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