Biological Organization and Macromolecules

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Questions and Answers

Which of the following correctly describes the hierarchy of biological organization?

Organs → Tissues → Organ Systems → Cells

Atoms → Molecules → Macromolecules → Cells (correct)

Cells → Macromolecules → Tissues → Organs

Atoms → Molecules → Cells → Organ Systems

What is the significance of biogenesis in cell theory?

Cell division is not essential for growth.

Only certain types of organisms can reproduce.

Cells can arise spontaneously from non-living matter.

All cells originate from pre-existing cells. (correct)

Which of the following macromolecules is NOT considered a carbohydrate?

Fatty acids (correct)

Glucose

Sucrose

Starch

What type of cells lack a nucleus?

Prokaryotic cells Signup and view all the answers

Which of the following best describes the process of dehydration synthesis?

Creating polymers from monomers by removing water. Signup and view all the answers

Which of the following statements correctly identifies characteristics of organic compounds?

Organic compounds commonly have a carbon backbone. Signup and view all the answers

What is the role of functional groups in organic compounds?

They provide specific properties that characterize the compound. Signup and view all the answers

What is the primary function of RNA in the cell?

Carry genetic information for protein synthesis Signup and view all the answers

Which of the following best describes the composition of carbohydrates?

CHO with nitrogen in chitin Signup and view all the answers

Which component is part of the structure of a nucleotide?

Nitrogenous base Signup and view all the answers

What type of bond links nucleotides together in nucleic acids?

Phosphodiester bonds Signup and view all the answers

What type of nucleic acid has deoxyribose as its sugar?

DNA Signup and view all the answers

During ATP hydrolysis, what is released that powers cellular work?

Gibbs free energy Signup and view all the answers

Which base is exclusive to RNA?

Uracil Signup and view all the answers

What is the primary site of cellular respiration in eukaryotic cells?

Mitochondria Signup and view all the answers

What substance is detoxified in peroxisomes?

Oxygen radicals Signup and view all the answers

What occurs during telophase in the cell cycle?

The nuclear envelope reforms and two nuclei appear Signup and view all the answers

What is the main purpose of the G1 checkpoint?

To verify that cells have sufficient size and nutrients Signup and view all the answers

How does cytokinesis differ between animal and plant cells?

Animal cells use actomyosin for membrane contraction, while plant cells deposit a new cell wall Signup and view all the answers

What initiates the binary fission process in bacteria?

Replication of the single circular chromosome Signup and view all the answers

What happens if DNA damage is detected at the G1 checkpoint?

Cell division is halted until the damage is repaired Signup and view all the answers

What defines the M checkpoint in the cell cycle?

It ensures the chromosomes are properly aligned before separation Signup and view all the answers

In which phase do animal cells undergo cleavage furrow formation?

Cytokinesis Signup and view all the answers

Which of the following statements about cell division checkpoints is true?

There are three main checkpoints that ensure cell cycle progression Signup and view all the answers

What is the main function of the plasma membrane?

Regulation of substance exchange Signup and view all the answers

Which of the following statements about prokaryotic cells is true?

They have a nucleoid region for DNA. Signup and view all the answers

What is the purpose of transport proteins in the plasma membrane?

To assist in the movement of hydrophilic molecules. Signup and view all the answers

What structural features help solve the upper limit of cell size?

Presence of organelles for nutrient and waste management. Signup and view all the answers

Which process describes the transport of secretory proteins within the endomembrane system?

Rough ER → Golgi → Secretory vesicle → Plasma membrane Signup and view all the answers

What defines the lower limit of cell size?

Inability to absorb nutrients and expel wastes effectively. Signup and view all the answers

Which of the following describes fluorescence microscopy?

It employs fluorescent dyes to visualize specimens. Signup and view all the answers

What is a key characteristic of eukaryotic cells compared to prokaryotic cells?

They have a nucleus and membrane-bound organelles. Signup and view all the answers

What is the primary function of meiosis in the context of gamete formation?

To produce haploid cells from diploid cells. Signup and view all the answers

During which stage of meiosis do homologous chromosomes undergo crossing over?

Prophase I Signup and view all the answers

What happens to chromosome pairs during metaphase I of meiosis?

Chromosomes align independently at the equator. Signup and view all the answers

What results from independent assortment during meiosis?

Haploid gametes with unique genetic combinations. Signup and view all the answers

In human beings, how many chromosomes do gametes contain?

23 chromosomes Signup and view all the answers

What is the outcome of meiosis II?

Four haploid cells with genetic variation. Signup and view all the answers

What role does crossing over play in meiosis?

It enhances genetic variation among offspring. Signup and view all the answers

Which of the following describes the chromosome configuration at the end of Prophase I?

