The Cell

Cell Theory

• 1-All living things are made of cells • 2-Cells are the basic unit of life • 3-All cells come from preexisting cells

• Hooke • Leeuwenhoek • Schleiden • Schwann • Virchow

Scientists

Microscopes

• Light microscope- resolves to about .2 um – magnification • Electron microscope- resolves to about .2 nm – Scanning (SEM)-cell surfaces – Transmission(TEM)-Internal contents – **what is the disdavantage?

– (note the newer STM, scanning tunneling, enables 3-D images and can be used w/ living)

Cell Size Limit

• Cells must divide when volume exceeds surface area (Mader text: p. 59; Glencoe text: section 9.1) • Cells vary in size from about 1 um (bacteria) to about 1m (sciatic neuron-nerve cell)

Prokaryotic Cells

• Lack membrane bound nucleus • DNA found in nucleoid region • Like many eukaryotic cells, these cells have cell walls, plasma membranes, flagella and ribosomes • Unlike eukaryotic cells, they may have a capsule and pili

The prokaryotic cell

Cellular Organelles

Nucleus

• controls all functioning of the cell • “Brain” of the cell • contains the hereditary information of DNA • DNA holds the coded instructions for making proteins and other important molecules • Nucleus is important because making proteins is one of the main functions of the cell • Chromatin is the granular material seen within the nucleus (DNA bound to protein)

2. Nucleolus: dark regions within the nucleus a. produces ribosome's B. In animal & plant cells

3. Ribosomes: organelle that carries out protein synthesis/interprets code from RNA. Made of rRNA and protein •Can be attached to ER or floating •In plants & animal cells

Cell Wall

• Found in plants, algae,

fungi, and almost all prokaryotes. Not in animals

• Made from

carbohydrates (cellulose in plant cells)

• Provides support,

protection and excessive uptake of H2O

• Outside the cell

membrane.

Cell Membrane

• Thin flexible

barrier around the cell.

• Selectively

permeable. Made of

– lipid bilayer – proteins – carbohydrate

chains

– Scattered

cholesterol

Endoplasmic Reticulum

• Endoplasmic Reticulum • •

Rough ER envelope

• Covered in ribosomes • Makes proteins and cell membrane

Smooth ER – Membranous maze connected to nuclear – no ribosomes present

– Also a membranous maze – Lipid synthesis – Detoxifies harmful substances – Cells in liver have a lot of smooth ER

Golgi Apparatus

• Center of manufacturing, processing, packaging

and shipping

• Enzymes here attach carbohydrates and lipids to

proteins

• After the ER makes the proteins, they move into

the Golgi Apparatus where they are modified

• From the Golgi Apparatus , modified proteins are

moved to their destinations

Lysosomes

• Small organelle filled with hydrolytic enzymes that cell uses to digest macromolecules. Important in phagocytosis • Acidic interior (pH-5) • Also functions to break down lipids, carbohydrates and proteins from food into particles that could be utilized by the rest of the cell • Debris removal of worn out organelles

Vacuoles

• Membrane bound sacs • Temporary storage areas for food water, enzymes and waste • Special types – Contactile –pumps out excess water in single celled water dwelling organisms (ex-aquatic protists, such as protozoans) – Central- large vacuole found in plants used for water storage

Chloroplasts

• Plant cells • Shaped like lenses • Double membrane • Use energy from sunlight to make energy-rich food molecules in a process known as photosynthesis Light energy + 6H 2 O + 6CO 2 ----  C 6 H 12 O 6 6O 2 +

Mitochondria

• Organelles that release energy from stored food molecules-Cellular respiration • Power house of the cell; ATP is made here • Energy released from the mitochondria is used by the cell for growth, development and movement

6O 2 + C 6 H 12 O 6 --------



6CO 2 + 6H20 +Energy

Centrioles

• Organelles made of microtubules and are involved in cell division • Animal cells only

Peroxisomes

• Specialized compartment bound by single membrane • Similar to lysosomes (contains enzymes) • Generation and degradation of H202 (hydrogen peroxide) to protect cell from it’s toxic effects

Cytoskeleton

• Microfilaments thinnest, made of protein, help cells change shape • Intermediate fibers Varied,rope-like, tension bearing • Microtubules Largest, anchorage and movement

Role of Cytoskeleton

• Extensions of plasma membrane –

Cilia

–

Flagella

– Both have 9 +2 microtubule arrangement except at base, which has 9 triplets-

Basal Body

• Identical in structure to

centriole

Cytoplasm

• Everything between the plasma membrane and the nuclear envelope • Semifluid (cytosol) with organelles suspended in it • Protoplasm=cytoplasm+nucleoplasm (inside nucleus)

Cell Junctions

• See Handout and/or book • Plant cells – Plasmodesmata- junctions between plant cells (walls) • Animal cells ~Tight junctions ~Anchoring junctions (desmosomes) ~Communicating (Gap) *Know exp of each!

• Cytology • Histology • Cytosol

Definitions