Podcast
Questions and Answers
The cell is a simple structure with no specialized organelles.
The cell is a simple structure with no specialized organelles.
False
The cytoplasm serves as a suspending medium for subcellular organelles.
The cytoplasm serves as a suspending medium for subcellular organelles.
True
The lipid bilayer of the plasma membrane allows all molecules to freely pass in and out of the cell.
The lipid bilayer of the plasma membrane allows all molecules to freely pass in and out of the cell.
False
Glycolysis occurs in the cytoplasm.
Glycolysis occurs in the cytoplasm.
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The cell membrane contains carbohydrates that are attached to proteins and lipids.
The cell membrane contains carbohydrates that are attached to proteins and lipids.
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The cytoskeleton consists of filaments and tubules.
The cytoskeleton consists of filaments and tubules.
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The outer membrane of the nucleus is smooth and not linked to any other structures.
The outer membrane of the nucleus is smooth and not linked to any other structures.
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Nuclear pores allow the passage of proteins and RNA.
Nuclear pores allow the passage of proteins and RNA.
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The cytoskeleton plays a role in preserving the shape of the cell.
The cytoskeleton plays a role in preserving the shape of the cell.
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Nucleoli are found in the cytoplasm and are involved in the assembly of cell membranes.
Nucleoli are found in the cytoplasm and are involved in the assembly of cell membranes.
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All living things have a basic building block in common, which is the cell.
All living things have a basic building block in common, which is the cell.
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Humans contain about 30 million cells.
Humans contain about 30 million cells.
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Cells arise from spontaneous generation.
Cells arise from spontaneous generation.
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Growth and development result from the increase in the number of cells.
Growth and development result from the increase in the number of cells.
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Cell junctions have no significance in cell structure.
Cell junctions have no significance in cell structure.
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DNA is stored in mitochondria.
DNA is stored in mitochondria.
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The rough endoplasmic reticulum (ER) is involved in protein synthesis.
The rough endoplasmic reticulum (ER) is involved in protein synthesis.
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Lysosomes have an internal pH of approximately 7.0.
Lysosomes have an internal pH of approximately 7.0.
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The Golgi apparatus is involved in protein modification and packaging.
The Golgi apparatus is involved in protein modification and packaging.
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Mitochondria generate ATP through oxidative phosphorylation.
Mitochondria generate ATP through oxidative phosphorylation.
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Both smooth and rough ER have ribosomes attached.
Both smooth and rough ER have ribosomes attached.
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Proteasomes are involved in digesting biological molecules.
Proteasomes are involved in digesting biological molecules.
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The inner membrane of mitochondria has folds called cristae.
The inner membrane of mitochondria has folds called cristae.
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The smooth ER is involved in lipid metabolism.
The smooth ER is involved in lipid metabolism.
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The lysosomal membrane allows substrates to freely enter and exit.
The lysosomal membrane allows substrates to freely enter and exit.
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Ubiquitin is a protein that labels cytosolic proteins for destruction.
Ubiquitin is a protein that labels cytosolic proteins for destruction.
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Peroxisomes are involved in the synthesis of proteins.
Peroxisomes are involved in the synthesis of proteins.
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Cell junctions allow cells to adhere to each other and form tissues.
Cell junctions allow cells to adhere to each other and form tissues.
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Tight junctions leave space between the plasma membranes of adjacent cells.
Tight junctions leave space between the plasma membranes of adjacent cells.
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Desmosomes are also known as gap junctions.
Desmosomes are also known as gap junctions.
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Connexins are proteins that form the gaps in gap junctions.
Connexins are proteins that form the gaps in gap junctions.
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Cell adhesion is important for cell communication and tissue development.
Cell adhesion is important for cell communication and tissue development.
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CAMs are involved in inhibiting cell communication.
CAMs are involved in inhibiting cell communication.
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Glycoproteins on cell surfaces function as identification tags.
Glycoproteins on cell surfaces function as identification tags.
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Peroxisomes contain primarily enzymes called oxidases and catalases.
