Lesson.3

Quipper Lesson 1.3: Components of the Cell II: Subcellular Organelles

Page 3-4: Cell as a Factory

  • Analogy of a Cell:

    • The cell is compared to a factory building.

    • It creates a barrier that organizes its machinery and employees (organelles).

Page 5: Role of Organelles

  • Functionality:

    • Organelles perform specific functions necessary for various cellular processes.

Page 6: Learning Objectives

  • At the end of the lesson, students should be able to:

    • Describe the composition and role of the nucleus and ribosomes in genetic control.

    • Distinguish the roles of organelles in the endomembrane system.

    • Compare the roles of chloroplasts and mitochondria in energy provision.

Page 8-9: Endosymbiotic Theory

  • Origin of Membrane-Bounded Organelles:

    • Mitochondria and chloroplasts have double membranes and their own genetic material.

    • Resulted from a large eukaryotic cell engulfing prokaryotes.

Page 11: Classification of Organelles

  • Three Groups of Organelles:

    • Endomembrane System: Includes endoplasmic reticulum, Golgi bodies, lysosomes, peroxisomes, and vacuoles.

    • Energy Houses: Mitochondria and chloroplasts.

    • Genetic Control: Nucleus and ribosomes.

Page 12: Structure of the Nucleus

The nucleus is often referred to as the control center of the cell. It houses the cell's genetic material (DNA) and is surrounded by a double membrane known as the nuclear envelope, which contains pores that regulate the entry and exit of molecules. Within the nucleus, the nucleolus is present, where ribosomal RNA (rRNA) is synthesized and combined with proteins to form ribosomes.

Functions of the Nucleus

  1. Genetic Information Storage: The nucleus contains the majority of the cell's genetic material, organized into chromosomes. This genetic information is essential for the regulation of cellular activities and the inheritance of traits.

  2. Ribosome Production: The nucleolus plays a crucial role in the production of ribosomes, which are necessary for protein synthesis in the cytoplasm.

  3. Gene Expression Regulation: The nucleus regulates gene expression by controlling which genes are turned on or off, thereby influencing the types and amounts of proteins produced in the cell.

Structure of Ribosomes

Ribosomes can be found free-floating in the cytoplasm or attached to the endoplasmic reticulum (ER), forming rough ER. They are composed of rRNA and proteins and are the sites of protein synthesis. Ribosomes translate messenger RNA (mRNA) into polypeptide chains, which fold into functional proteins.

Page 13: Endoplasmic Reticulum (ER)

The endoplasmic reticulum is a network of membranous tubules and sacs (cisternae) that extends from the nuclear envelope into the cytoplasm. There are two types of ER:

  1. Rough ER: Studded with ribosomes, rough ER is involved in the synthesis and initial folding of proteins destined for secretion or for use in membranes.

  2. Smooth ER: Lacking ribosomes, smooth ER is involved in lipid synthesis, detoxification of drugs and poisons, and calcium ion storage.

Page 14: Golgi Apparatus

The Golgi apparatus functions as the cell's "post office." It modifies, sorts, and packages proteins and lipids received from the ER for transport to their final destinations. This organelle is made up of flattened membranous sacs called cisternae.

The Golgi apparatus, also known as the Golgi complex, has several key functions:

  1. Protein Modification: It modifies proteins received from the endoplasmic reticulum (ER) by adding carbohydrates (glycosylation) or phosphate groups.

  2. Sorting and Packaging: It sorts and packages proteins and lipids into vesicles for transport to their destinations, such as lysosomes, the plasma membrane, or secretion outside the cell.

  3. Lipid Transport: It plays a role in the transport and modification of lipids.

  4. Formation of Lysosomes: It is involved in the formation of lysosomes, which contain digestive enzymes.

  5. Cell Signaling: It helps in the processing of signaling molecules.

Page 15: Lysosomes and Peroxisomes

Lysosomes

  • Function: Organelles that contain digestive enzymes to break down waste materials and cellular debris.

