Download Cells - TCbiology1500

“Cells”
Ch. 4
Cells
• Cells are small (Robert
Hook)
• All plants are made of
cells (Schleiden)
• All animals are made of
cells (Schwann)
The Cell Theory
1. All living things are composed of cells
•
Organisms can be categorized as single celled or multicellular
2. Cells are the basic unit of structure
and function in living organisms.
3. All cells come from preexisting cells.
• New cells arise from old cells
Why aren’t cells larger?
• Smaller cells function more efficiently!
• The information from the DNA can be relayed
quickly
• The rate at which exchange takes place depends
on the surface area of the cell, the total area of its
cell membrane.
• The rate at which food and oxygen are
used
up and waste products are produced depends on
the cell's volume.
Surface to Volume Ratio
Basic Cell Structure
• Cells range in size (They may be microscopic or as
big as an ostrich egg.!!)
• All cells have 2 structures in common
•Cell membrane- barrier that surrounds the cell
•Cytoplasm- clear jelly like fluid that is within the cell.
The Plasma Membrane
•
•
All living cells are surrounded by a plasma
membrane
Basic Structure- Fluid Mosaic Model
• Lipid bilayer composed of phospholipids
• Head= Phosphate- polar
(hydrophilic)
• Tail= Fatty acids- nonpolar
(hydrophobic)
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Membrane Proteins
•
Another major component of the
membrane is a collection of
membrane proteins
• some proteins form channels
that span the membrane
• these are called
transmembrane
proteins
• other proteins are integrated
into the structure of the
membrane
• for example, cell surface
proteins are attached to
the outer surface of the
membrane and act as
markers
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Cell Types:
Prokaryotes vs. Eukaryotes
Prokaryote
Eukaryote
• Smaller than eukaryotes
• Contain a cell membrane
and cytoplasm but lack a
nucleus
• Include single cell organism
such as bacteria
• Almost all bacteria have a
cell wall. Some have a
capsule that encloses the
cell wall.
• Generally larger than
prokaryotes
• Contain a cell membrane,
cytoplasm, nucleus, and
organelles (specialized
structures that perform
specific activities within the
cell)
• Included some single-celled
organisms and all
multicellular organisms such
as plants, animals, fungi, and
protists.
Prokaryotic Cells
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Eukaryotic Animal Cell
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Eukaryotic Plant Cell
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Nucleus
•
The nucleus is the command
and control center of the cell
• it also stores hereditary
information
•
The nuclear surface is bounded
by a double-membrane called
the nuclear envelope
• groups of proteins form
openings called nuclear
pores that permit proteins
and RNA to pass in and out
of the nucleus
Chromatin and Chromosomes
• Chromatin- granular
tissue within the
nucleus that’s
composed of DNA and
protein
• Chromosomescondensed chromatin;
visible during cell
division
Organelles
• Found in the cytoplasm
• Act like specialized organs within the cell.
• “little organs”
Ribosomes
• Responsible for the
assembly of proteins
• Made of RNA and
protein
• Translate information
from the DNA
• Found on Rough
Endoplasmic Reticulum
Endomembrane System
•
•
•
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Endoplasmic Reticulum
Golgi Complex
Lysosomes
Peroxisomes
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Endoplasmic Reticulum
• The region of the ER dedicated to protein
synthesis is called the rough ER
 the rough spots are due to embedded ribosomes
• The region of the ER that aids in the manufacture
of carbohydrates and lipids is called the smooth
ER
 the surface of this region looks smooth because it
contains few to no embedded ribosomes
Rough and Smooth
Endoplasmic Reticulum
Golgi Complex
• Sometimes referred to as the Golgi Body or Golgi
Apparatus
• Receives proteins produced by the rough ER.
• Function in the collection, packaging, and
distribution of molecules manufactured in the cell.
• These proteins are modified with the attachment
of carbohydrates and lipids
• “Packages and Ships the product”
Lysosomes
• The Golgi complex also gives rise to
lysosomes
 these membrane-bounded structures contain
enzymes that break down macromolecules
and old cell components
• worn-out cell parts are broken down and their
components recycled to form new parts
• particles that the cell has ingested are also digested
Peroxisomes
•
Peroxisomes are vesicles that isolate
certain types of chemical reactions

the reactions that are confined to these
organelles function to
1. detoxify harmful by-products of metabolism
2. convert fats to carbohydrates in plants seeds for
growth
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Organelle DNA
•
•
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DNA is the cells genetic information/ blue-prints.
