hydroxyl group ($ -OH $) but does not readily donate $ H^+ $ as an acid (it's an alcohol).
- Option b: The structure is acetaldehyde ($ CH_3CHO $), it has a carbonyl group ($ C = O $) and no carboxyl group, so it's not an acid.
- Option c: The structure has a carboxyl group ($ -COOH $) (the $ -C( = O)-OH $ group). Carboxylic acids can donate $ H^+ $ from the carboxyl group, so this is an acid (like acetic acid if we consider the structure $ CH_3COOH $ - here the structure is similar with a methyl group and a carboxyl group).
# Answer: c (the structure with $ -C( = O)-OH $ group)

### Question 17: Describe the pH scale and what it measures
# Brief Explanations:
- **pH Scale Range**: The pH scale ranges from 0 to 14.
- **Neutral Point**: A pH of 7 is considered neutral (e.g., pure water at 25°C has a pH of 7, where the concentration of $ H^+ $ ions ($ [H^+] $) is equal to the concentration of $ OH^- $ ions ($ [OH^-] $), $ [H^+]=[OH^-] = 1\times10^{-7}\ M $).
- **Acidic Range**: pH values less than 7 are acidic. In acidic solutions, the concentration of $ H^+ $ ions is greater than the concentration of $ OH^- $ ions ($ [H^+]>[OH^-] $). As the pH decreases from 7 to 0, the acidity increases (e.g., pH 1 is more acidic than pH 3).
- **Basic (Alkaline) Range**: pH values greater than 7 are basic (alkaline). In basic solutions, the concentration of $ OH^- $ ions is greater than the concentration of $ H^+ $ ions ($ [OH^-]>[H^+] $). As the pH increases from 7 to 14, the basicity increases (e.g., pH 13 is more basic than pH 9).
- **What it Measures**: The pH scale measures the concentration of hydrogen ions ($ H^+ $) in a solution. Mathematically, $ pH=-\log_{10}[H^+] $, where $ [H^+] $ is the molar concentration of hydrogen ions.
# Answer: The pH scale ranges from 0 - 14. pH 7 is neutral (equal $ [H^+] $ and $ [OH^-] $). pH < 7 is acidic ($ [H^+]>[OH^-] $), pH > 7 is basic ($ [OH^-]>[H^+] $). It measures the hydrogen ion ($ H^+ $) concentration in a solution (via $ pH = -\log_{10}[H^+] $).

### Question 18: What are steroids? How do they differ from fats? Two functions in cells
# Brief Explanations:
- **What are Steroids?**: Steroids are a type of lipid characterized by a carbon skeleton with four fused rings (three six - membered rings and one five - membered ring). Examples include cholesterol, hormones like estrogen and testosterone.
- **Difference from Fats**:
    - **Structure**: Fats (triglycerides) are composed of glycerol and three fatty acid chains. Steroids have a four - ringed carbon structure, while fats have a glycerol - fatty acid ester structure.
    - **Function and Role in Energy Storage**: Fats are mainly used for energy storage and insulation. Steroids are not used for energy storage; they have more regulatory and structural roles.
- **Two Functions in Cells**:
    - **Structural Role**: Cholesterol (a steroid) is a component of cell membranes. It helps to maintain the fluidity and integrity of the cell membrane.
    - **Hormonal Role**: Steroid hormones (e.g., estrogen, testosterone) act as chemical messengers. They regulate various physiological processes such as growth, development, and reproduction (e.g., testosterone is involved in male sexual development and muscle growth; estrogen is involved in female sexual development and the menstrual cycle).
# Answer:
- Steroids: Lipids with 4 fused carbon rings (3 six - membered, 1 five - membered).
- Difference from fats: Fats = glycerol + 3 fatty acids (energy storage); Steroids = 4 - ringed structure (regulatory/structural, not energy storage).
- Two functions: 1. Structural (e.g., cholesterol in cell membranes). 2. Hormonal (e.g., estrogen/testosterone regulate growth/reproduction).

### Question 19: Basic building blocks of proteins, lipids, and polysaccharides
# Brief Explanations:
- **Proteins**: The basic building blocks of proteins are amino acids. There are 20 different amino acids that can be linked together via peptide bonds to form proteins.
- **Lipids (Fats)**: The basic building blocks of fats (triglycerides, the most common type of fat) are glycerol (a three - carbon alcohol with three hydroxyl groups) and fatty acids (long - chain carboxylic acids). For other types of lipids like phospholipids, the building blocks also include a phosphate group in addition to glycerol and fatty acids (or a similar alcohol - fatty acid structure).
- **Polysaccharides**: The basic building blocks of polysaccharides are monosaccharides. For example, starch and glycogen are polysaccharides made up of glucose monomers; cellulose is a polysaccharide made up of glucose monomers (with a different linkage).
# Answer:
- Proteins: Amino acids.
- Lipids (fats): Glycerol and fatty acids (for triglycerides).
- Polysaccharides: Monosaccharides (e.g., glucose for starch, glycogen, cellulose).

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QUESTION IMAGE

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Explanation:

Question 14: Which of the following is a carbohydrate?

Answer:

Question 15: Reaction for building and breaking substances