Homologous chromosomes are condensed and paired. Signup and view all the answers

Study Notes

Biological Organization

Cells are fundamental units of life, organized hierarchically.
From atoms to molecules, macromolecules, organelles, cells, tissues, organs, organ systems, and ultimately, organisms.
Human physiology focuses on organs and organ systems.
Ecology and evolution concern populations, communities, and ecosystems.

Macromolecules

All organisms share the same four major macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

Cell Theory

All organisms are composed of cells, the smallest units of life.
New cells arise only from pre-existing cells, the basis of biogenesis.
Cell division serves reproduction, growth, and repair in multicellular organisms.

Cell Types

Two fundamental cell types exist: prokaryotes and eukaryotes.
Prokaryotes (bacteria and archaebacteria) are small (10-6m) and lack a nucleus.
Eukaryotes (protists, fungi, plants, and animals) are larger (100µm) and possess a nucleus and organelles.

Carbon Compounds and Macromolecules

Organic compounds are based on carbon atoms covalently bonded to hydrogen atoms, forming backbones.
Common elements like oxygen, nitrogen, phosphorus, and sulfur are also linked to the carbon backbone.
Functional groups attached to the carbon backbone confer diverse properties to organic compounds, essential for life.
Macromolecules or polymers are large organic compounds assembled by living cells.

Carbohydrates

Most abundant macromolecules, primarily composed of carbon, hydrogen, and oxygen (with nitrogen in chitin).
Monosaccharides (simple sugars) have the general formula (CH2O)n, where n represents the number of carbon atoms.
Examples of monosaccharides include glucose, fructose, galactose, and glucosamine.
Disaccharides (two sugars) store energy, such as maltose, sucrose, and lactose.
Dehydration synthesis joins monosaccharides to form disaccharides.

Microscopy

Microscopes are crucial for visualizing cells.
Light microscopes utilize visible light optics, allowing observation of live specimens with limited resolution and magnification.
Electron microscopes employ electron optics, enabling observation of fixed specimens with higher resolution and magnification.

Cell Size Limitations

Cell size is limited by the surface area to volume ratio.
Large cells face challenges in efficient nutrient uptake and waste removal.
Solutions include compartmentalization (organelles) and elongated shapes (microvilli).
Larger organisms have more cells, not larger cells.

Minimal Cell Components

All cells, prokaryotic or eukaryotic, share basic components.
These include a cell membrane (plasma membrane), DNA, ribosomes, cytoplasm, and protein synthesis machinery.

Plasma Membrane

A thin (9nm) phospholipid bilayer embedded with proteins.
Acts as a semipermeable barrier, favoring the passage of hydrophobic molecules while restricting hydrophilic molecules.
Transport proteins facilitate the passage of hydrophilic substances.

Prokaryotic Cells

Prokaryotes lack membrane-bound cytoplasmic organelles like a nucleus, mitochondria, and Golgi apparatus.
Smaller than eukaryotes, typically 10-100 times smaller.
Key features include:
- Nucleoid (DNA-containing region, not membrane-bound)
- Single circular chromosome
- Cell wall (peptidoglycan: protein + carbohydrate)
- Capsule (sticky polysaccharide for attachment, found in pathogenic bacteria)
- Pili (extensions for attachment, found in pathogenic bacteria)
- Flagella (for locomotion)

Endomembrane System

A network of interconnected membranes involved in protein transport and secretion.
Ribosomes on the rough endoplasmic reticulum (RER) synthesize proteins.
Secretory proteins move from RER to Golgi, then to secretory vesicles, and finally to the plasma membrane.
Other functions include synthesis of cytoplasmic proteins, lipid synthesis, cleavage, and degradation (lysosomes).

Nucleic Acids

Informational macromolecules composed of carbon, hydrogen, nitrogen, oxygen, and phosphorus.
Monomers are nucleotides, linked by phosphodiester bonds.
Two types:
- DNA (deoxyribonucleic acid): stores genetic information, composed of four deoxyribonucleotides.
- RNA (ribonucleic acid): involved in protein synthesis, composed of four ribonucleotides.

DNA vs. RNA Comparison

Criteria	DNA	RNA
Overall structure	Double helix, antiparallel, complementary (G=C, A=T)	Single stranded
Monomers	Deoxyribonucleotides	Ribonucleotides
Pentose sugar	Deoxyribose	Ribose (extra OH)
Bases	G, A, T, C	G, A, U, C
Function	Store genetic information	Carry genetic info for protein synthesis
Location in cell	Euk. nucleus, cytoplasm	Euk. nucleus, cytoplasm
Chromatin	Form of DNA packaged/complexed with proteins

Nucleotide Structure

Composed of a phosphate group, a sugar, and a nitrogenous base.
Phosphate groups are ionized (–O–).
Sugar is either deoxyribose (DNA) or ribose (RNA).
Nitrogenous bases are either:
- Purines (adenine (A), guanine (G))
- Pyrimidines (cytosine (C), thymine (T, in DNA) uracil (U, in RNA)

DNA Structure

Two antiparallel and complementary strands linked by phosphodiester bonds.
Base pairing follows purine-pyrimidine rules (A with T or U, G with C)

ATP

Is a high energy molecule due to unstable phosphate bonds.
Broken bonds release free energy useful for cellular work.

