2. You're invited...
Objectives:
When you complete this chapter, you should be able
to:
•Examine the principles of cell theory.
•Describe the components of cell using a diagram.
•Identify the components of the endomembrane system in a eukaryotic cell.
•Examine the importance of the endomembrane system in a eukaryotic cell.
•Examine the components of a cytoskeleton using diagrams and examples.
•Describe the characteristics and functions of the extracellular matrix in a
cell sing an example.
•Examine the properties that are unique to living organisms.
•Examine the laws of thermodynamics.
•Examine the importance of energy to all living organisms.
•Examine the characteristics of sunlight.
•Examine how the wavelength of light affects photosynthesis.
•Examine the role of pigments in photosynthesis.
•Describe the process of photosynthesis using a flowchart.
•Examine the different methods used by photosynthetic organisms to fix
carbon.
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What is a Cell?
The cell is the basic unit of structure and function
in living things. Cells vary in their shape size,
and arrangements but all cells have similar
components, each with a particular function.
Some of the 100 trillion of cells make up human
body.
All human cell are microscopic in size, shape and
function.
The diameter range from 7.5 micrometer (RBC)
to 150 mm (ovum).
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What is a Cell?
- Cell is defined as the fundamental living unit of any
organism.
- Cell is important to produce energy for metabolism
(all chemical reactions within a cell)
- Cell can mutate (change genetically) as a result of
accidental changes in its genetic material (DNA).
- Cytology: the study of the structure and functions of
cells.
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Cell History
Cytology- study of cells
Used a microscope to examine cork
(plant)
Hooke called what he saw "Cells“
He described the cells as tiny boxes or a
honeycomb
He thought that cells only existed in
plants and fungi
1665 – Robert Hooke
Cork Cells
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Cell History
1673- Anton van Leeuwenhoek
1673- Used a handmade microscope to
observe pond scum & discovered single-
celled organisms
He called them “animalcules”
He also observed blood cells from fish,
birds, frogs, dogs, and humans
Therefore, it was known that cells are
found in animals as well as plants
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Cell History
1858 - Rudolph Virchow
1858- Rudolf Virchow,
German physician, after
extensive study of cellular
pathology, concluded that cells
must arise from preexisting
cells.
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Cell Theory
The 3 Basic Components of the Cell Theory
were now complete:
1. All organisms are composed of one
or more cells. (Schleiden & Schwann)(1838-
39)
2. The cell is the basic unit of life in all
living things. (Schleiden & Schwann)(1838-
39)
3. All cells are produced by the division
of preexisting cells. (Virchow)(1858)
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Components of All
CELLS
1) THE CELL (PLASMA) MEMBRANE
The cell membrane is a thin, dynamic
membrane that encloses the cell and controls
what enters and leaves the cell.
This membrane separates the cell’s content
from the external environment.
It is consist mainly of a Phospholipid Bilayer.
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Components of All
CELLS
2. CYTOPLASM
Is a gel-like matrix of water, enzymes,
nutrients, wastes, and gases and contains
cell structures (organelles).
Fluid around the organelles called cytosol.
Most of the cells metabolic reactions occur
in the cytoplasm.
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Components of All
CELLS
3. DNA (deoxyribonucleic acid)
DNA, or deoxyribonucleic acid, contains the
information needed for the creation of proteins
(which include enzymes and hormones) and is
stored in the nucleus, as already said, in the
form of chromatin or chromosomes.
The nucleus is the site of DNA duplication,
which is needed for cell division (mitosis) and
organism reproduction and growth.
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Contraints on CELL
Size
A cell exchanges substances with its environment at a
rate that keeps pace with its metabolism. These
exchanges occur across the plasma membrane, which
can handle only so many exchanges at a time.
The rate of exchange across a plasma membrane
depends on its surface are: “The bigger it is, the more
substance can cross it during a given time”.
Cell size is limited by a physical relationship called the
Surface-to-Volume Ratio. By this ratio, an object’s volume
increases with the cube of its diameter, but its surface
increases only with the square.
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Contraints on CELL
Size
Base on the Picture, when a cell expands in diameter, its
volume increases faster that its surface are does.
o If the cell gets too big, the inward flow of nutrients and the outward
flow of wastes across that membrane will not be fast enough to keep
the cell alive.
o Surface-to-Volume limits also affects the form of colonial organisms
and multicelled bodies.
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The NUCLEUS
Brain of Cell
Bordered by a porous
membrane - nuclear
envelope.
Contains thin fibers of
DNA and protein called
Chromatin.
Rod Shaped
Chromosomes
Contains a small round
nucleolus
•produces ribosomal RNA
which makes ribosomes.
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The NUCLEUS
2 Important Function:
1) It keeps the cell’s genetic
material-DNA-safe from
metabolic processes that might
damage it.
2) It controls the passage of certain
molecules across its membrane.
