Download a. Cell membrane

History of the Cell
• Robert Hooke (1665) – Used compound
scope to examine thin cork slices. Coined
the term “cell” referring to the many little
boxes. Actually saw dead plant cells
• Anton van Leeuwenhoek (1673) with his
simple scope, observed first living cells
• Matthias Schleiden (1838) and Theodor
Schwann stated that all plants and animals
(respectively) are made up of cells .
• Rudolph Virchow (1855) – cells come only
from other cells
The Cell Theory
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All living things are made up of cells
Cells are the basic unit of structure
and function in all living things
Cells come from pre-existing cells
Cells vary by:
1. Size – Range from 2m (giraffe nerve cell from leg
to spine) to .2um (bacteria - Mycoplasm)
Limited by the ratio between outer
surface area and their volume.
As the surface area to volume ratio
decreases, it makes it difficult for
information to get around cell and also
nutrients to get and then be circulated around
the cell
Side
Length
Surface Area
LxWx6
Volume
LxWxH
Surface area to
Volume ratio
1mm
6mm2
1mm3
6 to 1
2mm
24mm2
8mm3
3 to 1
3mm
54mm2
27mm3
2 to 1
2. Shape – Form reflects function.
Red Blood Cells are like tubes at Sesame Place
so they flow easier
Nerve cells are like electrical wires
Cheek cells (Epithelial cells) are flat to act like a
shield
White Blood cells are amoeboid shaped to move
and squeeze into all areas
3. Internal Organization –
– Organelles – internal structures in a cell. Each has a
specific function
All cells contain:
a. Cell membrane – thin membrane.
Porous to certain compounds
b. Cytoplasm – “cell’s liquid”
Organelles are suspended in it
c. Ribosomes – Protein factories in cells
d. DNA
Types of cells
1. Prokaryotic cells
– cells that lack a nucleus
and membrane bound
organelles
- Bacteria & Archaebacteria
- Have a cell wall, cell
membrane, cytoplasm,
DNA & ribosomes
- Pigments and enzymes
are suspended in
cytoplasm suspended
in cytoplasm
2. Eukaryotic Cells –
contain a membrane
bound nucleus and
membrane bound
organelles.
- Much more complex cell
- All cells other than
bacteria.
- Protists, Fungus,
Animals and Plants
Nucleus
Comparing the Two
Cytoplasm
DNA
Cell Membrane
Parts of the Eukaryotic cell
• Three main components:
– Nucleus
– Cell membrane
– Cell organelles
Cell membrane
Central Problem #1: A living system MUST be
separated from its environment if it is to maintain
complex order in a chaotic physical world.
Cell Membrane
– Separates the cell’s internal environment
from the external environment.
- Allows for the passage of some
substances based on size and
concentration
– Selectively Permeable
Some things can pass
through while others
can’t
• Made up of a bilipid layer (lipid bilayer) – 2
layers of phospholipids with proteins floating
through it.
• Tails of phospholipids are hydrophobic while
the heads are hydrophilic
Peripheral membrane proteins do not
penetrate the hydrophobic core of the
membrane. They can be easily removed
without destroying the membrane structure.
• Integral proteins : these are fully
incorporated into the membrane and are in
contact with both the inside and the outside
of the cell. Some can act as channel ways
for the transport of substances. Others have
carbohydrate attached to them – recognition
sites
Integral proteins
Peripheral protein
• In the "fluid mosaic model" of
membrane structure, the membrane is
a fluid phospholipid bilayer in which
protein molecules are either partially or
wholly embedded. These layers easily
move around.
Rap
Cell Organelles
Cytoplasm – area between nuclear
envelope and plasma membrane
– “cell’s liquid” Made of gelatinous cytosol
where nutrients and minerals carried in
solution within it.
•
•
Typical Animal Cell
Typical Plant Cell
Mitochondria
- Powerhouse of the cells.
–
–
–
- Where cellular respiration occurs and glucose is broken
down to release energy (in the form of ATP) to the cell.
Found in greater numbers in cells such as muscle cells &
liver cells (2500/cell)
Double membraned with Cristae (folds) to > surface area
for reactions to take place
Have their own DNA (mDNA) and ribosomes. Replicate by
binary fission as needed
Cristae
Double Membrane
Ribosomes
 Most numerous organelle in the cell.
 Site of protein synthesis.
 Not membrane bound therefore, they are
in prokaryotic cells.
 Made up of RNA and protein.
 May be free floating in cytoplasm or
attached on Endoplasmic Reticulum
Endoplasmic Reticulum
– Channels or passageways in
the cell. There are two types
of ER:
1 – Rough with ribosomes
attached for the production
and distribution of proteins.