DNA is ordinarily found in the nucleus.
There are two organelles that possess their own DNA
1. Mitochondria
2. Chloroplasts
Mitochondria
• “Power House”
• Release energy stored in
food molecules to power
growth, development,
and movement within
the cell.
• Found in plants and
animal cells.
Chloroplasts
• Found in plants and other photosynthetic organisms. (Not
found in animal and fungal cells)
• Site of photosynthesis: process by which sunlight, Carbon
dioxide, and water are used to make carbohydrates and
Oxygen
• Chlorophyll is the green pigment within the chloroplasts
that give plants their color.
Centrioles
• Occur in pairs in the
cytoplasm
• Contain a circular DNA
molecule
• Anchor and assemble
microtubules
• Function in cell division
Unique Plant Characteristics
• Plant cells have three structures present
that are absent in animals cells
• Cell Wall
• Central Vacuole
• Chloroplast
Cell Wall
• Protect and
support the plant
cell
• Composed of
cellulose
(polysaccharide)
Vacuole
• Sac-like structures
within the cell that
store water, salts,
proteins, and
carbohydrates.
• Plants have a large
water vacuole that
helps to support
heavy structures
• Small vacuoles are
called vesicles
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Theory of Endosymbiosis
• This theory proposes that some of today’s
eukaryotic organelles evolved by a symbiosis
in which one cell of a prokaryote species was
engulfed by and lived inside another species
of of prokaryote.
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Vacuoles
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Cilia and Flagella
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Cell Wall
• found in plants, fungi, and
many protists
• comprised of different
components than
prokaryotic cell walls
• function in providing
protection, maintaining cell
shape, and preventing
excessive water
loss/uptake
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Cell Membrane
• The cell membrane takes in
food and oxygen and
eliminates wastes.
• Fluid Mosaic Model- Lipid
Bilayer with proteins
embedded throughout.
• The proteins may aid in the
movement of molecules
through the membrane.
• Selectively permeable the
membrane allows some
things to pass through and
others cannot
Diffusion
• Terms to Review:
• Solute- part of the solution that is being dissolved
• Solvent- part of the solution that is doing the
dissolving
• Concentrations- amount of solute in a given amount
of solvent
• Molecules are in constant random motion
• Molecules tend to move from an area of high
concentration to an area of low concentration.
• The process by which molecules move across a cell
membrane from high concentration to low
concentration is known as Diffusion
Diffusion and Osmosis
• Movement of water and nutrients into a cell or
elimination of wastes out of cell is is essential
for survival
• This movement occurs across a biological
membrane in one of three ways
• diffusion
• membrane folding
• through transport proteins
Diffusion
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Osmosis
• Osmosis- the diffusion of
water
• Concentration GradientWater diffuses from an
area of high
concentration to an area
of low concentration.
• Water will move until
equilibrium is reached
The Effects of Osmosis on Cells
• Remember that water will move across the cell membrane until
equilibrium is reached. At that point both sides of the membrane are
isotonic.
• Prior to equilibrium, the side of the membrane with a higher solute
concentration is “above strength” or hypertonic and the side with the
lower solute concentration is “below strength” or hypotonic.
• Osmotic pressure is created by the diffusion of water. An animal cell
placed in a hypotonic solution may burst due to this pressure. A plant
cell placed in a hypotonic solution will no burse because they have a
cell wall.
Osmosis in Animals Cells
Osmosis in Plant Cells
Bulk Passage
• Phagocytosis is
endocytosis of
particulate (solid)
matter
• Pinocytosis is
endocytosis of liquid
matter
Exocytosis
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Facilitated Diffusion
Active Transport
• Requires the input of energy
• utilizes protein channels that open only when energy is supplied
• energy is used to pump substances against or up their
concentration gradients
• allows cells to maintain high or low concentration of certain
molecules
• One of the most important channels that performs active
transport in cells is the sodium-potassium pump
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