Peroxisomes contain primarily enzymes called oxidases and catalases.
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Humans contain about 30 trillion cells, experiencing a loss of 70 billion cells every day.
Humans contain about 30 trillion cells, experiencing a loss of 70 billion cells every day.
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Cells can arise from spontaneous generation when in favorable conditions.
Cells can arise from spontaneous generation when in favorable conditions.
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Growth and development are caused by both an increase in cell number and their differentiation into different types.
Growth and development are caused by both an increase in cell number and their differentiation into different types.
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The hierarchy of biological organization begins with the population level.
The hierarchy of biological organization begins with the population level.
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All living things share a common building block, which is the organ.
All living things share a common building block, which is the organ.
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The cytoskeleton allows molecules to move around the cell and interact with each other.
The cytoskeleton allows molecules to move around the cell and interact with each other.
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Nucleoli are located within the cytoplasm and are responsible for the assembly of nucleotides.
Nucleoli are located within the cytoplasm and are responsible for the assembly of nucleotides.
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Chromatin is a combination of DNA and proteins that forms chromosomes.
Chromatin is a combination of DNA and proteins that forms chromosomes.
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The inner nuclear membrane is rough and studded with ribosomes.
The inner nuclear membrane is rough and studded with ribosomes.
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Nucleoplasm is the gel-like substance found inside the nucleus that surrounds chromatin and nucleoli.
Nucleoplasm is the gel-like substance found inside the nucleus that surrounds chromatin and nucleoli.
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The cell membrane is solely responsible for regulating the internal environment of the cytoplasm.
The cell membrane is solely responsible for regulating the internal environment of the cytoplasm.
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The cytoplasm includes only the cytosol and does not contain any organelles.
The cytoplasm includes only the cytosol and does not contain any organelles.
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Carbohydrates attached to proteins and lipids in the cell membrane serve a role in communication and recognition.
Carbohydrates attached to proteins and lipids in the cell membrane serve a role in communication and recognition.
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Glycolysis occurs exclusively in the mitochondria of eukaryotic cells.
Glycolysis occurs exclusively in the mitochondria of eukaryotic cells.
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The cytoplasmic matrix plays an essential role in cell shape and internal organization.
The cytoplasmic matrix plays an essential role in cell shape and internal organization.
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The fate of DNA is influenced by signals that the cell receives.
The fate of DNA is influenced by signals that the cell receives.
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The smooth endoplasmic reticulum (ER) is where protein synthesis occurs.
The smooth endoplasmic reticulum (ER) is where protein synthesis occurs.
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The Golgi apparatus is responsible for the degradation of biological molecules.
The Golgi apparatus is responsible for the degradation of biological molecules.
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Mitochondria contain enzymes for the Krebs cycle and oxidative phosphorylation.
Mitochondria contain enzymes for the Krebs cycle and oxidative phosphorylation.
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The primary function of peroxisomes is the synthesis of proteins.
The primary function of peroxisomes is the synthesis of proteins.
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The lysosomal membrane has a neutral pH that is optimal for enzyme activity.
The lysosomal membrane has a neutral pH that is optimal for enzyme activity.
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Protein complexes in proteasomes are arranged in a single ring structure.
Protein complexes in proteasomes are arranged in a single ring structure.
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Tight junctions allow for the leakage of substances between adjacent cells.
Tight junctions allow for the leakage of substances between adjacent cells.
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Desmosomes are a type of gap junction that allows cell communication.
Desmosomes are a type of gap junction that allows cell communication.
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Lysosomes can destroy aged cell organelles by engulfing them.
Lysosomes can destroy aged cell organelles by engulfing them.
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Connexins are proteins that form a pore known as the connexon in gap junctions.
Connexins are proteins that form a pore known as the connexon in gap junctions.
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The outer membrane of mitochondria is impermeable to all molecules.
The outer membrane of mitochondria is impermeable to all molecules.
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Cell adhesion molecules (CAMs) play a role in the regulation of the cell cycle.
Cell adhesion molecules (CAMs) play a role in the regulation of the cell cycle.
