Eukaryotes

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Questions and Answers

What is the diameter of the nuclear pore in its resting state?

9 nm (correct)

5 nm

15 nm

12 nm

What is a primary function of the nucleolus within the nucleus?

Synthesis of DNA

Transportation of mRNA

Transcription and processing of rRNA (correct)

Modification of proteins

Which component is crucial for the translation of mRNA into an amino acid sequence?

mRNA

tRNA (correct)

ribosomal proteins

rRNA

What distinguishes rough endoplasmic reticulum from smooth endoplasmic reticulum?

Presence of ribosomes Signup and view all the answers

What role does the nuclear localization sequence play in relation to nuclear pores?

It facilitates the transport of proteins into the nucleus. Signup and view all the answers

Which of the following statements about ribosomes attached to the rough ER is accurate?

They translate secretory and membrane proteins. Signup and view all the answers

What happens to ribosomal subunits after their assembly in the nucleolus?

They get exported to the cytoplasm. Signup and view all the answers

Which statement best describes the function of the endoplasmic reticulum?

It acts as the site for protein synthesis and processing. Signup and view all the answers

Which of the following accurately describes the function of nuclear pores?

They facilitate communication between the nucleus and the cytoplasm. Signup and view all the answers

What is the primary role of ribosomal RNA (rRNA) in the cell?

To facilitate the assembly of proteins during translation. Signup and view all the answers

Which of the following correctly describes post-translational modifications?

They modify proteins after their synthesis to alter their function. Signup and view all the answers

What is the main function of the endoplasmic reticulum (ER) in eukaryotic cells?

To synthesize and process proteins and lipids. Signup and view all the answers

Which statement best describes the nuclear localization sequence?

It is essential for the import of larger molecules into the nucleus. Signup and view all the answers

In which of the following processes is mRNA involved during gene expression?

Both transcription and translation. Signup and view all the answers

What best characterizes the 'fluid mosaic' model of the plasma membrane?

It allows lateral movement of phospholipids and proteins. Signup and view all the answers

Which of the following correctly describes the role of transcription factors?

They regulate the transcription of specific genes. Signup and view all the answers

What is the role of the plasma membrane in eukaryotic cells?

Maintains concentration gradients of ions across the cell membrane. Signup and view all the answers

Which of the following organelles is primarily responsible for ribosomal RNA processing?

Nucleus Signup and view all the answers

What are the key functions of the endoplasmic reticulum in eukaryotic cells?

Protein synthesis and lipid metabolism. Signup and view all the answers

Which structure within the nuclear envelope assists in regulating the transport of molecules in and out of the nucleus?

Nuclear pore complex Signup and view all the answers

Post-translational modifications happen primarily in which cellular organelle?

Endoplasmic reticulum Signup and view all the answers

How do ribosomes contribute to cellular function?

By synthesizing proteins from amino acids. Signup and view all the answers

Which of the following describes a key characteristic of eukaryotic cells?

They possess a defined nucleus. Signup and view all the answers

What mechanism is involved in the selective permeability of the plasma membrane?

Both active transport and passive diffusion. Signup and view all the answers

What is the total number of chromosomes in a human somatic cell?

46 Signup and view all the answers

What is the primary process by which mitosis contributes to cellular function?

Asexual reproduction. Signup and view all the answers

What is the product of meiosis?

Four haploid daughter cells. Signup and view all the answers

In the context of chromosomal structure, what does the term 'nucleosome' refer to?

DNA wound around histone proteins. Signup and view all the answers

What is the significance of identifying homologous chromosomes in a karyotype?

They originate from different parents. Signup and view all the answers

Which of the following statements is true regarding the genetic material in cells?

Each chromosome contains many genes. Signup and view all the answers

What does the term '2n' represent in terms of chromosome count?

Total number of chromosomes in diploid cells. Signup and view all the answers

Why is the understanding of meiosis important in genetics?

It helps in understanding inheritance patterns. Signup and view all the answers

What is the primary function of BRCA1 in relation to the cell cycle?

Repairing double-strand breaks in DNA Signup and view all the answers

What occurs during the S phase of the cell cycle?

Chromosomes are duplicated Signup and view all the answers

Which phase of mitosis involves the breakdown of the nuclear envelope?

