Cell Structure and Eukaryotic Cells

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Questions and Answers

What is the primary function of the Golgi apparatus in protein trafficking?

To break down proteins into amino acids

To synthesize proteins

To modify and package proteins for transport (correct)

To store proteins for future use

Which structure in prokaryotic cells is responsible for providing strength and support?

Cell Wall (correct)

Slime Capsule

Plasmid

Pili

What prevents polyspermy during fertilization in mammalian ovum?

Follicle cells

Zona pellucida (correct)

Flagellum

Cortical granules

What type of ribosomes are found in prokaryotic cells?

70S Ribosomes Signup and view all the answers

Which of the following structures is involved in the exocytosis of proteins?

Golgi apparatus Signup and view all the answers

What is the primary energy source for spermatozoa to facilitate movement?

Mitochondria Signup and view all the answers

What is a primary function attributed to mesosomes in prokaryotic cells?

Respiration Signup and view all the answers

What role do lysosomes play in a cell?

They contain digestive enzymes Signup and view all the answers

What is the primary function of the rough endoplasmic reticulum (RER)?

Protein folding and processing Signup and view all the answers

Which structure within the nucleus is known for ribosome production?

Nucleolus Signup and view all the answers

What is the role of the Golgi apparatus in a eukaryotic cell?

Modifying and packaging proteins and lipids Signup and view all the answers

Which organelle is involved in cellular respiration within eukaryotic cells?

Mitochondria Signup and view all the answers

What type of cells are humans primarily composed of?

Eukaryotic cells Signup and view all the answers

What structural feature do centrioles possess?

Hollow cylinders with microtubules Signup and view all the answers

What is contained within the matrix of mitochondria during cellular respiration?

Enzymes needed for respiration Signup and view all the answers

Which component is NOT part of the ultrastructure of eukaryotic cells?

Cell wall Signup and view all the answers

What type of cells can give rise to all types of specialized cells, including placental cells?

Totipotent cells Signup and view all the answers

Which stem cells are sourced from adult bone marrow?

Adult stem cells Signup and view all the answers

What is a potential risk associated with the transplantation of stem cells?

Infection Signup and view all the answers

Which of the following characteristics is influenced by only one gene?

Gender Signup and view all the answers

What process allows cells to become specialized based on a stimulus?

Differential gene expression Signup and view all the answers

Which term describes the observable characteristics of an organism resulting from gene-environment interactions?

Phenotype Signup and view all the answers

What type of variation includes traits like mass and height?

Continuous variation Signup and view all the answers

Which of the following terms is used to describe inheritance involving multiple genes?

Polygenic inheritance Signup and view all the answers

What is the primary purpose of meiosis?

Production of haploid gametes Signup and view all the answers

Which process contributes to genetic variation in meiosis?

Crossing over Signup and view all the answers

What is an example of an aneuploid condition?

Down’s Syndrome Signup and view all the answers

What defines a pluripotent stem cell?

Can differentiate into all cell types except placental cells Signup and view all the answers

What phenomenon is characterized by the failure of homologous chromosomes or sister chromatids to separate?

Non-disjunction Signup and view all the answers

Which mutation involves the swapping of genes between two non-homologous chromosomes?

Translocation Signup and view all the answers

What is monosomy?

Absence of one chromosome in a pair Signup and view all the answers

What type of stem cells can differentiate into many different types of cells?

Multipotent cells Signup and view all the answers

Which environmental factor can influence the polygenic characteristic of height?

Nutrition Signup and view all the answers

What role do proto-oncogenes play in relation to lung cancer?

They regulate the cell cycle and can become oncogenes when activated. Signup and view all the answers

How does temperature affect the fur color of Siamese cats?

It activates the gene that darkens their fur only at specific temperatures. Signup and view all the answers

What is the consequence of DNA methylation?

It permanently suppresses gene transcription. Signup and view all the answers

Which histone modification leads to activation of chromatin?

Acetylation Signup and view all the answers

What occurs to the Lac operon in the presence of lactose?

Gene transcription for lactose digesting proteins is initiated. Signup and view all the answers

What is a characteristic of epigenetic modifications?

They can be permanent and affect gene activation. Signup and view all the answers

Which modification typically suppresses gene transcription in DNA?

DNA methylation Signup and view all the answers

Study Notes

Cell Structure

All living organisms are made of cells and share common features.
Multicellular organisms have specialized cells forming tissues, organs and organ systems.
Human cells are eukaryotic - containing a nucleus and membrane-bound organelles.

