Transcript Cell Structure and Function (Chapter 7)

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

Prokaryotes
Have a cell membrane &
cytoplasm, but do not have a
nucleus
 Ex. Bacteria such as E.coli


Eukaryotes
Have a nucleus, cell membrane,
cytoplasm & 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)

Prokaryotes & Eukaryotes
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
Almost all eukaryotic cells,
including plants and animals
have a nucleus
 Prokaryotes do not have a
nucleus
 Controls most cell process 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
Found in all eukaryotic cells
 Not found in prokaryotes
 A network of protein filaments
that helps the cell maintain its
shape
 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
 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
Lysosomes
Found in animal cells only
 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 or no
vacuoles
 Plant cells have a large central
vacuole
 Store materials such as water,
salts, proteins & carbohydrates

Chloroplasts
Found in all plant cells
 Some prokaryotes have them,
but most do not
 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

Cell Membrane
Regulates what enters and leaves
the cell (selectively permeable)
 Provides protection and support
 Lipid bilayer – two layers of lipids

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
 Many substances move across
the membrane by diffusion
 Does not require energy
(passive transport)

Diffusion
Osmosis

The diffusion of water

Isotonic – equal concentration
 Nothing

Hypertonic – higher concentration
 Water

moves out of the cell
Hypotonic – lower concentration
 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



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


Exocytosis – movement out of
the cell
Phagocytosis
Pinocytosis