Prometaphase Signup and view all the answers

How does the presence of mutated BRCA1/2 affect DNA repair processes?

Utilizes an error-prone DNA repair process Signup and view all the answers

What is the result of cytokinesis following the mitotic phase?

Separation into two individual daughter cells Signup and view all the answers

Which statement best describes the role of the cell cycle restriction point?

It determines progression towards the G0 phase Signup and view all the answers

Which stage of interphase involves the cell making proteins in preparation for division?

G2 phase Signup and view all the answers

What is the primary function of NADH in the electron transport chain?

To donate electrons to the electron transport chain Signup and view all the answers

How many ATP molecules are generated from one molecule of NADH during cellular respiration?

2.5 ATP Signup and view all the answers

What role does ATP Synthase play in cellular respiration?

It catalyzes the reaction converting ADP to ATP Signup and view all the answers

What is the primary consequence of the proton motive force generated during the electron transport chain?

It is used to convert ADP to ATP Signup and view all the answers

In addition to ATP production, what happens to the energy harvested in earlier stages of respiration in brown adipocytes?

It is released as heat Signup and view all the answers

Which mobile electron carrier is involved in the electron transport chain?

Coenzyme Q Signup and view all the answers

What type of phosphorylation occurs during the ATP synthesis process in the electron transport chain?

Oxidative phosphorylation Signup and view all the answers

What is produced as a byproduct when oxygen is reduced in the electron transport chain?

Water Signup and view all the answers

What is the primary role of adenosine triphosphate (ATP) in cellular processes?

Transfer of chemical energy Signup and view all the answers

How is ATP regenerated from ADP in the cell?

Through substrate level phosphorylation Signup and view all the answers

Which mechanism describes the formation of ATP by directly adding a phosphate group from a substrate?

Substrate level phosphorylation Signup and view all the answers

What is the result of the hydrolysis of ATP?

Release of energy, ADP, and inorganic phosphate Signup and view all the answers

What does the term 'OIL RIG' represent in the context of oxidation and reduction reactions?

Oxidation Is Loss, Reduction Is Gain Signup and view all the answers

In the context of bioenergetics, what does 'exergonic' refer to?

Reactions that release energy Signup and view all the answers

What role does NADH play in cellular respiration?

It acts as an electron donor Signup and view all the answers

What is the consequence of a substrate being converted from a higher to a lower energy product?

Release of energy used to form ATP Signup and view all the answers

What is the product formed when pyruvate undergoes reduction in anaerobic conditions?

Lactate Signup and view all the answers

During the citric acid cycle, which molecule is produced from the oxidation of acetyl CoA?

Citrate Signup and view all the answers

How many NADH molecules are generated per complete turn of the citric acid cycle?

3 Signup and view all the answers

Where does oxidative phosphorylation primarily occur within the cell?

Inner mitochondrial membrane Signup and view all the answers

What mechanism is primarily used to generate ATP in the citric acid cycle?

Substrate-level phosphorylation Signup and view all the answers

Which process involves the transfer of electrons and is crucial for generating reduced coenzymes?

Oxidation-reduction Signup and view all the answers

Which of the following correctly describes the function of NAD+ in cellular respiration?

It is reduced to NADH. Signup and view all the answers

What is the role of chemiosmosis in energy transfer during oxidative phosphorylation?

It creates a proton gradient. Signup and view all the answers

What is the primary function of the Poly A tail added during post-transcriptional modifications?

To enhance the stability and export of RNA Signup and view all the answers

What is required to open the double-stranded DNA template for transcription?

RNA polymerase Signup and view all the answers

Which codon is recognized as the start codon during the translation process?

AUG Signup and view all the answers

What is the role of transcription factors in the process of gene regulation?

To bind to promoters and initiate transcription Signup and view all the answers

Why is the genetic code described as 'degenerate'?

Because different codons can specify the same amino acid Signup and view all the answers

What process involves the removal of introns and joining of exons in the RNA transcript?

Splicing Signup and view all the answers

What is the main function of RNA polymerase during transcription?

To create an RNA strand from a DNA template Signup and view all the answers

In what way can alternative splicing contribute to protein diversity?

By allowing different exons to be combined in various ways Signup and view all the answers

What is the primary purpose of post-translational modifications?

