Chapter 1- Eukaryotic cell structure Flashcards
Cell
A unit of space enclosed by a membrane, which is the basis of all living organisms
Plasma membrane
The external cellular membrane, which is composed of amphipathic phospholipids and protein. It separates the relatively constant internal cellular environment from the potentially hostile external environment. The protein composition of the membrane varies between cell types, but the lipid composition is common to all cells. The two sides of the plasma membrane have a different lipid composition. Proteins and lipids are not randomly distributed throughout the membrane
Characteristics of a cell (8)
- Many cells contain the same inorganic ions and organic molecules- carbohydrates, lipids, proteins, and nucleic acids
- A plasma membrane
- Systems that link the internal and external environment
- The ability to transform external energy sources into utilizable energy that powers cellular reactions
- The ability to convert ingested nutrients into necessary components of the cell, and to eliminate waste products
- The ability to synthesize macromolecules
- A DNA genome
- The ability to replicate, transferring the cell’s genetic information to offspring
Prokaryotes
Cells with single stranded DNA lacking a defined nucleus and internal membrane structures. Includes common bacteria and archaea. Prokaryotes are usually unicellular but can form colonies or filaments
3 major domains
Archaea, eubacteria (common bacteria), and eukaryotes
All organisms are grouped into one of these 3 domains
Nucleoid region
Prokaryotes contain a single circular strand of DNA, which is confined to a separate mass in the cell called the nucleoid. The nucleoid is not surrounded by a membrane or envelope
Eukaryotes
Includes single celled organisms like yeasts and fungi, as well as multicellular plants and animals. Eukaryotes have a defined nucleus with a well defined membrane that contains most of the cell’s DNA. They also have extensive membrane systems and intracellular organelles surrounded by membranes
Compartmentalization in eukaryotic cells
The intracellular membrane systems in eukaryotes establishes cellular compartments, which allows for subcellular organization. Due to these compartments, different chemical reactions that require different environments can occur simultaneously
Chemical structure of water
In water, two hydrogen atoms share their electrons with an unshared pair of electrons of an oxygen atom. Water is polar because oxygen is more electronegative than hydrogen, and therefore electrons are unevenly distributed in the molecule. The hydrogens have a partial positive charge while oxygen has a partial negative charge
Hydrogen bond
A relatively weak bond where a hydrogen that is bonded to an electronegative atom forms a bond with another electronegative atom (like O or N). Partially positive atoms (like hydrogen) are attracted to partial negative atoms (like oxygen). Water molecules interact with each other to form hydrogen bonds.
How does hydrogen bonding contribute to the properties of water?
The large number of hydrogen bonds contributes to the stability of water. The atoms of water can also hydrogen bond to other ions and other chemical structures. When water interacts with other molecules, its orientation changes. For example, water molecules near membranes are more ordered due to the amphipathic nature of cell membranes. Liquid water has a high amount of hydrogen bonds, which accounts for its high heat of vaporization. Hydrogen bonds are disrupted as water transitions from liquid to the vapor state
How does water interact with other biological molecules?
Water can be present on/within nucleic acid and protein molecules, and it stabilizes these molecules. Substances that are required for cellular functions are dissolved in an aqueous medium, and their activities are influenced by the orientation of water molecules. Microenvironments with different structures of water form on the surface of macromolecules and lipid membranes because water interacts with groups on these molecules. Microenvironments can change the activity of ions and molecules in different areas of the cell
Tetrahedral structure
5 molecules of water form a tetrahedral structure due to hydrogen bonding. This is because each oxygen shares its electrons with 4 hydrogen atoms, and each hydrogen shares electrons with another oxygen. This tetrahedral structure is responsible for the crystal structure of ice. As ice transitions to liquid water, only a few hydrogen bonds are broken
Why does water act as a solvent?
Water has a polar nature and it is able to form hydrogen bonds, which allows it to dissolve inorganic (salts) and organic molecules
How does water dissolve salts?
Salts are held together by attraction of positively and negatively charged atoms or groups. In water, the electrostatic forces in the salt are overcome, as the ions in the salt are attracted to the dipoles of water. Na+ is attracted to oxygen, Cl- is attracted to hydrogen. In solution, the ions are surrounded by a shell of water
Which organic molecules are soluble in water?
Organic molecules that contain weakly polar groups are soluble in water, as the polar groups are attracted to molecules of water. This is why sugars and alcohols are soluble in water
Amphipathic molecules
Molecules that contain both polar and nonpolar groups
Does water dissolve amphipathic molecules?
