Transcript Cell membrane - Leavell Science Home

CELLS
Cell Structure and Function
Intro to Cells
• A cell is the smallest unit that can carry on
all the processes of life
• The development of the microscope enabled
scientists to take their first close look at
cells
Discovery of the Cell
• 1665 – Robert Hooke
– Examined cork (plant tissue) using a
microscope
– The “little boxes” he observed under the
microscope reminded him of the small rooms
where monks live, so he named them cells
Robert Hooke
Discovery of the Cell
• 1673 – Anton van Leeuwenhoek
– First person to observe living cells under
a microscope
Anton van Leeuwenhoek
I. The Cell Theory - summary of before
mentioned scientists and other biologists is one of
fundamental concepts of biology.
1. All living things are composed of
cells.
2. Cells are the basic units of
structure and function in all living
things.
3. New cells are produced from
existing cells.
II. Cells
A. Cells come in many
shapes and sizes.
a. Smallest- 0.2
micrometers (bacteria)
b. Largest- birds egg and giant amoeba (1000
micrometers).
B. Prokaryotes and Eukaryotes- Scientists
divide cells Into two groups depending on
whether they have a nucleus or not.
1. Prokaryotes (Bacteria) - no nucleus!
a. Smaller and simpler than
cells of eukaryotes.
b. Do have cytoplasm and cell
membrane.
c. Still carry out all activities
associated with life.
2. Eukaryotes - do contain nucleus and
membrane bound organelles (includes
plants, animals, fungi).
a. Contain cytoplasm and
plasma (cell) membrane.
b. Also contain dozens of other
specialized structures called
organelles (means tiny
organs).
C. Multicellular Organization
1. Cells are specialized to perform one or a few
functions in multicellular organisms.
2. The levels of organization include:
Cells --> Tissues --> Organs --> Systems --> Organism
D. Cell structure as it relates to the function
1. Cells come in a variety of shapes, and the shape
helps determine the function of the cell.
– Nerve cells are long to transmit messages in the
body.
– Red blood cells are disk shaped to move through
blood vessels.
E. Cell structure as it relates to the function
1. Animal cells can signal to
one another in various ways.
– (A) Hormones produced in
endocrine glands are
secreted into the bloodstream
and are sent throughout the
body.
– (C) Nerve signals are
transmitted along axons to
remote target cells.
F. Receptor Proteins
1. An animal cell depends on
multiple extracellular signals.
Every cell type has receptor
proteins that respond to specific
signal molecules produced by other
cells.
2. These signal molecules work in
combinations to regulate the
behavior of the cell. For example,
cells may require multiple signals
(blue arrows) to survive, (red
arrows) to divide or not, and (green
arrows) to differentiate.
3. If deprived of survival signals,
most cells undergo a form of cell
suicide known as programmed cell
death.
III. Cell Structure
A. Plasma Membrane (cell membrane) – thin,
flexible barrier around the cell.
1. Regulates what enters
and exits the cell. Important
in maintaining homeostasis.
2. Support and protect cells,
while allowing them to
interact with surroundings.
3. Made of double-layered sheet called- lipid bilayer.
Lipid molecules
4. Membrane is a “mosaic” of many different kinds
of molecules (protein channels and pumps,
carbohydrate that help cells recognize each other.
B. Cell Wall - found in plants, algae, fungi, nearly
all prokaryotes. NOT animal cells
1. Lies outside the cell membrane- provides
support and protection for the cell
2. It’s a strong layer made from fibers of
carbohydrates (like cellulose) and proteins
C. Cytoplasm – The “juice” inside the plasma
membrane, but not including nucleus. Also contains
many important organelles.
D. Nucleus - large structure containing cell’s genetic
material- controls cell’s activities (“brain”)
1. Controls most of cell processes and contains
hereditary information (DNA) (controls activities
by making proteins)
2. Found in eukaryotic cells
3. Chromatin and Chromosomes - granular
material visible inside the nucleus.
a. Chromatin - DNA bound to protein.
b. Chromosomes - chromatin condenses when
cell gets ready to divide. Contains genetic material
passed from one generation to the next.
c. Nucleolus - small dense region in nucleus
where ribosomes are made.
d. Nuclear envelope - double membrane layer
surrounding the nucleus containing tiny nuclear
pores (allows materials to move into and out of
nucleus. i.e. RNA).
E. Cytoskeleton 1. Network of protein
filaments that help the cell to
maintain its shape and
involved in many forms of cell
movement
2. Made up of microtubules
and microfilaments
a. Microtubules- serve as “tracks” along
which organelles are moved. Important in
cell division- help to separate chromosomes.
Also form cilia and flagella which allow cells
to move
b. Microfilaments - long, thin
fibers function in movement
and support the cell
F. Organelles in the Cytoplasm- (act like
specialized “organs” in the cell)
1. Ribosomes - makes proteins.
2. Endoplasmic Reticulum - cell’s internal
transport system.
a. Connects nucleus to the cell membrane and
acts as a transportation network in the cell.
b. Rough ER - (has ribosomes attached –
makes proteins) and Smooth ER (no
ribosomes) breaks down toxins and organics.