To modify the structure and function of proteins after synthesis Signup and view all the answers

During which stage does the ribosome initially bind to the mRNA?

Initiation Signup and view all the answers

What dictates the order of amino acids in a polypeptide chain during translation?

Mature mRNA transcript Signup and view all the answers

What is the impact of a frameshift mutation on the protein produced?

It produces a completely different protein due to shifting the reading frame Signup and view all the answers

What role does tRNA play during the process of translation?

It recognizes codons and brings the corresponding amino acids Signup and view all the answers

Which type of mutation may not affect the phenotype of an organism?

Silent mutation Signup and view all the answers

What modification occurs during glycosylation?

Attachment of carbohydrate groups Signup and view all the answers

What is a common consequence of a nonsense mutation?

A truncated protein that is usually nonfunctional Signup and view all the answers

Which statement accurately describes the function of RNA polymerase during transcription?

It unwinds the DNA double helix to expose bases for transcription. Signup and view all the answers

What role do transcription factors play in the transcription process?

They determine which genes are expressed in a particular cell. Signup and view all the answers

How do codons in mRNA relate to the genetic code?

Codons consist of three nucleotides and specify amino acids. Signup and view all the answers

What describes post-transcriptional modifications?

They involve the addition of a poly-A tail and splicing of introns. Signup and view all the answers

During translation, what is the primary role of transfer RNA (tRNA)?

To bring amino acids to the ribosomes for protein assembly. Signup and view all the answers

Which of the following accurately defines the coding strand of DNA?

It has the same sequence as the final RNA transcript except for the base uracil. Signup and view all the answers

What factor influences the rate of transcription in cells?

The concentration of transcription factors and mRNA levels. Signup and view all the answers

What occurs during the initial stage of transcription?

The DNA double helix is unwound and the coding strand is exposed. Signup and view all the answers

What does the Principle of Segregation state about alleles during gamete production?

Each gamete carries only one allele from each gene pair. Signup and view all the answers

Which statement best describes polygenic inheritance?

It involves multiple genes affecting a single trait. Signup and view all the answers

How can Punnett squares be useful in genetics?

They predict the probability of offspring inheriting particular genotypes. Signup and view all the answers

What is the primary difference between monogenic and polygenic conditions?

Monogenic conditions involve traits affected by one gene, whereas polygenic conditions involve multiple genes. Signup and view all the answers

Which of the following best represents X-linked inheritance?

Males are more likely to express X-linked disorders than females. Signup and view all the answers

During the inheritance of a trait governed by multiple alleles, how are the possible genotypes determined?

Through combinations of alleles from multiple genes that contribute to the trait. Signup and view all the answers

Which characteristic is common in traits that have a polygenic inheritance pattern?

The effects of individual genes are additive in determining the phenotype. Signup and view all the answers

What role do alleles play in determining the phenotype of an organism?

Their expression can be masked by other alleles leading to recessive traits. Signup and view all the answers

What outcome is expected when a homozygous recessive organism is used in a test cross with an individual expressing a dominant phenotype?

All offspring will show the dominant phenotype. Signup and view all the answers

Which statement accurately describes polygenic inheritance?

It means multiple genes contribute to a single phenotype. Signup and view all the answers

In the context of monogenic conditions, which of the following is an example of an autosomal dominant disorder?

Huntington's disease Signup and view all the answers

What defines X-linked inheritance in terms of genetic expression in different sexes?

Males only have one X chromosome, making them more susceptible to X-linked diseases. Signup and view all the answers

Which principle explains how alleles of one gene segregate independently of another gene during gamete formation?

Principle of Independent Assortment Signup and view all the answers

Which of the following conditions results from mutations in a single gene?

Cystic fibrosis Signup and view all the answers

Which statement best explains the genetic outcome from a Punnett square involving a heterozygous individual and a homozygous recessive individual?

Half of the offspring will exhibit the dominant phenotype. Signup and view all the answers

How does polygenic inheritance typically influence physical traits?

It results in a continuous range of phenotypic variations. Signup and view all the answers

What characterizes the inheritance pattern of Cystic Fibrosis?

It requires mutant alleles from both parents to manifest. Signup and view all the answers

Which of the following correctly describes how Duchenne Muscular Dystrophy is inherited?

