3.1.2 Anatomy Of A Generalized Cell Flashcards
3 Basic componentes of the cells
- Nucleus
- Plasma membrane
- Cytoplasm
The nucleus is the ________ _________ of the cell.
Control center
The main parts of the nucleus
Nuclear envelope
Nucleolus
Chromatin
What is the nuclear envelope?
Double membrane barrier around the nucleus
Function of the nuclear pores
Allow only selective substances to pass to the nucleus
What is the nucleoplasm?
Jellylike fluid present in the nucleus
Nucleolus
Site where ribosomes are assembled
Synthesis of ribosomes
Ribosomes are assembled in the nucleolus and then transported out to through the nuclear pores to the cytoplasm, where they serve as actual sites for protein synthesis.
Chromatin
When a cell is not dividing, its DNA is wound around histones to form a loose network of “beads on a string” called chromatin
Chromosome
When a cell is dividing, the chromatin threads coil and
condense to form dense, rodlike bodies called chromosomes.
What is the plasma membrane?
A barrier that contains the cell contents and separates them from the surrounding environment.
The structure of the plasma membrane contains:
Two phospholipid layers (Phospholipid bilayer)
Cholesterol
Floating proteins
What does the term “mosaic” refer to?
The scattering of the different proteins within the phospholipid bilayer
The phospholipids are arranged:
Tail to tail
Describe the properties of head and tail of the membrane in terms of polar and non polar
Head - hydrophilic (polar)
Tail - Hydrophobic (non polar)
True or False
The membrane is permeable to most of the water soluble molecules
False
The membrane is impermeable due to the hydrophobic layer
How can water enter the cell?
Through aquaporins
Con lipids enter the cells through the membrane without a channel?
Yes
The phospholipid membrane is lipid soluble
Membrane proteins
Transporters
Receptors
Enzymes
Anchor proteins
Function of the transporters
Carry a molecule from one side of the plasma membrane to another
Function of the receptors
Can bind to an extracellular molecule to activate an extracellular process
Function of the enzymes
Transform the molecules to another form
Function of the anchor proteins
Link the extracellular structure with the intracellular structures
What are glycoproteins
Branching sugar groups attached to most of the proteins in the extracellular space.
Function of the glycoproteins
1) Act as carriers in membrane transport
2) Provide receptor sites for hormones and other chemicals
3) They act as receptors that certain bacteria, viruses, or toxins can bind to
4) They act as enzymes in the membrane to transform a molecule into another form.
5) Facilitate cellular recognition (cell-cell interactions), which is important in development and immune
response.
What are the glycolipids
Phospholipids associated with sugar groups that are components of cell membranes.
Function of the glycolipids
Facilitate cellular recognition
Determination of blood groups
What do we mean by the term “glycocalyx”?
Because of the presence of glycolipids and glycoproteins in the plasma membrane, the cell surface is a fuzzy, sticky, sugar-rich area called the glycocalyx.
Function of the glycocalyx
•Protection: Cushions the plasma membrane and protects it from chemical injury
•Immunity to infection: Enables the immune system to recognize and selectively attack
foreign organisms.
•Defense against cancer: Changes in the glycocalyx of cancerous cells enable the immune
system to recognize and destroy them.
•Transplant compatibility: Forms the basis for compatibility of blood transfusion and organ
transplants.
•Cell adhesion: Glycoproteins in the glycocalyx act as an adhesive or cellular glue, which
bind cells together so that tissues do not fall apart
•Fertilization: Enables sperm to recognize and bind to eggs.
•Control the volume of red blood cells in the blood vessels
Footloose cells
Blood cells
Sperms
Three ways for bounding cells
Glycocalyx (glycoproteins act as an adhesive or cellular glue)
Wavy contours ( Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion)
Cell junctions
Types of cell junctions
Tight junctions
Desmosomes
Gap junctions
Tight junctions
Tight junctions are impermeable (not allowing fluid to pass through) junctions that encircle the cells and bind them together into leakproof sheets, adjacent plasma membranes fuse together tightly and prevent
substances from passing through the extracellular spaces between the cells
Tight junctions in the small intestine
These junctions prevent digestive enzymes from seeping into the bloodstream.
Desmosomes
Desmosomes are anchoring junctions placed along the sides of adjacent cells. They prevent cells subjected to mechanical stress (such as heart muscle cells and skin cells) from being pulled apart.
Structure of the desmosomes
Buttonlike thickenings of adjacent plasma membranes (plaques) that are connected by fine protein
filaments.
Thicker protein filaments extend from the plaques inside the cells to the plaques on the cells’ opposite
sides, thus forming an internal system of strong “wires.”
Function of the gap junctions
Allow communication
Where are most of the gap junctions found?
In the heart
Structure of the gap junctions
cells are connected by hollow (empty) cylinders composed of proteins (called
connexons)
The site for the most cellular activities
The Cytoplasm
The three major components of the cytoplasm
Cytosol
Organelles
Inclusions
What is the cytosol
A semitransparent fluid that suspends organelles and inclusions
The biggest component of the cytosol
Water
It dissolves nutrients and a variety of solutes (dissolved substances) such as ions (sodium and potassium), macromolecules, calcium, and enzymes.
