MCB 250 UIUC - Exam 1 Flashcards

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Questions and Answers

What runs 5'-3' and what runs 3'-5'?

One strand of DNA runs 5'-3', and the complementary strand runs 3'-5'.

What does hydrogen bonding define in DNA?

The specificity of base pairing.

What are the major and minor grooves in DNA?

They are the indentations that run along the DNA helix.

Which of the following are structural features of B-DNA? (Select all that apply)

10.5 base pairs per turn Signup and view all the answers

What forces are responsible for DNA structure?

Base pairing (H-bonds), base stacking, hydrophobic interactions, and repulsion of negatively charged phosphate groups. Signup and view all the answers

What are stacked base pairs responsible for in the DNA structure?

They undergo hydrophobic interactions and van der Waals forces. Signup and view all the answers

How do proteins recognize the nucleotide of double-stranded DNA?

By forming non-covalent bonds with chemical groups on the edges of paired bases within the major groove. Signup and view all the answers

What happens to the absorption of UV light when dsDNA is heated above its Tm?

The A260 will increase. Signup and view all the answers

What types of chemical bonds can proteins form with the major groove of DNA?

Hydrogen bonds with H-bond acceptors and donors. Signup and view all the answers

How can a DNA-binding protein recognize a specific DNA sequence?

By forming hydrogen bonds with 'spare' groups in the major groove. Signup and view all the answers

Match the following DNA sequences with what a protein sees inside a major groove:

3'-ACAA-5' = A sequence recognized by proteins 5'-TCTT-3' = A sequence recognized by proteins Signup and view all the answers

What allows sequence-specific DNA binding proteins to recognize specific sequences?

Interactions with H-bond donors and acceptors in the grooves. Signup and view all the answers

Is DNA structure uniform along the helix?

No, it is not uniform and can vary. Signup and view all the answers

Which of the following statements about prokaryotes is correct?

Transcription and translation occur simultaneously Signup and view all the answers

What distinguishes eukaryotes from prokaryotes?

DNA is contained in a membrane-bound nucleus in eukaryotes Signup and view all the answers

What is the Universal Tree of Life based on?

Comparisons of ribosomal small subunit RNAs. Signup and view all the answers

Which of the following statements about the central dogma of molecular biology is true?

DNA makes RNA, and RNA makes proteins Signup and view all the answers

What is metabolism?

The sum total of all of the chemical reactions of the cell. Signup and view all the answers

What are the two main categories of metabolism?

Catabolism and anabolism Signup and view all the answers

In eukaryotic molecular biology, transcription and translation occur simultaneously.

False Signup and view all the answers

What is the role of RNA polymerase?

To make RNA using DNA as templates Signup and view all the answers

What is an example of a hydrophobic biomolecule?

Fatty acids. Signup and view all the answers

What factors affect the strength of hydrogen bonds?

Both A and B Signup and view all the answers

Water is a non-polar molecule.

False Signup and view all the answers

What is the Henderson-Hasselbalch equation used for?

It relates the pH, pKa, and the ratio of protonated and deprotonated forms of an acid. Signup and view all the answers

What does pH measure?

Concentration of H+ ions Signup and view all the answers

What is the significance of weak interactions in biology?

They allow dynamic interactions between molecules. Signup and view all the answers

Match the following nucleotide bases with their classifications:

Adenine = Purine Guanine = Purine Cytosine = Pyrimidine Thymine = Pyrimidine Signup and view all the answers

Study Notes

Prokaryotes vs. Eukaryotes

Prokaryotes consist of bacteria and archaea, lacking a nucleus with direct DNA contact to cytoplasm; transcription and translation occur simultaneously.
Eukaryotic cells have a membrane-bound nucleus; transcription occurs in the nucleus and mRNA is transported to the cytoplasm for translation, which does not occur simultaneously.

Universal Tree of Life

Based on comparisons of ribosomal small subunit RNAs, illustrating evolutionary relationships among all living organisms.

Cell Sizes and Evolution

Bacterial cells are significantly smaller than eukaryotic cells. Mitochondria are thought to have evolved from bacterial endosymbionts.

Central Dogma of Molecular Biology

Describes the flow of genetic information: DNA is transcribed into RNA, which is then translated into proteins.
Reverse transcription also occurs; RNA can function enzymatically and regulate processes.

Protein Function

Proteins, primarily enzymes, catalyze chemical reactions crucial for metabolism.
Other proteins assist in cellular movement, regulation, and structure, while RNAs can serve similar enzymatic and regulatory roles.

Metabolism Overview

Represents the comprehensive network of cellular chemical reactions, encompassing catabolism (energy generation through breakdown) and anabolism (building cellular components).

Molecular Biology Mechanisms

In bacteria, transcription and translation occur closely in the cytoplasm; while in eukaryotes, they are separated by RNA processing in the nucleus.

Chemical Bonds in Biology

Strong bonds, such as covalent, are vital for molecule stability and energy storage; weak bonds (ionic, hydrogen, van der Waals) are crucial for molecular interactions.

Aromatic Structure and Light Absorption

Aromatic rings exhibit resonance structures with delocalized electrons, absorbing UV light; beta-carotene exemplifies this by absorbing light in the blue range (~450 nm).

Stereochemistry and Biological Implications

Stereoisomerism is important in biology; 19 of 20 amino acids can exist as L- or D- isomers, with organisms predominantly utilizing L-isomers.
Molecular interactions depend on precise alignment mainly due to the chiral nature of many biological interactions.

pH and Biological Effects

pH measures hydrogen ion concentration (-log[H+]); biological molecules have variable charges based on local pH.
pKa provides insight into the ionization of weak acids/bases, relevant in amino acids and other biomolecules.

DNA Structure and Function

DNA features a double helix with complementary base pairs stabilized by hydrogen bonds. Bases adhere to Chargaff's rules: A=T and C=G.
Major and minor grooves of DNA are key sites for protein interactions, allowing proteins to read specific sequences based on chemical bonding.

Historical Contributions to Genetics

Research spanning from Mendel's work on heritable traits to Griffith's experiments illustrating DNA as a transforming material, culminating in Hershey and Chase's demonstration of DNA as hereditary material through bacteriophage studies.

Nucleotide Structure

Nucleotides in DNA (deoxyribonucleotides) include adenine, guanine, cytosine, and thymine, while RNA contains uracil instead of thymine.
Strands of DNA and RNA are linked by phosphodiester bonds, signifying structural integrity essential for genetic encoding.

Functions and Properties of Water in Biology

Water's polarity facilitates hydrogen bonding, underpinning biological processes as a solvent and involving hydrophobic interactions critical for protein folding and cellular structures.

Importance of Weak Interactions

Dynamic weak interactions are vital in biological processes, allowing flexible molecular interactions, especially in enzyme-substrate complexes.

DNA Denaturation

Heating DNA leads to "hyperchromaticity," characterized by increased UV light absorbance, a result of strand separation which also changes the chemical environment surrounding bases.

Interaction of Proteins with DNA

Proteins recognize specific DNA sequences primarily through hydrogen bonds with bases in the major groove, highlighting the importance of base exposure and alignment for biochemical specificity.

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Description

Prepare for your MCB 250 Exam 1 with these flashcards covering key concepts like prokaryotes and eukaryotes. Each card presents essential definitions and distinctions that will aid in your understanding of cellular biology. Test your knowledge and get ready for success in this important microbiology course!