It follows an X-linked recessive inheritance pattern. Signup and view all the answers

How does phenylketonuria impact the metabolism of phenylalanine?

Phenylalanine is converted into toxic phenylketone due to a deficiency. Signup and view all the answers

What is one of the primary effects of increased CAG repeats in specific genes?

It decreases protein stability and function. Signup and view all the answers

Which statement best describes the role of personalised medicine in treating genetic disorders?

It customizes therapies based on individual genetic profiles. Signup and view all the answers

What role do enhancers play in gene regulation?

They alter the rate of transcription by binding to transcription factors. Signup and view all the answers

Which of the following statements about steroid hormones is true?

They alter gene expression by binding to intracellular receptors. Signup and view all the answers

What is the primary function of the TATA box in gene transcription?

To serve as a binding site for RNA polymerase. Signup and view all the answers

What role does aldosterone play in the body?

Enhances Na+ retention in the kidney Signup and view all the answers

How do repressor transcription factors contribute to gene regulation?

They decrease transcription by binding to specific regions. Signup and view all the answers

Which of the following statements accurately describes the movement of sodium and water in the renal system?

Sodium movement determines water movement in the kidneys. Signup and view all the answers

What determines the specific combination of transcription factors needed to activate a gene?

The requirements of combinatorial regulation. Signup and view all the answers

What mechanism is primarily involved in sodium reabsorption in the nephron?

Facilitated diffusion through ENaC and Na+/K+-ATPase Signup and view all the answers

Which category of steroid hormones includes cortisol?

Glucocorticoids Signup and view all the answers

What effect does increased blood volume due to aldosterone have on tissue fluid formation?

It increases pressure driving the formation of tissue fluid. Signup and view all the answers

What role do gene targets play in the action of aldosterone?

They promote transcription of ENaC and Na+/K+-ATPase. Signup and view all the answers

Which of the following statements accurately describes the role of basal transcription factors?

They facilitate the binding of RNA polymerase to the TATA box. Signup and view all the answers

What is a primary consequence of the action of steroid hormones on target cells?

Altered gene expression over hours to days. Signup and view all the answers

What are transcription factors primarily responsible for in the cell?

Regulating the rate of transcription Signup and view all the answers

Which part of a transcription factor binds to specific DNA sequences?

DNA Binding Domain Signup and view all the answers

What is the main function of the basal transcription machinery?

To initiate transcription of DNA Signup and view all the answers

How do transcription factors affect gene expression in response to environmental factors?

They can upregulate or downregulate transcription levels Signup and view all the answers

What role do steroid hormones play within biological systems?

They regulate gene expression and influence cellular activity Signup and view all the answers

What effect would a mutation in a transcription factor typically have on a cell?

It could disrupt normal gene regulation Signup and view all the answers

Which of the following best describes the function of transactivation domains in transcription factors?

They interact with proteins that enhance transcription Signup and view all the answers

In the context of eukaryotes, what are common diseases associated with transcription factor dysfunction?

Cancers and metabolic conditions Signup and view all the answers

Study Notes

Eukaryotic Cell Structures

Eukaryotic cells contain membrane-bound organelles and non-membrane-bound organelles.
Key organelles include: nucleus, nucleolus, plasma membrane, cytosol, lysosome, proteasome, ribosome, peroxisome, mitochondrion, Golgi, endoplasmic reticulum, and cytoskeleton.

Learning Outcomes

Students should be able to identify and describe the main structures of membrane-bound and non-membrane-bound organelles in eukaryotic cells.
Students should be able to explain the functions of these organelles.

Why This Topic is Relevant

Understanding how to target specific properties of one cell type over another.
Targeting drugs to specific organelles (increased efficacy, reduced side effects).
Targeting functions of parasite organelles to combat infection, while sparing host cells.

General Features of Eukaryotic Cells

Many organelles and structures are shared among different cell types.
Cells adapt to survive in diverse physiological conditions.
Changes to cellular machinery allow processes to be targeted pharmacologically.

Plasma Membrane (1)

Defines the cell surface, acting as a boundary.
Impermeable to large molecules.
Selectively permeable to small molecules.
Allows differences between internal (cytosol) and external (extracellular fluid) environments.

Plasma Membrane (2)

Maintains biochemical constraints for biological activity (e.g., glycolysis).
Maintains concentration gradients of ions across the membrane (e.g., nerve firing, muscle contraction, insulin release).