Amphipathic molecules dissolve in water if attraction of the polar group to water overcomes the hydrophobic interactions from nonpolar parts of the molecule
Cations
Positively charged ions
Anions
Negatively charged ions
Electrolytes
Molecules that dissociate in water to form ions (cations or anions). The ions facilitate the conductance of an electrical current
Nonelectrolytes
Molecules that dissolve in water but do not carry a charge or dissolve into charged molecules. This includes sugars and alcohols
Strong electrolytes
Salts that dissociate completely in water
Salts in biological systems
Salts of alkali metals (Li, Na, K) and acids like hydrochloric and sulfuric acid dissolve completely in water at low concentrations. Since these compounds are at low concentrations in biological systems, they always dissociate completely. Salts only exist as ions in solution, not as complete molecules like NaCl. In water, the dissociated anions of organic salts react with free protons (H+) from the dissociation of water to form the undissociated acid
Acid equilibrium
Some acids, like lactic acid, do not dissociate completely in water. They form an equilibrium between the dissociated components and the components that have not dissociated. The products of the reaction reform the undissociated reactant while other molecules dissociate
What determines whether an electrolyte completely dissociates in water?
It is depends on the electrolyte anion’s affinity for a proton. There is more dissociation if the dipole forces of water that interact with the anion are stronger than the electrostatic forces between the anion and a proton
Weak electrolytes
Molecules that do not dissociate completely in water. They have a lower capacity to carry an electrical charge than strong electrolytes
Hydronium ion
H3O+. The hydronium ion forms when protons interact with the oxygen of another water molecule. Water dissociates into OH and H, producing free protons that will interact with other molecules
pH
The inverse logarithm of the number of protons in a solution, or pH= log (1/H+). Blood plasma and interstitial fluid have a neutral pH of 7.4. Gastric juice has a normal pH of 1.5-3.
Proton donor
A Bronsted-Lowry acid is described as a proton donor. For example, HCl is considered a strong acid because it totally dissociates in water, releasing a proton.
Proton acceptor
A Bronsted-Lowry base is described as a proton acceptor. For example, OH- is considered a strong base because it readily associates with protons to form water.
Weak acids
Most organic acids in biological systems partially dissociate and are classified as weak acids. They establish equilibrium between the proton donor, an anion of the dissociated acid, and a proton. The anion formed in this dissociation is a base because it can accept a proton to reform the acid
Conjugate pair
A weak acid and its base (anion) that was formed during dissociation
Small Keq
The smaller the Keq value, the less the tendency of a conjugate acid to release a proton and the weaker the acid. Water has a low Keq and is considered a very weak acid
Blood pH
In mammals, there are different intra- and extracellular aqueous environments. However, the pH of these different environments is in a dynamic steady state. The blood pH reflects changes in pH in tissues. The normal blood pH range is 7.35-7.45. Any pH value outside of this range indicates potential disease. Measuring blood pH is normal practice since irregular increase or decrease may lead to life threatening conditions.
Acidosis
A blood pH below 7.35, due to increase in acid (excess lactic acid or ketones) or the loss of the bicarbonate base. This can be caused by a metabolic or respiratory change.
Alkalosis
Blood pH above 7.45. This is also due to a metabolic or respiratory change. Metabolic alkalosis is caused by retention of bicarbonate and ingestion of bases. Respiratory alkalosis is caused by hyperventilation, overdose of some drugs, or fever
Metabolic acidosis
It can indicate conditions like diabetes, hypoxemia, and metabolism of xenobiotics that form acids. Loss of bicarbonate changes the acid-base balance and occurs in severe diarrhea, uremia, and chronic renal diseases.
