Cell Biology Overview Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary role of the smooth endoplasmic reticulum (SER) in muscle cells?

Storage and release of calcium ions (correct)

Modification of lipids only

Production of secreted proteins

Synthesis of neurotransmitters

Who was the first person to observe cells and name them?

Robert Hooke (correct)

Matthias Schleiden

Anton van Leeuwenhoek

Theodor Schwann

Which of the following molecules is synthesized in the smooth endoplasmic reticulum?

Glycoproteins

Insulin

Steroid hormones (correct)

Antibodies

Which statement is NOT one of the principles of cell theory?

Cellular processes occur only in specialized tissues. Signup and view all the answers

What distinguishes the cis face of the Golgi apparatus?

It is the receiving end for transport vesicles. Signup and view all the answers

Which process occurs in the Golgi apparatus for proteins synthesized in the ER?

Glycosylation and other post-translational modifications Signup and view all the answers

Which of the following is a characteristic feature of prokaryotic cells?

They reproduce mainly by binary fission. Signup and view all the answers

What is a primary function of the Golgi apparatus related to membrane traffic?

Control of protein addressing Signup and view all the answers

What is the primary function of the cell as an information unit?

Store hereditary information. Signup and view all the answers

What is one reason eukaryotic cells are generally larger than prokaryotic cells?

They contain more genetic material. Signup and view all the answers

Which type of cell is likely to have a large smooth endoplasmic reticulum?

Liver cells involved in detoxification Signup and view all the answers

What are cisternae in the Golgi apparatus?

Flattened stacks of membranes Signup and view all the answers

Which of the following correctly distinguishes prokaryotic from eukaryotic cells?

Prokaryotic cells are unicellular, whereas eukaryotic cells can be unicellular or multicellular. Signup and view all the answers

Which process do prokaryotic cells primarily use for cell division?

Binary fission Signup and view all the answers

Which modification is NOT typically done by the Golgi apparatus?

Detoxification of toxins Signup and view all the answers

What is a fundamental similarity between all living cells?

They exhibit very few differences between species. Signup and view all the answers

What is the primary function of the nucleus in a eukaryotic cell?

The synthesis of proteins Signup and view all the answers

Which statement about the nucleolus is correct?

It participates in the assembly of ribosome components. Signup and view all the answers

What is the primary role of nuclear pores?

To control the exchange of materials between the nucleoplasm and cytoplasm Signup and view all the answers

What is the nuclear lamina primarily made of?

Intermediate filaments Signup and view all the answers

How do small molecules and ions pass through nuclear pores?

By passive diffusion Signup and view all the answers

What is the primary role of lysosomes in a cell?

Digesting biomolecules Signup and view all the answers

What aspect of the nuclear envelope is true?

It is continuous with the endoplasmic reticulum. Signup and view all the answers

How do lysosomes become activated?

By fusing with phagocytic vacuoles Signup and view all the answers

During cell division, what role does the nuclear lamina play?

It facilitates the deconstruction and reconstruction of the nuclear envelope. Signup and view all the answers

Which organelles are replaced every 10 days in some tissues?

Mitochondria Signup and view all the answers

What structure is described as having a 'basketball hoop' appearance in its composition?

Nuclear pore Signup and view all the answers

What types of lysosomes are identified based on their functional states?

Primary and secondary Signup and view all the answers

What kind of enzymes do peroxisomes contain?

Oxidative enzymes Signup and view all the answers

What is the function of digestive enzymes inside lysosomes?

Break down biomolecules into smaller particles Signup and view all the answers

Which process involves the transport of proteins and lipids into the Golgi apparatus?

Vesicular transport Signup and view all the answers

What happens during the progression of content through the Golgi apparatus?

Content moves from the Cis face to the Trans face Signup and view all the answers

What is a primary function of peroxisomes in eukaryotic cells?

Detoxify potentially toxic molecules Signup and view all the answers

Which statement about mitochondria is correct?

They contain their own circular DNA. Signup and view all the answers

What by-product is generated by peroxisomal activities?

Hydrogen peroxide Signup and view all the answers

How do mitochondria reproduce within eukaryotic cells?

By division, similar to binary fission Signup and view all the answers

What is the role of catalase in peroxisomes?

To convert hydrogen peroxide into water Signup and view all the answers

What is a characteristic of the inner mitochondrial membrane?

It contains a higher proportion of proteins compared to lipids. Signup and view all the answers

Which of the following functions is NOT associated with mitochondria?

