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Cell Structure
Analysis of the functional interrelationships of cell structures
Cell Biology: the study of cells – the structural and function units of
all living organisms
morphologically cells
vary in shape and size
red blood
cells
bacteria
human
sperm cells
white blood
cells
platelets
cancer cells (myeloma)
nerve cell
cells also vary physiologically
portion of skeletal
muscle cells
1:2
Cell Theory
1. Cells are the basic unit of life
2. All organisms are made of one or more
cells
3. Cells come from pre-existing cells
Cells
Tissues
Organs
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Nucleus and Nucleoid
a nucleoid (which consists of the organisms DNA)
is NOT enclosed in a membrane = prokaryotic cell
eukaryotic cell =
DNA contained
within a membrane
1:5
Eukaryotic Cells
• Bounded by cell
membrane
• Cytoplasm inside cells
composed of aqueous
solution, organelles and
molecules
• Various fibres compose
a cytoskeleton to give
shape and structure
Nucleus
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Contains genetic material which
controls/directs the activities of the cell
function: “brain” of cell, i.e. determines
metabolism, growth, differentiation, &
reproduction of cell
Nucleus enclosed in a nuclear envelope
Within nuclear envelope is
chromosome/chromatin, nucleoplasm
and nucleoli
Chromosomes/chromatin are long
strands of DNA wrapped around protein
molecules which make up genes (units of
heredity)
nucleoplasm is a highly viscous liquid
Nucleoli is the site where rRNA is
assembled (rRNA then travels to the
cytoplasm for protein syntheis)
DNA packed in Chromosomes
Chromatin vs. Chromosome
Ribosome
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consist of 2 non–
identical subunits
formed from rRNA &
proteins
function: protein
synthesis
found attached to
endoplasmic reticulum
or free in cytoplasm
polysome: group of
ribosomes
simultaneously
synthesizing same
protein
Membranous Canals
• Includes endoplasmic reticulum, golgi
apparatus, vacuoles and lysosomes
Endoplasmic Reticulum
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Series of membranous canals exist in
cytoplasm
Can extend from nuclear envelope to
cell membrane
rough endoplasmic reticulum:
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ribosomes attached to surface
function: synthesize proteins for
secretion
NOTE: unlike free ribosomes that
synthesize proteins for use within cell
smooth endoplasmic reticulum:
– no ribosomes attached to surface
– functions:
1. synthesis of lipids, e.g. cell membrane
& hormones
2. metabolism of carbohydrates, e.g.
synthesis of glycogen
3. detoxify drugs & wastes in cell, e.g.
alcohol
Golgi Apparatus
• resembles flattened stack of hollow tubes,
i.e. similar to smooth endoplasmic reticulum, but
closer to cell membrane
• function: sorting, modification (assembly), & packaging
of substances for storage or secretion
e.g. produces glycolipids by joining carbohydrates to
lipids
• receives vesicles from endoplasmic reticulum that
contain newly synthesized proteins/lipids
proteins/lipids sorted, modified, & packaged into new
vesicles that bud off
vesicles transported within cell or moved to cell
membrane for export by exocytosis
Vacuoles
• large, membrane enclosed sac
• vesicle: small vacuole
• functions: storage or transport
• formed by:
1. budding off (pinching off) from Golgi apparatus
2. endocytosis of cell membrane
3. extension of endoplasmic reticulum membrane
Lysosomes
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vesicle formed by Golgi
apparatus, which
contains hydrolytic
enzymes
• functions:
1. cellular digestion of food
particles, i.e. fuses with
food vacuoles &
enzymatically digests
proteins, carbohydrates,
& lipids
2. disposal of damaged cell
organelles, e.g.
mitochondria
3. breakdown of whole cell,
i.e. releases contents
into cell cytoplasm
Energy related organelles
Mitochondria
• function: cellular respiration (aerobic metabolism), i.e. converts
glucose (carbohydrates) to energy (ATP)
• chemical reaction:
C6H12O6 + 6O2
6CO2 + 6H2O + energy (ATP)
• cristae (singular: crista): shelf–like structures formed from folded
inner membrane with enzymes on surface for cellular respiration
– Provides lots of surface area for cell. resp. reaction.
• matrix: solution surrounded by
cristae contains DNA
Choloroplast
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function:
photosynthesis in
plant cells, i.e.
converts sunlight
energy to
carbohydrates
Made up of
membranous stacks
called grana, which
contain chlorophyll
pigments
chlorophyll: chemical
that absorbs sunlight
energy & allows
photosynthesis to
occur
Basic Photosynthesis
Works hand in hand
with cellular respiration
Organelles made up of
Membranes:
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Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Vesicles
Cell membrane
Mitochondria
Chloroplast
Note: Membranes are composed of phospholipids
Cell Shape
Other Organelles
• Cell wall:
– rigid cellular layer that surrounds the cell membrane
in plant cells
– Provides protection, shape, and support for the cell
– Composed of cellulose
• Cytoskeleton
– network of protein fibres
– functions: maintain cell shape, anchor organelles, &
involved in motility
Characteristics of Living Things
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Living things are made of cells.
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Living things obtain and use energy.
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Living things grow, reproduce and repair.
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Living things produce waste.
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Living things respond to their environment.
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Living things have a life span.
By the end of this section you
should be able to
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Prokaryotic cell verses a eukaryotic cell
Describe the following cell structures and their functions
– Cell membrane
– Cell wall
– Chloroplast
– Cytoskeleton
– Cytoplasm
– Golgi bodies
– Lysosomes
– Mitochondria – including cristae and matrix
– Nucleus - including nuclear pore, nucleolus, chromatin, nuclear envelope, and chromosomes
– Ribosomes (and polysomes)
– Smooth and rough endoplasmic reticulum
– Vacuoles
– Vesicles
State the balanced chemical equation for cellular respiration and photosynthesis
Describe how the following organelles function to compartmentalize the cell and more materials
through it:
– Rough ER and smooth ER
– Vesicles
– Golgi bodies
– Cell membrane
Identify cell structures depicted in diagrams and electron micrographs