Bio131 chapter 4: Introduction to cells (endomembrane system, endosymbiotic theory, cytoskeletal proteins, cell junctions)

The endomembrane system consists of which organelles

nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vacuoles, vesicles and plasma membrane

The nuclear envelope is connected to the _____ __, which is also continuous with the _____ _____

Rough ER, Smooth ER

Membranes and proteins produced by the ER move via _____ ______ to the ______

transport vesicles, golgi

The golgi pinches off _____ _______ and other _________ that give rise to ______, other types of ______ and __________

transport vesicles, vesicles, lysosomes, specialized vesicles, vacuoles

The lysosome is available for…

fusion with another vesicle for digestion

A __________ ________ carries proteins to the ______ ________ for ________

transport vesicle, plasma membrane, secretion

The plasma membrane expands by ______ of _______; proteins are _______ from the cell by _________

fusion, vesicle, secreted, exocytosis

What are mitochondria? Are they in plants or animals?

Sites of cellular respiration to make atp, in both plants and animals

What is cellular respiration

A metabolic process that uses oxygen to generate ATP

What are chloroplasts? Are they in plants or animals?

Sites of photosynthesis, found in plants and algae

Mitochondria having its own DNA is like what organism? What theory does this support?

Bacteria-like, supports endosymbiotic theory

What is the structure of a mitochondria

Outer membrane, intermembrane space, inner membrane, cristae, matrix, ribosomes in the matrix, DNA

A chloroplast is a type of…

plasmid

Where are chloroplasts found

in plants and some protists

Describe chloroplast structure

Mitochondria and chloroplasts display the following

similarities with bacteria that led to the endosymbiont

theory:

Enveloped by a double membrane

Contain ribosomes and multiple circular DNA molecules

Grow and reproduce somewhat independently in cells

The endosymbiont theory is…

An early ancestor of eukaryotic cells engulfed a

nonphotosynthetic prokaryotic cell, which formed an

relationship with its host

The host cell and endosymbiont merged into a single

organism, a eukaryotic cell with a mitochondrion

At least one of these cells may have then taken up a

photosynthetic prokaryote, becoming the ancestor of cells

that contain chloroplasts

The cytoskeleton is a

network of fibers extending throughout the cytoplasm

What does the cytoskeleton do?

Organizes cell’s structures and activities like movement, holds organelles in place, helps hold cell shape

The cytoskeleton helps to…

to support the cell and maintain its

shape

The cytoskeleton provides _________ for many organelles and molecules,

and is very ______

anchorage

dynamic

The cytoskeleton interacts with ______ __________ to produce _____

motor proteins, motility

Inside the cell, ________and other organelles can use motor

protein “feet” to “walk” along the _______ provided by the

cytoskeleton

vesicles, tracks

What are the 3 main fibers that make up the cytoskeleton?

Microtubules, microfilaments, intermediate filaments

Whats the thickest cytoskeleton fiber?

Microtubules

Whats the thinnest cytoskeleton fiber

Microfilaments (also called actin filaments)

Which cytoskeleton fiber is in the middle in terms of thickness?

Intermediate filaments

Microtubules structure, diameter, protein subunits

Hollow tubes, 25nm w/ 15nm lumen

tubulin (a dimer consisting of a-tubulin and b-tubulin)

Microtubule function

maintain cell shape, cell motility, chromosome movement in cell division, organelle movements

Microfilaments (actin filaments) Structure, diameter and protein subunit

2 intertwined strands of actin, 7nm, actin

Microfilaments (actin filaments) Function

Maintain cell shape, changes in cell shape, muscle contraction, cytoplasmic streaming (plants), cell motility, cell division(animal cells)

Intermediate filaments structure, diameter, protein subunits

fibrous proteins coiled into cables, 8-12nm, one of several different proteins (such as keratin)

intermediate filaments function

maintain cell shape, anchorage of nucleus and certain other organelles, formation of nuclear lamina

Microtubules are hollow rods constructed from globular

protein dimers called

tubulin

What can tubulin rapidly do?

lengthen or shorten itself

3 main functions of microtubules

Shape and support cell, guide movement of organelles, separate chromosomes during cell division

In animal cells, microtubules grow out from a _______

near the ________

centrosome

nucleus

The centrosome is a…

“microtubule-organizing center”

What does the centrosome have in it

a pair of centrioles, each with 9 triplets of microtubules arranged in a ring

Microtubules control the beating of…

cilia and flagella

What are cilia and flagella?

microtubule-containing extensions projecting from some

cells

What is the difference in number of flagella and cilia

Flagella are limited to one or a few per cell, while cilia occur

in large numbers on cell surfaces

Besides number per cell, how else do cilia and flagella differ?

in terms of beating patterns

Microfilaments are _____________, built from ___________

thin solid rods, molecules of globular actin subunits

What is the structural role of microfilaments?

to bear tension, resisting pulling forces within the cell

1. Help entire parts of cell move

2. Provide structure to cells

Bundles of microfilaments make up the core of _________ of intestinal cells

microvilli

Microfilaments that function in cellular motility interact with

the motor protein:

myosin

actin and myosin interact to cause what

muscle contraction, amoeboid movement of white blood cells, and cytoplasmic streaming in plant cells

Intermediate filaments are larger than _________ but

smaller than __________

microfilaments, microtubules

Intermediate filaments are only found in the cells of….

some animals, including vertebrates

Intermediate filaments are more _________ cytoskeleton

elements than the other two classes

permanent

Intermediate filaments reinforce ____ _______, and ______ organelles in place

cell shape, fix

The cell wall is an extracellular structure that distinguishes

plant cells from animal cells

Functions of cell wall

protects the plant cell, maintains its shape, and

prevents excessive uptake of water

Plant cell walls are made of…

cellulose microfibrils embedded in other polysaccharides and protein

Most cells synthesize and secrete materials that are

_________ to the plasma membrane

external

These extracellular materials are involved in many…

essential cellular functions

Plant cell walls may have multiple…

layers

Primary cell wall structure

thin and flexible

Middle lamella

thin layer between primary walls of adjacent cells

Secondary cell wall (in some cells) is added between the…

plasma membrane and the primary cell wall

Structure of plant cell walls

Animal cells lack cell walls but are covered by an elaborate…

extracellular matrix (ECM)

The ECM is made up of what

glycoproteins such as collagen, proteoglycans, and fibronectin

ECM proteins bind to cell-surface receptor proteins in the

plasma membrane called

integrins

What do cell junctions help with

help form tissues that work as 1 unit

Neighboring cells in an animal or plant often adhere,

interact, and communicate through what way

direct physical contact

What intercellular junctions facilitate adherence, interaction, and communication

Plasmodesmata

Tight junctions

Desmosomes

Gap junctions

Which cell junction(s) are in plants

plasmodesmata

What cell junctions are in animal cells

tight junctions, desmosomes, gap junctions

What are Plasmodesmata

channels that perforate plant cell

walls

What can pass thru plasmodesmata

water and small solutes (and

sometimes proteins and RNA) can pass from cell to cell

Where are the 3 animal cell junctions especially common?

epithelial tissue (skin, organ layers)

What do tight junctions do?

prevent fluid from moving across a layer of cells, while also allowing the free passage of small molecules and ions between adjacent cells, think of the bladder needing to contain urine and not leak

Desmosomes (anchoring junctions) do what?

Hold neighboring cells together tightly to provide mechanical strength, think of the heart pumping blood

What do gap junctions do?

Run from inside of one cell to inside of another to allow substances to pass thru, think electrical charge in heart