Plasma Membrane (3)

Composed of phospholipids, proteins, and cholesterol.
Phospholipids are amphipathic (having both hydrophilic and hydrophobic parts).
Form a lipid bilayer.
Exhibits "fluid mosaic" model with phospholipid and protein movement.

Plasma Membrane (4)

Studded with proteins (e.g., ion channels, receptors, transporters).
Allows cells to receive signals and transport molecules.

A Quick Recap (1)

Proteins carry out cellular functions, resulting from gene expression and made outside the nucleus in ribosomes.
Protein information is encoded in DNA, which is contained within the nucleus for protection.

A Quick Recap (2)

When a gene is expressed, a disposable mRNA copy of DNA is created (transcription).
The mRNA is exported to the cytoplasm to associate with ribosomes, where protein assembly occurs (translation).
In eukaryotic cells, transcription and translation are spatially and temporally separated.

Nucleus

Keeps the chromosomal DNA safe.
Composed of two lipid bilayers (the nuclear envelope) with pores.
The pores allow communication with the cytoplasm and regulate movement of molecules.
Larger molecules require a nuclear localization sequence for transport.

Nucleus - Movement Through Membrane

mRNA and ribosomal subunits move from the nucleus to the cytoplasm to support translation.
Other molecules such as histones, DNA/RNA polymerases, and transcription factors also move through the membrane.
Nucleotides, ions, and signal molecules are also transported across.

Nuclear Pore

Pores have a diameter of 9nm in their resting state
Interactions with nuclear localization sequences cause conformational changes and pore dilation.

Nucleolus

Located inside the nucleus, it does not have a membrane.
Contains condensed chromatin with genes for ribosomal RNA (rRNA).
Site of rRNA transcription and processing.
Assembles ribosomal subunits (rRNA + ribosomal protein).
Ribosomal subunits are exported to the cytoplasm.

Ribosome

Site of protein translation.
Converts mRNA codons into amino acid sequences.
tRNA acts as an adaptor molecule to select the correct amino acid.
Free ribosomes and ribosomes associated with endoplasmic reticulum exist.

Ribosome (Secretion of Proteins)

Secretory proteins and membrane proteins are initially assembled by ribosomes connected to the rough endoplasmic reticulum (rough ER).
These proteins are then transported via vesicles to the Golgi apparatus for further processing.

Endoplasmic Reticulum

Network of interconnected tubules and vesicles continuous with the nuclear membrane.
Rough ER: Associated with ribosomes, involved in protein synthesis, secretion, and modification of secreted and transmembrane proteins, with post-translational modification.
Smooth ER: Involved in lipid and steroid synthesis, carbohydrate metabolism, calcium storage, and is particularly well-developed in muscle cells (as sarcoplasmic reticulum).

Golgi Apparatus

Part of the endomembrane system.
Physically separates and performs advanced post-translational modification (e.g., adding sugars).
Communicates with other parts of the cell through vesicles moving to other organelles.

Vesicular Structures

Lysosomes are membrane-bound vesicles containing hydrolytic enzymes (general destruction).
They are responsible for cellular breakdown
Peroxisomes are also membrane-bound vesicles that are involved in beta-oxidation of fatty acids and in the synthesis of cholesterol, bile acids, steroid hormones, and transcription factors in some types of cells.

Proteasome

Large protein complex not membrane-bound.
Involved in protein degradation, targeting misfolded or excess proteins within the cell.
The degradation process involves a ubiquitin tag.

Mitochondria

Important energy source (ATP) through glycolysis, Krebs Cycle, but mostly in mitochondria.
Crucial for muscle contraction.

Cytoskeleton

Protein structure that provides support and structure to the cell.
Dynamic system involved in cell shape changes, vesicle movement, and the cell cycle.

Summary

These cellular features are common to most eukaryotic cells.
Students need to be able to identify and describe the main structures.
Students need to explain the function of the organelles using basic terms.

Studying That Suits You

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Description

Explore the fascinating world of eukaryotic cells and their diverse organelles. This quiz will test your knowledge on both membrane-bound and non-membrane-bound organelles, their structures, and functions. Understand the importance of these organelles in targeting drugs and combating infections.