3. Golgi Apparatus - “post office” of the cell
a. Carbohydrates and lipids attached to
proteins are “packaged”.
b. Then sent to final destination.
Golgi
Apparatus
4. Lysosomes - “clean-up” crew of the cell.
a. Break down lipids, carbohydrates, proteins
from food particles (little “digestive sacs”).
b. Break down ‘old’ cell parts, removing debris.
Lysosomes
5. Vacuoles - storage “sacs”- store water,
salts, proteins, carbohydrates
a. Large in plant cells (single large
vacuole)
b. In animals, smaller vacuoles
called vesicles. They transport
substances within the cell
6. Chloroplasts - found in plants and some
other organisms (none found in animals and
fungi).
a. Produce energy-rich food molecules from
sunlight by photosynthesis.
b. Green pigment- chlorophyll found in
photosynthetic membranes.
7. Mitochondria - found in nearly all
eukaryotic cells.
a. Use energy from food to power growth,
development and movement.
b. Cells that require more energy- have
more mitochondria.
D. Mitochondrial DNA - DNA is also found in the
mitochondria. Essential for normal function of
both organelles.
1. This DNA is inherited from the mother only.
CELL Movement
I. Homeostasis – Keeping it balanced
A. Homeostasis – Every living organism regulates its
internal environment to maintain a stable condition.
Homeostasis exists at the cellular and the organism level.
1. Cellular examples: Cells maintain a stable internal
acidity (pH), blood sugar (glucose) levels keep balanced,
and water concentrations keep balanced.
2. Organism examples: Warm-blooded animals maintain a
constant internal body temperature.
Click on link to see how blood glucose is regulated.
http://www.bbc.co.uk/schools/gcsebitesize/biology/humansasorganisms/6homeostasisrev4.shtml
The next section will show how water and other molecule
levels are regulated inside the cell.
II. Movement Through the Membrane
A. Cell Membrane - regulates what enters and
exits the cell and provides support and
protection
1. Lipid BilayerDouble layered sheet
(not soluble in water)
a. Contains protein molecules that form
chemical “pumps” and channels to
move material across membrane
b. Carbohydrate
molecules act like “ID
cards” allowing cells
to identify each other
B. Diffusion- Movement of materials from
areas of high concentration to areas of low
concentration
1. All living cells have a liquid interior
(cytoplasm) and are surrounded by liquid.
2. Diffusion causes many
substances to move across
cell membrane but does not
require the cell to use energy
(called passive transport).
3. Equilibrium- when the
concentration of molecules
are equal on both sides of
membrane.
Why is it important not to put
saltwater animals into freshwater
and freshwater animals into
saltwater?
C. Osmosis- Diffusion of water molecules
through selectively permeable membrane
1. Most membranes are selectively
permeable (some materials can pass
across membrane and others cannot) like
“sieve”
2. Effects of osmosis on cell (i.e. Red blood)
a. Isotonic- “same strength”
Water moves in and out of cell at the
same speed. Cell stays the normal
shape.
These all refer to concentration of solute molecules
Isotonic
solution
b. Hypotonic- “below strength”
More dissolved particles inside the cell,
so there is more water outside than
inside. Water enters a cell by osmosis,
causing the cell to swell and burst.
hypotonic
solution
Isotonic
solution
c. Hypertonic- “above strength”
Concentration of dissolved molecules is
higher outside of cell, so lower water
concentration outside. Water flows out
of cell. Causes the cell to shrink.
hypotonic
solution
hypertonic
solution
Isotonic
solution
Why are snails afraid of salt?
3. Osmotic Pressure- osmosis exerts pressure
on hypertonic side of selectively permeable
membrane
a. Cells filled with salts, sugars, proteins and
other molecules- always hypertonic to fresh
water
b. Osmotic pressure produces movement of
water into cell that is surrounded by fresh
water.
c. Fortunately cells don’t come into contact
with fresh water. Usually bathed in isotonic
solutions (e.g. blood) or protected by cell
wall (e.g. bacteria) or mechanism to pump
out excess water (contractile vacuole)
D. Facilitated Diffusion- membrane proteins
help (faciliate) the movement of certain molecules
across the cell membrane by diffusion (from high
conc. To low conc.) that can’t diffuse through lipid
bilayer directly.
1. Many different protein
channels for ions, sugars,
salts.
