Cell Structure and Function All living organisms are made up of cells

Cell Structure and Function

All living organisms are made up of cells.

Cells are:• The basic unit of structure and function of a living organism.

– Organisms can be unicellullar

– Organsims can be multicellular

History of the cell.• 1665 Anton van Leevwenhoek: constructed

first simple microscope.• Viewed pond water and saw tiny moving

structures • he called “wee little beasties” or

“animalcules

• .

• 1670 Robert Hooke– English scientist – invented first compound light microscope.– Viewed cork– Named tiny, hollow units and called them

“cells”.

Approximately 200 years later…

• 1833 Robert Brown– First to view a nucleus within a cell.– Scientist now knew that there were structures

within the “cells” and they were not hollow like the cork.

• 1835 Two German scientist, Theodor Schwann (Zoologist) and Matthias Schleiden (Botanist) collectively came to the conclusion:– that all plants and all animals are made up

of cells.

• 1855 Rudolf Virchow recorded that “all cells come from other like and pre-existing cells.

• 1869 Fredrick Miescher: – Discovered: DNA’s presence (not its

structure) but did not know its importance until much later.

– He called it nuclein.

• 1879 Walter Flemming: Identified chromosomes in the nucleus. Once again did not know the true importance of them.

The Cell Theory

• 1. Every living organism is made up of one or more cells.

• 2. Cells are the basic unit of structure and function of all living organisms.

• 3. All cells arise from like, pre-existing cells.

Two types of cells exist: Prokaryotic and Eukaryotic Cells

Prokaryotic Cells

• Word means “before nucleus”• Includes all bacteria

– Believed to be the first cells on Earth in the primordial soup

Traits:

• Lack a nucleus • Lacks all membrane bound organelles.• Genetic material just floats around the

center of the cell.

Eukaryotic Cells

• Word means “contains a true nucleus”

• Examples includes all animals, plants, fungi, and protist.

• TRAITS:

• Evolved from prokaryotic cells.– Theory is one prokaryotic cell engulfed

another and now there was a cell within another cell.

• Eukaryotic cells contain a nucleus and membrane bound organelles.

• Organelles are “tiny organs” within a cell, each having their own function.

Two types of eukaryotic cells:

Plant-like Animal-like

Traits common to both prokaryotic and eukaryotic

cells

-Plasma / cell membranes-Cytoplasm-Cell wall-Genetic material-Ribosomes

Cell Membrane

Plasma or Cell Membrane: Function:

1. Outer boundary of the cell-separates one cell from another

2. Allows for interaction between like cells within a tissue.

3. Acts as a “gatekeeper”-regulates what is allowed to enter or leave the cell.

4.Aids in protection and support.-keeps out bacteria-provides some shape

OxygenFood MoleculesWater

Carbon dioxideCellular WasteExcess water

Fluid Mosaic Model

-model of the structure of a cell membrane-discovered in 1972

The cell membrane:-Consist of a double layer of phospholipids

with proteins and some carbohydrates scattered throughout the bilayer.

-known as a phospholipid bilayer

Components of the Cell Membrane

Carbohydrate chains

Phospholipid bilayer

Proteins: - receptor proteins - transporting proteins - adhesion proteins

Used for cell recognition

Type of lipid

Phospholipid-type of lipid

-most abundant component in the membrane

Hydrophobic Tail-water fearing-nonpolar

Hydrophilic Head-water loving-polar

Extracellular Fluid: Cells watery environment

Intracellular Fluid: Cells liquid center/cytoplasm

Several types of proteins embedded in the bilayer:

1. Receptor proteins: act as a docking area for items to attach to like hormones.

2. Transporting proteins:

-transports items across the bilayer

3. Adhesion Proteins:

-project outward from bilayer and help cells within a tissue to stick together.

Cytoplasm:1. -liquid part of the cell2. -found in all areas between the nucleus and the cell membrane

3.-made mostly of water with salts, amino acids, nucleotides, etc… dissolved in it.

Function: -to suspend and allow structures to move about.

Cell Wall:1.-surrounds cell membrane

-found in plants, fungi, some bacteria and some protist.2.-located outside the cell membrane3.-provides shape and support

4. -has openings so items can pass through.

5. -made up of cellulose and pectin in plants and chitin in fungi.

Turgor Pressure:1. -Pressure created by water

-cell loses water-turgor pressure decreases-cell wall bows inward-cell shrinks in size

2. Cell takes in water- turgor pressure increases- cell wall bulges out- cell swells

Genetic Material:1.-made up of DNA2.-has instructions for making all cellular proteins.

Prokaryotic Cells:-Have no nucleus-DNA is free floating-DNA is in 1 circular

loop

Eukaryotic Cells:-DNA contained in a nucleus-many linear pieces of DNA known as

chromosomes.

Ribosomes:

The cells “workbench”

Job: Makes proteins, in their linear form, by assembling amino acids in the correct order based on DNA’s code.

Ribosomes are made up of RNA and proteins.

Found attached to the endoplasmic reticulum

or

Free floating in the cytoplasm

Continue on to Bacteria lecture

Continue on to Viruses