Respiratory acidosis
Respiratory acidosis occurs when carbon dioxide is retained, caused by conditions that restrict exhalation of carbon dioxide. These conditions include emphysema, trauma, asthma, polio, and severe obesity
Hypoxemia
Excess lactic acid production, which can occur in long distance runners
Carbonic acid
H2CO3, which is a weak acid that is important in controlling pH in mammals. Carbon dioxide is constantly produced in catabolic reactions and is removed by the lungs. Medical conditions that restrict exhalation of carbon dioxide from the lungs lead to accumulation of carbonic acid and respiratory acidosis
CO2/HCO3 system
Carbon dioxide, when dissolved in aqueous systems, is involved in equilibrium reactions. Carbonic acid (H2CO3) is in equilibrium with dissolved carbon dioxide, or CO2 and water. Dissociated carbonic acid can also form a proton and bicarbonate (HCO3). Therefore, the increase or decrease of one component – CO2, H2CO3, H+, or HCO3- causes a change in pH. The CO2/ HCO3- system is extremely important for maintaining pH homeostasis
Henderson-Hasselbach equation
Defines the relationship between pH and concentrations of conjugate acid and base. A change in any component of an equilibrium reaction requires a corresponding change in the other components. For example. an increase in acid/protons decreases the concentration of conjugate bases and increases the concentration of the conjugate acid. pH = pK’ + log [conj. base] / [conj. acid]
Buffering
The ability of a solution to resist a change in pH when an acid or base is added. This is important for regulating pH in the body. For example, cellular production of acids leads to the acidification of blood, where the H+ is buffered by several different bases. These bases include HCO3-, hemoglobin and HPO42-. As a result, the pH of the blood will decrease due to the using of all the bases to buffer resulting in loss of buffering capacity
Buffering capacity
Depends on the concentrations of the conjugate acid and base. The higher the concentration of conjugate base, the more it can react with a high H+ concentration. However, if all bases are consumed, buffering capacity decreases and pH will also decrease drastically. For this reason, bicarbonate is very important to pH. Bicarbonate buffers against acid, and if too much is lost, the pH would decrease and the patient would likely die
Embryonic stem cells
In the postfertilization period of an egg, these cells have the potential to develop into every cell of every organ in the adult organism. They are referred to as pluripotent cells
Multipotent cells
Cells that can differentiate into a limited number of different cell types. They are found in differentiated tissues. The genome of differentiated cells can be reprogrammed to form multipotent or pluripotent cells, suggesting that parts of its genome are suppressed rather than lost entirely
Catabolic reactions
Degradative reactions
Anabolic reactions
Synthesis reactions
Cytosol
Intracellular fluid
Chemical composition of mammalian cells
In different types of cells, the concentrations of intracellular inorganic ions are mostly the same, however, the ion concentration intracellularly is much different from that in the extracellular environment. Certain ions are more prevalent inside the cell, while others are more prevalent outside the cell. With some exceptions, total cation equals total anion concentration in different fluids
All cells contain the same genome, except for which cells?
Erythrocytes- mature erythrocytes don’t contain DNA
Major intracellular ions
Cations- potassium, magnesium (present in both environments)
Anions- inorganic phosphate, organic phosphate, and proteins
Major extracellular ions
Cations- sodium, magnesium (present in both environments)
Anions- chlorine, bicarbonate, smaller amounts of phosphate and sulfate
Integrins
Transmembrane proteins that bind to the cytoskeleton inside the cell and participate in bidirectional signaling across the membrane. Integrins are how the outer surface of the plasma membrane interacts with other cells
Cytoskeletal elements
Allow the plasma membrane to be involved in determining cell shape and movement
Transport of substances through the plasma membrane
The membrane contains lipids, which excludes many substances. However, transport mechanisms allow ions, organic molecules, and water to move across the membrane
Protein receptors
Proteins on the outer surface of the plasma membrane which bind to extracellular signals like hormones or neurotransmitters. Therefore, protein receptors allow for intracellular communication
Nuclear envelope
The two membranes that surround the nucleus. The outer membrane is continuous with membranes of the endoplasmic reticulum. The envelope contains nuclear pore complexes. The nuclear envelope may play a role beyond just being a barrier between the nuclear matrix and the cytoplasm- the nuclear envelope of progeria patients appears distorted
Perinuclear space
The space between the two membranes of the nuclear envelope, which is continuous with the lumen of the rough endoplasmic reticulum
Nuclear pore complexes
Multi protein complexes that cross the nuclear envelope. They allow for controlled movement of particles and large molecules between the nuclear matrix and the cytoplasm. Transport of macromolecules requires energy. It is facilitated by cargo proteins and soluble transport factors which cycle between the 2 compartments
Nuclear matrix
An intricate meshwork of proteins spread throughout the nucleus
Hutchinson-Gilford progeria syndrome (HGPS)
This syndrome is observed in 1 in 4 million births. These patients experience accelerated aging, 6-8 times the normal rate. Symptoms include limited growth, loss of hair, small fragile bodies, wrinkled skin, atherosclerosis, distinct facial features, and cardiovascular problems common to the elderly. They do not exhibit any neurodegeneration. Patients rarely live past their early teens
Biochemical basis of HGPS
The nuclear envelope of these patients appears to be distorted. Lamina A is a structural protein in the nucleus that is involved in nuclear synthesis of DNA and RNA. It is formed from a precursor and attached to the nuclear membrane by an enzyme catalyzed reaction. HGPS patients have a deficit in this reaction, which leads to accumulation of abnormal lamina A in normal cells with aging. The presence of the abnormal protein causes blebbing of the nucleus, changes gene expression, and interferes with mitosis
Nucleolus
An intranuclear sub compartment. It is involved in RNA processing and ribosome synthesis, which is required for protein synthesis in the cytosol
Nuclear lamina
A meshwork structure that underlies the inner nuclear membrane and supports the structure of the nucleus
Functions of the plasma membrane (5)
- Transport of ions and small molecules
- Exo- and endocytosis
- Cell-cell recognition
- Receives small and large molecules using receptors
- Cell morphology and movement
Nucleus
Contains most of the genome of the cell, involved in DNA synthesis and repair, and in RNA synthesis. The nucleus contains the proteins and enzymes that help with replicating DNA and repairing DNA.