22. Structure of Nucleus
NUCLEAR ENVELOPE
The nuclear envelope is a double-layered membrane perforated with pores,
which control the flow of material going in and out of the nucleus.
The outer layer is connected to the endoplasmic reticulum, communicating with
the cytoplasm of the cell. The exchange of the large molecules (protein and
RNA) between the nucleus and cytoplasm happens here.
The inner layer of animal cell nuclei is covered and supported by the nuclear
lamina , a dense mesh of fibrous proteins.
The two layer of a nuclear envelope connect at nuclear pores.
23. Structure of Nucleus
CHROMATIN & CHROMOSOMES
Chromosomes contain DNA in a condensed form attached to a
histone protein.
Chromatin is comprised of DNA. There are two types based on
function.
Heterochromatin: highly condensed, transcriptionally
inactive mostly located adjacent to the nuclear membrane
Eurochromatin: delicate, less condensed organization of
chromatin, located in a transcribing cell
24. Structure of Nucleus
NUCLEOLUS
It is an irregularly shaped region,
dense with proteins and nucleic acids,
where subunits of ribosomes are being
produced.
The subunits pass through nuclear
pores into the cytoplasm, where they join
and become active in protein synthesis.
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The ENDOMEMBRANE
SYSTEM
It is a series of interacting organelles between the
nucleus and the plasma membrane.
MAIN FUNCTIONS:
o Is to make lipids, enzymes, and proteins for
insertion into the cell’s membranes or secretion to
the external environment.
o It is also destroy toxins, recycle wastes, and has
other special functions.
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The ENDOMEMBRANE
SYSTEM
Small, membrane-enclosed sacs called VESICLES
form by budding from other organelles or when a
patch of plasma membrane sinks into the cytoplasm.
Many types carry substances from one organelle to
another:
PEROXISOMES
LYSOSOMES
ENDOCYTIC and EXOCYTIC
CENTRAL VACUOLE
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The ENDOMEMBRANE
SYSTEM
Vesicles
Endocytic and exocytic: Transport or store
polypeptides and lipids
Peroxisomes: Digest fatty acids and amino
acids; break down toxins and metabolic by-
products
Lysosomes: Intracellular digestion (animals)
Central vacuole: Storage; fluid pressure
(plants)
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The ENDOMEMBRANE
SYSTEM
ENDOPLASMIC RETICULUM
network of interconnected parallel membranes (maze), that is
continuous with the nuclear membrane;
2. Two types:
a. Rough Endoplasmic Reticulum (RER)
1. ER studded with ribosomes;
2. Function = protein synthesis and intraceluar
transportation of molecules ;
b. Smooth Endoplasmic Reticulum (SER)
lacks ribosomes;
1. Function = lipid & cholesterol synthesis and Stores
calcium.
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MITOCHONDRIA
Break down organic compounds by
aerobic respiration (oxygen-requiring)
Produce ATP
kidney-shaped organelle whose inner
membrane is folded into shelf-like partitions
called cristae;
"Powerhouse" of the cell = site of cellular
respiration where energy is released from
glucose.
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CHLOROPLASTS
Produce sugars by
photosynthesis
Double membrane
Center section contains grana
Thylakoid (coins) make up the
grana.
Stroma - gel-like material
surrounding grana
Found in plants and algae.
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CYTOSKELETON
Microtubule
Microfilaments
Framework of the cell
Contains small microfilaments and larger microtubules.
They support the cell, giving it its shape and help with the
movement of its organelles.
Is a network of fibers extending throughout the cytoplasm
Fibers appear to support the endoplasmic reticulum, mitochondria,
and “free” ribosomes
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CYTOSKELETON
FUNCTIONS:
Organizes and moves cell parts
Reinforces cell shape
Interactions between motor proteins and
microtubules in cilia, flagella, and pseudopods can
move the whole cell
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Components of
Cytoskeleton
MICROTUBULE
Are long, hollow cylinders that consist of subunits
of the protein tubuli.
They form a dynamic scaffolding for many
cellular processes, rapidly assembling when they
are needed, disassembling when they are not.
Guide movement of organelles (their function is
to move things around in the cell)
Help separate the chromosome copies in dividing
cells
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Components of
Cytoskeleton
MICROFILAMENTS
Are fibers that consists primarily of subunits of a protein
called Actin.
It connect plasma membrane proteins to other proteins
inside the cell.
Solid rods of globular proteins.
Important component of cytoskeleton which offers
support to cell structure.
Microfilaments can slide past each other, causing
shortening of the cell
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Components of
Cytoskeleton
INTERMEDIATE FILAMENTS
Are the most stable elements of the cytoskeleton, forming
a framework that lends structure and resilience to cells and
tissues in multicelled organisms.
Intermediate filaments are twisted protein strands slightly
thicker than microfilaments; they form much of the
supporting framework in many types of cells.
