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BASIC UNIT OF LIFE: THE CELL Chapter 3
BASIC UNIT OF LIFE: THE CELL
Chapter 3
All Organisms are made up of cellsEukaryotes- Moth Juniper
Protozoans Ciliates in water on plant
Prokaryotes Bacteria in insect gut and on surface of insect and tree
Cell theory
All living organisms are made up of cells
All cells come from other cells
Theory refers to the body of knowledge that has been developed through scientific inquiry
Two Cell Categories
Prokaryote Eukaryote Cell membrane Cytoplasm DNA (in a loop) Ribosomes (for
creating proteins) Cell wall Very small DNA is loose in
cytoplasm
Cell membrane Cytoplasm DNA (in strands) Ribosomes Many other organelles Cell wall in plants Variable size – larger
than prokaryotes Nucleus holds DNA
The organisms that cause colors in the hot springs of Yellowstone are single celled and have been around since the beginning of life on this planet. Would these organisms be prokaryotes or eukaryotes? Would their cells have a nucleus?
A. Prokaryotes, yesB. Prokaryotes, noC. Eukaryotes, yesD. Eukaryotes, no
http://serc.carleton.edu/microbelife/extreme/extremeheat/yellowstone.html
Basic Cell Structures
Cell Membrane Nuclear double
membrane around nucleus
Mitochondria for energy
Processing and packaging organelles
Lysosomes – digestion Cytoskeleton - support
Plasma Membranes
Bilayer Structure
Molecules Found in the cell Membrane
Cholesterol increases membrane flexibility
Types of Membrane Proteins
1. Receptor proteins – Bind to external molecules which cause reactions in
cell Ex. Target cells can detect hormones in blood –
regulate development of secondary sexual characteristics
2. Recognition proteins Typically have attached carbohydrate chains Give the cell identity – other cells can recognize them Ex. During development cells interact & work together
to develop structures. Recognition is essential. Ex. Autoimmune disease = faulty self-recognition
Visual examples
Receptor proteins Recognition proteins
Types of Membrane Proteins3. Transport proteins
Move other molecules across the cell membrane
Transmembrane proteins only Ex. Nerve cell fire – Na ions moved across
4. Enzymatic proteins Increase rate of chemical reactions
associated with the cell membrane Ex. cAMP formation regulated – internal
messenger created
Visual Examples
Transport proteins Enzymatic proteins
Why is the cell membrane considered a fluid mosaic?A. It’s primarily made up of water with
dispersed fats and proteins in a mosaic pattern
B. Proteins move back and forth through the membrane from inside to outside of the cell and back in a fluid mosaic pattern.
C. It’s made up of several different types of molecules, like a mosaic, and many of those molecules float around in the lipid bilayer.
Cell Structure and Function Cells are factories
Need raw materials to enter the cell Need to eliminate wastes Need to export products produced in the
cell Need to keep up-to-date on needs of
surrounding cells and tissues
Endocytosis
Exocytosis
Animation of endocytosis and exocytosis
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio02.swf::Endocytosis%20and%20Exocytosis
Other means of movement
Passive Transport Active Transport Requires no input
of energy
Diffusion Osmosis (diffusion
of water across a membrane)
Requires energy input to move molecules across the cell membrane or around in the cell
Primary – uses ATP Secondary
DiffusionKey: Molecules tend to move from an area of high concentration to an area of low concentrationWhen moving across a membrane – diffusion may be facilitated by a transport protein
Osmosis
Irrigation problems
Irrigation can lead to a build up of soil salinity
If soil develops a similar (or higher) salt content than the plant cells, water doesn’t flow as easily into plant roots. Soil salt concentrations make plants and soil
more alike in fluid concentration (isotonic) - so water doesn’t flow across the cell membranes into the plant roots.
Soil salinity creates drought like conditions in which plants can’t get water
PassiveTransport
Active Transport
The object depicted in the figure:
A) is a bacterial cell.B) could be either a plant or an animal cell.C) is a ribosome. D) is an animal cell.E) is a plant cell.