Primary role of the cytosol in the cell
Dissolving nutrients and various solutes
True or False
Inclusions are found in all types of cells
False
Some examples of inclusions include
• Lipid droplets common in fat cells
• Glycogen granules abundant in liver and muscle cells
• Pigments such as melanin in skin and hair cells
• Mucus and other secretory products
• Various kinds of crystals
Structure of the mitochondria
Rod shaped, double membrane, inner membrane folded into projections called cristae
Function of the mitochondria
Produce ATP (carry out cellular respiration))
Replication of mitochondria happens by which process?
Pinching process
Ribosomes are made up of
Ribosomal RNA
Proteins
Structure of the ribosomes
They don’t have membranes
Function of the ribosomes
Ribosomes are the actual sites of protein synthesis in the cell.
Where are the ribosomes found
Some are free in the cytoplasm or attached to rough endoplasmic reticulum (ER).
Ribosomes that float freely in the cytoplasm manufacture proteins that function inside the cell, while others attach to membranes of rough ER, produces proteins that function outside the cell.
Function of the endoplasmic reticulum
Serves as a mini circulatory system for the cell because it provides a network of channels for carrying substances (primarily proteins) from one part of the cell to another.
Structure of the endoplasmic reticulum
System of fluid filled tunnels that coil and twist through the cytoplasm
Structure of the rough ER
It is rough as it is studded with ribosomes
Function of the rough ER
- The proteins made on its ribosomes migrate into the rough ER tunnels, where they fold into their functional three-dimensional shapes. These proteins are then dispatched to other areas of the cell in small “sacs” of membrane called transport vesicles that carry substances around the cell.
- The Rough ER is the site of production for all membrane components, including transmembrane proteins and phospholipids, for most of the cell’s organelles
In what type of cells is the rough ER found?
abundant in cells that make (synthesize) and export (secrete) proteins—for example, pancreatic cells, which produce digestive enzymes to be delivered to the small intestine.
The difference between rough endoplasmic reticulum and the smooth endoplasmic reticulum
Rough - ribosomes are present
Smooth - no ribosomes are present
Function of the smooth endoplasmic reticulum
Lipid metabolism
Detoxification of drugs
Where are the smooth ER found
In the liver cells
In cells that produce steroid-based hormones, such as the cells of the male testes that manufacture testosterone.
Traffic director for cellular proteins
Golgi apparatus
Function of the golgi apparatus
modify, package, and ship proteins, which are sent to it by the
rough ER via transport vesicles, in specific ways depending on their final destination
What are lysosomes
Bag containing powerful digestive enzymes
How are the lysosomes formed?
The enzymes they contain are formed by ribosomes on the rough ER and packaged by the golgi apparatus. They do arise by budding from the Golgi apparatus.
Function of the lysosomes
Lysosomal enzymes are capable of digesting worn-out or nonusable cell structures and most foreign substances that enter the cell; lysosomes function as cellular “stomachs.”
What type of cells are the lysosomes mostly made up of?
Phagocytes
Cells that dispose of bacteria and cell debris
What are peroxisomes?
Membranous bags containing powerful enzymes (oxidase and catalase) that detoxify a number of harmful or toxic substances, including alcohol and formaldehyde, and neutralize the free radicals within the cell.
How do the enzymes in the peroxisomes work?
Oxidase enzyme converts free radicals to hydrogen peroxide (H2O2), which is still dangerous.
The enzyme catalase then converts hydrogen peroxide to water.
Catalase also converts alcohol and formaldehyde to water.
Where are the peroxisomes mostly found?
liver and kidney cells, which are very active in detoxification.
How do the peroxisomes replicate
replicate themselves by simply pinching in half, like mitochondria, but most peroxisomes appear to bud directly from the ER.
What is the cytoskeleton?
A network of protein structures that extend throughout the cytoplasm.
Function of the cytoskeleton
It provides structure for cells, supports organelles, facilitates intracellular transport, and provides the machinery for the movement of cells.
The cytoskeleton is made up of
Microfilaments
Intermediate filaments
Microtubules
What are the cytoskeleton components made up of
Microfilaments_Actin subunits (fine filaments)
Intermediate filaments_Fibrous subunits (strong and stable)
Microtubules_Tubulin subunits (tube like structures)
The thickness of the cytoskeleton components
Microfilaments_7nm
Intermediate filaments_10nm
Microtubules_25nm
structures formed from the components of the cytoskeleton
Microfilaments_Blue network
Intermediate filaments_Purple network around the pink nucleus
Microtubules_Gold network around the pink nucleus
Function of the microfilaments
Facilitate the movement
Change shape (muscle contraction)
Function of the intermediate filaments
They form desmosomes between cells and provide internal support to resist pulling forces on the cell.
Function of the microtubules
- Provides structure for cells and gives it shape
- Supports organelles within the cell
- Facilitates intracellular transport
- Provides the machinery for the movement of cells (eg, cilia and flagella).
- They form centrioles that are important for cell division.
Centrioles
A centrosome consists of paired centrioles located near the nucleus.
Centrioles are cylindrical rod-shaped bodies that are made up of nine triplets of fine microtubules.
Function of the centrioles
- Centrioles generate microtubules (bases of cilia and flagella)
- Form mitotic spindle during cell division.
Which cellular appendages rely on microtubules for their movement?
Cilia and flagella
Microtubule based extension
Cilia, flagella
