Transcript bioch7 - Otterville R

Basic Structure of a Cell
1
Introduction to Cells
Cells are the basic units of organisms
Cells can only be observed under
microscope
Basic types of cells:
Animal Cell
Plant Cell
Bacterial Cell
2
Number of Cells
Organisms may be:
• Unicellular –
composed of one cell
• Multicellularcomposed of many
cells that may
organize
3
Cells May be Prokaryotic or
Eukaryotic
 Prokaryotes include bacteria &
lack a nucleus or membrane-bound
structures called organelles
Eukaryotes include most other cells
& have a nucleus and membranebound organelles (plants, fungi, &
animals)
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Prokaryotes
Nucleoid region
contains the DNA
•Cell membrane &
cell wall
• Contain ribosomes
(no membrane) to
make proteins in
their cytoplasm
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Eukaryotic Cell
Contain 3 basic cell
structures:
• Nucleus
• Cell Membrane
• Cytoplasm with
organelles
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Two Main Types of
Eukaryotic Cells
Plant Cell
Animal Cell
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Organelles
Very small size
Can only be observed under a
microscope
Have specific functions
Found throughout cytoplasm
8
Organelles Found in Cells
Examples of Organelles include:
Endoplasmic reticulum (rough & smooth) –
canals for movement
Golgi Bodies – wrap & export proteins
Nucleolus – makes ribosomes
Lysosomes – digests & gets rid of wastes
Ribosomes – makes proteins
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Golgi Bodies
• Stacks of flattened
sacs
• Have a shipping side &
a receiving side
• Receive & modify
proteins made by ER
• Transport vesicles
with modified proteins
pinch off the ends
Transport
vesicle
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Lysosome
• Contain digestive
enzymes
• Break down food and
worn out cell parts for
cells
• Programmed for cell
death (lyse & release
enzymes to break down
& recycle cell parts)
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Nucleolus
•
Cell may have 1 to 3
nucleoli
• Inside nucleus
• Disappears when cell
divides
• Makes ribosomes that
make proteins
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Smooth & Rough Endoplasmic
Reticulum
Smooth ER lacks
ribosomes &
makes proteins
USED In the cell
Rough ER has
ribosomes on its
surface & makes
proteins to
EXPORT
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Cell Powerhouse
Mitochondrion
( mitochondria )
Rod shape
Site of Cellular
respiration
14
In Animal Cells:
Mitochondria
Active cells like
muscles have more
mitochondria
Burn sugars to
produce energy ATP
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Surrounding the Cell
Cell membrane
Lies immediately
against the cell wall
in plant cells
Made of protein and
phospholipids
Selectively permeable
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Cell or Plasma Membrane
Cell membrane
Living layer
Controls the
movement of
materials into and
out of the cell
Selectively
permeable
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Cytoplasm of a Cell
Cytoplasm
Jelly-like substance
enclosed by cell
membrane
Provides a medium
for chemical
reactions to take
place
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More on Cytoplasm
Cytoplasm
Contains organelles
to carry out
specific jobs
Examples:
chloroplast &
mitochondrion
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Control Organelle
Nucleus
Controls the normal
activities of the cell
Bounded by a
nuclear membrane
Contains chromosomes
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More on the Nucleus
Nucleus
Each cell has fixed
number of
chromosomes that
carry genes
Genes control cell
characteristics
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Plant Cell Organelles
Chloroplast
Contain the green
pigment chlorophyll
Traps sunlight to
make sugars (food)
Process called
photosynthesis
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Plant Cell
Cell wall
Dead layer
Large empty spaces
present between
cellulose fibers
Freely permeable
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Plant Cell
Cell wall
Made of cellulose
which forms very
thin fibers
Strong and rigid
Found in plant cells
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Plant Cell
Cell wall
Protect and support
the enclosed
substances
(protoplasm)
Resist entry of
excess water into
the cell
Give shape to the cell
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Plant Cell Organelles
Vacuole
Have a large central
vacuole
Surrounded by tonoplast
Contains cell sap
Sugars, proteins,
minerals, wastes, &
pigments
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Different kinds of plant
cells
Onion Epidermal Cells
Guard Cells
root hair
Root Hair Cell
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vacuole
cytoplasm
nucleus
mitochondrion
glycogen
granule
Animal cell
No cell wall or
chloroplast
Stores glycogen
in the
cytoplasm for
food energy
cell
membrane
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Animal Cell Organelles
• Near the nucleus
• Paired structures
• Help cell divide
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Different kinds of animal
cells
white blood cell
Amoeba
red blood cell
muscle cell
cheek cells
sperm
nerve cell
Paramecium
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Similarities between plant
cells and animal cells
Both have a cell membrane
