Different Cell Types And Structures

BASIC CELL TYPES AND STRUCTURES

Basic Structure of a Cell

History of Cells & the Cell Theory

Rudolf Virchow

Cell Specialization

CELL THEORY

• All living things are made of cells
• Cells are the basic unit of structure and function in an organism (basic unit of life)

Cells come from the reproduction of existing cells (cell division)

Prokaryotes – The first Cells

• Cells that lack a nucleus or membrane-bound organelles
• Includes bacteria
• Simplest type of cell

Single, circular chromosome

Prokaryotes

• Nucleoid region (center) contains the DNA
• Surrounded by cell membrane & cell wall (peptidoglycan)

Contain ribosomes (no membrane) in their cytoplasm to make proteins

Eukaryotes

• Cells that HAVE a nucleus and membrane-bound organelles
• Includes protists, fungi, plants, and animals

More complex type of cells

Eukaryotic Cell

• Contain 3 basic cell structures:
• Nucleus
• Cytoplasm with organelles

Cell Membrane

Two Main Types of Eukaryotic Cells

Plant Cell

Animal Cell

Organelles

Organelles

• Very small structures (Microscopic)
• Perform various functions for a cell
• Found in the cytoplasm

May or may not be membrane-bound

Cell or Plasma Membrane

• Composed of double layer of phospholipids and proteins
• Surrounds outside of ALL cells
• Controls what enters or leaves the cell (selectively permeable)
• Living layer
• Outside
• of cell
• Inside
• of cell
• (cytoplasm)
• Cell
• membrane
• Proteins
• Protein
• channel
• Lipid bilayer
• Carbohydrate

chains

Phospholipids

• Heads contain glycerol & phosphate and are hydrophilic (attract water)
• Tails are made of fatty acids and are hydrophobic (repel water)
• Make up a bilayer where tails point inward toward each other

Can move laterally to allow small molecules (O2, CO2, & H2O to enter)

The Cell Membrane is Fluid

Molecules in cell membranes are constantly moving and changing

Cell Membrane Proteins

• Proteins help move large molecules or aid in cell recognition
• Peripheral proteins are attached on the surface (inner or outer)

Integral proteins are embedded completely through the membrane

Cell Membrane in Plants

• Lies immediately against the cell wall in plant cells
• Pushes out against the cell wall to maintain cell shape

Cell membrane

Cell Wall

• Found outside of the cell membrane
• Nonliving layer
• Supports and protects cell
• Found in plants, fungi, & bacteria

Cell wall

Cytoplasm of a Cell

• Jelly-like substance enclosed
• Provides a medium for chemical reactions to take place

cytoplasm

More on Cytoplasm

• Contains organelles to carry out specific jobs

cytoplasm

The Control Organelle – Nucleus

• Controls the normal activities of the cell

Contains the DNA in chromosomes

Bounded by a nuclear envelope (membrane) with pores Usually the largest organelle

More on the Nucleus

Each cell has fixed number of chromosomes that carry genes Genes control cell characteristics

Nucleus

Nuclear Envelope

• Double membrane surrounding nucleus
• Also called nuclear membrane
• Contains nuclear pores for materials to enter & leave nucleus

Nuclear pores

Inside the Nucleus –

• The genetic material (DNA) is found
• DNA is spread out
• And appears as CHROMATIN
• in non-dividing cells
• DNA is condensed & wrapped around proteins forming
• as CHROMOSOMES

in dividing cells

What Does DNA do?

• DNA is the hereditary material of the cell

Genes that make up the DNA molecule code for different proteins

Nucleolus

• Inside nucleus
• Disappears when cell divides

Makes ribosomes that make proteins

Cytoskeleton

• Helps cell maintain cell shape
• Also help move organelles around
• Made of proteins
• Microfilaments are threadlike & made of ACTIN

Microtubules are tubelike & made of TUBULIN

Cytoskeleton

MICROTUBULES

MICROFILAMENTS

Centrioles

• Found only in animal cells
• Paired structures near nucleus
• Made of bundle of microtubules
• Appear during cell division forming mitotic spindle

Help to pull chromosome pairs apart to opposite ends of the cell

Mitochondrion

• (plural = mitochondria)
• “Powerhouse” of the cell
• Generate cellular energy (ATP)
• More active cells like muscle cells have MORE mitochondria
• Both plants & animal cells have mitochondria

Site of CELLULAR RESPIRATION (burning glucose)

MITOCHONDRIA

• Surrounded by a DOUBLE membrane
• Folded inner membrane called CRISTAE (increases surface area
• for more chemical
• Reactions)
• Has its own DNA

Interior called MATRIX

Interesting Fact —

• Mitochondria Come from cytoplasm in the EGG cell during fertilization
• Therefore …

You inherit your mitochondria from your mother!

SPERM CELL

Endoplasmic Reticulum – ER

• Network of hollow membrane tubules
• Connects to nuclear envelope & cell membrane
• Functions in Synthesis of cell products & Transport

Two kinds of ER —ROUGH & SMOOTH

Rough Endoplasmic Reticulum (Rough ER)

• Has ribosomes on its surface

Makes membrane proteins and proteins for export out of cell

Rough Endoplasmic Reticulum (Rough ER)

• Proteins are made by ribosomes on ER surface
• They are then threaded into the interior of the Rough ER to be modified and

transported

Functions of the Smooth ER

• Makes membrane lipids (steroids)
• Regulates calcium (muscle cells)

Destroys toxic substances (Liver)

Ribosomes

• Made of PROTEINS and rRNA
• “Protein factories” for cell
• Join amino acids to make proteins through protein synthesis



Ribosomes

• Can be attached to
• Rough ER
• OR

Be free (unattached) in the cytoplasm

Golgi Bodies

• Stacks of flattened sacs
• Have a shipping side (cis face) & a receiving side (trans face)
• Receive proteins made by ER
• Transport vesicles with modified proteins pinch off the ends
• Transport vesicle
• CIS

TRANS

Golgi Bodies

• Look like a stack of pancakes
• Modify, sort, & package
• molecules from ER
• for storage OR

transport out of cell

Golgi Animation

Materials are transported from Rough ER to Golgi to the cell membrane by VESICLES

Lysosomes

• Contain digestive enzymes
• Break down food, bacteria, and worn out cell parts for cells
• Play important role in Programmed cell death (APOPTOSIS)

Lyse & release enzymes to break down & recycle cell parts)

Lysosome Digestion

• Cells take in food by phagocytosis

Lysosomes digest the food & get rid of wastes

Cilia & Flagella

Function in moving cells, in moving fluids, or in small particles across the cell surface

Cilia & Flagella

• Cilia are shorter and more numerous on cells

Flagella are longer and fewer (usually 1-3) on cells

Vacuoles

• Fluid filled sacks for storage
• Small or absent in animal cells

Plant cells have a large Central Vacuole

Vacuoles

• In plants, they store Cell Sap

Includes storage of sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes

Chloroplasts

• Found only in producers (organisms containing chlorophyll)
• Use energy from sunlight to make own food (glucose)

Energy from sun stored in the Chemical Bonds of Sugars

Brain storm

What is the largest eukaryotic cell?

Organelles

• Very small (Microscopic)
• Perform various functions for a cell
• Found in the cytoplasm

May or may not be membrane-bound

Cell or Plasma Membrane

• Composed of double layer of phospholipids and proteins
• Surrounds outside of ALL cells
• Controls what enters or leaves the cell
• Living layer
• Outside
• of cell
• Inside
• of cell
• (cytoplasm)
• Cell
• membrane
• Proteins
• Protein
• channel
• Lipid bilayer
• Carbohydrate

chains