Chromatin
A DNA-protein complex located in the nucleus, which is organized into chromosomes. This is how DNA is stored in the nucleus
Endoplasmic reticulum
A network of interconnecting membranes that extend from the nuclear envelope to the plasma membrane, found in the cytoplasm of eukaryotic cells. Some parts of the membranes have a smooth appearance, other parts of the membranes have a rough appearance. Newly synthesized proteins are modified in the lumen of the ER (inside the membrane). Along with the Golgi apparatus, the ER is involved in formation of other cellular organelles (lysosomes, peroxisomes) and calcium signaling
Ribosomes
The rough appearance of the RER is due to ribonucleoprotein particles (ribosomes) on the cytosolic side of the membrane.
Microsomes
Small vesicles formed during cell fractionation. The endoplasmic reticulum network is disrupted and the membrane reseals, forming the vesicles
Rough endoplasmic reticulum functions (2)
- Biosynthesis of proteins for incorporation into membranes and cellular organelles, and for export out of the cell
- Involved in the folding of proteins- if this system is disrupted, it can cause disease
Smooth endoplasmic reticulum functions
Involved in lipid synthesis. It contains enzymes (cytochromes P450) that catalyze hydroxylation of endogenous and exogenous compounds. These enzymes play a role in the synthesis of steroid hormones, removal of toxic substances, and drug metabolism
Endoplasmic reticulum functions (5)
- Membrane synthesis
- Synthesis of proteins and lipids for some organelles and for export
- Lipid and steroid synthesis
- Detoxification reactions
- Calcium signaling
Golgi apparatus
A network of cisternae and vesicles. It works with the endoplasmic reticulum, where proteins for specific destinations are synthesized. Enzymes in Golgi membranes catalyze transfer of carbohydrate units to proteins to form glycoproteins- this is important to determine the protein’s final destination. The Golgi is also a site of new membrane synthesis and helps to form lysosomes and peroxisomes
Cisternae
Flattened smooth membrane stacks
Golgi apparatus functions (3)
- Modification and sorting of proteins for incorporation into membranes and organelles, and for export
- Export of proteins
- Moves lipids in the cell
SNARE proteins
A family of proteins that help membrane vesicles to shuttle proteins between cisternae in the Golgi apparatus. The proteins pinch the vesicle off of one cisterna and help the vesicle to fuse with another cisterna
What is the role of vesicles in the Golgi apparatus?
Golgi apparatus vesicles transport proteins like hormones, blood plasma proteins, and digestive enzymes to the plasma membrane for secretion
Mitochondria functions (4)
- Production of ATP
- Cellular respiration
- Oxidation of pyruvate, amino acids, and fatty acids
- Urea and heme synthesis
Mitochondria
Powerhouse of the cell, responsible for synthesizing 90% of cellular ATP. They play a role in cell functions like apoptosis, formation of reactive oxygen species, cell signaling, and metabolic processes. Important for protein synthesis and have a key role in aging; cytochrome c, a component of the mitochondrial electron transport system, is an initiator of apoptosis
Mitosol
The internal matrix of the mitochondria
Cristae
Infoldings of the inner mitochondrial membrane
Structure of the mitochondria
The mitosol is surrounded by two membranes. The inner membrane forms cristae and contains small spheres that extend into the mitosol and are responsible for ATP synthesis. Components of the electron transport system and oxidative phosphorylation are part of the inner membrane. The metabolic pathways for oxidation of pyruvate and other compounds are located in the mitosol. Both the outer and inner membranes contain mechanisms for protein translocation
Mitochondrial DNA
Circular DNA that contains genetic information for 13 mitochondrial proteins and some RNAs. It is inherited through maternal transmission. There are several hundred genetic diseases of mitochondrial function
Cytochrome
Heme protein involved in an electron transport system in the endoplasmic reticulum or inner mitochondrial membrane
Mitochondrial proteins
Mitochondria also have requisite machinery to catalyze protein synthesis. Most mitochondrial proteins are derived from genes present in nuclear DNA and synthesized in the cytosol.