Synthesis of lipid bilayers Signup and view all the answers

What is present in the intermembrane space of mitochondria?

H+ protons and cytochrome c Signup and view all the answers

Which of the following substrates is typically involved in the oxidation reactions within peroxisomes?

Free hydrogen atoms linked to organic substrates Signup and view all the answers

What are the primary components that make up chromatin?

DNA and histones Signup and view all the answers

Which structure in the nucleus is responsible for ribosome production?

Nucleolus Signup and view all the answers

What is the primary role of mRNA in protein synthesis?

It provides the coding sequence for protein synthesis. Signup and view all the answers

What distinguishes rough endoplasmic reticulum (RER) from smooth endoplasmic reticulum (SER)?

RER has ribosomes attached to its surface. Signup and view all the answers

Which nitrogenous base is unique to RNA?

Uracil Signup and view all the answers

What is the process by which genetic information is copied from DNA to RNA called?

Transcription Signup and view all the answers

Which of the following statements about heterochromatin is true?

It is generally not active. Signup and view all the answers

What is the composition of a nucleotide?

Sugar, base, and phosphate Signup and view all the answers

What do ribosomes primarily function as in the cell?

Protein synthesis machinery Signup and view all the answers

How are amino acids added during protein synthesis?

Via tRNA carrying an anticodon Signup and view all the answers

What is the primary function of the smooth endoplasmic reticulum (SER)?

Lipid synthesis and detoxification Signup and view all the answers

What base pairs with adenine during DNA replication?

Thymine Signup and view all the answers

Which of the following best describes the structure of DNA as proposed by Watson and Crick?

Double helical structure Signup and view all the answers

Which part of the cell is primarily involved in dividing the cell into compartments?

Endomembrane system Signup and view all the answers

Study Notes

Cytology and Histology: Cell Structure

Cytology and histology are the study of cells and tissues, respectively
Cell theory is the unifying foundation of cell biology
Cell theory's three principles:
- All organisms are composed of one or more cells, and life processes of metabolism and heredity occur within these cells
- Cells are the smallest living things; the basic units of organization of life
- Cells arise only by division of a previously existing cell
Each cell is a complete living being; a cell can:
- Absorb and process food
- Reject waste
- Breathe
- Secret substances
- Reproduce
- Repair damaged parts
The cells of all living organisms are very similar to each other with few differences between species
A cell represents:
- A structural unit: supporting biological activities
- A reproduction unit: development of organs or repairing of organs
- An information unit: contains hereditary information
- A unit of function: ensures the realization of biological activities necessary for life

Prokaryotes vs. Eukaryotes

The world of cells is divided into two main groups fundamental different in internal structure and general organization
Two main types:
- Prokaryotic cells (bacteria, archaebacteria)
  - 1 to 10 µm in general size
  - Unicellular organisms
  - Genetic material not enclosed in a membrane (nucleoid)
  - Lack an internal membrane system
  - Cell division mainly by binary fission, which does not utilize a spindle
- Eukaryotic cells
  - 10 to 100 µm in general size
  - Uni or multicellular organisms
  - Genetic material enclosed in a membrane (nucleus)
  - Possess numerous membrane-bounded organelles
  - Cell division by mitosis, which utilizes a spindle

Prokaryotic Cell Division by Binary Fission

Prokaryotic cells divide by binary fission. This process involves:
- DNA replication
- Segregation of DNA
- Cell splitting into two identical daughter cells

Mitosis

Mitosis is a type of cell division in eukaryotic cells.

All cells share four major features in common
- Nucleoid (prokaryotes) or Nucleus (eukaryotes): The DNA contains genes coding for proteins
- Cytoplasm: A semifluid matrix containing sugars, amino acids, and proteins necessary for the cell's daily function
- Ribosomes: Synthesizing proteins
- Plasma membrane: A phospholipid bilayer with proteins embedded in it for functions like receptors, enzymes, channels, pumps

Prokaryotic Cells: Simple Organization

Prokaryotes lack nuclei and linear chromosomes, instead possessing a circular DNA ring (nucleoid region)
Many prokaryotes use plasmids, which are small, independently replicating DNA circles containing genes for selective advantage but not essential for survival
Prokaryotic cells have a cell wall (except mycoplasma)
- The cell wall consists of peptidoglycan, a carbohydrate matrix cross-linked to short polypeptide units, protecting the cell, maintaining its shape, and preventing water loss
- Cell wall protects the cell and gives it shape. Gram-negative have a thinner peptidoglycan layer and an outer membrane, leading to greater antibiotic resistance
The plasma membrane resembles eukaryotic cells made from a phospholipid bilayer with embedded intrinsic and peripheral proteins, necessary for control over intake and elimination of waste
- Possesses protein components with multiple functions (transporters, receptors, respiratory chain proteins)
Prokaryotic cells come in three basic shapes
- Cocci (spheres)
- Bacilli (rods)
- Spirilla (spirals)