  • Role: Involved in autophagy, recycling cellular components, and apoptosis (programmed cell death).

Peroxisomes

  • Function: Organelles that contain enzymes for oxidation reactions, breaking down fatty acids and detoxifying harmful substances.

  • Role: Involved in lipid metabolism and the production and breakdown of hydrogen peroxide.

Functions of Lysosomes:

  • Digestion: Break down waste materials and cellular debris.

  • Autophagy: Recycle damaged organelles.

  • Defense: Destroy pathogens in immune cells.

Functions of Peroxisomes:

  • Lipid Metabolism: Break down fatty acids and synthesize lipids.

  • Detoxification: Neutralize harmful substances like hydrogen peroxide.

  • Metabolism: Involved in the metabolism of reactive oxygen species.

Page 24: Vacoules

Vacuoles are membrane-bound organelles found in plant and fungal cells, as well as some protists and animal cells. Their functions include:

  1. Storage: Vacuoles store nutrients, waste products, and other substances.

  2. Structural Support: In plant cells, they maintain turgor pressure, helping to keep the cell rigid.

  3. Waste Disposal: They help in the degradation of waste materials.

  4. pH Regulation: Vacuoles can help maintain the pH balance within the cell.

  5. Defense: Some vacuoles contain compounds that deter herbivores or pathogens.

Overall, vacuoles play a crucial role in maintaining cellular homeostasis.

Page 26: Mitochondrion

  • Also known as the “powerhouse of the cell“

Mitochondria are known as the "powerhouses" of the cell. Their main functions include:

  1. ATP Production: They generate adenosine triphosphate (ATP) through cellular respiration, providing energy for cellular activities.

  2. Regulation of Metabolism: Mitochondria play a key role in metabolic pathways, including the citric acid cycle.

  3. Apoptosis: They are involved in programmed cell death, helping to remove damaged cells.

  4. Calcium Storage: Mitochondria help regulate calcium levels within the cell.

  5. Heat Production: In brown adipose tissue, they generate heat through non-shivering thermogenesis.

Cross-Section of a Mitochondrion

  • Outer Membrane: Smooth and permeable, contains porins.

  • Intermembrane Space: Area between the outer and inner membranes.

  • Inner Membrane: Folded into cristae, contains proteins for the electron transport chain.

  • Matrix: Enclosed by the inner membrane, contains enzymes for the Krebs cycle, mitochondrial DNA, and ribosomes.

Page 27: Chloroplast

  • Unique to plant and algae cells.

  • This organelle perform photosynthesis.

A chloroplast cross-section typically reveals several key structures:

  • Outer Membrane: A smooth membrane that encloses the chloroplast.

  • Inner Membrane: A membrane that regulates the passage of materials in and out of the chloroplast.

  • Stroma: The fluid-filled space inside the inner membrane, containing enzymes, DNA, and ribosomes.

  • Thylakoids: Membrane-bound sacs stacked in structures called grana, where photosynthesis occurs.

  • Granum: A stack of thylakoids.

  • Lumen: Inside of thylakoid

Page 28: Mitochondria vs Chloroplast

Mitochondria vs Chloroplast

Feature

Mitochondria

Chloroplast

Function

Energy production (ATP)

Photosynthesis (glucose production)

Location

Found in nearly all eukaryotic cells

Found in plant cells and some algae

Structure

Double membrane, inner folds (cristae)

Double membrane, thylakoids (stacked as grana)

DNA

Contains its own circular DNA

Contains its own circular DNA

Origin

Endosymbiotic theory (from proteobacteria)

Endosymbiotic theory (from cyanobacteria)

  • Both organelles are essential for energy metabolism in cells.

Page 34: Summary

Functions of Golgi Apparatus

  • Modification: Alters proteins and lipids received from the endoplasmic reticulum.

  • Sorting: Directs proteins to their appropriate destinations.

