Cell Biology: Organelles and Structures

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Questions and Answers

What is one primary function of membrane proteins?

Facilitating selective transport of substances across the membrane (correct)

Synthesizing carbohydrates for cellular energy

Transporting genetic material

Storing energy for the cell

Which property best describes phospholipids in the plasma membrane?

Hydrophilic heads face outwards (correct)

Both ends are hydrophilic

Hydrophobic tails face outwards

Hydrophilic heads face inwards

How do carbohydrate molecules contribute to cell function?

By degrading waste products in cells

By providing cellular immunological identity (correct)

By facilitating the absorption of nutrients

By acting as energy sources for proteins

What is the primary composition of cytoplasm?

Gelatinous fluid mainly consisting of water with various solutes Signup and view all the answers

What role do embedded proteins play in the plasma membrane?

They are involved in selective transport and may act as receptors Signup and view all the answers

What process involves the degradation of a cell's own components through lysosomal machinery?

Autophagy Signup and view all the answers

What is the main role of lysosomes in the context of cell health?

To initiate programmed cell death Signup and view all the answers

Which of the following options correctly defines autolysis?

Destruction of a cell by its own enzymes Signup and view all the answers

What cellular structure contains digestive enzymes and is responsible for breaking down excess cell parts?

Lysosome Signup and view all the answers

What role do microfilaments play in cellular movement?

Facilitating gliding and contraction Signup and view all the answers

How does the centrosome assist during cell division?

By directing the organization of microtubules Signup and view all the answers

Which component of the cell is primarily responsible for muscle contraction?

Microfilaments Signup and view all the answers

What is one of the functions of the lysosome in the immune response?

Destroying invading viruses Signup and view all the answers

What is the diameter range of microfilaments?

3-6 nm Signup and view all the answers

What does apoptosis refer to in cellular biology?

Programmed cell death Signup and view all the answers

What is the primary function of mitochondria in a cell?

Cellular aerobic respiration Signup and view all the answers

Which structure of the mitochondrion enhances its ability to perform chemical reactions?

Cristae Signup and view all the answers

What is a key role of the Rough Endoplasmic Reticulum (RER)?

Protein production Signup and view all the answers

The Smooth Endoplasmic Reticulum (SER) is especially abundant in which type of cells?

Cells that secrete steroids Signup and view all the answers

Which of the following is NOT a function of the Rough Endoplasmic Reticulum?

Lipid metabolism Signup and view all the answers

What does ATP stand for, and what is its role in the cell?

Adenosine triphosphate; energy storage Signup and view all the answers

Which component of the mitochondrion is involved in the production of ATP?

Cristae Signup and view all the answers

The Rough Endoplasmic Reticulum is characterized by the presence of which structure?

Ribosomes Signup and view all the answers

What is the primary function of the Golgi apparatus in a eukaryotic cell?

Modify, sort, and package proteins and lipids. Signup and view all the answers

Which cellular component acts as a selective barrier to control what enters and leaves the cell?

Cell Membrane Signup and view all the answers

What is the main function of the nucleolus within the nucleus?

To produce ribosomes. Signup and view all the answers

Which statement correctly describes the function of mitochondria?

They generate ATP through cellular respiration. Signup and view all the answers

What is the role of ribosomes in eukaryotic cells?

To synthesize proteins. Signup and view all the answers

Which component of eukaryotic cells is involved in synthesizing lipids and storing ions?

Smooth Endoplasmic Reticulum (SER) Signup and view all the answers

What is one of the main functions of the cytoplasm within the cell?

To serve as the site for metabolic activities. Signup and view all the answers

How does the rough endoplasmic reticulum (RER) differ from the smooth endoplasmic reticulum (SER)?

The RER has ribosomes attached, whereas the SER does not. Signup and view all the answers

What is the primary function of meiosis in cellular biology?

To create gametes for sexual reproduction. Signup and view all the answers

During which phase of meiosis do homologous chromosomes align at the metaphase plate?

Metaphase I Signup and view all the answers

What distinguishes meiosis from mitosis in terms of the number of resulting cells?

Meiosis creates four haploid cells. Signup and view all the answers

In which phase do sister chromatids finally separate during meiosis?

Anaphase II Signup and view all the answers

How does the chromosome number of daughter cells produced in meiosis compare to the parent cell?

Daughter cells have half the number of chromosomes as the parent. Signup and view all the answers

What is a key purpose of meiosis related to genetic variation?

Crossing over and independent assortment Signup and view all the answers

Which of the following best describes the result of meiosis II?

Four haploid cells are produced, each with a single set of chromosomes. Signup and view all the answers

What is the significance of the haploid state of cells produced by meiosis?

It ensures that offspring receive the correct chromosome number when fertilization occurs. Signup and view all the answers

What is the primary function of lysosomes in a cell?