surrounding the cytoplasm
Both have a nucleus
Both contain mitochondria
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Differences between plant
cells and animal cells
Animal cells
Plant cells
Relatively
smaller in size
Relatively
larger in size
Irregular shape
Regular shape
No cell wall
Cell wall present
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Differences between Plant
Cells and Animal Cells
Animal cells
Plant cells
Vacuole small or
absent
Large central
vacuole
Glycogen as food
storage
Starch as food
storage
Nucleus at the
center
Nucleus near cell
wall
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Compound Microscope
• Instrument for
observing small
objects
• Magnify images
up to 2000X
their size
34
Different parts of
a microscope
35
Revolving
nosepiece
Eyepiece
Clip
Body tube
Coarse
adjustment
Fine adjustment
Condenser
Arm
Iris diaphragm
Stage
Objective
Mirror
Condenser
control knob
Base
36
The cell is the Basic Unit
of Life
• Cell is the smallest unit of living organisms
• Unicellular organisms are made of one cell
only
• The cells of multicellular organisms are
specialized to perform different functions
– e.g. mesophyll cells for photosynthesis
and root hair cells for water absorption
37
Levels of organization
• Cells are
grouped
together and
work as a
whole to
perform special
functions
38
Tissue
• A group of similar cells to
perform a particular function
– Animals : epithelial tissue,
muscular tissue
– Plants : vascular tissue,
mesophyll
39
Organ
• Different tissues group together
to carry out specialized functions
– Heart : consists of muscles,
nervous tissue and blood
vessels
– Leaf : consists of epidermis,
mesophyll and vascular tissue
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The Structures of a Leaf
(Plant Organ)
Chloroplast
Palisade
Mesophyll Cell
Spongy Mesophyll
Cell
Air Space
Stoma
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The Structures of a Heart
(Animal Organ)
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System
• Several organs and tissues work together
to carry out a particular set of functions in a
co-ordinated way
– Human : digestive, respiratory, excretory,
circulatory and reproductive systems
– Plant : root and shoot systems
43
Human Body Systems
Examples of systems :
 Digestive System
 Respiratory System
 Circulatory System
 Nervous System
 Reproductive System
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Examples of a Human Body System
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Examples of a Human Body System
The Respiratory System
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Examples of a Human Body System
Circulatory System
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Examples of a Human Body System
Nervous System
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Levels of Organization
CELLS
(muscle cells,nerve
cells)
TISSUES (muscle, epithelium)
ORGANS (heart, lungs,
stomach)
SYSTEMS (circulatory system)
ORGANISM (human)
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It’s You!
50
The Plasma Membrane
-
Gateway to the Cell
51
Photograph of a Cell
Membrane
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Cell Membrane
The cell
membrane is
flexible and
allows a
unicellular
organism to
move
53
Homeostasis
• Balanced internal condition of
cells
• Also called equilibrium
• Maintained by plasma membrane
controlling what enters & leaves
the cell
54
Functions of Plasma
Membrane
 Protective barrier
 Regulate transport in & out of cell
(selectively permeable)
 Allow cell recognition
 Provide anchoring sites for filaments
of cytoskeleton
55
Functions of Plasma
Membrane
 Provide a binding site for enzymes
 Interlocking surfaces bind cells
together (junctions)
Contains the cytoplasm (fluid in cell)
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Structure of the Cell
Membrane
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Membrane Components
Phospholipids
Cholesterol
Proteins
(peripheral and integral)
Carbohydrates (glucose)
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Phospholipids
Make up the cell
membrane
Contains 2 fatty
acid chains that
are nonpolar
Head is polar &
contains a –PO4
group
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FLUIDFluid
MOSAIC
MODEL
mosaic
model
FLUID- because individual phospholipids and proteins can
move around freely within the layer, like it’s a liquid.
MOSAIC- because of the pattern produced by the scattered
protein molecules when the membrane is viewed from
above.
60
Cell Membrane
Polar heads are hydrophilic “water loving”
Nonpolar tails are hydrophobic “water fearing”
Makes membrane “Selective” in what crosses
61
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Cell Membrane
The cell membrane is
Hydrophobic
made of 2 layers of
molecules pass
phospholipids called the
easily;
hydrophillic
lipid bilayer
DO NOT
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Solubility
• Materials that
are soluble in
lipids can pass
through the
cell membrane
easily
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Semipermeable Membrane
Small molecules and larger hydrophobic
molecules move through easily.
e.g. O2, CO2, H2O
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Semipermeable Membrane
Ions, hydrophilic molecules larger than
water, and large molecules such as proteins
do not move through the membrane on their
own.