  • Packaging: Encases materials in vesicles for transport.

  • Secretion: Releases substances outside the cell.

Layers of Epidermis

  1. Stratum Corneum: Outermost layer, composed of dead cells.

  2. Stratum Lucidum: Thin, clear layer found in thick skin.

  3. Stratum Granulosum: Contains keratinocytes undergoing keratinization.

  4. Stratum Spinosum: Provides strength and flexibility.

  5. Stratum Basale: Deepest layer, where cell division occurs.

Graphical Representation of Subcellular Organelles

  • Nucleus: Control center, contains DNA.

  • Mitochondria: Powerhouse, produces ATP.

  • Ribosomes: Protein synthesis.

  • Endoplasmic Reticulum: Smooth (lipid synthesis) and Rough (protein synthesis).

  • Golgi Apparatus: Modifies and packages proteins.

  • Lysosomes: Digests waste materials.

Over all summary

Components of the Cell: Subcellular Organelles

  1. Nucleus: Contains genetic material (DNA) and controls cell activities.

  2. Mitochondria: Powerhouse of the cell, produces energy (ATP) through respiration.(houses the cellular respiration)

  3. Ribosomes: Sites of protein synthesis, can be free-floating or attached to the endoplasmic reticulum.

  4. Endoplasmic Reticulum (ER):

    • Rough ER: Studded with ribosomes, involved in protein synthesis and processing.(synthesizes proteins)

    • Smooth ER: Lacks ribosomes, involved in lipid synthesis and detoxification.(Synthesizes lipids)

  5. Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.

  6. Lysosomes: Contain digestive enzymes to break down waste materials and cellular debris.

  7. Peroxisomes: Break down fatty acids and detoxify harmful substances.

  8. Cytoskeleton: Provides structural support and facilitates cell movement.

  9. Photosynthesis: occurs in the chloroplasts(present only in plant and algal cell)

  10. Eukaryotic cell: houses DNA in nucleus

  11. Nuclear pores: allow the exchange of materials through the nuclear envelope.

  12. Lysosomes; Vacoules; Peroxisome: the digestion centers of the cell.

Sample Quiz: Components of the Cell - Subcellular Organelles

  1. What is the function of the nucleus?

    • A) Genetic material storage

    • B) Energy production

    • C) Protein synthesis

  2. Which organelle is known as the powerhouse of the cell?

    • A) Ribosome

    • B) Mitochondria

    • C) Golgi apparatus

  3. What is the role of ribosomes?

    • A) Lipid synthesis

    • B) Protein synthesis

    • C) DNA replication

  4. Which organelle is responsible for packaging and distributing proteins?

    • A) Endoplasmic reticulum

    • B) Lysosomes

    • C) Golgi apparatus

  5. What is the function of lysosomes?

    • A) Digestion of waste materials

    • B) Energy production

    • C) Photosynthesis

Situational Questions for Subcellular Organelles

  1. If a cell is unable to replicate its DNA, which organelle is likely malfunctioning?

  2. A cell is experiencing low energy levels. Which organelle's function might be compromised?

  3. If a cell cannot produce proteins, which organelle might be affected?

  4. A cell shows signs of lipid accumulation. Which type of ER could be involved?

  5. If proteins are not being properly modified and packaged, which organelle is likely at fault?

  6. A buildup of waste materials is observed in a cell. Which organelle may be malfunctioning?

  7. In a plant cell, if photosynthesis is not occurring, which organelle is likely damaged?

  8. If a cell is losing too many nutrients, what organelle's integrity might be compromised?

Answers for Situational questions:

  1. Nucleus

  2. Mitochondria

  3. Ribosomes

  4. Endoplasmic Reticulum

  5. Golgi Apparatus

  6. Lysosomes

  7. Chloroplasts

  8. Cell Membrane

Answers for quiz sample:

  1. A

  2. B

  3. B

  4. C

  5. A