Cell Bio - Final Exam study guide

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Cytoskeleton

A network of filaments and tubules in the cytoplasm of the cell that provides structure and shape.

Microtubules

Cylindrical structures composed of tubulin that are involved in cell organization, shape determination, and intracellular transport.

Dynamic instability

The ability of microtubules to rapidly switch between growth and shrinkage. Even in the same cell at the same time

Motor proteins

Molecules like kinesins and dyneins that move along microtubules and microfilaments, transporting cellular cargo.

Intermediate filaments

Fibrous proteins that provide mechanical support and stability to cells.

Actin filaments

Thin filaments composed of actin that contribute to cell movement and shape.

Cell motility

The ability of cells to move and change position in response to their environment.

Adherens junctions

Cell junctions composed of cadherins that connect the actin cytoskeletons of adjacent cells.

Desmosomes

Strong cell junctions that provide mechanical adhesion between cells through intermediate filaments.

Tight junctions

Cell junctions that seal spaces between cells to maintain selective permeability and tissue compartmentalization.

Cilia

Hair-like structures that extend from the surface of some cells, aiding movement and fluid transport. Built from microtubules in the 9+2 arrangement

Flagella

Long, whip-like structures that propel cells, such as sperm, through liquid environments. Built from microtubules in the 9+2 arrangement

Mitosis

The process of nuclear division that results in two daughter nuclei, each with the same number of chromosomes as the parent nucleus.

Chromatids

Identical copies of a chromosome that are joined at the centromere before being separated during mitosis.

Spindle fibers

Microtubules that form the mitotic spindle and pull chromatids apart during mitosis.

Cytokinesis

The division of the cell's cytoplasm that occurs at the end of mitosis.

Anaphase

The stage of mitosis where sister chromatids separate and move towards opposite poles of the cell.

Nuclear envelope

The double membrane that surrounds the nucleus and breaks down during mitosis.

Cell cycle

The series of phases that cells go through as they grow and divide.

G1 phase

Gap phase of the cell cycle where the cell grows and synthesizes proteins. During this phase, the cell also assesses its size and energy reserves to ensure it is ready for DNA synthesis in the S phase.

S phase

The phase of the cell cycle where DNA replication occurs. During this phase, each chromosome is duplicated to produce sister chromatids. Replication ONLY occurs in this phase

G2 phase

The second gap phase where the cell prepares for mitosis. During this phase, the cell continues to grow and produces the proteins and organelles necessary for cell division.

M phase

The phase of the cell cycle that includes mitosis and cytokinesis. Is divided into subphases, prophase, prometaphase, metaphase, anaphase, and telophase. Ends with the formation of two daughter cells

Epithelial cells

Cells that line surfaces and cavities of organs and structures throughout the body.

Myosin

A motor protein that interacts with actin filaments to enable muscle contraction and other types of movement.

Kinesins

Motor proteins that move along microtubules toward the plus end, typically transporting cargo away from the cell center. Some can also promote catastrophe

Dyneins

Motor proteins that move along microtubules toward the minus end, involved in retrograde transport. They are vital for function but not microtubule stability

Cell adhesion

The process by which cells interact and attach to neighboring cells through specialized proteins.

Cadherins

Transmembrane proteins that mediate cell-cell adhesion.

Cytoskeletal reorganization

The dynamic rearrangement of cytoskeletal elements in response to cellular signaling or environmental stimuli.

Microfilaments

structures composed of actin that provide structural support and function by interacting with myosin to generate forces that drive movement as well as provide mechanical support.

Astral microtubles

microtubules located at the centromere of each chromosome that attach to the kinetochore. They are essential for: proper spindle positioning, orientation during cell division, acting as anchors that connect the mitotic spindle to the cell cortex and also play a role in spindle movement and separation of chromosomes during mitosis.

Kinetochore microtubules

microtubules that extend from the centrosome to the kinetochore of each chromosome, playing a crucial role in the separation of sister chromatids during cell division.

Polar microtubules

microtubules that do not attach to chromosomes but extend from the spindle poles to the cell's midline, helping maintain the spindle structure and ensuring proper alignment of chromosomes during cell division. They facilitate spindle pole separation and contribute to the elongation of the cell during mitosis

Dynamic microtubules

microtubules that rapidly grow and shrink, allowing for flexible cellular processes such as cell shape changes, motility, and intracellular transport. Their dynamic instability is crucial for mitosis and other cellular functions.

