The Cell

The basic unit of life

Blood Cells(Red, Platelet and White)

Macrophage killing bacteria

Nerve Cell

Human Cheek Cell

Elodea (plant) Cells

Sperm and Egg Cells

Paramecium(single celled organism)

Amoeba(single celled organism)

Bacteria Cells

Cellular Variation• Cells come in numerous shapes and sizes.

Their shape is usually somehow related to their function.

• Some organisms like plankton, amoeba and bacteria are composed of a single cell. Bacteria cells do not contain a nucleus.

• Other, more complex organisms, are composed of huge numbers of different cells. Humans are made up of about 100 trillion cells.

Van Leeuwenhoek the “father of microscopy”

Robert Hooke + Cork = “Cells”

Times have changed, yet …

The Cell Theory

1.All living things are composed of cells.

2.Cells are the basic unit of life.

1.All cells come from preexisting cells.

How big is a cell?

Why are cells so small?• plant & animal cells range from ~ 10-100

micrometers

• Cells stay small due to cell surface area to volume ratio (SA : V)

• As cells get larger:– volume increases – proportionate amount of surface area available for

exchanging nutrients & wastes decreases

• A small cell has more SA per V than a large cell so it is much more efficient!

Cell Structure

• Eukaryotic cells include both plant & animal cells

• Have the following :

1.The nucleus (& DNA)2.The cell membrane3.The cytoplasm.4.Organelles.

Organelles

• A membrane-bound compartment in a cell with a specialized function.

The Cell Membrane

• “The gatekeeper of the cell”

• Controls what goes in and out of cell.

• Forms A barrier with outside environment.

• Composed of a phospholipid bilayer with embedded proteins.

• “Selectively permeable” picky about what moves in and out.

The Nucleus• The “control center” of

the cell.• Bound by the porous

nuclear envelope (membrane).

• Contains the DNA (the chromatin or chromosomes) which directs protein synthesis.

• Controls cellular chemical reactions.

• Contains the nucleolus (site of ribosomal RNA production).

DNA (chromatin or chromosomes)

• DNA (deoxyribonucleic acid) is found within the nucleus.

• The DNA contains the genetic material of the organism which codes for protein production.

• Normally it is unwound and called the chromatin material.

• Before and during cell division, the DNA coils up into chromosomes.

Ribosomes• Site of protein

synthesis.• rRNA (produced by a

special type of chromatin) is the structural subunit of ribosomes. It is found in the nucleolus.

• Composed of 2 subunits, each a mix of rRNA and proteins.

• Often located on the endoplasmic reticulum, but can be free in the cytoplasm.

Rough Endoplasmic Reticulum

• Site of protein synthesis.• Ribosomes attach to

make proteins.• Wrapped around nucleus

to receive ribosomes.• Newly produced proteins

move to the smooth ER and are packaged into vesicles which are sent to Golgi apparatus.

Smooth Endoplasmic Reticulum

• Produces different substances in different cells.

• Produce steroid hormones in the testes and adrenal cortex.

• Produce drug detoxifying enzymes in liver cells.

• Produce vesicles which contain newly synthesized proteins.

Golgi Apparatus• Composed of stacks of

saccules (flattened vesicles).

• Receives transport vacuoles containing proteins from RER.

• Modifies, stores, packages and distributes proteins.

• Eventually proteins are packaged in secretory vesicles and released from the Golgi apparatus.

The Cell Wall

• Present only around plant cells and some bacteria.

• Located outside the cell membrane.

• Protects and supports plant cell.

• Composed of the polysaccharide cellulose.

• Not as “picky” about what passes through it.

Cytoplasm

• The viscid, semi fluid matter contained within the plasma membrane of a cell.

• Suspends the cell’s organelles.

• Composed mostly of water.

• Location of many cellular chemical reactions. (Cellular metabolism)

Mitochondria

• Mitochondria are the powerhouse of the cell.

• They are the site of cellular respiration which converts glucose into ATP energy, water and carbon dioxide.

• C6H12O6 + 6O2 6CO2 + 6H2O + ENERGY

• Bound by a double membrane.

Chloroplast• Found only in plant cells.• Location of

photosynthesis (the transformation of light energy into chemical energy).

• 6CO2 + 6H2O + ENERGY C6H12O6 + 6O2

• Bound by a double membrane.

• Belong to the “plastid” group of organelles which include leucoplasts and chromoplasts.

Vesicles and Lysosomes

• Small, membrane bordered structures.

• Vesicles are used for transport of substances within the cell.

• Lysosomes contain digestive enzymes which can break down materials in the cell. Act as a “cleanup crew” for the cell.

Vacuoles

• Large, membrane bound storage structures.

• In plant cells vacuoles are extremely large and also help to support the plant.

Cytoskeleton

• A variety of filaments and fibers that support cell structure and drive cell movement.

• Microtubules and actin filaments make up the skeleton.

• Cilia and flagella are used for movement.

Centrioles

• Centrioles are only present in aimal cells.

• Centrioles aid in cell division.

• They are composed of a pattern of microtubules.