Lufts disease
The first disease involving mitochondrial energy transduction, reported in 1962. Symptoms included general weakness, excessive perspiration, a high caloric intake without an increase in body weight, and an elevated basal metabolic weight. The patient had a defect in the mechanism that controls mitochondrial oxygen utilization
Leber Hereditary Optic Neuropathy
The first disease identified due to a mutation of mtDNA. It causes sudden blindness in early adulthood
Mitochondrial disease
Some conditions result from mutations of mitochondrial DNA, others result from mutations of nuclear DNA that code for mitochondrial proteins. Many of these diseases involve skeletal muscle and CNS. Mitochondrial DNA damage may be due to free radicals formed in the mitochondria. Mitochondrial abnormalities have been implicated in the pathophysiology of schizophrenia, bipolar disorder, Parkinson disease, Alzheimer disease, and cardiomyopathies
Lysosomes
Responsible for intracellular digestion of extracellular and intracellular substances. They have one membrane and an internal acidic pH of 5. They contain enzymes called hydrolases, but the enzyme content of the lysosome varies depending on the tissue and the functions of the tissue. Lysosomes are responsible for the intracellular digestion of extracellular and intracellular substances. The material broken down by hydrolases is recycled and used for other purposes
Hydrolases
A class of glycoprotein enzymes located in the lysosomes. They catalyze hydrolytic cleavage of carbon-hydrogen, carbon-oxygen, carbon-nitrogen, and carbon phosphorus bonds found in biological macromolecules. Lysosomal hydrolases are most active at an acidic pH. They split molecules into simple, low weight compounds that can be recycled.
Phagocytosis
A process by which cells ingest foreign particles, like microorganisms and viruses
Pinocytosis
The process by which cells ingest fluids
Endocytosis
The process by which the cell ingests specific proteins
Digestive vacuoles
Also called secondary lysosomes. They are vesicles that contain material to be digested and lysosomal hydrolases to carry out the digestion
How do cells ingest foreign particles, liquids, and proteins?
Phagocytosis, pinocytosis, and endocytosis are receptor mediated processes. The material from the exterior of the cell is enclosed in plasma membrane bound vesicles. The vesicles containing the external material fuse with primary lysosomes to form digestive vacuoles, where they are digested
Pathological conditions due to lysosomal enzymes
When the lysosomal membrane is disrupted, the lysosomal enzymes cause digestion of the cell. Pathological conditions related to the release of lysosomal enzymes include arthritis, allergic responses, several muscle diseases and drug induced tissue destruction
Autophagy
A regulated process where the lysosome hydrolyzes cellular components. Cellular proteins, nucleic acids, lipids, and organelles like the mitochondria, are in a dynamic state of synthesis and degradation, with lysosomes being responsible for degrading these molecules. Substances to be degraded are either identified and taken up by lysosomes or are first encapsulated within membrane vesicles that fuse with primary lysosomes. Autophagy is important in both stressed and normal cells, and starvation and specific hormones induce autophagy
Residual bodies
Vesicles containing material that couldn’t be digested by lysosomes. The contents of residual bodies are removed from the cell by exocytosis
Lipofuscin
A chemically heterogenous, pigmented material found in some residual bodies. It contains polyunsaturated fatty acids and proteins. It is also called “age pigment” or “wear and tear pigment”. Lipofuscin has been observed in mature neurons and muscle cells, and it has been implicated in the aging process
Lysosome functions (2)
- Apoptosis
- Cellular digestion- hydrolysis of proteins, carbohydrates, lipids, and nucleic acids
Gout
Uric acid is formed by catabolism of purines, which are heterocyclic compounds containing nitrogen that are found in nucleic acids. Uric acid is normally excreted in the urine. In gout patients, excess uric acid is produced, which causes uric acid to increase in the blood. Urate crystals are also deposited in the joints. Symptoms include inflammation, pain, swelling, and increased warmth of some joints, especially the big toe
How are lysosomal enzymes related to gout?