Stable microtubules

microtubules that are more permanent and resist depolymerization, often found in structures like cilia and flagella, providing stability and support to cellular architecture.

Basal bodies

Organizing centers for microtubules, typically found at the base of cilia and flagella, playing a crucial role in the formation and maintenance of these structures. Organized by microtubule triplets in a 9×3 pattern

Process of dynamic instability

Tubulin dimers bind to GTP before adding to the microtubule GTP is then hydrolyzed to GDP, GTP-tubulin is more stable and promotes microtubule growth, GDP-tubulin is less stable and favors disassembly. If the GTP cap is lost the exposed GDP tubulin triggers rapid depolymerization (catastrophe). New GTP-tubulin can bind to the shrinking end, growth resumes in a rescue.

MAP’s (Microtubule-Associated Proteins)

Proteins that regulate microtubule stability and organization, influencing their dynamics and interactions with other cellular components. They bind along microtubules and prevent depolymerization while also cross-linking microtubules to each other or to other structures.

+TIP’s (Plus-End Tracking Proteins)

Proteins that stabilize the growing ends of microtubules, promoting polymerization and helping link microtubules to other cellular structures. They also help to guide microtubule growth toward target areas.

Stathmin

A protein that destabilizes microtubules by sequestering tubulin dimers and promoting depolymerization, thus regulating microtubule dynamics.

Katanin

A microtubule-severing protein that cuts microtubules into shorter fragments, facilitating their disassembly and turnover within cells.

CLASP proteins

Proteins that enhance microtubule stability and rescue them from depolymerization, thereby promoting their assembly and maintenance in dynamic cellular environments.

Catastrophe

A phenomenon where microtubules undergo rapid depolymerization, leading to the disassembly of their structure.

Rescue

The process by which microtubules are stabilized and converted from a shrinking state to a growing state, counteracting depolymerization.

Microtubule Organizing Centers (MTOC’s)

Play a central role in regulating the organization, nucleation and dynamics of microtubules. They act as hubs that control where and how microtubules are assembled and anchored. They are also fundamental to the spatial and functional organization of microtubules.

Spatial regulation

The control of microtubule organization in relation to their position and function within the cell, ensuring proper cellular structure and dynamics.

Abnormalities in microtubules

Can lead to nemaline myopathy and actinopathies. These are conditions that affect muscle structure and function, often resulting in muscle weakness and loss of mobility.

Abnormalities in Intermediate filaments

Can result in desmin-related myopathy and other disorders related to muscle integrity, leading to symptoms such as muscle weakness and structural defects.

Abnormalities in microtubules

Can result in cardiomyopathies and impaired mechanical function of the heart muscle, potentially leading to heart failure and other cardiovascular issues.

Stress fibers

Thick contractile bundles of actin filaments that are organized in antiparallel arrays which allow myosin II motors generate tension. They are anchored to focal adhesions and connect the cytoskeleton to the extracellular matrix, playing a critical role in cellular mechanics, adhesion and force generation.

Stress fiber morphology

Typically elongated with a tensioned shape that has a strong presence in cells under mechanical stress or involved in wound healing.

Lamellipodia

Thin, sheet-like projections of the plasma membrane that are rich in branched actin filaments. They play a key role in cell migration and are essential for changes in cell shape.

Lamellipodia morphology

Typically broad, cells with these characteristics often have a wide and flat leading edge which is critical for smooth continuous movement over 2d surfaces and efficient migration during processes like wound healing and tissue regeneration.

Filopodia

Made up of long, unbranched parallel bundles of actin filaments that are regulated by formin proteins. They play a role in environmental sensing, guiding the direction of cell movement and establishing initial adhesion points.

Filopodia morphology

Characterized by slender, finger-like projections that extend from the leading edge of a migrating cell, facilitating exploratory behaviors and enhanced interactions with surrounding environments.

Cortical actin network

A dynamic network of actin filaments located beneath the plasma membrane of the cell surface, providing structural support, enabling shape changes, and facilitating motility through interactions with other cellular components.

