Post on 25-Dec-2015
CHAPTER FOUR: CELL STRUCTURE AND FUNCTION
7.1 History of the Cell Robert Hooke (1665) – Used compound
scope to examine thin cork slices. Coined the term “cell” referring to the many little boxes. Actually saw dead plant cells
Anton van Leeuwenhoek (1673) – Use simple scope (one lens), observed first living cells.
Matthias Schleiden (1838) and Theodor Schwann stated that all plants and animals (respectively) are made up of cells .
Rudolph Virchow (1855) – cells come only from other cells.
The Cell Theory All living things are made up of cells Cells are the basic unit of structure
and function in all living things Cells come from pre-existing cells
Side Length
Surface Area
VolumeSurface area
to Volume ratio
1mm 6mm2 1mm3 6 to 1
2mm 24mm2 8mm3 3 to 1
3mm 54mm2 27mm3 2 to 1
7.2 Introduction to Cells
Cells vary by: 1. Size – Range from 2m (giraffe nerve cell from
leg to spine) to .2um (bacteria) Limited by the ratio between outer surface
area and their volume.
As the surface area to volume ratio decreases, it makes it difficult for nutrients and waste to get around cell.
2. Shape – Structure is related to function
Red Blood Cells are biconcave disks
Nerve cells are electrical wires
Skin cells (Epithelial cells) are flat
White Blood cells creep along and squeeze into all areas
3. . Internal Organization – Internal Organization – Organelles – internal structures in a cell, each with a specific functionAll cells contain:
a. cell membrane – thin membrane,
porous to certain compounds
b. cytoplasm – gel-like substance where organelles, ions, organic compounds are suspended in it
c. ribosomes – Protein factories in cells
d. DNA
Compare/Contrast
Types of cellsTypes of cells 1. Prokaryotic cells
– cells that lack a nucleus and membrane bound organelles
- two Groups: Bacteria and Archaebacteria
- have a cell wall, cell
membrane, cytoplasm, DNA,
ribosomes
- enzymes and other molecules are suspended in cytoplasm
2. Eukaryotic Cells – contain a membrane bound nucleus and membrane bound organelles
- much more complex cell
- all cells other than bacteria
-includes these groups: Protists, Fungus, Animals and
Plants
Nucleus
7.3 Cell Parts and FunctionsThree main components:
nucleus cell membrane cellular organelles
Cell membrane
Cell Membrane
– separates the cell’s internal environment from the external environment.
- allows for the passage of some substances based on size and concentration
selectively permeable
Phospholipid BilayerOf Cell Membrane
made up of a bilipid layer (lipid bilayer) – two layers of phospholipids with proteins
floating through it; referred to as Fluid Mosaic Model
tails of phospholipids are hydrophobic while the heads are hydrophilic – WHY???
Peripheral membrane proteins - do not penetrate the hydrophobic core of the membrane; can be easily removed without destroying the membrane structure.
Integral membrane proteins - fully incorporated into the membrane and are in contact with both the inside and the outside of the cell; some act as channels or tunnels for the transport of substances, others have carbohydrates attached to them – recognition sitesPeripheral
protein
Integral protein
In the "fluid mosaic model" of membrane structure, the membrane is a fluid phospholipid bilayer in which protein molecules are either partially or wholly embedded. These layers easily move around.
Cellular Organelles
Cytoplasm
- Made of gelatinous material where nutrients and minerals are carried in solution
Typical Animal Cell Typical Plant Cell
Mitochondria - powerhouse of the cells.
