4.2 INTRODUCTION TO CELLS

CELL DIVERSITY (SHAPE)  Cells come in a variety of shapes  The shape typically reflects the function of the cell  Consider the nerve cell…  Long and thin with many extensions

CELL DIVERSITY (SHAPE)  Cells come in a variety of shapes  The shape typically reflects the function of the cell  Consider the skin cell…  Flat, plate like shape

CELL DIVERSITY (SIZE)  Cells vary greatly in size  Longest include nerve cells in giant squid and giraffe  Heaviest is thought to be ostrich egg

CELL DIVERSITY (SIZE)  Size limited by relationship of cell’s surface area to its volume  Large surface area is good to let large amounts of nutrients in and out

CELL DIVERSITY (SIZE)

3 BASIC PARTS OF A CELL 1. Plasma membrane  Cell outer boundary  Barrier between cell and “outside world”  All things entering and leaving the cell must go through plasma membrane

3 BASIC PARTS OF A CELL 2. Cytoplasm  Region inside cell  Includes fluid and cytoskeleton  Includes all organelles except nucleus  Cytosol – “liquid” portion of the cytoplasm where organelles are suspended

3 BASIC PARTS OF A CELL 2. Cytoplasm  Cytosol – “liquid” portion of the cytoplasm where organelles are suspended

3 BASIC PARTS OF A CELL 3. Nucleus  Membrane bound organelle that contains DNA  Controls most functions of a cell

2 BASIC TYPES OF CELLS 1. Prokaryotes  no membrane bound nucleus  No membrane bound organelles  Can have nucleoid region where genetic material is concentrated

2 BASIC TYPES OF CELLS 1. Prokaryotes  Domain Bacteria and domain Archea

2 BASIC TYPES OF CELLS 1. Eukaryotes  Have membrane bound nucleus  Have membrane bound organelles

2 BASIC TYPES OF CELLS 1. Eukaryotes  Domain Eukarya

CELLULAR ORGANIZATION  Over time, cells began to form groups  2 types of groups

CELLULAR ORGANIZATION 1. Colonies  Group of genetically identical cells  Not truly multicellular  No coordinated cellular activities

CELLULAR ORGANIZATION 2. True Multicellularity  Cells have roles  Like cells form tissues  Like tissues form organs  Like organs form organ systems

4.3 EUKARYOTIC CELL ORGANELLES

3 PARTS 1. Plasma Membrane 2. Nucleus 3. Organelles

3 PARTS 1. Plasma Membrane  Selectively permeable – lets only specific molecules in and out of cell  Composed of lipids and proteins  Fluid mosaic model – acts like a fluid  Proteins are like boats floating on water

3 PARTS 1. Plasma Membrane

3 PARTS 1. Plasma Membrane  Peripheral proteins – loosely attached to inside or outside of membrane

3 PARTS 1. Plasma Membrane  integral proteins – permanently attached to cell membrane  Embedded in membrane  May have carbohydrate attached that is a site for viruses and hormones to attach to

ORGANELLES 2. Mitochondria  “mighty mitochondria” – powerhouse of cell  Where ATP is made  Have their own DNA  Have outer membrane and inner membrane  Cristae – folds of inner membrane

ORGANELLES 2. Mitochondria

ORGANELLES Endoplasmic reticulum (ER)  Transports substances around cell  2 types

ORGANELLES 3. Smooth ER  Creates and stores lipids and steroids  Breaks down toxins in liver

ORGANELLES 4. Rough ER  Studded with ribosomes

ORGANELLES 5. Ribosomes  Make proteins  Attach to RNA

ORGANELLES 5. Ribosomes

ORGANELLES 6. Golgi apparatus  Makes complex molecules out of simple molecules  Processing and packaging

ORGANELLES 6. Golgi apparatus

ORGANELLES 7. Lysosome  Digests old molecules, waste, foreign substances and old organelles  “cleans up” cell

ORGANELLES 8. Centrioles  Help animal cells divide

ORGANELLES 9. Cytoskeleton  Gives shape to the cell  Microtubules – hold organelles in place  Spindle fibers used in cell division  Microfilaments – help cell movement and muscle contraction  Made of actin

ORGANELLES 9. Cytoskeleton

ORGANELLES 10. Cytoplasm  fluid with suspended organelles  Fluid called cytosol

NUCLEUS FEATURES 1. Nuclear envelope  Surrounds nucleus  Double layer  Has nuclear pores that provide entry and exit to nucleus

NUCLEUS FEATURES 1. Nuclear envelope

NUCLEUS FEATURES 2. Nucleolus  Produces the subunits that form ribosomes

NUCLEUS FEATURES 3. Chromatin  DNA concentrated here when cell not dividing  Forms chromosomes before cell division

4.4 PLANT CELL ORGANELLES

ORGANELLES The following are organelles that are found in plant cells, but are much less pronounced or not found at all in animal cells.

ORGANELLES 1. Vacuoles  Storage bubbles  Can store nutrients, waste, nutrients, or water  Can take up 90% of the cell

ORGANELLES 2. Plastids  Create and store chemical compounds like lipids and starches  Some have pigments

ORGANELLES 3. Chloroplasts  Type of plastid  Produces energy for the cell through photosynthesis  “plant mitochondria”  Contain chlorophyll pigment (green color)

ORGANELLES 3. Chloroplasts

ORGANELLES 4. Cell wall  Made of cellulose (a starch)  Protection and support  Surrounds the cell membrane