Microvilli

Composed of tight bundled structures organized into a core of parallel actin filaments stabilized by proteins like fimbrin and villin. They also increase surface area for absorption like in the the intestine for example.

Contractile rings

Composed of contractile actomyosin structures that are organized in circumferential bundles of actin filaments and myosin. They pinch the cell into two during cell division. These structures form during cytokinesis, primarily in animal cells, leading to the separation of daughter cells.

Structures actin doesn’t typically form

Hollow tubes, helical coils at a large scale, intermediate-size rope-like fibers such as microtubules or intermediate filaments, axonemes and dense crystalline lattices.

Arp 2/3 complex

A protein complex that initiates the formation of new actin filaments by nucleating their growth from the sides of existing filaments. It plays a crucial role in the regulation of actin filaments and is involved in various cellular processes including cellular movement and shape.

Intermediate fibers

They provide mechanical strength and stress resistance, structural support and cell integrity, intercellular connectivity, signal transduction, cellular response and protection against apoptosis. They consist of various proteins that form a network within the cell providing tensile strength.

Cell motility

The process by which cells move and navigate through their environment, often involving changes in cell shape and the interaction of the cytoskeleton.

Crawling/locomotion on substrates

A type of cell motility where cells move across surfaces through processes involving actin polymerization and contraction, enabling them to adhere to and traverse various substrates. This movement often involves lamellipodia and filopodia which are driven by actin polymerization.

Amoeboid movement

A type of cell motility characterized by the use of pseudopodia, allowing cells to crawl and change shape as they navigate their environment. Driven by actomyosin contractions and cortical actin flow. This type of movement is commonly observed in amoebas and some white blood cells, enabling them to engulf particles and migrate.

Ciliary and flagellar beating

A type of cell motility where cells use hair-like structures called cilia and flagella to propel themselves through liquid environments. These movements are orchestrated by the coordinated beating of the cilia or flagella, driven by microtubule rearrangements and motor protein activity.

Chemotaxis

The movement of cells toward or away from specific chemical signals in their environment, enabling them to navigate toward nutrients or away from toxins. This process is crucial for immune responses and cellular development.

Intracellular transport via cytoskeleton

The process by which cellular components are moved within a cell, utilizing the cytoskeletal network (microtubules, microfilaments, and intermediate filaments) along with motor proteins like kinesins and dyneins. This transport is essential for the distribution of organelles, vesicles, and proteins.

Collective cell migration

The coordinated movement of groups of cells, often occurring during processes such as embryonic development, wound healing, and cancer metastasis, where cells communicate and move as a collective unit.

Processes that aren’t considered part of cell motility

Cell division, apooptosis, endocytosis, exocytosis, cell shape changes without migration, and growth in place

Functions of cilia in tracheal cells

Help to move mucus and trapped particles out of the respiratory tract, playing a crucial role in maintaining airway hygiene and facilitating breathing.

Primary ciliary dyskinesia

A genetic disorder characterized by the dysfunction of cilia, leading to respiratory issues, chronic sinusitis, and infertility due to impaired movement of cilia. Symptoms include a chronic wet cough, chronic nasal congestion, recurrent respiratory infections, bronchioectasis, otitis media, and shortness of breath as well as reduced exercise tolerance.

The effect increased light has on flagellar beat frequency

is an increase in the frequency of beating, enhancing motility and allowing for better swimming efficiency in certain organisms. If light is too intense it can also trigger negative phototaxis.

The effect decreased light has on flagellar beat frequency

is a decrease in the frequency of beating, which can reduce motility and swimming efficiency in certain organisms. Some algae may adjust their movement to search for higher light intensities needed for photosynthesis.

9+2 arrangement

arrangement of microtubules in cilia and flagella, where nine doublet microtubules surround a central pair of single microtubules, providing structural support and facilitating movement.

Kinesin movement

This protein has two head domains that bind to the microtubule. One head binds tightly to the microtubule and ATP binds to the head which triggers a conformational change, throwing the other head forward and allowing it to bind to the next tubulin, effectively "walking" along the microtubule.

Myosin II

Motor protein that interacts with actin filaments, playing a crucial role in muscle contraction and cellular movement. It consists of two heavy chains and two pairs of light chains, forming a structure that enables it to ''walk'' along actin filaments using energy from ATP.

