Transcript Cell Structure and Function (Honors)

Cell Structure and Function
Chapter 7
Biology
Miller • Levine
The Scientists…

Robert Hooke (1665)



Viewed cork under a
microscope
Called the chambers he
saw “cells”
Anton van
Leeuwenhoek (1674)

First to see living
organisms in a drop of
water
The Scientists…

Matthias Schleiden (1838)


Theodor Schwann (1839)


All plants are made of cells
All animals are made of cells
Rudolf Virchow (1855)

All cells come from preexisting
cells
The Cell Theory
All living things are composed of
cells
 Cells are the basic units of
structure and function in living
things
 New cells are produced from
existing cells

Unicellular vs. Multicellular
Unicellular – single-celled
organism
 Multicellular – many-celled
organism

Cell specialization – cells are
specialized to perform certain
functions
 Cells → Tissues → Organs → Organ
systems → Organism

Prokaryotes vs. Eukaryotes
All cells have a cell membrane,
cytosol, and ribosomes
 Prokaryotes

Do not have a nucleus or other
membrane-bound organelles
 Ex. Bacteria such as E.coli
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
Eukaryotes
Have a nucleus and organelles
 Ex. Plants, Animals, Fungi

Prokaryotes vs. Eukaryotes
Basic Cell Structures

Cell membrane – thin, flexible
barrier around the cell; protects
the cell


Present in all cells
Cytoplasm – material inside the
cell membrane (not including the
nucleus)

Present in all cells
Cell Wall
Found in many organisms,
including plants, algae, fungi
and nearly all prokaryotes
 Not found in animal cells
 Lies outside the cell membrane
 Main function is to provide
support & protection for the cell

Nucleus
All eukaryotic cells, including
plants and animals have a
nucleus
 Prokaryotes do not have a
nucleus
 Controls most cell processes and
contains the DNA

Nucleolus and Nuclear Envelope

Nucleolus:
Inside the nucleus
 Where ribosomes are made


Nuclear Envelope:
Double-membrane layer around
the nucleus
 Allows material to move into and
out of the nucleus

Nucleus
Cytoskeleton
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
Found in all eukaryotes but not
prokaryotes
A network of protein filaments that
helps the cell maintain its shape


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Microtubules – hollow tubes of protein that
help maintain cell shape, are involved in cell
division, aid in movement of organelles
Microfilaments – long, thin fibers that
function in the movement and support of the
cell
It also is involved in cell movement
Ribosomes
Found in all cells
 Main function is to make
proteins
 Can be found floating in the
cytosol or attached to
endoplasmic reticulum

Endoplasmic Reticulum (ER)
Found only in eukaryotic cells
 Where components of the cell
membrane are assembled
 Two kinds: Smooth ER & Rough
ER

Smooth ER: no ribosomes; makes
lipids; detoxifies harmful
substances
 Rough ER: has ribosomes; involved
in making proteins

Endoplasmic Reticulum
Golgi Apparatus



Found only in
eukaryotic cells
Enzymes attach
carbohydrates &
lipids to proteins
Send proteins to
their final
destination in
vesicles
Lysosomes
Found in animal cells only
 Contain digestive enzymes
 Break down lipids,
carbohydrates & proteins from
food into particles that can be
used by the cell
 Also break down “dead”
organelles

Vacuoles
Not found in prokaryotes
 Animal cells have small vacuoles
 Plant cells have a large central
vacuole
 Store materials such as water,
salts, proteins & carbohydrates

Chloroplasts
Found in all plant cells
 Also found in some plant-like
protists, such as algae
 Use the energy from sunlight to
make energy-rich food
molecules during photosynthesis

Chloroplasts
Mitochondria
Found in
eukaryotic
cells only
 Release
energy from
stored food
molecules
(cellular
respiration)
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Cilia and Flagella
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Cilia
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Short, numerous
projections that
look like hairs
Used for cell
movement

Flagella
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Longer and less
numerous than
cilia


A cell usually has
one or two
flagella
Used for cell
movement
Plasma Membrane
Regulates what enters and leaves
the cell (selectively permeable)
 Provides protection and support
 Phospholipid bilayer – two layers
of phospholipids

Proteins run through the layers
 Carbohydrates are attached to
some of the proteins
 Fluid Mosaic Model

Cell Membrane
Diffusion


Molecules move from an area of high
concentration to an area of low
concentration
Movement continues until equilibrium is
reached

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Molecules still move across the membrane,
but there is no overall change
Many substances move across the
membrane by diffusion
Does not require energy (passive
transport)
Diffusion

An increase in any of the
following will increase the rate of
diffusion:
Concentration
 Temperature
 Pressure

Diffusion
Osmosis
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The diffusion of water

Isotonic – equal concentration
 Nothing

Hypertonic – higher concentration
of solute
 Water

moves out of the cell
Hypotonic – lower concentration of
solute
 Water

happens
moves into the cell
No energy is required
Effects of Osmosis on Cells
Osmotic Pressure
In pure water, an animal cell
would burst
 Plant cells are protected by their
cell wall
 Some freshwater organism have
special structures like contractile
vacuoles to get rid of extra
water

Facilitated Diffusion
Some molecules cannot cross the
membrane without help
 Some of the proteins in the
membrane form protein channels
 Materials still move from higher to
lower concentrations
 No energy is required

Facilitated Diffusion
Active Transport
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Materials move
from lower
concentration to
higher
concentration
Requires an
input of energy
Works kind of
like a pump
Transport of Large Amounts

Endocytosis – movement into
the cell
Phagocytosis – “cell eating” – solid
particles
 Pinocytosis – “cell drinking” –
particles dissolved in water

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Exocytosis – movement out of
the cell
Phagocytosis
Pinocytosis