66
Types of Transport
Across Cell
Membranes
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Simple Diffusion
• Requires NO
energy
• Molecules
move from
area of HIGH
to LOW
concentration
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DIFFUSION
Diffusion is a PASSIVE
process which
means no energy is
used to make the
molecules move,
they have a natural
KINETIC ENERGY
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Diffusion of Liquids
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Diffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient (HIGH to
LOW)
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Osmosis
• Diffusion of water
across a membrane
• Moves from HIGH
water potential (low
solute) to LOW water
potential (high
solute)
Diffusion across a membrane
Semipermeable
membrane
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Diffusion of H2O Across A
Membrane
High H2O potential
Low solute concentration
Low H2O potential
High solute concentration73
Cell in Isotonic Solution
10% NaCL
90% H2O
ENVIRONMENT
CELL
10% NaCL
90% H2O
NO NET
MOVEMENT
What is the direction of water movement?
equilibrium
The cell is at _______________.
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Cell in Hypotonic Solution
10% NaCL
90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement?
75
Cell in Hypertonic Solution
15% NaCL
85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
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Cells in Solutions
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Isotonic Solution
NO NET
MOVEMENT OF
H2O (equal amounts
entering & leaving)
Hypotonic
Solution
CYTOLYSIS
Hypertonic
Solution
PLASMOLYSIS
78
Cytolysis & Plasmolysis
Cytolysis
Plasmolysis
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Osmosis in Red Blood
Cells
Isotonic
Hypotonic
Hypertonic
80
hypotonic
hypertonic
hypertonic
isotonic
isotonic
hypotonic
81
Three Forms of Transport Across the Membrane
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Passive Transport
Simple Diffusion
 Doesn’t require energy
 Moves high to low
concentration
 Example: Oxygen or
water diffusing into a
cell and carbon dioxide
diffusing out.
83
Passive Transport
Facilitated diffusion
Doesn’t require energy
Uses transport
proteins to move high to
low concentration
Examples: Glucose or
amino acids moving from
blood into a cell.
84
Proteins Are Critical to
Membrane Function
85
Types of Transport Proteins
• Channel proteins are embedded in the
cell membrane & have a pore for
materials to cross
• Carrier proteins can change shape to
move material from one side of the
membrane to the other
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Facilitated Diffusion
Molecules will randomly move through
the pores in Channel Proteins.
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Facilitated Diffusion
• Some Carrier
proteins do not
extend through the
membrane.
• They bond and drag
molecules through
the lipid bilayer and
release them on the
opposite side.
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Carrier Proteins
• Other carrier
proteins
change shape
to move
materials
across the cell
membrane
89
Active Transport
Requires energy or
ATP
Moves materials from
LOW to HIGH
concentration
AGAINST
concentration gradient
90
Active transport
Examples:
Pumping Na+
(sodium ions) out
and K+ (potassium
ions) in against
strong
concentration
gradients.
Called Na+-K+ Pump
91
Sodium-Potassium Pump
3 Na+ pumped in for every 2 K+ pumped
out; creates a membrane potential 92
Moving the “Big Stuff”
Exocytosis
- moving
things
out.
Molecules are moved out of the cell by vesicles that fuse
with the plasma membrane.
This is how many hormones are secreted and how nerve
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cells communicate with one another.
Exocytosis
Exocytic
vesicle
immediately
after fusion
with plasma
membrane.
94
Moving the “Big Stuff”
Large molecules move materials into the cell by
one of three forms of endocytosis.
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Pinocytosis
Most common form of endocytosis.
Takes in dissolved molecules as a vesicle.
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Pinocytosis
• Cell forms an
invagination
• Materials dissolve
in water to be
brought into cell
• Called “Cell
Drinking”
97
Example of Pinocytosis
pinocytic vesicles forming
mature transport vesicle
Transport across a capillary cell (blue).
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Receptor-Mediated Endocytosis
Some integral proteins have receptors
on their surface to recognize & take in
hormones, cholesterol, etc.
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Receptor-Mediated Endocytosis
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Endocytosis – Phagocytosis
Used to engulf large particles such as
food, bacteria, etc. into vesicles
Called “Cell Eating”
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Phagocytosis About to Occur
102
Phagocytosis
- Capture
of a Yeast
Cell (yellow)
by
Membrane
Extensions
of an
Immune
System Cell
(blue)
103
Exocytosis
The opposite of endocytosis is exocytosis. Large
molecules that are manufactured in the cell are
released through the cell membrane.
Inside Cell
Cell environment
104
Videos
• Click a hyperlink to choose a video.
•
Diffusion
•
Osmosis
•
Passive Transport
•
Active Transport
•
Endocytosis and Exocytosis
Video
Video 1
Diffusion
• Click the image to play the video segment.
Video 2
Osmosis
• Click the image to play the video segment.
Video 3
Passive Transport
• Click the image to play the video segment.
Video 4
Active Transport
• Click the image to play the video segment.
Video 5
Endocytosis and Exocytosis
• Click the image to play the video segment.