Cell Wall
Not found in animals
A major component of the cell wall is
the complex carbohydrate,
Cellulose
If the concentrations of a particular molecule are equal on both sides of the membrane, facilitated diffusion will:
A) insure that the molecule becomes concentrated outside the cell.B) insure that the molecule stays impermeable to the membrane.C) insure that the molecule becomes concentrated inside the cell.D) insure that the concentrations inside and outside the cell are both increased.E) be ineffective.
Connections Between Cells:
1. Tight Junctions
> hold cells in place> keep fluids from passing around edges of cells
blood brain barrierlining of gut
Connections Between Cells:
2. Desmosomes
> throughout body
Connections Between Cells:
3. Gap Junctions
>Allows small molecules, but not large proteins and organelles to move between cells.
Cell Size
Chicken egg = 40-60 mm (1mm = 1/1000 m)
Paramecium caudatum = 60X 230 um (1 um = 1/1000 mm)
Red blood cell = 1.9-7.5 um Bacteria 0.5-2 um
Why not bigger?
Ostrich
What limits the size of cells?
Much of what occurs in a cell depends on the movement of materials in and out of the cell through the plasma membrane
Rate of production and waste removal is dependent on cell volume
Rate of movement across the membrane depends on surface area of cell
As cell size increases, volume increases as a cubed unit while surface area as a square unit.
Surface to volume ratio
Radius 1 cm 2 cm 3 cmSurface area (cm2)
12.57 50.26 201.06
Volume (cm 3)
4.19 33.51 268.08
SA/V 3 1.5 0.75
Nucleus and chromosomes
Cytoskeleton
Made up of protein fibers that can expand, contract, move past one another.
Microfilaments underlie the cell membrane and cytoskeletal elements can break down and reform to allow changing shape in Amoeba.
Cell locomotion:
Mitochondria – have own DNA!
Mitochondria con’t
Number in a cell may vary Cells with high energy demands like
muscles have more than other cells Process known as aerobic respiration
(Kreb cycle & electron transport phosphorylation) takes place here. Sugar (C6H12O6) + 6H2O + 6O2 => 6 CO2 + 12 water
(H2O) + Energy Breaks down sugar to release the energy in the
chemical bonds Oxygen is used and Carbon dioxide is a waste
biproduct.
Chloroplasts
Only in Plant Cells and Single-celled Algae
Have own DNA!
Similar in some ways to bacteria that do photosynthesis – especially DNA
Evolution of Eukaryote Cells
Lysosomes – Waste removal
Up to 50 different types of enzymes!
Endoplasmic Reticulum
Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum
Golgi Apparatus
Vacuoles
Cells can be Single-celled Organisms
Euglena can engulf other organisms or do photosynthesis to get food for building blocks and energy. Eyespot Flagellum Contractile Vacuole
Cells Specializations Within a Multicellular
Organism All cells have the same genetic material.
Cells specialize because some genes are turned off and others are turned on.
Ex. Lining of small intestine
Ex. Nerve cell
Design Organelle Analogies Analogy
Includes similes and metaphores Similes compare things using words “as”
or “like” Ex. You are as stubborn as a mule. Ex. Life is like a box of chocolates.
Metaphores compare 2 unlike things for secondary meaning Ex. The gum was bursting with flavor. Ex. The relationship between them began
to thaw.
The organelle in the figure is found in:
A) animals only.B) plants only.C) plants, animals, and bacteria.D) plants and animals.E) bacteria only.
What is it?
The lysosomes in a human cell contain approximately ________ different type(s) of digestive enzymes.
A) 1B) 500C) 10D) 4E) 50
According to the theory of endosymbiosis, the origin of chloroplasts probably involved:
A) the formation of cell walls around the photosynthetic pigments.B) the formation of colonies of cyanobacteria.C) the engulfing of small photosynthetic prokaryotes by larger cells.D) the accumulation of free oxygen in ocean waters.E) All of the above are correct.
Read chapter 4 on Energy
