Download The Cell - myndrs.com

The Cell Theory



All living things are
made up of one or
more cells
The cell is the
functional unit of life
All living cells interact
with the environment,
use energy, grow and
come from preexisting cells
The cell as a factory:

The parts of a cell can be compared to the
workers and jobs in a factory


Each department in a factory has specific jobs
that need to be done or else the factory
becomes less efficient and eventually shut
down.
The same idea is true for the cell, if one of its
components stops working efficiently then the
cell or the organism could die.
Cell Membrane:


The “gate keeper” or “bouncer” of the cell
Decides which materials enter, which ones stay and
which ones leave a cell.




Keeps the good ones in and bad ones out.
Every cell has a cellular membrane (including both animal
and plant cells).
It is a phospholipid bilayer with protein molecule inside it.
More about the cell membrane will be seen in section D
Cytoplasm



The rest of the cell
material that is inside the
cell membrane but
outside the nucleus
Organelles and vacuoles
are considered part of the
cytoplasm
Usually the cytoplasm is
referred to as the semiliquid material that
surrounds the organelles
of a cell
Nucleus





The “control center” or the
“Boss”
With few exceptions all plant
and animal cells possess a
nucleus (plural form is nuclei).
Dark mass usually seen in the
middle of the cell
Contains the DNA or
chromatin of the cell which
are the instructions for all the
activities of the cell.
It also contains nucleoplasm.
Chromatin



Floats in the
nucleoplasm
Made of DNA and
Protein
Is known as
chromosomes when it
is coiled up for cell
division
Nuclear Envelope




The membrane that
encloses the contents
of the nucleus.
“the Boss’ office”
Protects DNA
It has pores in it for
larger materials to
pass in and out.
Nuclear
pore
Nucleolus


A visible darker staining
region inside the
nucleus.
It is where RNA and
the materials for
ribosomes are made.
nucleolus
Cell Organelles



Like your body which has organs to
perform the necessary functions for life,
similarly cells have organelles which
perform the necessary function of
particular cells.
Many organelles are bound by their own
membrane(s)
The proportion of the different organelles
inside a particular cell depends on the
function of the cell.

For example a cell that produces a lot of
hormones will have a large amount of golgi
apparatus which is the organelle responsible
for packaging the products of a cell.
Vacuole




“long term Storage
Containers”
Vacuoles serve a variety of
functions, including storing
nutrients, wastes and water.
Irregular shape
They are usually much
larger in plant cells than in
animal cells.


Example: in the plant cell they
take up almost the entire cell.
They help maintain the shape
of the cell
Ribosomes




The “workers” that put together the
products of the cell.
Non-membranous, and consists of two
unequal sized subunits.
The location of protein synthesis
Made from RNA from the nucleolus
Ribosomes


Some are free in the cytoplasm or become
loosely clustered together to form Polysomes
A polysome is a cluster of ribosomes attached to
the same mRNA molecule; each ribosome is
producing a copy of the same enzyme/protein.


The proteins produced by free ribosomes in
cytoplasm are generally used within the cell
Other ribosomes are embedded in the rough
endoplasmic reticulum (RER).

The products of ribosomes in the RER are often
secreted from the cell
Endoplasmic Reticulum:


The “assembly line”
for the products of
the cell
Consists of
membranous
channels that wind
through the
cytoplasm usually
close to the nucleus
There are two types of endoplasmic
reticulum:
1) Rough endoplasmic reticulum
2) Smooth endoplasmic reticulum
Rough Endoplasmic Reticulum:




AKA “rough ER” or “RER”
The ER that has
ribosomes embedded in it.
Manufactures proteins for
other cells
Assists in the movement
of molecules from one
area of the cell to another
Smooth Endoplasmic Reticulum




Aka : Smooth ER or “SER”
Lack ribosomes
Manufactures steroids
Example: testicle cells which produce
testosterone have abundant amounts
of smooth ER.
Transporting products


When products of the RER and the SER
accumulate, sections of the ER filled with
these products break free in a process
known as blebbing or budding
The result is a collection of small
membrane bound sacs called vesicles
which contain the biochemicals.
Vesicle




“transport containers”
Double membrane bound sacs
carrying different products and
substances from one part of the
cell to another.
Sometimes called transition or
transport vesicles as they are
used to bring the products to the
golgi apparatus for further
processing or to the cell
membrane for secretion out of
the cell.
They can also carry food, waste
products, digestive enzymes.
Golgi Apparatus