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Ribosomes are found on both types of endoplasmic reticulum.
Ribosomes are found on both types of endoplasmic reticulum.
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Cisterns are the flattened containers that make up the Golgi apparatus.
Cisterns are the flattened containers that make up the Golgi apparatus.
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Glycoproteins act as identification tags on cell surfaces, recognized by other cells.
Glycoproteins act as identification tags on cell surfaces, recognized by other cells.
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The proteasome is responsible for detoxifying the cell.
The proteasome is responsible for detoxifying the cell.
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Ubiquitin is a molecule that labels proteins for degradation by lysosomes.
Ubiquitin is a molecule that labels proteins for degradation by lysosomes.
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Chemical detoxification and lipid metabolism are functions of the lysosome.
Chemical detoxification and lipid metabolism are functions of the lysosome.
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Cell junctions are not significant for the formation of tissues and organs.
Cell junctions are not significant for the formation of tissues and organs.
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Humans contain about 30 trillion cells, with around 70 million cells dying and being replaced daily.
Humans contain about 30 trillion cells, with around 70 million cells dying and being replaced daily.
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Cells only arise from spontaneous generation when conditions are favorable.
Cells only arise from spontaneous generation when conditions are favorable.
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The hierarchy of biological organization starts with the organ at the lowest level.
The hierarchy of biological organization starts with the organ at the lowest level.
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All living things share a common building block, which is the cell.
All living things share a common building block, which is the cell.
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Growth and development can occur through an increase in the number of cells and their differentiation into similar types.
Growth and development can occur through an increase in the number of cells and their differentiation into similar types.
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The outer layer of the nuclear envelope may be connected to the cytoskeleton.
The outer layer of the nuclear envelope may be connected to the cytoskeleton.
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Chromatin consists solely of DNA without any associated proteins.
Chromatin consists solely of DNA without any associated proteins.
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The nucleoplasm is a semi-fluid substance found within the cytoplasm of the cell.
The nucleoplasm is a semi-fluid substance found within the cytoplasm of the cell.
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The cytoskeleton is responsible for the transport of materials within the nucleus.
The cytoskeleton is responsible for the transport of materials within the nucleus.
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Nucleoli are primarily responsible for the assembly of ribosomes and are found within the nucleus.
Nucleoli are primarily responsible for the assembly of ribosomes and are found within the nucleus.
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The plasma membrane is comprised solely of proteins that facilitate molecule movement in and out of the cell.
The plasma membrane is comprised solely of proteins that facilitate molecule movement in and out of the cell.
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The cytoplasm serves only as a fluid environment for cellular reactions and does not support any organelles.
The cytoplasm serves only as a fluid environment for cellular reactions and does not support any organelles.
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The structural composition of the cytoplasm includes a viscous aqueous solution known as cytosol.
The structural composition of the cytoplasm includes a viscous aqueous solution known as cytosol.
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Carbohydrates attached to proteins and lipids within the cell membrane do not play a role in cellular communication.
Carbohydrates attached to proteins and lipids within the cell membrane do not play a role in cellular communication.
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Glycolysis is the final stage of cellular respiration occurring in the cytoplasm.
Glycolysis is the final stage of cellular respiration occurring in the cytoplasm.
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The Golgi apparatus is primarily responsible for the synthesis of ATP.
The Golgi apparatus is primarily responsible for the synthesis of ATP.
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Lysosomes have a pH of approximately 5.0, which is ideal for the activity of their enzymes.
Lysosomes have a pH of approximately 5.0, which is ideal for the activity of their enzymes.
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The rough endoplasmic reticulum is continuous with the smooth endoplasmic reticulum and contains ribosomes.
The rough endoplasmic reticulum is continuous with the smooth endoplasmic reticulum and contains ribosomes.
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The proteasome is an organelle that generates ATP through the Krebs cycle.
The proteasome is an organelle that generates ATP through the Krebs cycle.
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Mitochondria have triple membranes that are critical for their function.
Mitochondria have triple membranes that are critical for their function.
