lecture two slides #55-73

Question 1

what is a cytoskeleton?

Answer 1

A network of protein fibers. such as microfilaments (actins), intermediate filaments, and microtubules.

Question 2

characteristics of microfilaments (protein fibers)

Answer 2

• 7 nanometers two
• two protein chains
• actins
• cellular movements (contraction, pinching during cell division)

Question 3

characteristics of intermediate filaments (protein fibers)

Answer 3

• Tetramers (te - tray - mers) of protein form a cable
• structural support of the cell.
• such as keratin found in hair and nails.

Question 4

characteristics of microtubules (protein fibers)

Answer 4

• tubulin proteins
• originate from nucleation centers
• have a positive end (away from center) and negative end (toward the center)
• intracellular transports, organizing metabolism, stability of a cell (minimizing compression)
• dividing cells: movement of chromosomes in mitosis

Question 5

characteristics of flagella & cilia

Answer 5

• flagellum: 1 long tail
• cilia: short, small flagella

Question 6

characteristics of centrioles
(cen - tri - oles)

Answer 6

• barrel-shapes
• appear in pairs
• organize microtubules
• vital for cell division
• found in animals & protists (primarily)
• basal body: a form of centrioles in flagellum or cilia

Question 7

characteristics of vacuoles
(va - cul - ul)

Answer 7

• found in plants & most protists
• storage centers (water, sugar, ions, pigment, etc.)
• central vacuoles (plants) store water, pigment, etc., remove toxins, and also maintain turgor pressure against cell wall.

Question 8

how do cells shuttle substances inside?

Answer 8

• if short distances, golgi complex.
• if long-distance, molecular motors (dynein move towards center, kinesin moves outwards)

Question 9

characteristics of cell walls (plasma membrane)

Answer 9

• provides protection & support
• found in bacteria, fungi, plants, & protists
• cell walls in plants are cellulose
• cell walls in fungi are chitin

Question 10

characteristics of animal cells (plasma membrane)

Answer 10

• extracellular matrix
• glycoproteins
• collagens
• cell movements, signaling, & gene expression
• integrin: mediate the outside world with the inside world

Question 11

what is intercellular junctions and its characteristics?

Answer 11

• allows for communication via direct contact or intercellular junctions.
• in plants, it’s referred to as plasmodesmata
• in animal cells, there are tight junctions, gap junctions, and desmosomes.

Question 12

what is plasmodesmata
(plas - mo -des - mata)

Answer 12

• plasmodesma (singular) a channel between two plant cells that allows them to transport materials (water and nutrients) from one cell to the next

Question 13

what is tight junctions? & its characteristics.

Answer 13

• tight junctions hold cells together
• prevents materials from leaking between cells
• predominantly made of two proteins (claudins & occludins)
• found mainly in epithelial tissues (internal organs, internal cavities, & most of the skin)

Question 14

what function do desmosomes perform?
(des - mo - somes)

Answer 14

• holds two adjacent cells together via cadherin
• keeps the cells in a sheet-like structure in organs & tissues that stretch (heart & muscles)

Question 15

what is the function of gap junction and its importance?

Answer 15

• functions like plasmodesmata (plants)
• allows for transporting ions, nutrients, and etc., between two adjacent cells
• importance for proper function of heart muscle cells