Cell Structure & Cell Structure & FunctionFunction

Cell Structure & Cell Structure & FunctionFunction

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.

• Theodor Schwann – 1839 –animals are made of cells

• Rudolf Virchow – 1855 – all cells come from other cells.

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

The Cell TheoryThe cell theory states that: •all living organisms are made of one or more cells•cells are the basic units of structure and function •cells come only from pre-existing cells

Prokaryotic Cell• Prokaryotic-• Do not have a

nucleus • Do not have

internal membrane-bound structures– Most unicellular

organisms are prokaryotes.

– Bacteria

Eukaryotic Cell• Eukaryotic-• Has a nucleus • Has internal

membrane-bound structures– Most multicellular

organisms are eukaryotes.

– Yeast and algae (unicellular, eukaryotes)

– Plant and animal

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

Organelles• “little organs”• Specialized parts within a cell that

has a specific function

• Cytoplasm – • Gel like material

that protects, supports and suspends organelles.

Features Common to Cells:

Features Common to Cells:

• Cell membrane – Semi-permeable • Controls what enters and leaves the cell.

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”• Contains genetic

material: – Chromosomes– DNA

• 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)– No ribosomes– Produce and

store lipids

Golgi ApparatusVesicles

• Flattened tubular membranes

• Packaging plant• Modify, sort,

package, and transport proteins throughout the cell

VACUOLES• Storage areas

Temporary storage of materials– Store food,

enzymes, waste, water

• 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• 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

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.

Features Common to Cells:

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 CellsPlant

• Has chloroplasts• Large central vacuole• Has cell wall• No centrioles

Animal• No chloroplasts or cell

wall• Small vacuoles• Has centrioles