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The smooth endoplasmic reticulum is involved in carbohydrate metabolism.
The smooth endoplasmic reticulum is involved in carbohydrate metabolism.
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The cytoplasmic structure known as the cis-Golgi is closest to the cell membrane.
The cytoplasmic structure known as the cis-Golgi is closest to the cell membrane.
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DNA replication occurs in the rough endoplasmic reticulum.
DNA replication occurs in the rough endoplasmic reticulum.
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Acid hydrolases in lysosomes are responsible for digesting biological molecules.
Acid hydrolases in lysosomes are responsible for digesting biological molecules.
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Proteins destined for destruction are labelled with a protein called ubiquitin.
Proteins destined for destruction are labelled with a protein called ubiquitin.
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Peroxisomes primarily synthesize proteins through enzymatic activity.
Peroxisomes primarily synthesize proteins through enzymatic activity.
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Tight junctions allow space between the plasma membranes of adjacent cells.
Tight junctions allow space between the plasma membranes of adjacent cells.
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Cell adhesion is facilitated by proteins known as CAMs, which promote tissue development.
Cell adhesion is facilitated by proteins known as CAMs, which promote tissue development.
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Glycoproteins on cell surfaces act as receptors for hormones exclusively.
Glycoproteins on cell surfaces act as receptors for hormones exclusively.
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Connexins form a structure called connexon in gap junctions, facilitating cell communication.
Connexins form a structure called connexon in gap junctions, facilitating cell communication.
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Cell junctions play a significant role in facilitating nutrient transfer and chemical signaling between cells.
Cell junctions play a significant role in facilitating nutrient transfer and chemical signaling between cells.
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Apoptosis is solely a process of cell division.
Apoptosis is solely a process of cell division.
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Desmosomes function primarily to form seals between adjacent cells.
Desmosomes function primarily to form seals between adjacent cells.
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The role of peroxisomes includes the detoxification of harmonic substances in the cell.
The role of peroxisomes includes the detoxification of harmonic substances in the cell.
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Study Notes
The Hierarchy of Biological Organisation
- The hierarchy starts with atoms and ends with the biosphere.
- Cells form the foundation for tissues, organs, organ systems, organisms, populations, and ecosystems.
The Cell
- All living things are made up of cells.
- The human body contains approximately 30 trillion cells, with billions being replaced daily.
- Cells arise only from pre-existing cells through cell division.
- Growth and development result from the increase in cell numbers and differentiation into various types.
Basic Structure of the Eukaryotic Cell
- The cell is a complex internal structure, not merely a collection of molecules.
- It contains numerous specialized organelles.
- It has distinct internal micro-environments.
The Cell/Plasma Membrane
- Composed of a lipid bilayer with embedded proteins and attached carbohydrates.
- Acts as a barrier, isolating the cell and regulating molecule movement in and out.
- Maintains a unique intracellular pH environment.
- Responds to changes in the cell's internal and external environments.
The Cytoplasm
- This viscous, aqueous solution fills the space between the cell membrane and nucleus.
- Provides a suspension medium for subcellular organelles.
- The fluid part outside all organelles is called the cytosol.
- It's the site of numerous cellular processes:
- Protein synthesis
- The initial stage of cellular respiration (glycolysis)
- The events of mitosis and meiosis
- Facilitates molecule movement and interaction within the cell.
The Cytoskeleton
- Composed of filaments (actin) and tubules.
- The mesh of actin filaments beneath the plasma membrane links with membrane proteins, potentially connecting with molecules in the extracellular matrix (ECM).
- This protein scaffolding maintains cell shape, allows for shape changes, provides a framework for movement and material transport.
The Nucleus
- Enclosed by a double membrane known as the nuclear envelope.
- The inner membrane is smooth, while the outer membrane may be connected to the endoplasmic reticulum (ER).
- Nuclear pores regulate the passage of molecules through the envelope, allowing proteins and RNA to move in and out.
- Contains chromatin, a mixture of DNA and proteins forming chromosomes.
