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Questions and Answers
Which organelle is responsible for digesting macromolecules in the cell?
Which organelle is responsible for digesting macromolecules in the cell?
Where are lysosomal enzymes made before being transferred to the Golgi apparatus?
Where are lysosomal enzymes made before being transferred to the Golgi apparatus?
What is the process called when lysosomes use enzymes to recycle the cell's own organelles and macromolecules?
What is the process called when lysosomes use enzymes to recycle the cell's own organelles and macromolecules?
What is the main function of central vacuoles in mature plant cells?
What is the main function of central vacuoles in mature plant cells?
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Which vacuole is responsible for pumping excess water out of cells in freshwater protists?
Which vacuole is responsible for pumping excess water out of cells in freshwater protists?
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What is the solution called that is contained in the central vacuole of plant cells?
What is the solution called that is contained in the central vacuole of plant cells?
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How do some lysosomes arise?
How do some lysosomes arise?
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What is the name of the process when some types of cell engulf another cell by forming a food vacuole?
What is the name of the process when some types of cell engulf another cell by forming a food vacuole?
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What is the acidic environment inside the lysosome important for?
What is the acidic environment inside the lysosome important for?
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What is the main difference between prokaryotic and eukaryotic cells?
What is the main difference between prokaryotic and eukaryotic cells?
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Which organelles are involved in the production of hydrolytic enzymes and lysosomal membranes?
Which organelles are involved in the production of hydrolytic enzymes and lysosomal membranes?
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Which of the following is a characteristic of prokaryotic cells?
Which of the following is a characteristic of prokaryotic cells?
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What is the function of ribosomes in cells?
What is the function of ribosomes in cells?
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What is the region between the plasma membrane and nucleus called in eukaryotic cells?
What is the region between the plasma membrane and nucleus called in eukaryotic cells?
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What is the function of the plasma membrane in cells?
What is the function of the plasma membrane in cells?
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What is the function of the nucleus in eukaryotic cells?
What is the function of the nucleus in eukaryotic cells?
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What is the main function of cytosol in cells?
What is the main function of cytosol in cells?
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Which organelle is responsible for synthesizing lipids, detoxifying drugs and poisons, and storing calcium ions?
Which organelle is responsible for synthesizing lipids, detoxifying drugs and poisons, and storing calcium ions?
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What is the function of the Golgi apparatus?
What is the function of the Golgi apparatus?
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What is the role of the nuclear envelope?
What is the role of the nuclear envelope?
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What is the basic fabric of biological membranes?
What is the basic fabric of biological membranes?
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Where is most of the DNA in a eukaryotic cell located?
Where is most of the DNA in a eukaryotic cell located?
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What is the function of the nucleolus?
What is the function of the nucleolus?
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What regulates the entry and exit of molecules from the nucleus?
What regulates the entry and exit of molecules from the nucleus?
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What is the function of the endomembrane system?
What is the function of the endomembrane system?
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True or false: Lysosomal enzymes are synthesized in the Smooth ER and then transferred to the Golgi apparatus for further processing?
True or false: Lysosomal enzymes are synthesized in the Smooth ER and then transferred to the Golgi apparatus for further processing?
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True or false: Vacuoles are large vesicles derived from the ER and Golgi apparatus, performing various functions in different types of cells?
True or false: Vacuoles are large vesicles derived from the ER and Golgi apparatus, performing various functions in different types of cells?
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Study Notes
Cell Study
- Cells are usually too small to be seen by the naked eye, making microscopes and biochemistry essential tools for studying them.
Microscopy
- Microscopes are used to visualize cells.
- In a light microscope (LM), visible light is passed through a specimen and then through glass lenses.
- Lenses refract (bend) the light to magnify the image.
Prokaryotic and Eukaryotic Cells
- There are two types of cells: prokaryotic and eukaryotic.
- Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells.
- Protists, fungi, animals, and plants all consist of eukaryotic cells.
- Basic features of all cells:
- Plasma membrane
- Semifluid substance called cytosol
- Chromosomes (carry genes)
- Ribosomes (make proteins)
- Prokaryotic cells:
- No nucleus
- DNA in an unbound region called the nucleoid
- No membrane-bound organelles
- Cytoplasm bound by the plasma membrane
- Eukaryotic cells:
- DNA in a nucleus that is bounded by a double membrane
- Membrane-bound organelles
- Cytoplasm in the region between the plasma membrane and nucleus
- Generally larger than prokaryotic cells
Cell Size and Metabolic Requirements
- Metabolic requirements set upper limits on the size of cells.
- The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell.
- The surface area to volume ratio of a cell is critical.
- As a cell increases in size, its volume grows proportionately more than its surface area.
Eukaryotic Cell Structure
- A eukaryotic cell has internal membranes that divide the cell into compartments (organelles).
- The cell's compartments provide different local environments so that incompatible processes can occur in a single cell.
- The basic fabric of biological membranes is a double layer of phospholipids and other lipids.
- Plant and animal cells have most of the same organelles.
Nucleus
- The nucleus contains most of the cell's genes and is usually the most conspicuous organelle.
- The nuclear envelope encloses the nucleus, separating it from the cytoplasm.
- The nuclear envelope is a double membrane; each membrane consists of a lipid bilayer.
- Pores, lined with a structure called a pore complex, regulate the entry and exit of molecules from the nucleus.
