Transcript Physical Oceanography

Cell Structure &
Function = Ch 4-5
Cells= Ch 4
• A cell is the smallest unit that can carry
on all of the processes of life
• Discovery of Cells
–Hooke discovered cells in slices of
cork.
–Leeuwenhoek first to observe living
cells in organisms
Cell Theory
• All living things are composed of 1
or more cells (uni- vs. multi)
• Basic units of structure and
function in an organism
• Come only from existing cells
Cell shape
• Reflects its function
• Cells are DIFFERENTIATED!
Cell Size
• Although varied,
basically all similar in
structure & size
• 10 -30 micrometers
• Largest cell = eggs
Cells must be small b/c:
• Surface to volume ratio needs to be
high
– LOTS of materials need to pass
through cell membrane
• Diffusion only works well across very
short distances
• Nucleus can only handle so much info
at once -would “short out” if cells
were much larger
Cellular Organization
• Multicellular eukaryotes are
organized into:
• cells→ tissues → organs →
organ systems → organisms
Two Types of Cells
• Prokaryotes
(only bacteria)
–NO Nucleus
• Eukaryotes (all
other cells)
–DO Have
nucleus
PROKARYOTES (bacteria)
• Have cell membrane + cell wall
• No membrane-bound organelles
• NO NUCLEAR MEMBRANE
–DNA in loop in mid-cell
EUKARYOTES
• More complex
• Contain membrane-bound organelles
• Includes ALL
animals,
plants,
protists, &
fungi
Cell Membrane
• Maintain
homeostasis
• Allows interior of
cell to differ from
its surroundings
• Selectively
Permeable-certain
things allowed
in/out
• Support & protect
Cell Membrane
• Phospholipid
bi-layer
“Heads” =
hydrophillic (love water)
“Tails” =
hydrophobic (fear water)
Fluid Mosaic Model
• Phospholipids
move around not static
Cell Membrane
• Embedded with proteins, has
cholesterol, lipids
–Regulate passage of
materials in & out of cell
Proteins associated with
the membrane
• Peripheral: inside or outside
membrane
– Markers that identify cell type
– Receptors/Carrier Protein that recognize and bind to specific
BIG substances
• Integral: Extends throughout the
membrane
– Channels/Transport proteins that allow passage of
materials into/out of cell
How do the proteins stay in
the membrane?
• Proteins are made of
different types of amino
acids (some polar, some
not)
• Non-polar a.a. are in the
center part (tail region),
and the polar a.a. are in
the outside (head region)
Nucleus
• Control
center of the
cell
• Contains
DNA/genetic
info
Nucleus
• The nucleus is surrounded by a membrane called
the nuclear envelope.
Nucleolus
• WITHIN the nucleus
• where DNA is concentrated when it is in the
process of making ribosomal RNA.
Cytoplasm
• Space between
cell membrane +
nuclear
membrane
• Cytosol is fluid
• Contains
organelles
Cytoskeleton
• Made of
protein fibers
• Helps cell
move &
maintain
shape.
• Includes
microtubules,
microfilaments,
intermediate
filaments.
Centrioles
• Two short cylinders of
microtubules
• Involved in animal cell division.
Mitochondria
• Powerhouse of
the cell
– Converts sugar
to ATP
–# varies
depending on
cell type
Mitochondria
• Double membrane
• Own DNA
• Previously a prokaryote?
Ribosomes
• Assembly site for proteins; made
of rRNA and proteins
• Free= protein used in cell
• Attached= proteins for export
Endoplasmic Reticulum
• Transport system of the cell
• Amount of E.R. varies with cell activity
• ROUGH E.R. -
ribosomes assemble/produce
proteins prepares for export
or insertion into the cell
membrane.
• SMOOTH E.R. –
– Builds lipids and
participates in
detoxification of toxins.
Golgi Apparatus
• Packaging & Secreting
• Membrane-bound storage sacs that pinch off
vesicles to send products to the cell's
membrane/surface
Vesicles
• Include: lysosomes (digestive enzymes)
and peroxisomes (detoxification
enzymes)
• Classified by their contents.
• Protein Synthesis
– Rough ER, Golgi apparatus, and vesicles work
together to transport proteins to their
destinations in/out of cell.
Flagella (few) & Cilia (many)
• Hair-like, extend from cell
• Used for movement, prey capture
Cell Components
Animal Cell
Plant Cell
•Cell Wall
•Central
Vacuole
•Plastids
Cell Wall
• Rigid
• Provides support and
protection
• Outside the Plasma
membrane
Vacuoles
• Membrane-bound space filled
with water +
dissolved
solutes;
provides
support in
plant cells
• Store enzymes & metabolic
waste
Plastid
• Store starch and pigments.
Chloroplast
• Double-membraned
• For photosynthesis & storage
Comparing Cells
Homeostasis & Transport
Chapter 5
Cellular Transport
• Cells transport substances into
and out of the cell to maintain
homeostasis
• Two categories of transport
–Passive (no energy required)
–Active (energy required)
Diffusion (passive
transport)
• Mixing of two substances by random
movement of molecules (kinetic
energy) from an area of HIGH
concentration to a LOW concentration
• “Down” a concentration gradient
• Diffusion
–Eventually reaches EQUILIBRIUM
–equilibrium = no concentration
gradient
Diffusion across
membranes
• Ability depends on:
–size
–solubility
–nature of membrane
Osmosis
Osmosis
• Diffusion of WATER
through a cell
membrane, from
areas of high water
concentration to
area of low water
concentration
Water Potential
• Hypotonic = More water, LESS
SOLUTE – outside cell
• Hypertonic = less water, MORE
SOLUTE – outside cell
• Isotonic = equal water, EQUAL
SOLUTE
Osmosis in Plant Cells
• Water constantly flows into plants
(hypotonic) b/c water is absorbed by
roots and presses against the cell
wall…it will not burst b/c of turgor
pressure
• Plants will wilt via plasmolysis because
there is not enough water and water
rushes out (hypertonic)
Facilitated Diffusion
(passive transport)
• Uses integral (carrier)
proteins move stuff
in/out
• Proteins are specific for
molecules
• Stops when equilibrium
is reached
Ion Channels (passive
transport)
• Proteins (carrier) in the membrane that
transport ions
• Protein is specific for ion
• May be “gated” or always open
Active Transport
• Requires energy
• Protein pumps pass molecules
in only one direction
• Enables a cell to “stockpile”
stuff
• Goes up concentration gradient
–From LOW to HIGH
concentration= uphill
Important Protein Pumps
• 1. Sodium-Potassium Pump—this allows
Na+ and K+ into and out of cells….important
in nerve and muscle cells to keep this
“firing” and sending messages!
• 2. Proton Pump—in
photosynthesis…pumps H+ (from water
splitting) across chloroplast membrane to
make ATP for plant processes
Pumps in your body
• Sodium potassium: Move
sodium out and
potassium in
• 3 Na+ out 2 K + in
• ATP drives pump
Sodium-potassium pump
• Creates charge gradient to
conduct electrical impulses impt. For nervous system
What about extra large
particles? How do they get
into and out of cell?
Endocytosis - ingestion
• Uses vesicles to ingest
macromolecules,
external fluid
• Pinocytosis –
cellular
drinking
• Phagocytosis
– cellular
eating
Exocytosis - excretion
Excrete proteins,
waste, toxins