AKA “Golgi bodies”
May looks similar to smooth ER, but it
is a set of about 7 or 8 flattened
saccules between ER and the cell
membrane
“Packages, processes and labels” the
products from the ER
Makes concentrated packages of
proteins
Put carbohydrate chains (labels) on
the packages of proteins so that
specific cells recognize them once
they are released in the blood.
Makes lysosomes
Golgi Apparatus:



New vesicles called secretory vesicles with the
newly modified products form by blebbing from
the golgi apparatus.
The vesicles move towards and join the cell
membrane so that their contents are expelled
from the cell.
This process is know as exocytosis which will be
taught later in this section.
Secretory Pathway

Shows the
interrelationships
between cell
organelles
Lysosomes




“Janitors or quality control”
Vesicle-like structures that
contain hydrolytic enzymes
used for digestion of molecules
in the cells.
Have a double membrane
Multicellular organisms use
them to digest unwanted cells
(dying cells) and cell parts that
are defective (autodigestion)

Think of them as the quality control
or health board, that can shut
down the cell at any time.
Mitochondrion:




“The Generator” or “power
house” of the cell
Plural form “mitochondria”
Performs Cellular Respriation
Fluid filled, with a complex
internal membrane


The inner fluid is called the
matrix
The inner membrane which
folded in the matrix is called the
cristae.
Cellular Respiration


A series of chemical reactions that give the cell all
the energy it needs
The energy is saved in the high energy bonds of an
ATP (adenosine triphosphate) molecule.
Net Chemical Reaction:
Glucose + oxygen → Carbon dioxide + water + energy
Balanced Chemical Reaction:
C6H12O6 + 6O2 → 6CO2 + 6H2O + 38 ATP
Chloroplasts



Chloroplasts are specialized
organelles found in all higher
plant cells and some
photosynthetic protists.
The place where
photosynthesis takes place.
These organelles contain the
plant cell's chlorophyll, which
enable them to capture
sunlight energy
Chloroplasts



They have a double outer membrane.
Inside the inner membrane the fluid filled
space is called the stroma
Within the stroma are other membrane
structures including the thylakoids.
 Thylakoids are flattened sacs that
contain chlorophyll and are piled up like
a stack of coins, each stack is called a
granum (plural is grana)
 There are membranous connections
between the grana called lamellae
Photosynthesis
Net Chemical Reaction:
Carbon dioxide + water + energy → Glucose + oxygen
Balanced Chemical Reaction:
6CO2 + 6H2O → C6H12O6 + 6O2
Sunlight
+
Chlorophyll
Cell Wall





The cell wall provides and
maintains the shape of these
cells and serves as a protective
barrier.
Made of cellulose
Has large pores that allow many
molecules to enter.
Not found in animal cells
Restricts the size and shape of a
cell.
Cytoskeleton:




Helps maintain the cell’s shape
Anchors the organelles
Allows the cell and its organelles to move
Constist of two basic types of structures:
1.
Microtubules: assembled by the Microtubule
organizing center (MTOC) which is found near the
nucleus. Form spindle fibers during cell division and
make cillia and flagella.
2.
Actin filaments (AKA microfilaments): long thin
protein fibers, usually found in bundles. Capable of
contracting. Found especially in muscle cells and
microvilli.
Both can assemble and disassemble.
Centriol:




“Traffic Cop”
Organizes organelles
and chromosomes
during cell
reproduction
Microtubules arranged
in a specific pattern.
Found in the MTOC at
right angles to each
other.
Plant cells vs Animal cells

There are some
structures that plant cells
possess that animal cells
do not. Including:




Cell wall
Chloroplasts
Also, plant cells have
larger vacuoles (that
sometimes appear to take
up the entire cell).
Plant cell do not have a
centriole!
Cell membrane
Lysosome
Nucleus
Nucleolus
Centriol
Cytoplasm
Rough ER
Smooth ER
Nuclear
Envelope
Ribosomes
Vacuole
Golgi Apparatus
Mitochondrion
Cell Wall
Cell membrane
Cytoplasm
Lysosome
Vacuole
Nucleus
Rough ER
Nucleolus
Smooth ER
Nuclear
Envelope
Chloroplast
Mitochondrion
Ribosomes
Golgi Apparatus