Cellular Organization and Nucleus Structure

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Questions and Answers

What is the primary function of endocytosis in a cell?

  • Releases substances from the cell
  • Promotes cell differentiation
  • Brings substances into the cell (correct)
  • Regulates the cell's membrane potential

Which phase of interphase is primarily responsible for DNA replication?

  • G2 phase
  • S phase (correct)
  • M phase
  • G0 phase

What is the role of MPF (M-phase promoting factor) in the cell cycle?

  • Promotes cell differentiation
  • Inhibits cell division
  • Stimulates mitosis and the cell cycle transition (correct)
  • Triggers the transition from prophase to metaphase

What distinguishes a malignant tumor from a benign tumor?

<p>Malignant tumors can metastasize to other parts of the body (A)</p> Signup and view all the answers

What happens to a cell when a gene is 'turned off'?

<p>The specific protein coded by the gene is not produced (C)</p> Signup and view all the answers

What is the name of the DNA strand that provides a template for mRNA synthesis?

<p>Template strand (C)</p> Signup and view all the answers

Which enzyme is essential for the transcription of DNA into RNA?

<p>RNA polymerase (D)</p> Signup and view all the answers

What RNA nucleotide replaces thymine in the synthesized RNA strand?

<p>Uracil (D)</p> Signup and view all the answers

During translation, which molecule functions to bring amino acids to the ribosome?

<p>tRNA (B)</p> Signup and view all the answers

What happens when a cell is placed in a hypertonic solution?

<p>Cell shrinks (A)</p> Signup and view all the answers

What distinguishes facilitated diffusion from simple diffusion?

<p>It involves carrier proteins (D)</p> Signup and view all the answers

What is the primary difference between pinocytosis and phagocytosis?

<p>Phagocytosis involves large particles, pinocytosis involves fluids (C)</p> Signup and view all the answers

What is the role of a selectively permeable membrane?

<p>To enable only specific molecules to enter or exit (A)</p> Signup and view all the answers

What are the two general classes of cells?

<p>Somatic and Germ (A), Prokaryotic and Eukaryotic (B)</p> Signup and view all the answers

How are the two layers of phospholipids arranged in the plasma membrane?

<p>Hydrophilic heads facing outward, hydrophobic tails inward (C)</p> Signup and view all the answers

What body system utilizes recognition proteins to assess cell conditions?

<p>Immune system (D)</p> Signup and view all the answers

What is the main function of cell membrane carrier proteins?

<p>They facilitate the movement of substances across the membrane. (A)</p> Signup and view all the answers

Which of the following distinguishes cytosol from cytoplasm?

<p>Cytoplasm includes organelles and cytosol, cytosol is only the liquid part. (A)</p> Signup and view all the answers

What is the primary role of a nucleosome?

<p>To package and regulate the accessibility of DNA (D)</p> Signup and view all the answers

Which structure would you find in non-dividing cells?

<p>Chromatin (C)</p> Signup and view all the answers

What occurs during the process of transcription?

<p>RNA is synthesized from a DNA template (B)</p> Signup and view all the answers

Flashcards

Endocytosis

The process of bringing substances into a cell.

Exocytosis

The process of releasing substances from a cell.

MPF (M-phase promoting factor)

A factor that promotes the transition into mitosis.

Benign vs Malignant Tumors

Benign tumors are non-cancerous; malignant tumors are cancerous.

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Cellular Differentiation

The process by which cells become specialized in structure and function.

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Phospholipid bilayer

A double layer of phospholipids forming the plasma membrane, with hydrophobic and hydrophilic regions.

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Membrane proteins

Proteins embedded in the plasma membrane that perform specific functions such as transport and recognition.

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Cytosol vs Cytoplasm

Cytosol is the fluid part of the cytoplasm; cytoplasm includes organelles within that fluid.

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Nucleosome

A structural unit of DNA wrapped around histone proteins, playing a key role in packaging DNA.

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Chromatin vs Chromosomes

Chromatin is DNA in a loosely packed form; chromosomes are tightly coiled during cell division.

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Template DNA

The strand of DNA that serves as a template for mRNA synthesis.

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Triplets

Sets of three consecutive nitrogen bases in DNA that code for specific amino acids.

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RNA polymerase

The enzyme that synthesizes RNA from a DNA template.

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Codon

A sequence of three nucleotides in mRNA that codes for one amino acid.

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Gene

A segment of DNA that contains the instructions to make proteins and determine traits.

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Transcription

The process by which DNA is copied to produce mRNA, which carries genetic information to the ribosomes.

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Intron vs Exon

Introns are non-coding regions, while exons are coding regions of genes.

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Diffusion

The passive movement of molecules from high to low concentration.

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Osmosis

The passive movement of water across a selectively permeable membrane.

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Facilitated diffusion

A type of passive transport that uses carrier proteins to move substances.

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Endocytosis vs Exocytosis

Endocytosis is the intake of substances, while exocytosis is the expulsion of substances from the cell.

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Study Notes

Cellular Level of Organization

  • Cells: Two general types exist.
  • Plasma membrane: Separates the cell from its environment, composed of a phospholipid bilayer.
  • Membrane proteins: Various types have specific functions, including recognition of abnormal cells.
  • Carrier proteins: Facilitate specific molecule movement across the membrane.
  • Cytoplasm: Contains cytosol and organelles.
  • Organelles: Perform specific functions, with examples like microvilli, centrioles, cilia, flagella, ribosomes, rough endoplasmic reticulum (RER), smooth ER, Golgi apparatus, lysosomes, peroxisomes, mitochondria, proteosomes, nucleus, and nucleolus.

Nucleus

  • Nucleosomes: DNA-protein structures.
  • Chromatin: DNA in non-dividing cells.
  • Chromosomes: DNA in dividing cells.
  • Triplets: Three consecutive nitrogenous bases that code for specific amino acids.
  • Genes: Functional units of heredity, Sequences of nucleotides for protein production.

DNA and Protein Synthesis

  • Transcription: DNA into RNA.
  • RNA polymerase: Enzyme for transcription.
  • RNA nucleotides: Thymine replaced by Uracil.
  • Codons: Three-base sequence on mRNA.
  • Translation: mRNA into protein.
  • tRNA: Transfer RNA with anticodons.
  • Anticodons: Complementary to codons.
  • mRNA start codon: AUG.

Cellular Transport

  • Diffusion: Movement of substances from high to low concentration.
  • Osmosis: Water movement across a membrane.
  • Isotonic solution: No net water movement.
  • Hypotonic solution: Water moves into the cell.
  • Hypertonic solution: Water moves out of the cell.
  • Passive transport: Movement without energy (diffusion and osmosis).
  • Active transport: Requires energy (like sodium-potassium exchange pump).
  • Facilitated diffusion: Substances move down their concentrations gradient through protein channels.
  • Symport (cotransport): Substances move in the same direction.
  • Antiport (countertransport): Substances move in opposite directions.
  • Endocytosis: Cell takes in substances (pinocytosis, phagocytosis).
  • Exocytosis: Cell releases substances (secretory vesicles).

Cell Cycle and Cell Division

  • Cell cycle phases: Interphase, mitosis, cytokinesis.
  • Interphase: Cell growth and DNA replication; contains S phase.
  • DNA replication enzyme: Enzyme binds the nucelotides together covalently.
  • Cytokinesis: Cytoplasmic division.
  • M-phase promoting factor (MPF): Regulates cell cycle progression.

Cellular Differentiation

  • Cellular specialization: Cellular differentiation due to gene activation/repression.

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