S-layer, Capsule, Flagella and Pili

S-layer: An additional glycoprotein layer providing surfaces or protection
Capsule: A gelatinous layer on the cell wall that enhances cell adhesion, evasion of immune response and virulence.
Flagella: Slender flexible protein filaments assisting the movement in liquid environments
Pili: Hair-like structures that assist in adhesion and bacterial conjugation (genetic exchange)

Bacterial Conjugation

Bacterial conjugation is a process of genetic transfer between two bacteria through a pilus

Cell Division: Binary Division

The genetic material is first duplicated. The daughter cells are identical to the mother cell, forming a colony of genetically identical cells.

Archaea

Archaea have unusual membrane lipids distinct from bacteria. Peptidoglycan is not found on the cell wall.

Eukaryotic Cells

Eukaryotic cells are distinctly more complex than prokaryotes. Their defining feature is compartmentalization (endomembrane systems and organelles).
Eukaryotic organisms include animals, plants, fungi and protists (as well as most algae)

Shape

Examples of eukaryotic cell shapes include globular (isolated cells), lenticular (erythrocytes), flagellate (spermatozoids) and some that extend in form (nervous cells)

Size

Some eukaryotic cells are visible to the naked eye (hen's egg is 3cm) and others need magnification (leukocytes are ~5μm and muscle cells are ~250μm)

Turnover Rate

Turnover rate varies depending on the cell type and its function: for example, WBCs have a turnover of 1–2 weeks, platelets typically last 10- 12 days and hepatocytes or pancreatic cells can last for a few months.

Organization Eukaryotic Cell

Eukaryotic cells have components of a plasma membrane and a cytosol, containing individualized and highly specialized organelles
These organelles include the nucleus, mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes and cytoskeleton

The Nucleus

Round or spherical shape with a typically central location in the cell
Houses the genetic material (DNA)
Exhibits a dark-staining area called the nucleolus, involved in ribosome synthesis
Nucleus and nucleolus surrounded by the nuclear envelope
Composed of DNA (deoxyribonucleic acid) wrapped around protein "histones"

The Nuclear Envelope

Double phospholipid bilayer
Contains pores that allow molecules to diffuse between the nucleoplasm (inside the nucleus) and the cytoplasm (outside the nucleus)
Active and passive transport mechanisms for specific materials

Nucleolus

Highly visible dark-staining region within the nucleus involved in ribosome production
Contains the nucleolar organizer (containing rRNA genes) which is a part of certain chromosomes

Chromatin: DNA Packaging

DNA is packaged by being wrapped around protein histones, forming chromatin
Two types of chromatin:
- Heterochromatin: generally inactive
- Euchromatin: active

Primary Structure of DNA

Definition: nucleotide polymer
Composed of:
- Phosphate
- Sugar (deoxyribose)
- Nitrogenous bases: A, T, C, G
  - Pyrimidine: C, T, U (Uracil)
  - Purine: A and G

Secondary Structure of DNA

Double helix structure
Two complementary strands joined together by hydrogen bonds.
A-T (2 hydrogen bonds) and C-G (3 hydrogen bonds)
Antiparallel strands

Structure of Chromatin

Composed of DNA wrapped around protein histones.
Two forms:
- Heterochromatin: generally not active
- Euchromatin: active

Chromatin Compaction Levels

Condenses further into chromatin fibers, which forms distinct structures called chromosomes (at the time of cell division)

From Chromatin → Chromosome

Chromosome is the result of strong spiralization of chromatin, allowing for physical division and distribution

Ribosomes

Ribosomes are complex molecular assemblies
Comprised of ribosomal RNA (rRNA) and proteins
They synthesize proteins
Free ribosomes form proteins used in the cytoplasm, nucleus and other components
Some ribosomes associate with the endoplasmic reticulum which synthesize membrane proteins found in the endomembrane system or for export from the cell