Myosin I

A motor protein that interacts with actin filaments, Involved in intracellular transport and plays a role in cellular processes, such as endocytosis. It consists of a single heavy chain and a light chain, enabling it to 'walk' along actin filaments using ATP for energy.

Myosin V

A motor protein that transports cargo within cells by moving along actin filaments. It consists of two heavy chains and two light chains, and uses ATP to provide the energy for its movement, crucial for processes like organelle transport.

Myosin VI

A motor protein that moves cargo along actin filaments in the opposite direction compared to other myosins. It consists of two heavy chains and light chains, utilizing ATP for energy, playing a role in various cellular processes including endocytosis.

Sarcomere

The basic structural unit of a striated muscle fiber, comprised of alternating thick and thin filaments that slide past each other during contraction, resulting in muscle shortening.

Z-disc

The boundary structure of a sarcomere that anchors thin filaments and helps define the borders of each sarcomere, playing a critical role in muscle contraction.

M-line

The region in the middle of the sarcomere where thick filaments are anchored and is associated with the structural organization of muscle contraction.

I-band

The light region of a sarcomere that contains only thin filaments and spans the distance between two adjacent Z-discs, appearing less dense under a microscope. This is the area that shortens during contraction.

A-band

The dark region of a sarcomere that contains both thick and thin filaments, spanning the full length of the thick filaments and does not change in length during muscle contraction.

H-zone

The region within the A-band of a sarcomere that exclusively contains thick filaments and is the area that appears lighter under a microscope. This zone shortens during muscle contraction as the thin filaments slide past the thick filaments.

Thick filaments

Myosin proteins that form the core of a sarcomere, responsible for muscle contraction by interacting with thin filaments.

Thin filaments

Actin proteins that form the outer part of a sarcomere, involved in muscle contraction by interacting with thick filaments.

Titin

A large elastic protein that functions as a molecular spring, anchoring thick filaments to the Z line in a sarcomere, and contributing to its elasticity during muscle stretch and contraction.

Sarcomere function in contraction

Myosin heads attach to actin filaments at specific binding sites. ATP is used on myosin heads to perform a power stroke and pull the actin filaments inward toward the M-line shortening the sarcomere causing muscle contraction.

Muscle contraction energy transfer

During muscle contraction, energy is transferred from ATP to the myosin heads, enabling them to perform power strokes that pull actin filaments and shorten the sarcomere.

Process of muscle contraction

Muscle begins in a resting state where tropomyosin blocks myosin binding sites on actin. When calcium ions are released, they bind to troponin, causing a conformational change that moves tropomyosin and exposes the binding sites, allowing myosin heads to attach and initiate contraction.

Role of calcium in muscle contraction

Calcium ions are critical in muscle contraction, as they bind to troponin, leading to a conformational change that uncovers myosin binding sites on actin, thus facilitating cross-bridge formation and contraction.

Myosin mutations

Can cause impaired force generation or defective cross-bridge cycling leading to myopathies and cardiomyopathies especially hypertrophic cardiomyopathy.

Actin mutations

Can lead to muscle weakness and various myopathies by affecting the stability and function of the actin filaments essential for contraction. Can also cause respiratory difficulties due to weakened diaphragm muscles

Troponin complex mutations

Disrupted calcium sensing and impaired contraction regulation which can cause dilated cardiomyopathy, hypertrophic cardiomyopathy, and poor contraction or abnormal relaxtion of cardiac and skeletal muscles.

Tropomyosin complex mutations

inability to properly regulate exposure of myosin binding sites on actin which can cause muscle stiffness, weakness or tremors.

Titin mutations

Loss of sarcomere elasticity and structural support which can cause dilated cardiomyopathy, skeletal muscle disorders such as tibial muscular dystrophy, and increased risk of heart failure.

Nebulin mutations

Abnormal thin filament length and an instability in actin filaments which can cause muscle weakness such as nemaline myopathy, and poor muscle tone such as hypotonia.

Effects of microgravity on muscle tissue

Microgravity leads to muscle atrophy and a decline in muscle strength and function due to reduced mechanical loading and altered muscle metabolism.