Key Concepts in Cell Biology and Genetics for Exams

Common properties of all living cells

Similar basic chemistry, self-replicating, evolved from a common ancestral cell.

Evidence for an RNA world

Ribozymes exhibit enzymatic activity, RNA can store information, and RNA is involved in genome replication.

Distinguishing features of the three domains of life

Eukaryotes have a nuclear envelope; Bacteria and Archaea are prokaryotes, with Bacteria being more diverse.

Evolution of eukaryotic cells

Through endosymbiosis and the incorporation of prokaryotic cells as organelles.

Evidence for endosymbiosis

Organelles contain their own DNA, resemble prokaryotes, and can divide independently.

Major families of small organic molecules in cells

Sugars, fatty acids, amino acids, and nucleotides.

Formation of biological polymers

Through condensation reactions, also known as dehydration reactions.

Role of fatty acids in cells

They are components of cell membranes and serve as energy reserves.

Building blocks of proteins

Amino acids.

Function of nucleotides in cells

They are the subunits of DNA and RNA, and carry energy.

Primary structure of a protein

The specific sequence of amino acids in the polypeptide chain.

Weak interactions in cells

Van der Waals attractions, electrostatic attractions, hydrogen bonds, and hydrophobic interactions.

Protein shape determination

Its amino acid sequence.

Types of protein structures

α-helices and β-sheets, which are part of their secondary structure.

Example of quaternary structure

Collagen, which consists of multiple polypeptide chains.

How enzymes work

They bind to ligands and chemically transform them, speeding up reactions.

Allosteric regulation

Regulation by binding outside of the catalytic site of an enzyme.

Function of a centromere

It is the point of junction between sister chromatids.

Telomeres

The stable ends of linear chromosomes that protect them from degradation.

Regulation of chromosomal structures

Through ATP-dependent chromatin remodeling complexes and histone modifications.

Significance of the nucleolus

It is the site where rRNA genes are transcribed into rRNA.

Role of histones

They organize DNA into nucleosomes, which compact the DNA.

Types of DNA repair mechanisms

Mismatch repair and homologous recombination.

Function of the mismatch repair system

It removes replication errors that escape proofreading.

Common type of spontaneous mutation

Depurination or deamination.

Template for DNA replication

A strand of DNA serves as a template for synthesizing a complementary strand.

Interactions stabilizing protein structure

Non-covalent interactions, including hydrogen bonds and hydrophobic interactions.

Protein maturation

Through processes like folding, post-translational modifications, and assembly.

Roles of covalent and non-covalent interactions in proteins

Covalent interactions stabilize structure; non-covalent interactions facilitate function.

Role of ribozymes

They catalyze chemical reactions, supporting the RNA world hypothesis.

Differences between eukaryotic and prokaryotic chromosomes

Eukaryotic chromosomes are linear and contain introns, while prokaryotic chromosomes are circular.

Function of the Golgi apparatus

It processes and packages proteins and lipids for secretion or delivery.

Endocytosis

The import of materials into the cell mediated by vesicle formation.

Exocytosis

The export of materials from the cell via secretory vesicles.

Role of phospholipids in membrane structure

They form bilayers with hydrophilic heads and hydrophobic tails.

Function of the cytoskeleton

It provides structural support and facilitates directed movements in cells.

Amyloid structures

Misfolded proteins that can aggregate and are associated with diseases.

Chromatin remodeling and gene expression

It regulates access to DNA, influencing transcriptional activity.

Roles of condensin and cohesin in cell division

Cohesin holds sister chromatids together, while condensin aids in chromosome condensation.

Function of ATP in cellular processes

It provides energy for various cellular activities, including motor protein action.

Modifications regulating protein function

Phosphorylation, ubiquitination, and other post-translational modifications.

Feedback inhibition

A process where the end product of a pathway inhibits an earlier step, regulating the pathway.

Hydrogen bonds in protein structure

They stabilize secondary structures like α-helices and β-sheets.

Significance of 5' and 3' ends of nucleotides

They dictate the directionality of DNA and RNA synthesis.

Repair of double-strand DNA breaks

Through non-homologous end joining or homologous recombination.

Functions of the endoplasmic reticulum

Synthesis of proteins and lipids, and detoxification.

Epigenetic inheritance

The transmission of gene expression patterns that do not involve changes in the DNA sequence.

Role of G-proteins

They act as molecular switches in signaling pathways, regulated by GTP binding and hydrolysis.

Effects of mutations on DNA replication fidelity

Mutations can accumulate if not repaired, leading to potential cellular dysfunction.

Role of the proteasome

It degrades ubiquitinated proteins, controlling protein levels in the cell.

Consequences of failing to repair DNA damage

It can lead to mutations, cancer, and other serious cellular problems.

Chromosomal aberrations and phenotypic anomalies

They can result in developmental disorders and diseases.