- The nuclear side of the envelope is lined by the nuclear lamina, which is composed of proteins and maintains the shape of the nucleus.
- There is evidence for a nuclear matrix, a framework of protein fibers throughout the interior of the nucleus.
Chromosomes and Ribosomes
- In the nucleus, DNA is organized into discrete units called chromosomes.
- Each chromosome contains one DNA molecule associated with proteins, called chromatin.
- Chromatin condenses to form discrete chromosomes as a cell prepares to divide.
- The nucleolus, located within the nucleus, is the site of ribosomal RNA (rRNA) synthesis.
- Ribosomes are complexes made of ribosomal RNA and protein.
- Ribosomes build proteins in two locations:
- In the cytosol (free ribosomes)
- On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)
Endomembrane System
- The endomembrane system consists of:
- Nuclear envelope
- Endoplasmic reticulum
- Golgi apparatus
- Lysosomes
- Vacuoles
- Plasma membrane
- These components are either continuous or connected via transfer by vesicles.
Endoplasmic Reticulum
- The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells.
- The ER membrane is continuous with the nuclear envelope.
- There are two distinct regions of ER:
- Smooth ER, which lacks ribosomes
- Rough ER, whose surface is studded with ribosomes
- Functions of Smooth ER:
- Synthesizes lipids
- Detoxifies drugs and poisons
- Stores calcium ions
- Functions of Rough ER:
- Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates)
- Distributes transport vesicles, secretory proteins surrounded by membranes
- Is a membrane factory for the cell
Golgi Apparatus
- The Golgi apparatus consists of flattened membranous sacs called cisternae.
- The Golgi apparatus:
- Modifies products of the ER
- Manufactures certain macromolecules
- Sorts and packages materials into transport vesicles
Lysosomes
- A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules.
- Lysosomal enzymes work best in the acidic environment inside the lysosome.
- Hydrolytic enzymes and lysosomal membranes are made by rough ER and then transferred to the Golgi apparatus for further processing.
- Some lysosomes probably arise by budding from the trans face of the Golgi apparatus.
Vacuoles
-
Vacuoles are large vesicles derived from the ER and Golgi apparatus.
-
Vacuoles perform a variety of functions in different kinds of cells.
-
Examples of vacuole functions:
- Food vacuoles are formed by phagocytosis
- Contractile vacuoles, found in many freshwater protists, pump excess water out of cells
- Central vacuoles, found in many mature plant cells, contain a solution called sap
- The central vacuole plays a major role in the growth of plant cells### The Endomembrane System
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The endomembrane system consists of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane.
-
These components are either continuous or connected via transfer by vesicles.
The Endoplasmic Reticulum (ER)
- The ER accounts for more than half of the total membrane in many eukaryotic cells.
- The ER membrane is continuous with the nuclear envelope.
- There are two distinct regions of ER:
- Smooth ER, which lacks ribosomes.
- Rough ER, whose surface is studded with ribosomes.
Functions of Smooth ER
- Synthesizes lipids.
- Detoxifies drugs and poisons.
- Stores calcium ions.
Functions of Rough ER
- Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates).
- Distributes transport vesicles, secretory proteins surrounded by membranes.
- Is a membrane factory for the cell.
The Golgi Apparatus
- Consists of flattened membranous sacs called cisternae.
- Modifies products of the ER.
- Manufactures certain macromolecules.
- Sorts and packages materials into transport vesicles.
Lysosomes
- A membranous sac of hydrolytic enzymes that can digest macromolecules.
- Lysosomal enzymes work best in the acidic environment inside the lysosome.
- Hydrolytic enzymes and lysosomal membranes are made by rough ER and then transferred to the Golgi apparatus for further processing.
- Some lysosomes probably arise by budding from the trans face of the Golgi apparatus.
Functions of Lysosomes
- Digest macromolecules.
- Engulf and digest another cell by phagocytosis, forming a food vacuole.
- Use enzymes to recycle the cell's own organelles and macromolecules, a process called autophagy.
Vacuoles
- Large vesicles derived from the ER and Golgi apparatus.
- Perform a variety of functions in different kinds of cells.
- Types of vacuoles include:
- Food vacuoles, formed by phagocytosis.
- Contractile vacuoles, found in many freshwater protists, pump excess water out of cells.
- Central vacuoles, found in many mature plant cells, contain a solution called sap, and play a major role in the growth of plant cells.
Cellular Structure and Function
- The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell.
- The surface area to volume ratio of a cell is critical.
- As a cell increases in size, its volume grows proportionately more than its surface area.
The Nucleus
- Contains most of the cell's genes and is usually the most conspicuous organelle.
- The nuclear envelope encloses the nucleus, separating it from the cytoplasm.
- The nuclear envelope is a double membrane, each consisting of a lipid bilayer.
- Pores, lined with a structure called a pore complex, regulate the entry and exit of molecules from the nucleus.
- The nuclear side of the envelope is lined by the nuclear lamina, which is composed of proteins and maintains the shape of the nucleus.
Ribosomes
- Complexes made of ribosomal RNA and protein.
- Build proteins in two locations:
- In the cytosol (free ribosomes).
- On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes).
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Description
Test your knowledge on microscopy and cell study techniques with this quiz. Learn about the different types of microscopes used to visualize cells and explore how biochemistry plays a role in cell study.