2 – Smooth – Synthesis of
steroids (lipids) in gland cells,
Ca+ regulation in muscle cells
and breakdown of toxins
1
2
3
4
5
6
7
8 - 10
Nuclear Envelope
Nucleopore
Rough endoplasmic reticulum
(RER)
Smooth endoplasmic reticulum
SER)
Ribosome on the RER
Proteins that are transported in
…Transport vesicle
Golgi apparatus
Golgi Apparatus (Bodies)
o Stack of smooth flat sacs.
o Processing, packaging and secreting
organelle of the cell.
o Much like a processing & exporting plant.
Work in close association with ER
Lysosomes
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
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
Single membrane - are the cells' garbage
disposal system.
They breakdown worn out organelles
such as mitochondria & produce
hydrolytic enzymes to that degrade DNA,
proteins, lipids &carbohydrates
Responsible for the un-webbing of hands
of fetus while developing in utero
These are rare in plant cells
Cytoskeleton
Network of protein strands that provide support and mobility
of organelles in cytoplasm.
2 components of cytoskeleton
- Microfilaments – made of actin (protein threads). Involved
with cellular movement and muscle contractions
–
Microtubules – larger structures. Involved in cell division,
make up flagella and cilia. Also make up spindle fibers that
assist in chromosome migration during cell division.
9 – 2 arrangement
Cilia and Flagella
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




Extensions from cell membrane.
Assist in movement.
Have 9-2 arrangement like microtubules
Cilia - when short and multiple numbers.
Covering of Paramecium, lining of respiratory tract
and nasal passages.
Flagella- long and usually only 1 to a few. Sperm
cells, Euglena. Used for propulsion
Nucleus
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•
•
•
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•
Only in Eukaryotic cells.
Stores hereditary information in DNA.
Surrounded by a double nuclear envelope.
Nuclear pores perforate membrane.
Chromatin - strands of a combination of
DNA & protein within nucleus.
These will later become chromosomes.
Nucleolus (1 or >) produces ribosomes
Plant Cells
• Are eukaryotic and
have most of the same
organelles as animal
cells except:
1. Cell Walls
 Made up of cellulose &
pectin (glue between
walls)
 Gives cells rigidity,
protection & support.
 Is also porous.
Cell Wall
Primary cell wall
Forms just on the outer
surface. Expands by
adding on more cellulose.
Grows as cell grows
Secondary cell wall
Develops between primary
and cell membrane.
Tough and woody.
No more growth
2. Vacuoles
- Store enzymes, food, water and wastes.
- Huge water vacuole (Central Vacuole) in
plant cells.
- Gives plant cell “turgor” (full of water and
fully supported) – 90% of cells may be water.
- Some contain metabolic wastes which may
be toxic to other organisms (poison ivy).
3. Plastids
Double membrane, DNA containing to store
starch, fats or Pigments such as chlorophyll.
Chloroplast – where photosynthesis occurs.
Made up of stacks called Thylakoids. Here is
where the energy conversion occurs.
Leucoplast/Amyloplasts store starch
Typical Animal Cell
1. _______________
2. _______________
3. _______________ (Dots)
4. _______________
5. _______________
6. _______________
7. _______________
8. _______________
9. _______________
10._______________
11._______________
12._______________
13._______________
1
7(folds)
2
8
9 (Dots)
10
3
11
12
4
13
5
6
Typical
Plant Cell
Epithelial (Cheek) Cells
Cell Membrane
Nucleus
Cytoplasm
Cyclosis
Elodea
Onion Cells
Potato Cells
Red Blood Cells (& 2 White
Blood Cells)
Organelle
Function
Plant
Cells
Animal
Cells
Mitochondria
Site of cellular respiration - transfer of energy - Folds called
Cristae
Yes
Yes
Ribosomes
Site of Protein synthesis
Yes
Yes
Endoplasmic Reticulum
Rough - Protein packaging & transport site
Smooth - Sythesis of lipids
Yes
Yes
Golgi Apparatus
Processing & packaging center for cell secretions
Few
Many
Lysosomes
Produce hydrolytic enzymes
Few
Many
Cytoskeleton
Network of protein filaments - keep cell's shape and for
movement
Yes
Yes
Microfilaments &
microtubules
Support, movement and cell division
Yes
Yes
Cilia & Flagella
Cell movement & circulation Cilia - many & short, Flagella 1or 2 & long
Yes
Yes
Nucleolus
Production of ribosomes
Yes
Yes
Nucleus
Contains DNA, synthesizes RNA & Ribosomes
Yes
Yes
Chromatin
DNA & protein - genetic information
Yes
Yes
Cell Wall
Outmost layer of plant cell - support & protection Made of
cellulose & pectin glue between walls
Yes
No
Vacuole
Stores enzymes, wastes, water & food Large water in plants
- support
Yes, large
water vacuole
Many
Plastid
Stores food and pigments - Chloroplasts (photosynthesis) &
leucoplasts (stores starch)
Yes
No
Centrioles
Microtubules that function during cell division
No
Yes
Cell Membrane
Selectively permeable - made of a bilipid layer & proteins
Yes
Yes