Significance of introns in eukaryotic genes

They are non-coding sequences that can be involved in gene regulation.

Cyclobutane ring in DNA damage

It forms between adjacent thymine bases due to UV exposure, leading to replication errors.

Basic structural units of eukaryotic chromosomes

Nucleosomes, consisting of DNA wrapped around histone proteins.

Function of reader and writer proteins in chromatin modification

Reader proteins recognize histone modifications, while writer proteins add new modifications.

Significance of a calico pattern in cats

It results from random X-chromosome inactivation, leading to patchy coloration.

Distribution of eukaryotic genes across chromosomes

They vary among species and are influenced by evolutionary factors.

Role of the cytosol in cellular function

It is the site of many metabolic reactions and the medium for molecular interactions.

Influence of fatty acids on membrane fluidity

Saturated fatty acids make membranes less fluid, while unsaturated fatty acids enhance fluidity.

Basic types of genetic changes

Point mutations, gene duplications, exon shuffling, and horizontal gene transfer.

Germ cell mutations vs somatic cell mutations

Germ cell mutations can be passed on to progeny, while somatic cell mutations cannot.

Significance of the globin gene family

It consists of multiple genes coding for hemoglobin subunits expressed at different developmental stages.

Whole-genome duplications

They can result in tetraploid species, affecting gene families and diversity.

Exon shuffling

The recombination of exons from different genes that can create novel genes.

Mobile genetic elements

They can cause mutations and alter gene regulation, leading to developmental changes.

Horizontal gene transfer

The transfer of genes between organisms, often observed in bacteria.

Conserved DNA sequences

Functionally important genome regions that are retained across species.

Vertebrate genome changes

They can rapidly gain and lose DNA, affecting their structure and function.

DNA-only transposable elements

Elements that can move within genomes either through replicative or non-replicative transposition.

Percentage of human genome that consists of transposable elements

About 50%.

Retrotransposons

They transpose via an RNA intermediate that is reverse transcribed into DNA.

Role of viruses in genetic exchange

They can move between cells and transfer genetic material.

Approximate number of protein-coding genes in the human genome

About 20,000.

Gene regulation and phenotypic differences

Differences in gene regulation can explain how similar genomes can lead to diverse traits.

Insights from Neanderthal genomes

They suggest interbreeding events and reveal genetic traits unique to modern humans.

Primary mechanisms of genetic change

Mutations, gene duplications, horizontal gene transfer, exon shuffling, genomic rearrangements, and mobile genetic elements.

Structure of a lipid bilayer

Composed of phospholipids with hydrophilic heads and hydrophobic tails.

Synthesis of biological membranes

In the endoplasmic reticulum.

Functions of membrane lipids

They form the structural basis of membranes and influence fluidity.

Types of proteins in cell membranes

Transporters, anchors, receptors, and enzymes.

Integral membrane proteins vs peripheral proteins

Integral proteins are embedded in the membrane, while peripheral proteins are associated indirectly.

Role of cholesterol in membrane fluidity

It stabilizes membranes at high temperatures and prevents tight packing at low temperatures.

Active transport

The movement of molecules against their concentration gradient, requiring energy input.

Na+/K+ pump function

It pumps 3 Na+ out of the cell and 2 K+ into the cell per ATP hydrolyzed.

Role of the electron transport chain in cellular respiration

It transfers electrons and pumps protons to create a proton gradient for ATP synthesis.

Difference between glycolysis and fermentation

Glycolysis occurs under aerobic conditions and produces pyruvate, while fermentation occurs anaerobically and regenerates NAD+.

Stages of cellular respiration

Glycolysis, the citric acid cycle, and oxidative phosphorylation.

Location of the citric acid cycle in eukaryotic cells

In the mitochondrial matrix.

Primary function of the mitochondria

ATP production through oxidative phosphorylation.

Conversion of pyruvate in aerobic conditions

It is converted to acetyl CoA before entering the citric acid cycle.

Function of NADH in cellular respiration

It carries electrons to the electron transport chain.

Role of activated carriers in metabolism

They store and transfer energy to drive anabolic reactions.

How enzymes lower activation energy

By stabilizing the transition state and reducing randomness during reactions.

Difference between spontaneous and non-spontaneous reactions

Spontaneous reactions release energy and occur naturally, while non-spontaneous reactions require energy input.

Significance of the second law of thermodynamics in biology

It states that energy transfers increase disorder, requiring energy input to maintain order in living systems.

ATP generation during glycolysis

Through substrate-level phosphorylation.

Products of glycolysis

Two pyruvate molecules, two NADH, and a net gain of four ATP (two used).

Oxidative phosphorylation

The process of ATP production using the proton gradient established by the electron transport chain.

Role of oxygen in cellular respiration

It serves as the final electron acceptor in the electron transport chain.