- Contains one or more nucleoli, the sites of ribosome assembly, rich in RNA and proteins.
- Surrounded by a gel-like substance called the nucleoplasm.
DNA in the Cell
- DNA is stored within chromosomes in the nucleus.
- Its fate depends on signals the cell receives.
- These signals can cause DNA to remain quiescent, be transcribed into RNA for protein synthesis, or replicate for cell division.
From DNA to Protein
- DNA is transcribed into RNA.
- RNA is translated into protein.
The Endoplasmic Reticulum (ER)
- A network of interconnected membranous tubules and sacs extending from the nucleus into the cytoplasm.
- Two types:
- Rough ER, covered with ribosomes, involved in protein synthesis.
- Smooth ER, continuous with rough ER but lacking ribosomes, involved in lipid metabolism.
The Golgi Apparatus
- Stacks of flattened containers called cisterns or sacs located in the cytosol between the ER and cell membrane.
- The cis-Golgi is closer to the nucleus, while the trans-Golgi is nearer the cell membrane.
- Connected to cytoskeletal filaments.
- Involved in:
- Modifying proteins and lipids through glycosylation (carbohydrate attachment)
- Sorting and distributing them to other organelles.
- Packaging them for secretion from the cell.
The Mitochondrion
- Sausage-shaped, with a double membrane separated by an intermembrane space.
- The outer membrane is permeable to small molecules.
- The inner membrane has multiple folds (cristae) projecting inwards, containing the electron transport chain enzymes, the Krebs cycle, and the pathway for fatty acid beta-oxidation.
- Its interior (matrix) is where most cellular ATP is generated through oxidative phosphorylation.
- Abundant in cells with high energy demands.
The Lysosome
- Spherical or oval organelles with a single-layer membrane.
- Contains acid hydrolases (degradative enzymes) that digest most biological molecules.
- Maintains a pH of approximately 5.0, optimal for enzyme activity, providing a protective function.
- Vesicles from the Golgi apparatus fuse with lysosomes, delivering their contents for degradation.
- Also responsible for destroying aged cell organelles.
The Proteasome
- A multi-subunit enzyme complex arranged in four rings around a central hollow core.
- Degrades cytosolic proteins.
- Involved in controlling the cell cycle and apoptosis.
- Proteins destined for destruction are labeled with ubiquitin, directing them to the proteasome's core for enzyme-mediated breakdown.
The Peroxisome
- Similar to lysosomes, with a single lipid bilayer.
- Contains numerous enzymes, mainly oxidases and catalases.
- Involved in:
- Lipid metabolism, including the breakdown of very long-chain fatty acids (VLCFA)
- Chemical detoxification of the cell.
Cell Junctions
- Cells adhere to form tissues and organs.
- Common types of cell junctions:
- Tight junctions
- Anchoring/adhesive junctions (desmosomes)
- Gap/communicating junctions
The Tight Junction
- A protein complex between two cells creating a seal to prevent leakage through the cell membrane.
- No space is left between the plasma membranes.
- In polarized cells, they prevent the movement of membrane proteins from one side to the other.
The Anchoring/Adhesive Junctions
- Connect the cytoskeleton to neighboring cells or the extracellular matrix.
- Formed by intracellular anchor proteins linked to transmembrane adhesion proteins.
The Gap/Communicating Junctions
- Formed by proteins (connexins) that create tunnels between cells.
- Connexin proteins form pores (connexons) in the cell membrane.
- Enable cells to communicate, share nutrients (water, ions, sugars, amino acids), and transfer chemical and electrical signals.
Cell Adhesion
- The ability of one cell to attach to another or to the extracellular matrix.
- Plays a role in cell communication and regulation.
- Essential for tissue maintenance and development.
- Stimulates signals that regulate cell differentiation, cycle, migration, and survival.
- Occurs through cell adhesion molecules (CAMs).
Cell Recognition
- Cell surface proteins with attached sugars (glycoproteins) act as identification tags.
- These tags are specifically recognized by other cells.