Some of the symptoms of gout are caused by urate crystals, which are phagocytized by cells in the joint under normal circumstances. With gout, they accumulate in intracellular digestive vacuoles that contain lysosomal enzymes. The crystals cause physical damage to the vacuoles, releasing lysosomal hydrolases into the cytosol. The hydrolases are optimally active at an acidic pH, so their activity is decreased in cytosol. However, they still have some hydrolytic activity, causing digestion of cellular components and cellular autolysis
Human lysosomal acid lipase (hLAL)
An enzyme that hydrolyzes triacylglycerol to form free fatty acids and glycerol. It also hydrolyzes cholesterol esters to cholesterol and fatty acids. hLAL is a very important enzyme to cholesterol metabolism and makes cholesterol available for cells to use. There are two rare autosomal recessive diseases resulting from genetic deficiency of LAL: Cholesteryl Ester Storage Disease (CESD) and Wolman Disease
Cholesteryl Ester Storage Disease (CESD)
Autosomal recessive disease of hLAL enzyme dysfunction- it is usually diagnosed in adulthood and is characterized by hypercholesterolemia, hepatomegaly, and early onset of severe atherosclerosis. Patients do have hLAL activity, but at a level much lower than normal. They are able to hydrolyze triacylglycerol, but not cholesteryl esters
Wolman Disease
Autosomal recessive disease of hLAL enzyme dysfunction. This disease is diagnosed in infants, most of which do not survive to age 1. Patients have no hLAL activity. Both triacylglycerol and cholesteryl esters accumulate in tissues
Peroxisomes
An organelle with a single membrane that has the ability to produce and utilize hydrogen peroxide (H2O2). In the matrix of some peroxisomes, there is a high protein concentration, which leads to crystalline inclusions. They are used to oxidize long chain fatty acids, and for synthesis of glycerolipids, glycerol ether lipids, and isoprenoids. Over 50 enzymes catalyzing oxidative and biosynthetic reactions have been identified in peroxisomes from different tissues. More than 25 genetic diseases involve peroxisomes; grouped as disorders of peroxisome biogenesis.
How do cells protect themselves from hydrogen peroxide produced by peroxisomes?
Cells protect themselves from the toxicity of H2O2 by having peroxide producing and peroxide utilizing enzymes in one compartment.
Catalase
A heme enzyme that is present in peroxisomes. It catalyzes the conversion of hydrogen peroxide to water and oxygen. It also catalyzes the oxidation of different compounds by hydrogen peroxide
Zellweger syndrome
The most severe peroxisome biogenesis disorder. It is due to the absence of functional peroxisomes, which usually causes death by 6 months. Patients with this disease have a genetic defect in the mechanism for importing enzymes into the matrix of peroxisomes
Peroxisome biogenesis disorders
Peroxisomes are responsible for many important metabolic reactions. There are more than 25 disorders involving the enzymatic activities of peroxisomes. They are rare autosomal recessive diseases characterized by decreased levels of glycerol-ether lipids, and increased levels of long chain fatty acids and cholestanoic acid derivatives. These diseases can affect the liver, kidneys, brain, and the skeletal system. Some PBD conditions are caused by donor splice or missense mutations. In some, there is the absence of a single metabolic enzyme or a defect in a membrane transport component. Some of these diseases can be diagnosed prenatally by an assay of the amniotic fluid
Peroxisome functions (3)
- Lipid oxidation
- Oxidative reactions involving oxygen
- Utilization of hydrogen peroxide
Microtubules, intermediate filaments, and microfilament functions (4)
- Cell cytoskeleton
- Cell morphology
- Cell motility
- Intracellular movements
Cytosol functions (3)
- Metabolism of carbohydrates, amino acids, and nucleotides
- Synthesis of fatty acids
- Protein synthesis
Cytoskeleton
Made of microtubules, intermediate filaments, and actin filaments (microfilaments) which form a scaffolding in the cytoplasm. The cytoskeleton plays roles in intracellular transport of vesicles and organelles, and cell morphology and motility
Microtubules
Consists of multimers of tubulin- microtubules make up the cytoskeleton. The tubulin protein assembles rapidly into tubular structures and disassembles depending on the needs of the cell. Actin and myosin are also important filaments in skeletal muscles