2. Does not require addition
of energy (passive transport)
Facilitated Diffusion
E. Active Transport- movement of molecules
and ions against a concentration difference (from
low to high)
1. Requires input of energy
2. Small molecules “pumped” across
membrane (e.g. Na+ and K+ ions)
3. Large amounts of
material transported
through movements
of the cell
membrane
Sodium-Potassium Pump
Endocytosis vs. Exocytosis
• Endocytosis and exocytosis are active transport
mechanisms in which large substances cross the
membrane inside vesicles
Endocytosis
• In endocytosis, the cell membrane folds around
something in the external environment and forms
a pouch
• The pouch then pinches off and becomes a vesicle
in the cytoplasm
• Endocytosis includes pinocytosis, in which the
vesicle contains solutes or fluids, and
phagocytosis, in which the vesicle contains large
particles or cells
Endocytosis
Exocytosis
• In exocytosis, vesicles made by the cell fuse with
the cell membrane, releasing their contents into
the external environment
Exocytosis
UNIT III- CELLS
Cell Structure and
Function
Which cell structure contains the
cell's genetic material and controls
the cell's activities?
a.
organelle
b.
nucleus
c.
cell envelope
d.
cytoplasm
Which cell structure contains the cell's
genetic material and controls the cell's
activities?
a.
organelle
b.
nucleus
c.
cell envelope
d.
cytoplasm
Prokaryotes lack
a.
cytoplasm.
b.
a cell membrane.
c.
a nucleus.
d.
genetic material.
Prokaryotes lack
a.
cytoplasm.
b.
a cell membrane.
c.
a nucleus.
d.
genetic material.
Eukaryotes usually contain
a.
a nucleus.
b.
specialized organelles.
c.
genetic material.
d.
all of the above.
Eukaryotes usually contain
a.
a nucleus.
b.
specialized organelles.
c.
genetic material.
d.
all of the above.
The main function of the cell wall is to
a.
support and protect the cell.
b.
store DNA.
c.
direct the activities of the cell.
d.
help the cell move.
The main function of the cell wall is to
a. support and protect the cell
b. store DNA.
c. direct the activities of the cell.
d. help the cell move.
Which organelle makes proteins
using coded instructions that
come from the nucleus?
a.
Golgi apparatus
b.
mitochondrion
c.
vacuole
d.
ribosome
Which organelle makes proteins using
coded instructions that come from the
nucleus?
a.
Golgi apparatus
b.
mitochondrion
c.
vacuole
d.
ribosome
Which organelle converts food into
energy that the cell uses for growth,
development, and movement?
a.
chloroplast
b.
Golgi apparatus
c.
endoplasmic reticulum
d.
mitochondrion
Which organelle converts food into energy
that the cell uses for growth, development,
and movement?
a.
chloroplast
b.
Golgi apparatus
c.
endoplasmic reticulum
d.
mitochondrion
The cell membrane contains channels
and pumps that help move materials
from one side to the other. What are
these channels and pumps made of?
a.
carbohydrates
b.
lipids
c.
bilipids
d.
proteins
The cell membrane contains channels and
pumps that help move materials from one
side to the other. What are these channels
and pumps made of?
a.
carbohydrates
b.
lipids
c.
bilipids
d.
proteins
Diffusion is the movement of
molecules from
a.
an area of low concentration to an area
of high concentration.
b.
an area of high concentration to an area
of low concentration.
c.
an area of equilibrium to an area of high
concentration.
d.
all of the above
Diffusion is the movement of molecules from
a.
an area of low concentration to an area
of high concentration.
b. an area of high concentration
to an area of low concentration.
c.
an area of equilibrium to an area of high
concentration.
d.
all of the above
Which means of particle transport
requires input of energy from the
cell?
a.
diffusion
b.
osmosis
c.
facilitated diffusion
d.
active transport
Which means of particle transport requires
input of energy from the cell?
a.
diffusion
b.
osmosis
c.
facilitated diffusion
d.
active transport
The diffusion of water across a
selectively permeable membrane is
called
a.
osmotic pressure.
b.
osmosis.
c.
facilitated diffusion.
d.
active transport.
The diffusion of water across a selectively
permeable membrane is called
a.
osmotic pressure.
b.
osmosis.
c.
facilitated diffusion.
d.
active transport.
An animal cell that is surrounded by
fresh water will burst because the
osmotic pressure causes
a.
water to move into the cell.
b.
water to move out of the cell.
c.
solutes to move into the cell.
d.
solutes to move out of the cell.
An animal cell that is surrounded by fresh water
will burst because the osmotic pressure causes
a.
water to move into the cell.
b.
water to move out of the cell.
c.
solutes to move into the cell.
d.
solutes to move out of the cell.
Which term refers to cells having
different jobs in an organism?
a.
multicellular
b.
cell specialization
c.
levels of organization
d.
unicellular
Which term refers to cells having different
jobs in an organism?
a.
multicellular
b.
cell specialization
c.
levels of organization
d.
unicellular
What is the name of structure (a.)?
Rough Endoplasmic reticulum
What is the name of structure (b.)?
ribosome
Is this cell an animal or plant cell?
Animal cell
What is the name of structure (c.)?
Cell membrane
What is the name of structure (k.)?
nucleolus
What is the name of structure (g.)?
Golgi bodies
What is the name of structure (e.)?
Smooth endoplasmic reticulum
What is the name of structure (d.)?
mitochondria
What is the name of structure (m.)?
vacuole
What is the name of structure (k.)?
Cell membrane
What is the name of structure (j.)?
Cell wall
What is the name of structure (l.)?
chloroplast
What is the name of structure (f.)?
nucleus
What cell structures found in the
organism below is responsible for
removing excess water from the
inside of the cell?
Contractile vacuole
What cell process is taking place
below?
osmosis