The Hierarchy of Biological Organisation
- The simplest unit is the atom, which forms molecules, which in turn create cells.
- Cells are the basic building blocks of living things, forming organelles and tissues.
- Tissues form organs, which work together to create organ systems within a multicellular organism.
- Organisms are part of a population that resides in an ecosystem, which belongs to the biosphere.
The Cell
- Human body contains about 30 trillion cells, with 70 billion dying and being replaced each day.
- Cells arise only from pre-existing cells, by cell division.
- Growth and development are driven by the increase in cell number and their differentiation to various types.
Basic Structure of the Eukaryotic Cell
- Eukaryotic cell is not a simple "bag of molecules", instead it possesses a complex internal structure.
- Its structure contains many specialized organelles and different internal micro-environments.
The Cell (Plasma) Membrane
- Composed of a lipid bilayer with embedded proteins and attached carbohydrates.
- Acts as a barrier, regulating molecule movement into and out of the cell.
- Maintains a unique intracellular pH environment and responds to changes in the cell's environment.
The Cytoplasm
- Viscous, aqueous solution filling the space between cell membrane and nucleus.
- Suspends and solubilizes organelles and cellular molecules.
- Location for many cellular processes, including protein synthesis, glycolysis, and events of mitosis and meiosis.
The Cytoskeleton
- It's the protein scaffolding of the cell, preserving its shape and allowing for changes in shape if needed.
- Provides a frame for cell movement and a framework for transporting materials.
The Nucleus
- Surrounded by a double-layered nuclear envelope consisting of inner smooth membrane and outer membrane linked to the ER.
- It contains chromatin, a mix of DNA and proteins that form chromosomes.
- One or more nucleoli are present, where ribosomes are assembled.
- Nucleoplasm is the gel-like substance surrounding chromatin and nucleoli.
The Fate of DNA in the Cell
- DNA is stored in chromosomes within the nucleus, and its fate is dependent on signals the cell receives.
- These signals can influence DNA's function, whether to remain dormant, be translated into RNA for protein synthesis, or replicate for cell division.
From DNA to Protein
- DNA is transcribed into RNA.
- RNA is translated into protein.
The Endoplasmic Reticulum (ER)
- A network of interconnected membranous tubules and sacs extending from the nucleus into the cytoplasm.
- Two types: rough ER with ribosomes and smooth ER without.
- Rough ER is involved in protein synthesis, while smooth ER is involved in lipid metabolism.
The Golgi Apparatus
- Consists of stacks of flattened containers called cisterns or sacs, located in the cytosol between the ER and cell membrane.
- Modifies proteins and lipids through glycosylation, sorts and distributes them to organelles within the cell, packages them for secretion.
The Mitochondrion
- Sausage-shaped organelle with double membrane separated by the intermembrane space.
- Outer membrane is permeable to small molecules, while inner membrane, with cristae folds, is less permeable.
- Inner space, the matrix, contains enzymes for electron transport chain, Krebs cycle, and fatty acid β-oxidation.
- Generates most of the cellular ATP through oxidative phosphorylation.
The Lysosome
- Spherical or oval organelles with a single-layered membrane, containing acid hydrolases (degradative enzymes).
- Low pH (~5.0) is optimal for enzyme activity, facilitating degradation of biological molecules.
- Vesicles from the Golgi apparatus fuse with lysosomes to deliver content for degradation, and lysosomes also destroy aged organelles.
The Proteasome
- Multi-subunit enzyme complex arranged in four rings around a central hollow core.
- Degrades cytosolic proteins and is involved in control of the cell cycle and apoptosis.
- Proteins for degradation are labeled with ubiquitin, which directs them into the core for breakdown by enzymes.
The Peroxisome
- Similar to lysosomes with a single lipid bilayer, containing oxidases and catalases.
- Involved in lipid metabolism (VLCFA breakdown) and chemical detoxification of the cell.
Cell Junctions
- Cells adhere to each other to form tissues and organs.
- Common types of junctions: tight junctions, anchoring/adhesive junctions (desmosomes), gap/communicating junctions.
