Biology Chapter on Macromolecules

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Questions and Answers

What is a limitation of the light microscope?

It can view fine details inside cells.

It can only magnify up to 1000x. (correct)

It requires dead organisms for observation.

It cannot observe any organisms.

Which characteristic is specific to prokaryotic cells?

Presence of chloroplasts.

Presence of a nucleus.

Complex membrane-bound organelles.

Nucleoid region containing chromosomes. (correct)

What is an advantage of using a transmission electron microscope?

It provides a 3D view of specimens.

It allows observation of living organisms.

It can reveal internal structures in fine detail. (correct)

It can view the surface morphology of specimens.

Which component is NOT found in animal cells?

Cell wall. Signup and view all the answers

What is the primary function of ribosomes in cells?

Synthesize proteins. Signup and view all the answers

What role do the pores of the nuclear envelope play?

They allow RNA and DNA to exit the nucleus. Signup and view all the answers

What is a key characteristic of eukaryotic cells?

Presence of membrane-bound organelles. Signup and view all the answers

What is a disadvantage of the scanning electron microscope?

It cannot visualize internal structures. Signup and view all the answers

What is the primary difference between a monomer and a polymer?

Polymers consist of chains of monomers. Signup and view all the answers

Which macromolecule is primarily responsible for energy storage in plants and animals?

Lipids Signup and view all the answers

How do saturated fats differ from unsaturated fats?

Saturated fats lack double bonds and are usually solid at room temperature. Signup and view all the answers

What is a key characteristic of polysaccharides compared to monosaccharides and disaccharides?

Polysaccharides are usually larger and consist of many monosaccharide units. Signup and view all the answers

What role do hydrogen bonds play in protein structures?

They stabilize the secondary structure of proteins. Signup and view all the answers

Which of the following statements about nucleotide structure is accurate?

Nucleotides are composed of a sugar, a phosphate group, and a nitrogenous base. Signup and view all the answers

What biological role does symbiosis play in cellulose digestion by certain animals?

It enables cooperative relationships with microorganisms that aid in digestion. Signup and view all the answers

What type of bond forms between two amino acids to create a polypeptide?

Peptide bond Signup and view all the answers

Study Notes

The Molecules of Life

Macromolecules: The four major classes of macromolecules are carbohydrates, proteins, lipids, and nucleic acids.
Monomers and Polymers: Polymers are large molecules constructed from repeated smaller units called monomers.
Dehydration Synthesis and Hydrolysis: Dehydration synthesis removes a water molecule to join two monomers, while hydrolysis adds a water molecule to break a polymer into monomers.

Carbohydrates Serve as Fuel and Building Material

Types of Carbohydrates: Monosaccharides are simple sugars, disaccharides are two monosaccharides joined together, and polysaccharides are long chains of monosaccharides.
Glycosidic Linkages: Starch, glycogen, and cellulose are polysaccharides with different glycosidic linkages, which determine their structure and function.
- Starch: Used for energy storage in plants.
- Glycogen: Used for energy storage in animals.
- Cellulose: Provides structural support in plant cell walls.
Importance of α-glucose vs. β-glucose: α-glucose is found in starch and glycogen, while β-glucose is found in cellulose. Our digestive systems can break down α-glucose bonds but not β-glucose bonds, which is why cellulose is indigestible for humans.
Symbiosis: Symbiotic relationships exist between animals and microbes, such as termites, to digest cellulose.

Lipids are a Diverse Group of Hydrophobic Molecules

Types of Lipids: Fats, phospholipids, and steroids are major classes of lipids.
- Fats: Made up of glycerol and three fatty acid chains. Often used for energy storage.
- Phospholipids: Key components of cell membranes. Have a hydrophilic head and hydrophobic tails.
- Steroids: Composed of four fused rings. Examples include cholesterol and hormones.
Saturated vs. Unsaturated Fats: Saturated fats have no double bonds in their fatty acid chains, making them solid at room temperature. Unsaturated fats have one or more double bonds, making them liquid at room temperature.
Cis vs. Trans Fats: Cis fats have hydrogen atoms on the same side of the double bond, while trans fats have them on opposite sides. Trans fats are linked to health problems.