Waste breakdown Signup and view all the answers

What structure is responsible for detoxifying harmful substances in the cell?

Peroxisomes Signup and view all the answers

Which organelle is primarily involved in the process of photosynthesis?

Chloroplasts Signup and view all the answers

What is the role of vacuoles in plant cells?

Store nutrients and waste Signup and view all the answers

What structure is crucial for organizing microtubules during cell division?

Centrosome Signup and view all the answers

Which component of the cytoskeleton primarily provides structural support?

Microtubules Signup and view all the answers

What is the main purpose of the cell wall in plant cells?

Support and protection Signup and view all the answers

During which phase of mitosis do chromosomes align at the equatorial plate?

Metaphase Signup and view all the answers

What is a key feature of meiosis that distinguishes it from mitosis?

Involves two rounds of division Signup and view all the answers

What occurs during cytokinesis in animal cells?

Cytoplasm division Signup and view all the answers

Which of the following processes contributes to genetic variation during meiosis?

Crossing over Signup and view all the answers

What role do plasmodesmata play in plant cells?

Allowing communication between cells Signup and view all the answers

What is the result of mitosis?

Two diploid cells Signup and view all the answers

Which stage of cell division is characterized by the breakdown of the nuclear envelope?

Prophase Signup and view all the answers

Study Notes

Lysosomes

Membrane-bound organelles containing digestive enzymes
Digest materials taken into the cell, such as bacteria
Autophagy: breaks down the cell's own components through lysosomal activity
Autolysis: Destruction of a cell by its own enzymes
Lysosomes can help cells self-destruct through apoptosis (programmed cell death)

Centrosome

Organises microtubules within the cell
Composed of two centrioles (small clusters of microtubules)
Plays a crucial role in cell division
Centrioles are cylindrical structures positioned at right angles to each other
Act as organisers of the nuclear spindle during cell division

Microfilaments

Fine, thread-like protein fibres with a diameter of 3-6nm
Primarily composed of actin, the most abundant cellular protein
Involved in cellular movements such as gliding, contraction, and cytokinesis
Muscle contraction occurs when microfilaments associate with myosin

Microtubules

Cylindrical tubes with a diameter of 20nm
Play a role in intracellular transport, including the movement of carbohydrates

Plasma Membrane

Composed of a double layer (bilayer) of lipids, mostly phospholipids
Phospholipids have hydrophilic phosphate ends facing outwards and hydrophobic lipid tail regions facing inwards
Proteins are embedded in the bilayer or attached to its surface
Proteins involved in selective transport of substances across the membrane
Other proteins function as surface receptors for substances such as hormones, or act as enzymes

Functions of the Plasma Membrane

Regulates transport of substances in and out of the cell
Provides an immunological identity for the cell
Acts as receptors (recognition sites) for hormones
Enables directed cell or organelle movement

Cytoplasm

Gelatinous, semi-transparent fluid filling most cells
Site of metabolic reactions
Primarily composed of water with a variety of solutes, including glucose, proteins, and ions
Contains vital cellular chemicals, like sodium, phosphates, chlorides, amino acids, ATP, and storage material (e.g., oil droplets)

Mitochondria

The ‘powerhouse of the cell’
Possesses outer and inner membranes
Inner membrane folds into cristae, maximizing surface area for chemical reactions
Responsible for cellular aerobic (O2) respiration
Produces ATP (Adenosine triphosphate) through the catabolism of carbohydrates, fats, and proteins
Found in varying numbers depending on the cell's function, with greater numbers in cells that are physically and metabolically active (e.g., skeletal muscles).

Rough Endoplasmic Reticulum (RER)

Interconnecting membranous canals enclosing flattened sacs called cisternae
Covered in ribosomes, which synthesize proteins
Has a large surface area for chemical reactions
An extension of the outer nuclear membrane

Functions of Rough Endoplasmic Reticulum (RER)

Produces proteins, especially enzymes
Provides a pathway for transporting materials through the cell
Collects and stores synthesized materials
Forms a structural skeleton for maintaining cellular shape

Smooth Endoplasmic Reticulum (SER)

Similar features to RER, but lacking ribosomes
Found in large amounts in cells that secrete steroids (e.g., testosterone)