ATP Hydrolysis

The breakdown of ATP into ADP and Pi is a spontaneous and exergonic reaction.
Energy released powers:
- Chemical work (anabolic reactions)
- Mechanical work (cellular movement)
- Transport (molecular movement across membranes)

The ATP Cycle

ATP is continuously cycled:
- Dehydration synthesis (endergonic) generates ATP.
- Hydrolysis (exergonic) releases energy from ATP.
- Energy from cellular respiration (glucose) drives the ATP cycle.

Cellular Respiration

The process of breaking down glucose to generate energy (ATP).
Occurs primarily within mitochondria.

Photosynthesis

The process of converting light energy into chemical energy (glucose).
Happens in chloroplasts, specifically within thylakoid membranes.
Chlorophyll, a pigment within chloroplasts, plays a central role in photosynthesis.

Peroxisomes

Organelles responsible for detoxification of reactive oxygen species (O2).
Play a role in alcohol detoxification in liver cells.
Involved in fatty acid catabolism.

Cell Shape and Structure

Cell shape is determined by internal structures like cytoskeleton and external constraints.
Cell walls provide structural support and protection.

Cell Walls

Plant cell walls are composed of cellulose (β-glucose polymer).
Fungal cell walls utilize chitin (N-acetylglucosamine polymer).
Bacterial cell walls are made of peptidoglycan, a polymer of sugars and linked peptides.

Cell Division

The process of creating new cells from existing ones.
Two primary types: mitosis and meiosis.

Mitosis

Cell division for growth and repair in multicellular organisms.
Produces two identical daughter cells.
Four phases:
- Prophase: chromosomes condense, nuclear envelope breaks down, spindle forms.
- Metaphase: chromosomes align at the equator, attached to spindle fibers.
- Anaphase: sister chromatids separate and move to opposite poles.
- Telophase: chromosomes decondense, nuclear envelope reforms, two nuclei appear.
Cytokinesis (division of cytoplasm) follows mitosis.

Cytokinesis in Animals and Plants

Animals: cleavage furrow forms, pinching the cell membrane.
Plants: cell plate forms, derived from Golgi vesicles, eventually fusing with the plasma membrane, creating a new cell wall.

Bacterial Cell Division (Binary Fission)

Single circular chromosome replicates at the origin of replication.
Two origins separate as the bacterium elongates.
Cell membrane grows inward, creating a new cell wall.
DNA replication is not always synchronized with separation.

Checkpoints in Cell Cycle

Monitor progression of the cell cycle, ensuring proper completion of preceding phases:
- G1 (restriction) checkpoint in late G1.
- G2 checkpoint.
- M checkpoint.

The G1 Checkpoint

Ensures cell size and environmental conditions are favorable for entering the S phase.
Controls processes like:
- Anchorage dependence (division requires attachment to a surface).
- Density dependent inhibition (division stops when a surface is fully covered).
- DNA damage (division halts until damage is repaired).

Diploid and Haploid Cells

Somatic cells are diploid (2n), containing two copies of each chromosome.
Gametes (sperm and egg) are haploid (n), containing one copy of each chromosome.
Human diploid number is 2n=46.
Human haploid number is n=23.

Meiosis

Cell division that reduces the chromosome number by half, producing haploid gametes.
Consists of two nuclear divisions (meiosis I and meiosis II) but only one DNA replication in the S phase.

Meiosis I

Prophase I: chromosomes condense and pair up (synapsis), crossing over occurs.
Metaphase I: tetrads (paired chromosomes) align at the equator, independent assortment occurs.
Anaphase I: homologous chromosomes separate but not sister chromatids.
Telophase I: chromosomes decondense, nuclear envelope reforms, resulting in haploid nuclei.

Meiosis II

Prophase II: chromosomes recondense, no DNA replication.
Metaphase II: chromosomes align at the equator.
Anaphase II: sister chromatids separate, no longer identical due to crossing over.
Telophase II: chromosomes decondense, cytokinesis occurs, forming 4 haploid gametes (sperm or egg).

Variation in Offspring

Meiosis and random fertilization contribute to genetic variation:
- Crossing over creates unique combinations of genes.
- Independent assortment shuffles homologous chromosomes.
- Random combination of egg and sperm at fertilization produces genetically diverse offspring.

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Description

Explore the fundamental concepts of biological organization, including cell theory and the role of macromolecules in living organisms. From cells to organ systems and the differences between prokaryotes and eukaryotes, this quiz covers essential topics in biology. Test your knowledge of the building blocks of life and their significance in ecology and evolution.