The Tight Junction
- Protein complex between two cells creating a seal to prevent leakage of content through the cell membrane.
- Leaves no space between plasma membranes of adjacent cells, and in polarized cells, prevents membrane protein movement.
The Anchoring/Adhesive Junctions
- Attach the cytoskeleton to a neighboring cell or the extracellular matrix.
- Junction is made between intracellular anchor proteins and transmembrane adhesion proteins.
The Gap/Communicating Junctions
- Proteins form a tunnel (connexins) between cells, allowing cells to communicate and share nutrients and signals.
- Connexins form pores in the cell membrane called connexons, transferring chemical and electrical signals.
Cell Adhesion
- Ability of one cell to stick to another or the extracellular matrix.
- Important for cell communication and regulation, essential for tissue maintenance and development.
- Adhesion stimulates signals that regulate cell differentiation, cell cycle, migration, and survival.
- Occurs through the action of CAMs (Cell Adhesion Molecules).
Cell Recognition
- Some surface proteins have sugar chains attached, forming glycoproteins.
- These act as identification tags, specifically recognized by other cells, facilitated by cell recognition proteins.
Hierarchy of Biological Organisation
- The smallest unit of life is the cell.
- Organelles are subcellular structures with specific functions, and are found in a specific type of cell.
- Cells are the building blocks of tissues.
- Tissues form organs.
- Organs work together to form organ systems.
- Organ systems make up an organism.
- Organisms contribute to a population which then make up an ecosystem, and finally a biosphere.
The Cell
- All living organisms consist of cells.
- Humans have about 30 trillion cells.
- 70 billion cells die and are replaced every day.
- New cells are created by cell division.
- Cell growth and development is determined by differentiation and an increase in the number of cells.
Basic Structure of the Eukaryotic Cell
- The eukaryotic cell has a complex internal structure.
- It contains many different specialised organelles.
- The eukaryotic cell has different internal micro-environments.
The Cell (Plasma) Membrane
- The cell membrane is made up of a lipid bilayer.
- The cell membrane acts as a barrier.
- The cell membrane regulates the movement of molecules into and out of the cell.
- The cell membrane maintains a unique intracellular pH environment.
- The cell membrane responds to changes in the outside and inside of the cell.
The Cytoplasm
- The cytoplasm is a viscous aqueous solution.
- The cytoplasm occupies the space between the cell membrane and the nucleus.
- The cytoplasm serves as a suspending medium for other subcellular organelles.
- The cytosol is the uid part of the cytoplasm outside all the organelles.
- Cellular processes like protein synthesis, glycolysis, mitosis, and meiosis take place in the cytoplasm.
- The cytoplasm allows molecules to move around the cell and 'find' each other.
The Cytoskeleton
- The cytoskeleton consists of filaments and tubules.
- The cytoskeleton preserves the shape of the cell.
- The cytoskeleton allows the cell to change shape.
- The cytoskeleton provides a framework for movement, intracellular transport of materials, and anchors organelles.
The Nucleus
- The nucleus is surrounded by a double-layered nuclear envelope.
- The nuclear envelope has pores that regulate the passage of molecules.
- The nucleus contains chromatin, which consists of DNA and proteins that make up chromosomes.
- The nucleus contains one or more nucleoli, which are the sites of ribosome assembly.
- The nucleoli contain high amounts of RNA and proteins.
- The nucleoplasm surrounds the chromatin and nucleoli.
The Fate of DNA
- DNA in the cell is stored in chromosomes.
- Specific signals determine the fate of DNA.
- DNA may remain quiescent, be transcribed to RNA for new protein synthesis, or replicate for cell division.
From DNA to Protein
- DNA in the nucleus is transcribed into mRNA.
- mRNA exits the nucleus and is translated into protein by ribosomes in the cytoplasm.
The Endoplasmic Reticulum (ER)
- The ER is a network of interconnected membranous tubules and sacs.
- The ER extends from the nucleus into the cytoplasm.
- There are two types of ER: rough and smooth.
