Cell Biology:Cell Structure and Function

Lesson 1 – Eukaryotic Cells and Organelles (Inquiry into Life pg. 49-62)

Today’s Objectives Analyze the functional inter-relationships of

cell structures, including: Describe the major cell structures and their

functions State the balanced chemical equation for cellular

respiration Describe how the Endomembrane System

functions to compartmentalize the cell and move materials through it

Identify cell structures depicted in diagrams and electron micrographs

The Cell The cell is the

structural and functional unit of an organism.

It is the smallest structure capable of performing all the functions necessary for life.

The study of cells The study of cells had its birth with the

invention of the microscope, but it became a product of the 19th century. As biologists became increasingly familiar with the detailed microscopic features of organism they were able to make certain generalizations about cells.

In the late 1830’s two German biologists, Schleiden ( a botanist) and Schwann, (a zoologists) made similar claims.

They realized that all organisms they were studying were composed of cells. Their

discoveries are now generalized as

“ The cell is the building block of all

organisms.”

A few years later, Rudolph Virchow added the observation that cells “come from pre-existing cells.”

These two statements comprise what is now known as the Cell Theory.

Cell Theory Cell theory states:

All organisms are composed of one or more cells.

Cells are the basic unit of structure and function in an organism.

All cells come from other cells.

Cell Size Cells are very small. Most cells are between 1

micrometer (1 thousandth of a millimeter) and 100 micrometers.

Cell Size Small cells are advantageous to multicellular

organisms. Nutrients and wastes are passed through the cell

at its surface, therefore the amount of surface area affects the ability to material in and out of the cell.

As cells increase in volume, the proportionate amount of surface area decreases.

Surface Area: 96 cm2 192 cm2 384 cm2

Types of Cells There are two overall classifications of

cells: Prokaryotic cells (simple cells)

Do not contain nucleus or membrane enclosed organelles

Found in Bacteria, Archaea Usually exist as single celled organisms

(unicellular) Eukaryotic cells (complex cells)

possess nucleus and organelles Contains internal membranes Multicellular organisms

Prokaryotic Cells

Eukaryotic Cells

Examples of Eukaryotic cells include Plants, Animals, Protists, Fungi.

Prokaryotic cells are considered to be less efficient than Eukaryotic cells because the chemical reactions occur all over the cytoplasm rather than in areas of specialization.

Cell Organelles – Plant Cell

Cell Organelles – Animal Cell

Nucleus

Largest Organelle.

Surrounded by a double-layered membrane (the nuclear envelope).

Membrane has pores through which larger molecules pass. (Nuclear Pores)

Control center for the cell’s functions. (The brain).

Contains a fluid called the nucleoplasm.

Contains chromatin (DNA strands which forms chromosomes during cell division.)

Nucleus and Nuclear Envelope

Nucleolus

Dark region in the Nucleoplasm.

One or more found in the nucleus.

Site where ribosomal RNA (rRNA) is produced or stored.

Involved in interactions between the nucleus and the cytoplasm.

Chromatin

The hereditary material of the cell. Condenses to form chromosomes during

cell division. Composed of Protein and DNA

Chromosomes

Condensed chromatin Contains the hereditary

information. (genes) Rod-shaped bodies in the

nucleus, particularly during cell division

Each eukaryotic species has a characteristic number of chromosomes

A typical human cell has 46 chromosomes, but sex cells (eggs and sperm) have only 23 chromosomes.

Cytoplasm A semifluid (like a gel) medium composed of

water, salts and dissolved organic molecules Contains and supports all the cells

organelles.

Plasma Membrane

All cells are surrounded by a plasma membrane.

The material inside of a cell is the cytoplasm.

The plasma membrane regulates what enters and exits a cell.

Plasma Membrane (cell membrane) Composed of proteins and phospholipids (fats with

Phosphorus).

Acts as skin around the cells contents.

Acts as a selectively permeable membrane to allow movement of materials in and out of the cell.

Located around the outside of the cell.

Single membrane around the vacuoles/vesicles, lysosomes, E.R., Golgi Apparatus.

Double membrane around the nucleus and mitochondria

End of Part 1 Cell Organelle Jigsaw Half of groups research organelles on front

side Half of groups research organelles on back

side Half way through, 2 groups join to teach other

group about their organelles Location in cell Structure Function

The Endomembrane System Consists of:

Nuclear Envelope Endoplasmic reticulum Golgi apparatus Vesicles

This system compartmentalizes the cell so that particular enzymatic reactions are restricted to specific regions

Organelles of the endomembrane system are connected directly or by transport vesicles

System of interconnected flattened tubes, sacs, or canals.

Begins at the nuclear envelope and branches throughout the cytoplasm to the cell membrane.

Moves molecules from one area to another.

Smooth Endoplasmic Reticulum (Smooth ER)

-Location of lipid manufacture. Cells that produce steroid hormones, have an abundant smooth ER.

-Section of both types of ER can break free “blebbing” to produce small membrane bound sacs of either proteins or lipids called vesicles.

-Contains enzymes that synthesize lipids and related products such as steroids.

Like Smooth E.R., but with attached ribosomes.

Folds and processes proteins and packages them in transport vesicles

Abundant in cells that produce large amounts of protein for export from the cell.

Rough Endoplasmic Reticulum (Rough ER)

Golgi Apparatus (Golgi Body) Stack, of a half dozen or more flattened sacs. On one side receives protein-filled vesicles

from the E.R. Sorts the proteins and packages them in

vesicles at the other side. From here the vesicles move to different locations in the cell.