- where cellular respiration occurs =glucose is broken down to release energy (in the form of ATP) to the cell
- found in greater numbers in cells such as muscle cells and liver cells; double membrane with internal cristae (folds) to increase surface area
Cristae
Double Membrane
Ribosomes most numerous organelle,site of
protein synthesis (where proteins are made)
not membrane bound therefore, they are in prokaryotic cells.
made up of RNA and protein. may be free floating in cytoplasm
or attached on endoplasmic reticulum
Endoplasmic Reticulum – channels or passageways in
the cell; two types of ER:
1 – Rough with ribosomes attached for the production and distribution of proteins
2 – Smooth – Synthesis of steroids in gland cells, Ca++ regulation in muscle cells
1 Nucleus 2 Nuclear Envelope 3 Rough endoplasmic reticulum
(RER) 4 Smooth endoplasmic reticulum
SER) 5 Ribosome on the rough ER 6 Proteins that are transported 7 Transport vesicle 8 - 10 Golgi apparatus
Golgi Apparatus (Bodies)o stack of smooth flat sacs o processing, packaging and secreting
organelle of the cell o much like a processing & exporting
plant Work in close association with ER
Lysosomes single membrane sacs; are the cells'
garbage disposal system breakdown worn out organelles such as
mitochondria and produce hydrolytic enzymes to that degrade DNA, proteins, lipids and carbohydrates
responsible for the un-webbing of hands of fetus while developing in utero
Cytoskeleton- network of protein strands that provide support and mobility
of organelles in cytoplasm
Two components of cytoskeleton
- microfilaments – made of actin (protein threads); involved with cellular movement and muscle contractions
- microtubules – larger structures; involved in cell division, make up flagella and cilia, also make up spindle fibers that assist in chromosome migration during cell division
Cilia and Flagella extensions from cell membrane assist in movement cilia - when short and multiple numbers. covering of Paramecium, lining of respiratory tract
and nasal passages. flagella- long and usually only 1 to a few; sperm
cells, Euglena; used for propulsion
Nucleus only in Eukaryotic cells stores hereditary information in DNA surrounded by a double nuclear envelope;
nuclear pores perforate membrane chromatin - strands of a combination of
DNA and protein within nucleus; these will later become chromosomes.
nucleolus (1 or more) produces ribosomes
7.4 Plant Cells Are eukaryotic and have most of the same organelles as animal cells except:
1. Cell walls made up of cellulose and pectin (glue between walls)gives cells rigidity, protection & support. is also porous
2. Vacuoles - store enzymes, food, water and wastes- huge water vacuole in plant cells - gives plant cell “turgor” (full of water and fully supported) – 90% of cells may be water - some contain metabolic wastes which may be toxic to other organisms (poison ivy)
3. Plastids - double membrane, DNA containing to store
starch, fats or pigments such as chlorophyll - chloroplast – where photosynthesis occurs;
made up of stacks called thylakoids, where energy conversion occurs
- leucoplast - store starch
1. _______________2. _______________3. _______________ (Dots)
4. _______________5. _______________6. _______________7. _______________8. _______________9. _______________10._______________11._______________12._______________13._______________
Typical Animal Cell
Typical Plant Cell
Cheek Cells
Elodea
Onion Cells
Potato Cells
Organelle FunctionPlant Cells
Animal Cells
MitochondriaSite of cellular respiration - transfer of energy - Folds called
CristaeYes Yes
Ribosomes Site of Protein synthesis Yes Yes
Endoplasmic ReticulumRough - Protein packaging & transport site
Smooth - Sythesis of lipidsYes Yes
Golgi Apparatus Processing & packaging center for cell secretions Few Many
Lysosomes Produce hydrolytic enzymes Few Many
CytoskeletonNetwork of protein filaments - keep cell's shape and for
movementYes Yes
Microfilaments & microtubules
Support, movement and cell division Yes Yes
Cilia & FlagellaCell movement & circulation Cilia - many & short, Flagella -
1or 2 & longYes Yes
Nucleolus Production of ribosomes Yes Yes
Nucleus Contains DNA, synthesizes RNA & Ribosomes Yes Yes
Chromatin DNA & protein - genetic information Yes Yes
Cell WallOutmost layer of plant cell - support & protection Made of
cellulose & pectin glue between wallsYes No
VacuoleStores enzymes, wastes, water & food Large water in plants
- supportYes, large
water vacuoleMany
PlastidStores food and pigments - Chloroplasts (photosynthesis) &
leucoplasts (stores starch)Yes No
Centrioles Microtubules that function during cell division No Yes
Cell Membrane Selectively permeable - made of a bilipid layer & proteins Yes Yes