- The rough ER is studded with ribosomes and is involved in protein synthesis.
- The smooth ER does not have ribosomes and is involved in lipid metabolism.
The Golgi Apparatus
- The Golgi apparatus consists of flattened sacs called cisterns.
- The Golgi apparatus is located in the space extending from the ER towards the cell membrane.
- The Golgi apparatus has two parts: the cis-Golgi and the trans-Golgi.
- The Golgi apparatus remains in contact with cytoskeletal filaments.
- The Golgi modifies proteins and lipids through attachment of carbohydrates.
- The Golgi sorts and distributes proteins and lipids to other organelles in the cell.
- The Golgi packages molecules for secretion from the cell.
The Mitochondrion
- Mitochondria are sausage-shaped.
- Mitochondria have a double membrane separated by the intermembrane space.
- The outer mitochondrial membrane is permeable to small molecules.
- The inner mitochondrial membrane has multiple folds called cristae.
- The interior space of the mitochondrion is called the matrix.
- Mitochondria contain enzymes used in electron transport chain, Krebs cycle, and beta-oxidation of fatty acids.
- Mitochondria generate most of the cell's ATP through oxidative phosphorylation.
- Mitochondria are abundant in cells with high energy requirements.
The Lysosome
- Lysosomes have a single-layered membrane.
- Lysosomes contain acid hydrolases.
- Lysosomes have an internal pH of approximately 5.0.
- The pH in lysosomes is optimal for the activity of degradative enzymes.
- Lysosomes destroy aged cell organelles.
- Lysosomes degrade biological molecules.
The Proteasome
- The proteasome is a multi-subunit enzyme complex.
- The proteasome degrades cytosolic proteins.
- The proteasome is involved in regulating the cell cycle and apoptosis.
- Proteins destined for destruction are tagged with ubiquitin.
- Ubiquitinated proteins are directed to the proteasome for degradation.
Peroxisome
- Peroxisomes have a single lipid bilayer membrane.
- Peroxisomes contain many enzymes, especially oxidases and catalases.
- Peroxisomes are involved in lipid metabolism and breakdown of very long-chain fatty acids.
- Peroxisomes participate in chemical detoxification of the cell.
Cell Junctions
- Cell junctions connect cells to form tissues and organs.
- The main types of cell junctions are tight junctions, anchoring/adhesive junctions (desmosomes), and gap/communicating junctions.
The Tight Junction
- Tight junctions are protein complexes between two cells.
- Tight junctions create a seal, preventing leakage through the cell membrane.
- Tight junctions leave no space between the plasma membranes of adjacent cells.
- In polarized cells, tight junctions prevent movement of membrane proteins from one side to the other.
The Anchoring/Adhesive Junction
- Anchoring/adhesive junctions connect the cytoskeleton to a neighboring cell or the extracellular matrix.
- Anchoring/adhesive junctions are made up of intracellular anchor proteins and transmembrane adhesion proteins.
The Gap/Communicating Junction
- Gap junctions are formed by connexins that create a tunnel between cells.
- Connexins form a pore in the cell membrane called a connexon.
- Gap junctions allow cells to communicate with each other.
- Gap junctions allow for sharing of nutrients, ions, sugars, and amino acids.
- Gap junctions facilitate the transfer of chemical and electrical signals.
Cell Adhesion
- Cell adhesion refers to the ability of cells to stick to each other or the extracellular matrix.
- Cell adhesion is essential for cell communication and tissue maintenance and development.
- Cell adhesion stimulates signals that influence cell differentiation, cell cycle, cell migration, and cell survival.
- Cell adhesion is mediated by proteins called CAMs.
Cell Recognition
- Some cell surface proteins have short sugar chains attached to them, forming glycoproteins.
- Glycoproteins act as identification tags.
- These glycoproteins are specifically recognized by other cells.
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Description
Explore the hierarchy of biological organization, starting from atoms and culminating in the biosphere. Delve into the fundamental structure of eukaryotic cells, their essential components, and the critical role of the cell membrane in maintaining cellular integrity and function.
