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Chapter 4: A Tour of the Cell

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Yat-Long Poon

on 4 October 2016

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Transcript of Chapter 4: A Tour of the Cell

Cell (Plasma) Membrane:
Factory Security
A flexible boundary between the living cell and its surroundings.

Phospholipids
form a two-layer sheet called a
phospholipid bilayer

hydrophilic
heads
face outward
hydrophobic
tails
point inward
Cells come in all shapes and sizes
Nucleus: the CEO
contains most of the cell’s DNA - blueprints that the workers use

controls the cell’s activities by directing protein synthesis

DNA is associated with many proteins and is organized into structures called chromosomes
Ribosomes: the Factory Workers
Ribosomes are molecular machines involved in protein synthesis.
use instructions from the DNA to build proteins
cells that make a lot of proteins have a large number of ribosomes
some ribosomes are attached to the endoplasmic reticulum
other ribosomes float around in cytoplasm
Eukaryotes are more complex
Every organism that is not a bacterium or archaeon is a eukaryote
.

DNA is contained with a membrane-enclosed
nucleus

Eukaryotes have organelles
structures that perform specific functions.
Prokaryotes are simpler than eukaryotes
Bacteria and Archaea are prokaryotes.
plasma membrane
cytosol: an interior filled with a jellylike fluid
chromosomes: carry DNA
ribosomes: tiny structures that make proteins
no nucleus or other organelles
Cell Theory
Nucleus and Ribosomes: CEO and Factory Workers
Cells can be categorized as either prokaryotic or eukaryotic
Chapter 4: A Tour of the Cell
All organisms are composed of cells.
All cells come from other cells.
be large enough to house DNA, proteins, and structures needed to survive and reproduce

remain small enough to allow for a surface-to-volume ratio that will allow adequate exchange with the environment.
Membrane proteins are embedded in the lipid bilayer.

Some proteins form channels (tunnels) that allow molecules to pass through the membrane.

Other proteins serve as pumps, using energy to actively transport molecules into or out of the cell.
Outside the plasma membrane of most prokaryotes is a fairly rigid
cell wall
protects the cell
helps maintain its shape

Some prokaryotes have surface projections
help attach prokaryotes to each other or their substrate.
flagella (singular, flagellum) propel a prokaryotic cell through its environment
The nucleus and ribosomes are involved in the genetic control of the cell.
The double membrane
nuclear envelope
has pores that:
regulate the entry and exit of large molecules
connect with the cell’s network of membranes called the endoplasmic reticulum

The
nucleolus
is
a prominent structure in the nucleus
the site of ribosomal RNA (rRNA) synthesis
Endomembrane System
All the organelles in the cytoplasm and not inside the nucleus.
Endoplasmic Reticulum:
the Assembly Line
Largest component of the endomembrane system. An extensive network of sacs and tubules where things get made.

Smooth ER
: lacks attached ribosomes

Rough ER
: has ribosomes bound to the surface
Smooth ER
production of enzymes
storage of calcium ions

Rough ER
prodution of membranes
production of most proteins
Golgi Apparatus:
Shipping and Receiving
A warehouse and processing station for ER products
products travel in vesicles from ER to Golgi apparatus
one side of the Golgi stack receives the vesicles
the other sides ships out processed products
Golgi appartus:
The Amazon.com of the ER
Lysosomes:
the Janitors
Membrane-enclosed sacs of digestive enzymes
transport the enzymes wherever they're needed
made by Golgi apparatus
digest food
destroy bacteria
fuse with other vesicles containing damaged cell parts to be recycled
Vacuoles:
the Storage Units
Basically, the cell's storage bins
contain materials that will be digested by lysosomes
hold excess water
act as temporary "stomaches"
carry pigments
Plant cells each of a single large vacuole to hold water
Peroxisomes:
the Party Guys
They're like that guy you never remembered inviting to your party.

metabolic compartments that do not originate from the endomembrane system

how they are related to other organelles is still unknown

some peroxisomes break down fatty acids to be used as cellular fuel

So they're still good party guests!
Mitochondria and
Chloroplasts
These are the power generators of animal and plant cells.
Mitochondria:
the Power Generators
Organelles that carry out cellular respiration in nearly all eukaryotic cells (singular: mitochondrion)
cellular respiration
converts the chemical energy in foods to chemical energy in
adenosine triphosphate (ATP)

cristae
: folds of the inner mitochondrial membrane
increase the membrane’s surface area
enhances ability to produce ATP
Cholorplasts:
the Solar Panels
Aside from mitochondria, plants also have chloroplasts.

Chloroplasts are where photosynthesis occurs.

Chloroplasts contain

chloroplast DNA
ribosomes
many enzymes
a network of interconnected sacs called thylakoids
chlorophyll
Fun Fact
Mitochondria have their own DNA, separate from the DNA of the cell.

And in humans, we inherit that DNA only from our mothers.
Mitochondria and chloroplasts contain their own DNA and ribosomes.

The structure of their DNA and ribosomes is very similar to that found in prokaryotic cells.

This led to the
endosymbiont theory
of mitochondria and chloroplasts
mitochondria and chloroplasts used to be small prokaryotes
they began living within larger cells
eventually became mitochondria and chloroplasts inside the larger cells
Plant cells have rigid cell walls
Cytoskeleton and Cell Surfaces
made from proteins
support cell's shape
hold together organelles
involved in cell mobility
Cells contain a network of protein fibers that organizes the structures and activities of the cell.
Microtubules, intermediate filaments, and microfilaments
Cilia
Tight junctions
prevent leakage of fluid across a layer of epithelial cells.

Anchoring junctions
fasten cells together into sheets.

Gap junctions
are channels that allow small molecules to flow through protein-lined pores between cells.
keep plants upright
primarily composed of cellulose
plasmodesmata
: junctions that allow plants tissues to share water, nourishment, and chemical messages.
Junctions allow adjacent cells to interact and communicate
Cell Size
(outside of cell)
(inside of cell)
Every organism that is not bacteria or Archaea is a Eukaryote
Cell
Nucleus
Plants have both
chloroplasts and mitochondria
A cell is like a factory.
Each organelle is like an employee of this factory.
A cell is the smallest thing you can say is living.
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