Ultrastructure of Eukaryotic Cells

Nucleus: Double membrane, containing pores, DNA wrapped around histone proteins as chromatin, and nucleolus (ribosome production).
Rough Endoplasmic Reticulum (RER): Flattened sacs with ribosomes, folds and processes proteins.
Smooth Endoplasmic Reticulum (SER): Membrane-bound sacs, produces and processes lipids.
Golgi Apparatus: Curved, flattened sacs with vesicles, modifies and packages proteins and lipids, creates lysosomes.
Mitochondria: Oval shaped, double membrane (envelope), inner membrane folds into cristae, matrix contains enzymes for respiration.
Centrioles: Hollow cylinders with microtubule rings, involved in cell division.
80S Ribosomes: Two subunits, sites of protein synthesis.
Lysosomes: Vesicles with digestive enzymes, bound by a single membrane.

Protein Trafficking

Proteins are produced on ribosomes.
Proteins synthesized on RER ribosomes are folded and processed in the RER.
Proteins move from RER to Golgi apparatus in vesicles.
They are modified in the Golgi (e.g., adding carbohydrates to form glycoproteins).
Golgi packages proteins into vesicles for transport.
Some proteins are released from the cell via exocytosis.

Prokaryotic Cells

Cell Wall: Rigid outer covering of peptidoglycan, provides strength and support.
Slime Capsule: Protective layer, retains moisture and helps adhesion.
Plasmid: Circular pieces of DNA.
Flagellum: Tail-like structure that rotates for movement.
Pili: Hair-like structures for attachment to other bacteria, enabling plasmid exchange.
70S Ribosomes: Two subunits, sites of protein synthesis.
Mesosomes: Infoldings of the inner membrane, function is debated (may contain respiratory enzymes).

Mammalian Gametes and Fertilization

Ovum: Contains zona pellucida (protective coating), haploid nucleus, cortical granules (harden zona pellucida after sperm entry), and follicle cells.
Spermatozoa: Contains many mitochondria for energy, flagellum for movement.

Meiosis

Cell division producing genetic variation, resulting in haploid gametes (reduction division).
Crossing Over: Exchange of DNA sections between homologous chromosomes.
Independent Assortment: Random distribution of maternal and paternal chromosomes to daughter cells.

Chromosome Mutations

Changes in chromosome structure or number.
Translocation: Swapping of genes between non-homologous chromosomes.
Duplication: Extra copies of genes.
Deletion: Loss of genes.
Inversion: Reversal of gene order.
Aneuploidy: Abnormal chromosome number.
- Polysomy: More than two chromosomes in a pair (e.g., Down's Syndrome).
- Monosomy: Less than two chromosomes in a pair (e.g., Turner's Syndrome).

Stem Cells

Undifferentiated cells that can divide to form other cell types.
Multipotent: Produce many cell types (e.g., bone marrow stem cells).
Pluripotent: Produce many specialized cells, except placental cells.
Totipotent: Can produce all cell types, including placental cells (e.g., zygotes).
Applications: Treatment of diseases (diabetes, multiple sclerosis, Parkinson's), tissue replacement (spinal cord injuries).
Ethical issues: Embryos are destroyed for embryonic stem cell extraction, risk of infection and cancer development.

Specialisation of Cells

Differential gene expression leads to cell specialization.
Stimuli activate or suppress genes.
Activator and repressor molecules bind to promoter regions of DNA.
Active genes are transcribed into RNA, translated into proteins, which alter cell structure and function.

Phenotype

Observable characteristics of an organism resulting from the interaction of genes and environment.
Continuous Variation: Variation within a range (e.g., height, weight).
Discontinuous Variation: Limited to specific values (e.g., gender, shoe size).
Monogenic Inheritance: One gene influences a characteristic, often showing discontinuous variation.
Polygenic Inheritance: Multiple genes influence a characteristic, often showing continuous variation.
Environmental factors can influence polygenic characteristics (e.g., nutrition affecting height).

Epigenetic Modifications

Changes to DNA that do not alter the base sequence but affect gene activation.
DNA Methylation: Addition of methyl groups to DNA, suppressing gene transcription.
Histone Modification: - Acetylation: Adding acetyl groups, activating chromatin and allowing transcription. - Methylation: Adding methyl groups, activating or inactivating chromatin.

Lac Operon

Example of epigenetic control in bacteria.
Lac Operon: Contains genes for lactose digestion.
Repressor molecules suppress the operon in the absence of lactose.
When lactose is present, it prevents repressor binding, allowing gene transcription and protein production.

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Description

Explore the fascinating world of cell structure in this quiz focused on eukaryotic cells. Learn about various organelles such as the nucleus, endoplasmic reticulum, Golgi apparatus, and mitochondria, along with their functions. Test your knowledge of how these components work together in multicellular organisms.