Proteins have Many Structures, Resulting in a Wide Range of Functions

Proteins vs. Polypeptides: Proteins are complex three-dimensional structures made up of one or more polypeptide chains. Polypeptides are unbranched polymers of amino acids.
Peptide Bonds: Two amino acids are joined by a peptide bond, which forms through dehydration synthesis.
Amino Acid Structure: Each amino acid has a central carbon atom bonded to a hydrogen atom, a carboxyl group, an amino group, and a unique side chain (R group).
- R Group Properties: Amino acids can be grouped based on the chemical properties of their R groups, such as hydrophobic, hydrophilic, acidic, or basic.
Protein Structure: The precise sequence of amino acids in a polypeptide chain determines its primary structure. This primary structure influences its secondary, tertiary, and quaternary structures.
- Secondary Structure: Results from hydrogen bonding between backbone atoms of the polypeptide chain, forming α-helices and β-pleated sheets.
- Tertiary Structure: Three-dimensional shape of the polypeptide chain, stabilized by interactions including hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges.
- Quaternary Structure: Interaction between multiple polypeptides to form a functional protein.
Protein Denaturation: Certain conditions, such as heat, pH changes, or the presence of salts or heavy metals, can denature proteins, causing them to lose their functional structure.

Nucleic Acids Store and Transmit Hereditary Information

Nucleotide Structure: Nucleotides are the monomers of nucleic acids, composed of a nitrogenous base, a five-carbon sugar (ribose or deoxyribose), and a phosphate group.
DNA Structure: Deoxyribonucleic acid (DNA) is responsible for storing and transmitting genetic information. It has a double helix structure with two antiparallel strands of nucleotides held together by hydrogen bonds between complementary base pairs (adenine-thymine, guanine-cytosine).
RNA Structure: Ribonucleic acid (RNA) plays a key role in protein synthesis. It is typically single stranded and contains ribose sugar and the base uracil instead of thymine.

How We Study Cells

Light Microscope: Uses lenses and visible light to magnify images.
- Advantages: Allows viewing of living organisms and larger specimens.
- Limitations: Limited magnification (up to 1000x) and only surface features can be observed.
Stereoscopic (Dissecting) Microscope: Provides a three-dimensional view of larger specimens.
- Advantages: Allows observation of larger specimens in detail.
- Limitations: Cannot view microorganisms.
Transmission Electron Microscope (TEM): Uses a beam of electrons to view the internal structures of cells.
- Advantages: High resolution and can reveal internal details.
- Limitations: Requires thin samples and must be dead specimens.
Scanning Electron Microscope (SEM): Uses a beam of electrons to view the surface of cells and create a three-dimensional image.
- Advantages: High resolution and produces 3D images.
- Limitations: Requires dead specimens and only shows surface features.

A Panoramic View of the Cell

Cell Commonalities: All cells share basic characteristics including a plasma membrane, DNA, cytoplasm, and ribosomes.
Prokaryotic vs. Eukaryotic Cells:
- Prokaryotes: Simple cells lacking a nucleus and membrane-bound organelles. Example: Bacteria.
- Eukaryotes: Complex cells with a nucleus and membrane-bound organelles. Example: Animals, plants, fungi.
Plant vs. Animal Cells:
- Plant cells: Have cell walls, chloroplasts, and a central vacuole.
- Animal cells: Have lysosomes.
Cell Size Limits: There are upper and lower limits to cell size due to factors like metabolic requirements and surface area-to-volume ratio.
- Metabolic limits: Larger cells require more resources and efficient transport mechanisms.
- Surface area: Increased surface area is crucial for efficient exchange of materials with the environment.
Compartmentalization: Eukaryotic cells are compartmentalized, which increases efficiency and allows for more specialized functions.

The Nucleus and Ribosomes

Nuclear Envelope: A double membrane that encloses the nucleus, allowing regulated exchange of molecules between the nucleus and cytoplasm through nuclear pores.
Nucleolus: A region within the nucleus where ribosomal RNA (rRNA) is synthesized and assembled with proteins to create ribosomes.
Ribosomes: Sites of protein synthesis.
- Free Ribosomes: Found in the cytosol, synthesize proteins that will function within the cytosol.
- Bound Ribosomes: Associated with the endoplasmic reticulum, synthesize proteins that will be secreted, incorporated into membranes, or packaged in organelles.

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Description

Explore the essential macromolecules of life, including carbohydrates, proteins, lipids, and nucleic acids. Understand the concepts of monomers and polymers, along with the processes of dehydration synthesis and hydrolysis. Delve into the different types of carbohydrates and their roles in energy storage and structural support.