Ch 4

Ch 4CELL STRUCTURE AND

FUNCTION

The Cell• The cell is the smallest unit of life

that can carry out life processes.

Section 2 Introduction to CellsChapter 4

Cellular Organization

Discoveries Leading to The Cell Theory

• Robert Hooke – 1665 -observed cork through a light microscope.

• Anton Van Leewenhoek – 1675 -observed LIVING cells.

• Matthias Schleiden – 1883 –plants are made of cells.

• Theodor Schwann – 1839 –animals are made of cells

The Cell Theory• The cell theory states that all

living organisms are made of one or more cells, cells are the basic units of structure and function, and cells come only from pre-existing cells.

Two Basic Types of Cells

Prokaryotic Cell• Prokaryotic-

cells that do not have a nucleus and internal membrane-bound structures– Most unicellular

organisms are prokaryotes.

– Bacteria

Eukaryotic Cell• Eukaryotic-Cells

that do have a nucleus and internal membrane-bound structures.– Most multicellular

organisms are eukaryotes.

– Yeast and algae (unicellular, eukaryotes)

– Plant and animal

• Cytoplasm – Gel like material that protects, supports and suspends organelles.

Features Common to Cells:

All cells have either DNA or RNA or both.

Features Common to Cells:

• Cell membrane – Semi-permeable allows some materials in and keeps others out. This helps to maintain cellular homeostasis.

Structure of the Plasma Membrane

• Phospholipid Bilayer -2 layers ofphospholipids.

• Phospholipid- phosphate head attached to two lipids (fattyacid tails).

• Polar phosphate group allows membrane to interact with its environment.

• Fatty acid tails create a water-insoluble layer in the middle which is non-polar.

• Fluid mosaic model-membrane is flexible

• Cholesterol-keeps fatty acid tails from sticking together

• Transport proteins-allow needed substances to move through the membrane

Chapter 4Parts of the Cell

Nucleus• “Command center”• Surrounded by a

nuclear envelope• Contains genetic

material: – chromatin– chromosomes

• Nucleolus-makes ribosomes– Ribosomes-site

where proteins are made• Can be found floating

in the cytoplasm or attached to endoplasmic reticulum

Endoplasmic Reticulum (ER)

• Series of folded membranes allow a large amount of work to be done in a small amount of space

• Transportation unit for the cell

• Rough Endoplasmic Reticulum (RER)– Ribosomes attached– Protein synthesis

• Smooth Endoplasmic Reticulum (SER)– Produce and

store lipids

Golgi ApparatusVesicles

• Flattened tubular membranes

• Packaging plant• Modify, sort,

package, and transport proteins throughout the cell

VACUOLES• Storage sacs

Temporary storage of materials– Store food,

enzymes, waste• Plant cells have

one large vacuole.• Animal cells have

many small vesicles.

LYSOSOMES• Contain digestive

enzymes• Digest excess or

worn organelles, food particles, viruses, and bacteria

• Surrounded by membrane that prevents it from destroying the cell

• Can burst causing cell death

Chapter 4Mitochondria• Cellular respiration -converts food

into energy• Cell “Powerhouse”• Number of mitochondria depends upon the

function of the cell– Ex: muscles cells have more mitochondria than

fat cells

Centriole

• Help with cell reproduction

• Only found in animal cells

Plastids – Color pigments of cells

• Examples:– Chloroplast – Located in plant cells, some

bacteria, and protists.• Capture light energy to produce and store food• Contain chlorophyll-green pigment that traps

light energy

• Cytoskeleton – tiny fibers that give structure and support to the cell.– Microfilament- thin

and tubular…support the cell membrane.

– Microtubule- thick and tubular also branched. Act as “rails” on which materials move through the cell.

Features Common to Cells:

Cilia and Flagella• Aid in

movement and feeding

• Composed of microtubules

• Cilia-short, numerous hair-like projections that move in a wavelike motion

• Flagella-long, whip-like projections

Cell wall• Rigid outer

covering PLANT CELLS

• Located outside the cell membrane

• Provides support and protection

• Helps produce turgor pressure

•

Animal Cell

Plant Cell

Plant cell vs. Animal Cell

Plant vs Animal cells• Animal Cell vs. Plant cell

– Animal Cell • DO contain centrioles. • DO NOT contain a cell wall or plastids.

– Plant Cell • DO contain a cell wall, plastids, and a

large central vacuole. • DO NOT contain centrioles