Cells!

Have we always known about cells?

No, they are too small to see with just our eyes.

First, we needed the invention of the microscope to see things this small.

Compound microscope Specimen is magnified as light passes through several lenses.

Robert Hooke: English Scientist:

observed cork with a microscope. He thought the box-like structures he saw

looked like jail cells…

Anton Van Leewuenhooke:

Discovered bacteria, protizoa, and other microscopic organisms.

Electron Microscope

Some things are so small light waves totally miss them. Waves from electrons are used to “see” these very small objects.

Blood as seen with compound microscope

Blood seen with electron microscope

Pollen

Foot of house fly

Staple in Paper

Moth scales

Cell Theory:

Cells are the basic unit of life.

All cells come from pre-existing cells.

Exceptions to the cell theory

The First Cell could not have arisen from a pre-existing cell.

Viruses are not composed of cells but do contain genetic material.

Although considered organelles, Mitochondria and Chloroplasts contain genetic material and can reproduce inside a cell.

Two types of cells

Prokaryotic cells: Lack membrane bound structures such as a nucleus, mitochondria and chloroplasts.

Pro = before Karyotic = nucleus

Examples: Bacteria

Notice… no nucleus, no mitochondria, no chloroplasts

Eukaryotic cells

Have membrane bound structures such as a nucleus, mitochondria…

Eu = true Karyotic = nucleus

Examples: all other cells

Cell Size Prokaryotic/bacteria: very small… 1 to 10

micrometers Eukaryotic: bigger… from 10 to 100

micrometers Chicken egg cell = 6 cm (the whole egg) Nerve cell = 1 meter long Human egg cell = 100 micrometers Red blood cell = 9 micrometers Skin cell = 20 micrometers

White blood cell and bacteria

Cell size and surface area

Length of side (cm)

1 cm 3 cm

Total surface area (cm2)

Total volume (cm3)

Surface are to volume ratio

Cell size and surface area

Length of side (cm)

1 cm 3 cm

Total surface area (cm2)

1cm2 x 6 sides = 6cm2

9cm2 x 6 sides = 54 cm2

Total volume (cm3)

1x1x1 = 1cm3 3x3x3 = 27cm3

Surface are to volume ratio

6:1 54:27 = 2:1

Structural heirarchy: Atoms: elements = carbon, hydrogen Molecules: water, glucose Organelles: nucleus, ribosome Cells: muscle cell, blood cell Tissue: fat tissue, bone tissue Organ: Stomach, lung Organ system: digestive system Organism: us

Cell Organelles 1. Plasma membrane (cell membrane)

– Function: selectively permiable, keeps contents of cell in

– Structure: phospholipid bilayer

– In both plant and animal cells

Cytoplasm Function: site of many chemical

reactions, gives cell its shape

Structure: gel like substance made of 80% water.

Nucleus Function: the control center for all cell

functions. It controls growth and cell division

Structure: Envelope surrounding DNA

Nucleolus Function: Makes ribosomes

Structure: Dense body inside the nucleus

Endoplasmic Reticulum Function: Aids in the assembly and transport

of proteins and lipids.

Structure: a network of folded membranes that form channels from the cell membrane through the cytoplasm to the nuclear membrane

Ribosome: Function: assembles proteins

Structure: small dot like structures found on the E.R. or in cytoplasm

Mitochondria Function: break down carbohydrates

and sugars, making energy from the food we eat

Structure: 2 membranes, inner membrane folded, has own DNA

Golgi Complex Function: Packages materials for

release from the cell. Structure: Stacks of flattened

membranes and vesicles budding off

Lysosome Function: disposal and recycling units of the

cell. (little stomachs)

Structure: Membrane bound structures containing enzymes necessary for digesting certain material in a cell

Vacuole: Function: stores food, water, and waste

Structure: fluid filled sac (plant cells have large vacuoles)

Centriole: Function: aids in animal cell division

Structure: nine sets of three fused microtubles arranged in an open star shape and located just outside of the nucleus

Chloroplast Function: turns the sun’s energy into

food (photosynthesis) Structure: 2 membranes, oval, green

Cell Wall Function: support and structure for cell.

Structure: cellulose fibers

Cell Membrane

Phospholipid bilayer

Selective Permeability

The following substances can easily pass through the cell membrane….

Lipid soluble substances

Small stuff – Glucose, oxygen, carbon dioxide, ions

Passive Transport: no energy required

Diffusion: movement of molecules from a high concentration to a low concentration

Facilitated diffusion– Membrane proteins help molecules pass

through the cell membrane.

Osmosis: Movement of WATER molecules from a high to a low concentration.

Active Transport: requires energy (ATP)

Movement of molecules from a Low to a High concentration.

Facilitated transport:– Some membrane proteins require energy

to move molecules through the cell membrane.

Pinocytosis: cell drinking

Phagocytosis: cell eating

Cell Organelle Lab These pictures are what you should

have seen in the microscope…

Cork

Elodea

Cheek cells

Onion skin