Cell Structureand Function

Chapter 4

The History of Cell Biology

Cell: the smallest unit that can carry on all of the processes of life.

Robert Hooke: 1665

Studied natureUsed “light microscope” pg 69

Viewed a thin slice of cork

Saw many little boxesCELLS

Anton van Leeuwenhoek: 1673

First to observe living cells

Microscope lens was 10x that of Hooke

Was first able to see unseen world of microorganisms

First to view a REAL cell

Matthias Schleiden: 1838

Botanist

First to view plant cells

Concluded: All plants are composed of cells.

Theodor Schwann: 1839

Zoologist

Concluded: All animals were made of cells.

Rudolf Virchow: 1821 - 1902

Physician

All cells come from other cells.

CELL THEORY

1. All living organisms are composed of one or more cells.

2. Cells are the basic units of structure and function in an

organism.

3. Cells come only from the reproduction of existing cells.

Developments:

Discovery of cells and cell theory:

MICROSCOPE

Basic Characteristics of ALL living things:

1. made of organized parts2. obtain energy from their

surroundings3. perform chemical reactions

4. change with time5. respond to the environment

6. reproduce

Section 2: Introduction to Cells

In a body: pg 72 Different cells

Different shapes

Different functions

All in same body

Cell Shape

Shape reflects the different functions

PAGE 72

Cell Size

A few types of cells are large enough to be seen without a microscope

Ex. Giraffe’s nerve cells: 6 ½ ft long Human egg cell: size of a period

MOST cells: 1/500th the size of a period

WHY are cells MICROSCOPIC?

SURFACE AREA-TO-VOLUME RATIO

Nutrients and oxygen go inWaste goes out

BOTH pass through surface

Happens QUICKLY therefore need more surface area to volume page

73Cells MUST be microscopic!!!

BASIC PARTS OF A CELL

3 basic parts to all cells1. Cell Membrane

2. Cytoplasm

3. Nucleus

1. Cell Membrane

Also called the plasma membrane

Covers the surface

Acts as a barrier

All materials enter or exit through this

2. Cytoplasm

Hold all of the organelles

3. Nucleus

Control centerHolds DNAMembrane bound and free floating

DNA

Two Basic type of cells

PROKARYOTES

Lack a membrane-bound nucleus

Lack membrane-bound organelles

May have a nucleoid: concentrated area of DNA

DOMAIN Archaea DOMAIN Bacteria

EUKARYOTES

In organisms made up of one or more cells

Contain organelles Larger in size than

prokaryotes

Cellular Organization

Page 76

Cell Tissue Organ Organ System

1. Cell Membrane

Functions: A. Allows only certain molecules to

enter or leave the cell B. Separates reactions inside the cell

from outside the cell C. Excretes waste D. Interacts with environment

Parts of Cell Membrane

Phospholipids

Proteins Cell surface markers – emerge from

only one side of the membrane

Receptor proteins – recognizes and binds to substances outside the cell

Transfer proteins – helps substances move across the membrane

Enzyme –

2. Nucleus

Houses and protects genetic information Chromosomes: holds DNA

Nuclear Envelope: surrounds nucleus

Nucleolus: denser area in nucleus

3. Cytoplasm

Holds organelles

organelles

MitochondriaRibosomesEndoplasmic reticulumGolgi aparatusVesiclesMicrotubulesMicrofilamentscentrioles

Mitochondria

Mitochondria: tiny organelles that transfer energy into ATP

ATP: Adenosine triphosphate Powers the cell’s chemical reactions

HIGH in # in muscle cells! FEW in # in fat cells.

Ribosomes

Small, roughly spherical organellesResponsible for building proteinNo membraneMade of protein and RNACreated in nucleus, finished in

cytoplasmFound in

Cytoplasm Some endoplasmic reticulum

Endoplasmic Reticulum

Called ERSystem of tubes and sacs

(cisternae)Function as a “highway”: a path

along which molecules move from one part of the cell to another

2 types: Rough Smooth

Rough ER

System of interconnected, flattened sacs covered with RIBOSOMES

Pg 81Produces phospholipids and proteinsRibosomes on ER:

Produce digestive enzymes that contain proteins

Vesicles (sacs) pinch off and store these enzymes until they are released

Smooth ER

Smooth appearanceBuilds In ovaries and testes: produces

hormones

*abundant in liver and kidneys:

Long term alcohol and drug abuse:

Golgi Apparatus

Pg 82Another system of flattened,

membrane sacs

Sacs closest to the nucleus receive vesicles from the ER containing newly made proteins or lipids

Proteins get “address labels”

Types of Vesicles

VESICLE: small sacs that head to the plasma membrane and release contents outside of cell

1. LYSOSOME2. PEROXISOME3. others

Vesicles: Lysosomes

Vesicles from Golgi Apparatus that contain digestive enzymes

Breakdown proteins, carbs, fats, bacteria.

Responsible for breaking down cell when it is time to die!

Vesicles: Peroxisomes

Abundant in liver and kidney

Detoxify alcohol and other drugs

Also breakdown fatty acids

MAJOR FUNCTION OF CELL:protein synthesis pg 83

1. proteins assembled by ribosomes on rough ER

2. Vesicles transport proteins to thegolgi apparatus

3. Golgi modifies the proteins and packages them in new vesicles

4. Vesicles release proteins that have destination outside of cell

5. Vesicles needing to remain inside of cell stay.

Cytoskeleton

Network of thin tubes and filaments Give shape to the cell from the inside

ex. Tent poles

Also acts as a system of internal tracks to allow items to move around in cell

Microtubules, Microfilaments, &Intermediate filaments

Microtubules

Hollow tubes made of protein called “tubulin”

1. Hold organelles in place2. Maintain cell’s shape3. Act as track to guide organelles

Microfilaments

Finer than microtubules2 strands of intertwined protein

1. contribute to cell movement2. muscle contraction3. maintainance and changing of

shape

Intermediate Filaments

Rods that anchor the nucleus and other organelles to their place

Maintain INTERNAL shape of nucleus

How does a cell MOVE?Short, hair-like structures!

CILIA

Extend from surface of cell

Short Large #’s

Inner ear: vibrate and help detect sounds

Protisits: sweep food into mouthlike opening

FLAGELLA

Extend from surface of cellLongless #’s

Section 4: Unique features of plant cells

Plant cells have 3 additional kinds of structures

1. cell wall

2. large central vacuole

3. plastids

Why does a plant need these different structures?

Make their own food: photosynthesis

Must reach up towards the sun

Need to hold water

Cell Wall

Rigid layer outside of plasma membrane

Made of cellulose: a carb that makes the celllike a stiff box

2 layers: Primary wall Secondary wall

(wood)

Large Central Vacuole

Large, fluid-filled organelle

Mainly stores water

90% of the plants volume

Causes plant to stand upright

Chloroplasts

Used in photosynthesis

Use light energy

Contain chlorophyll:

green pigment that absorbs light and captures the light energy

chromoplasts

Colored pigment

Found in carrots: orange

flowers: red, purple, yellow & white