Eukaryotic Cell Structure

Cell Membrane: Regulates what enters and exits the cell, maintaining internal environment and communicating with other cells.
Cytoplasm: Gel-like substance containing organelles, serving as a medium for chemical reactions.
Nucleus: Control center of the cell, containing DNA and regulating gene expression, growth, metabolism, and reproduction.
Nucleolus: Located within the nucleus, responsible for ribosome production.
Ribosomes: Sites of protein synthesis, translating genetic information into proteins.
Endoplasmic Reticulum (ER): Network of membranes within the cytoplasm.
- Rough ER (RER): Contains ribosomes, synthesizes and processes proteins for export or use in the cell membrane.
- Smooth ER (SER): Lacks ribosomes, synthesizes lipids, detoxifies chemicals, and stores ions like calcium.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for storage or transport outside the cell.
Mitochondria: "Powerhouses" of the cell, generating ATP through cellular respiration, providing energy for cellular activities.
Lysosomes: (Animal cells only) Membrane-bound sacs containing digestive enzymes, breaking down waste materials, cellular debris, and foreign substances. Involved in autophagy (self-digestion of cellular components).
Peroxisomes: Small, membrane-bound organelles containing enzymes that detoxify harmful substances and break down fatty acids.
Cytoskeleton: Network of protein filaments throughout the cytoplasm, providing structural support, helping with cell movement, and organizing the cell's internal structure. Contains microfilaments, intermediate filaments, and microtubules.
Centrosome: (Animal cells only) Small structure near the nucleus, organizing microtubules during cell division, forming the mitotic spindle.
Vacuoles: Large sac-like structures primarily found in plant cells, storing nutrients, waste products, and maintaining turgor pressure. In animal cells, they are smaller and involved in storage and waste disposal.
Cell Wall: (Plant cells only) Rigid layer surrounding the cell membrane, providing additional support, protection, and maintaining shape. Primarily made of cellulose.
Chloroplasts: (Plant cells only) Green, membrane-bound organelles containing chlorophyll, site of photosynthesis, converting sunlight into chemical energy (glucose).
Plasmodesmata: (Plant cells only) Channels between adjacent plant cells, allowing communication and material transport.

Mitosis

Cell Division: Process resulting in two genetically identical daughter cells.
Occurs in Somatic (Body) Cells: Involved in growth, repair, and asexual reproduction.
Stages:
- Interphase: The cell grows, replicates its DNA, and prepares for division.
- Prophase: Chromatin condenses into chromosomes, each with two sister chromatids joined at the centromere. Nuclear envelope breaks down, spindle fibers form from centrosomes.
- Metaphase: Chromosomes align at the metaphase plate (center of the cell). Spindle fibers attach to centromeres.
- Anaphase: Sister chromatids are pulled apart by spindle fibers toward opposite poles. Each separated chromatid is now a chromosome.
- Telophase: Separated chromosomes reach opposite poles, new nuclear envelope forms, chromosomes decondense.
- Cytokinesis: Cytoplasm divides, resulting in two identical daughter cells. Cleavage furrow forms in animal cells, cell plate in plant cells.
Purpose: Growth of an organism, repair of damaged tissues, asexual reproduction, produces two diploid cells (full set of chromosomes).

Meiosis

Cell Division: Reduces chromosome number by half, producing four genetically distinct haploid cells.
Occurs in Germ Cells: Produces gametes (sperm and egg cells).
Stages: Two rounds of division, Meiosis I and Meiosis II, with similar stages as mitosis but different outcomes.
- Meiosis I:
  - Prophase I: Chromosomes condense, homologous chromosomes pair up (synapsis), crossing over occurs, leading to genetic variation. Nuclear envelope breaks down, spindle fibers form.
  - Metaphase I: Homologous chromosome pairs align at the metaphase plate, spindle fibers attach to each pair.
  - Anaphase I: Homologous chromosomes are pulled apart to opposite poles (sister chromatids remain attached).
  - Telophase I & Cytokinesis: Chromosomes reach poles, nuclear envelope reforms briefly, cell divides into two haploid daughter cells (half the number of chromosomes).
- Meiosis II:
  - Similar to mitosis, but starts with haploid cells.
  - Prophase II: Chromosomes condense, nuclear envelope breaks down, spindle fibers form.
  - Metaphase II: Chromosomes (still made of two sister chromatids) align at the metaphase plate.
  - Anaphase II: Sister chromatids are finally pulled apart to opposite poles.
  - Telophase II & Cytokinesis: Nuclear envelope reforms, cells divide, resulting in four haploid cells, each with a single set of chromosomes.
Purpose: Produces gametes (sperm and egg cells) for sexual reproduction, reduces chromosome number by half, introduces genetic diversity through crossing over and independent assortment.

Comparing Mitosis and Meiosis

Mitosis: Somatic cells, one division, two identical daughter cells, diploid, growth, repair, asexual reproduction.
Meiosis: Germ cells, two divisions, four distinct haploid cells, genetic diversity, sexual reproduction.

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Description

Explore the essential cellular components such as lysosomes, centrosomes, microfilaments, and microtubules through this quiz. Learn about their functions, roles in cell division, and contribution to cellular movements. Test your knowledge in cell biology and understand how these organelles interact to maintain cellular health.