• Messenger RNA (mRNA): carries genetic information from DNA to ribosomes • Transfer RNA (tRNA): carries amino acids to ribosomes

mRNA

Carries the genetic information from DNA in a cell to the protein synthesis machinery in the cytoplasm
Serves as a template for protein synthesis

Transcription

A process happening in the nucleus
DNA strands separate, with one strand serving as a template.
The rule of complementarity of the nitrogenous base is followed, producing a complementary RNA strand using RNA polymerase enzyme
Synthesized mRNA passes into cytoplasm for translation to protein

Translation

Happens in the cytoplasm
mRNA migrates to a ribosome
mRNA is read successively by codons to add amino acids by specific tRNA that carries the anticodon sequence.
AUG: start codon and UGA UAA UAG: stop codon

Expression of Genetic Information

The DNA triplet (nucleotides) corresponds to mRNA codon
Each codon corresponds to a specific anti-codon of tRNA
Each anti-codon corresponds to a specific amino acid

The Endomembrane System

Internal eukaryotic membrane system
Includes:
- Nuclear envelope
- Endoplasmic reticulum (rough and smooth)
- Golgi apparatus
- Lysosomes
- Vacuoles
Fills the cell and divides it into compartments
Channels the passage of molecules
Provides synthesis surfaces for lipids and proteins

Endoplasmic Reticulum (ER)

Involved in protein and lipid synthesis.
Two types:
- Rough ER (RER): has ribosomes, makes and modifies proteins destined for secretion and for membrane
- Smooth ER (SER): no ribosomes, synthesizes lipids and steroids, stores calcium ions, detoxification

Golgi Apparatus

A flattened stack of membranes (cisternae), involved in modifying, sorting, and packaging proteins and lipids
Three zones:
- Cis face: receiving end (closest to RER)
- Medial / Intermediate
- Trans face: shipping end

Functions of the Golgi

Modifies proteins and lipids made in ER
Directs molecules to their proper destinations (secreted or for endomembrane system use)

Transport Through the Golgi

Vesicles transport proteins and lipids through cisternae.
Vesicles bud from cis, pass through cisternae, and fuse with trans face
The final contents are dispatched to the proper cell locations in vesicles, transporting molecules

Lysosomes

Membrane-bound vesicles containing digestive enzymes
Break down biomolecules
Recycle cellular components and expel waste.
Two types
- Primary: Newly formed; non-active
- Secondary: fuse with other vesicles (phagocytic) containing ingested material, activating the digestive enzymes

Peroxisomes

Microbodies rich in oxidative enzymes (e.g., catalase)
Involved in oxidation reactions (e.g., breakdown of fatty acids)
Detoxify harmful substances
Produce hydrogen peroxide (byproduct), which catalase breaks down

Mitochondria

Sausage-shaped organelles
Two membranes:
- Outer membrane
- Inner membrane (cristae)
Divide by fission
Contain their own DNA and machinery for protein synthesis, but most enzymes required for division are encoded in the cell nucleus
Central role in cellular respiration producing ATP
Key compartments:
- Matrix: inside the inner membrane
- Intermembrane space: between outer and inner membrane

Mitochondrial Functions

Cellular respiration (ATP synthesis)
Steroid hormone synthesis (works with ER)
Thermogenesis
Calcium regulation
Cell death (apoptosis)

The Cytoskeleton

Network of protein fibers that supports cell shape and organizes internal structures
Three main types
- Actin filaments (microfilaments)
- Microtubules
- Intermediate filaments

Centrosomes and Centrioles

Microtubule-organizing center (MTOC)
Pair of barrel-shaped centrioles
Involved in microtubule formation, cell division, and other cellular activities

Intermediate Filaments

Durable protein fibers
Provide structural support to the cell
Composed of overlapping proteins, which provides mechanical stability to the cell

Summary of Eukaryotic Organelles

Nucleus: contains genetic material
Ribosomes: synthesize proteins
Endoplasmic reticulum: synthesizes and modifies proteins and lipids
Golgi apparatus: modifies, sorts, and packages proteins and lipids
Mitochondria: produce ATP through cellular respiration
Lysosomes: degrade waste materials
Peroxisomes: break down toxic molecules
Cytoskeleton: maintains cell shape, enables movement and facilitates transport

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on key concepts in cell biology, including the roles of organelles like the smooth endoplasmic reticulum and Golgi apparatus. This quiz covers foundational principles such as cell theory and distinctions between prokaryotic and eukaryotic cells. Challenge yourself to see how well you understand these essential topics in biology.