Like the post office of the cell.

• Many transport vesicles from the ER travel to the Golgi apparatus for modification of their contents.

• The Golgi is a center of manufacturing, warehousing, sorting, and shipping.

• The Golgi apparatus is especially extensive in cells specialized for secretion.

Vesicles and VacuolesVesicles and vacuoles (larger versions) are membrane bound

sacs with varied functions.Vacuoles Storage areas for water, nutrients, and salts. Vesicles A small vacuole Storage sites in various kinds of molecules. Transport and secretory vesicles move their contents within the

cell and in and out of the cell. Can be made by the Golgi Apparatus or from an infolding of

the cell membrane

Lysosomes Special vacuoles formed by the golgi

body. Contain powerful digestive enzymes that

break down unwanted, foreign substances or worn-out parts of cells

The Endomembrane System

Fig. 7.14

Ribosomes Contain rRNA and protein subunits. Function as sites for protein synthesis. Found on ER (proteins for export) or in the

cytoplasm (proteins for use in the cell).

- Several ribosomes together in a line, all producing the same protein is called a polyribosome.

Mitochondria (singular – Mitochondrion) Burn glucose to produce adenosine

triphosphate (ATP). Use up oxygen and give off carbon dioxide

(this process is called cellular respiration).

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy

Composed of two membranes.

-Considered the powerhouse of the cell.

- Their inner membranes loop back and fourth through the inner fluid, matrix, of the mitochondria increasing its surface area and producing shelf-like structures called cristae.

- This inner membrane is the site of cellular respiration

Cytoskeleton Protein components of

cytoskeleton provide internal structure to maintain the cell’s shape, anchor the organelles, and allows them to move when appropriate.

Composed of microfilaments (actin filaments)

and microtubules. Like the “bones and

muscles” of the cell

Cytoskeleton – Microfilaments (Actin Filaments)

Primarily functions to maintain cell structure and cell movements

Extremely thin protein fibers usually occurring in bundles.

Similar in composition to the protein in the muscle (allows for muscle contraction).

Cytoskeleton - Microtubules Maintain the shape of the cell and act as

tracks that organelles can move on.

Thin cylinders several times larger than microfilaments.

Found in both cytoplasm and certain organelles.

Used to construct material to make up Cilia, Flagella and Centrioles.

Tubulin

Other Organelles Centrioles:

short cylinders with a 9+0 pattern of microtubule triplets

Two centrioles lying at right angles form the centrosome which is the microtubule organizing center (MTOC)

Cilia and Flagella: Hair like projections that can move

in undulating fashion (like a whip) or stiffly (like an oar)

Cells with cilia and/or flagella are capable of movement

Cilia also line the respiratory system and help remove foreign material from the lungs

A cell is a living unit greater than the sum of its parts

While the cell has many structures that have specific functions, they must work together.

The enzymes of the lysosomes and proteins of the cytoskeleton are synthesized at the ribosomes.

The information for these proteins comes from genetic messages sent by DNA in the nucleus.

All of these processes require energy in the form of ATP, most of which is supplied by the mitochondria.

A cell is a living unit greater than the sum of its parts.

ABCD Quiz! I believe you all know how to play this game: Groups of 4

1 scorekeeper 4 contestants

I will show a clue about an organelle, each team member will guess one of the 4 choices provided

Team with highest score wins No notes or books allowed

Question 1 I am the largest organelle in a cell, and I

contain hereditary material. I am a: A) Ribosome B) Mitochondrion C) Nucleus D) Golgi Apparatus Answer is C

Question 2 I am composed of phospholipids and proteins

and I control what enters and exits the cell. I am a:

A) Plasma Membrane B) Lysosome C) Vesicle D) Smooth ER Answer is A

Question 3 I am kind of like the subway system of the cell

because I transport molecules from one place to another. I am a:

A) Rough ER B) Vesicle C) Lysosome D) Mitochondrion Answer is B

Question 4 I receive protein filled transport vesicles from

the ER which I then sort and repackage for use inside the cell. I am the:

A) Ribosome B) Vacuole C) Cytoplasm D) Golgi Apparatus Answer is D

Question 5 I synthesize protein and I can be found in the

cytoplasm or attached to another organelle. I can also be found in groups. I am a:

A) Mitochondrion B) Ribosome C) Lysosome D) Microfilament Answer is B

Question 6 I have attached ribosomes that synthesize

proteins which I then process and package. Cells that export a lot of protein have a lot of me! I am the:

A) Lysosome B) Nuclear Envelope C) Rough ER D) Smooth ER Answer is C

Question 7 I have a double membrane and I am the site

of cellular respiration and production of ATP. I am a:

A) Mitochondrion B) Golgi Apparatus C) Smooth ER D) Rough ER Answer is A

Question 8 My job is to digest nutrients for use in the cell

or to get rid of unwanted molecules and waste. I am a:

A) Vesicle B) Nucleus C) Lysosome D) Ribosome Answer is C

Question 9 I maintain the shape of the cell and allow

different organelles to move around the cytoplasm. I am the:

A) Cytoplasm B) Vesicle C) Cytoskeleton D) Plasma Membrane Answer is C

Question 10 I am capable of forming transport vesicles and

lipids and steroids are synthesized inside of me. I am:

A) Rough ER B) Smooth ER C) Golgi Apparatus D) Mitochondrion Answer is B