Basic Structure of a Cell

•No nucleus

•Archaea & Eubacteria

•One circular chromosome

•Extremely small

Prokaryotic Cells

• Has a nucleus!!!

• Membrane-bound organelles

• Plants, Animals, Fungi, & Protists

Eukaryotic Cells

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

Prokaryotes • Bacterial cells may have

plasmids, small accessory rings of DNA.

• Some bacteria have a capsule or a slime layer.

• Most bacteria have flagella.

• Some also have fimbriae that help cells attach to surfaces.

• Bacteria have a great metabolic diversity.

Comparison of Eukaryotic and Prokaryotic Cells

Eukaryotes • Eu-, “true,” karyon,

“nucleus”

• Genetic material contained in a nucleus

• Membrane-bound organelles

• Evolved from prokaryotic cells

• Includes protists, fungi, plants, and animals

•Eukaryotic

•No cell wall

•Heterotrophic

•Often highly

specialized in

multi-cellular

organisms

•May be motile

Cell wall •Outer layer that

maintains cell’s

shape & rigidity and

protects cell from

mechanical damage

•Made primarily of

cellulose

Central vacuole •Stores nutrients &

breaks down waste

products

•Contributes

significantly to plant

growth

Nuclear envelope

Nucleolus DNA

Centrosome

Golgi complex

Mitochondrion

Lysosome

Plasma membrane

CELL WALL

Wall of adjacent cell

Rough ER

Smooth ER

Ribosomes

CENTRAL VACUOLE

Micro-filaments

Intermediate filaments Micro-tubules

CHLOROPLAST Chloroplast •Contains chlorophyll,

which is the primary

pigment responsible

for photosynthesis

Organelles

• Very small (Microscopic)

• Perform various functions for a cell

• Found in the cytoplasm

• May or may not be

membrane-bound

Cell Wall • Nonliving layer that

supports and protects

the cell

• Found in plants, fungi,

& bacteria

• Made of cellulose in

plants

• Made of peptidoglycan

in bacteria

• Made of chitin in Fungi

Cell wall

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

Cytoplasm of a Cell

• Jelly-like substance

enclosed by cell

membrane

• Provides a medium

for chemical

reactions to take

place

cytoplasm

More on Cytoplasm

• Contains organelles

to carry out specific

jobs

• Found in ALL cells

cytoplasm

• Controls the normal

activities of the cell

• Contains the DNA in

chromosomes

• Bounded by a

nuclear envelope

(membrane) with pores

• Usually the largest

organelle

The Control Organelle - Nucleus

More on the Nucleus

Chromosomes:

• Tightly coiled DNA & Protein

• Contain hereditary material (genes)

• Chromosomes not dividing called

chromatin

• Each type of organism has a certain

# of them

• Humans = 46 (23 pairs)

• Fruit fly = 8 (4 pairs)

Nucleus

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

Nuclear Envelope

• Double membrane surrounding nucleus

• Also called nuclear membrane

• Contains nuclear pores for materials to enter & leave nucleus

• Connected to the rough ER

Nuclear

pores

Nucleolus

• Inside nucleus

• Cell may have 1 to 3

nucleoli

• Disappears when

cell divides

• Makes ribosomes

that make proteins

Endomembrane System

• System of transport throughout the cell

• Nuclear envelope

• Endoplasmic reticulum

• Golgi apparatus

• Lysosomes

• Vacuoles

Endomembrane System

Includes nuclear membrane connected to ER

connected to cell membrane (transport)

Endoplasmic Reticulum - ER

• Network of hollow membrane tubules throughout the

cytoplasm

• Connects to nuclear envelope & cell membrane

• Functions:

– Transports materials

through the cell

– Contains enzymes that

allow chemical reactions

– Wastes & other toxic

chemicals are made

harmless

• Two types:

– Smooth ER

– Rough ER

The endoplasmic reticulum

Rough ER: •Studded with ribosomes •Makes membrane proteins and proteins for export out of the cell

Smooth ER: •Lacks ribosomes on its surface •Is attached to the ends of rough ER •Makes cell products that are used inside the cell •Site of synthesis of lipids (including phospholipids and steroids) •Destroys toxic substances

Ribosomes

• Made of PROTEINS and rRNA

• Made in the nucleolus

• Found mostly on ER but also floating in cytoplasm

• Found in all types of cells

• “Protein factories” for cell

• Join amino acids to make proteins (process called protein synthesis)

Golgi Complex (or Apparatus)

• Flattened membrane

sacs

• Present in

almost all cells

• Receives protein and

lipid-filled vesicles

from ER

• Modifies, sorts, and

packages molecules

from ER for storage or

transport out of the cell

Vacuoles and Lysosomes

Vacuoles (large) and

vesicles (small) are

membranous sacs in the

cell that store

substances.

Lysosomes are vesicles

produced by the Golgi

apparatus.

Lysosomes contain

hydrolytic enzymes and

are involved in

intracellular digestion.

Vacuoles • Fluid filled sacks for storage

• Small or absent in animal cells

• Plant cells have a large Central Vacuole

• In plants, they store Cell Sap

• Includes storage of

sugars, proteins,

minerals, lipids,

wastes, salts, water,

and enzymes

• No vacuoles in bacterial cells

• Many protists have contractile vacuoles

Contractile Vacuole

• Found in unicellular protists like paramecia

• Regulate water intake by pumping out excess (homeostasis)

• Keeps the cell from lysing (bursting)

Lysosomes

• Contain digestive

enzymes

• Break down food,

bacteria, and worn out

cell parts for cells

• Some cells (i.e. certain

types of protists) take

in food by phagocytosis

• Lysosomes digest the

food and get rid of

wastes

Energy-Related Organelles

The two energy-

related organelles of

eukaryotes are

mitochondria and

chloroplasts .

Both organelles house

energy in the form of

ATP.

Mitochondrion (plural = mitochondria)

• Found in all eukaryotic cells

• “Powerhouse” of the cell

• Site of Cellular Respiration: generate cellular energy (ATP) by burning glucose

• More active cells like muscle cells have MORE mitochondria

Mitochondrion (plural = mitochondria)

Structure:

• Surrounded by a DOUBLE membrane

• Folded inner membrane called cristae (increases surface area for more chemical reactions)

• Interior called matrix

• Has its own DNA

Interesting Fact ---

• Mitochondria Come

from cytoplasm in

the EGG cell during

fertilization

Therefore …

• You inherit your

mitochondria from

your mother!

Chloroplasts

• Organelle found only in producers

• Never in animal, fungal, or bacterial cells

• Contains enzymes & pigments for Photosynthesis

• Photosynthesis: Use energy from sunlight to make food (glucose)

• Energy from sun stored in the Chemical Bonds of Sugars

• Contains its own DNA

Chloroplasts Structure: • Surrounded by DOUBLE membrane

• Outer membrane smooth

• Inner membrane modified into sacs called Thylakoids

• Thylakoids contain Chlorophyll – a green pigment which absorbs energy from the sun

• Thylakoids are organized into stacks called Grana and are interconnected

• Stroma – gel like material surrounding thylakoids

Process that uses solar energy to convert carbon dioxide and water into glucose and oxygen

Thylakoid discs

Stroma Inner

membrane

Outer membrane

Granum Structure of Chloroplast: • Surrounded by double

membrane

• Outer membrane is smooth

• Inner membrane is modified into sacs called Thylakoid Discs

• Thylakoid membranes contain Chlorophyll

• Thylakoids are organized into stacks called Grana and are interconnected

• Stroma – gel like material surrounding thylakoids

Cytoskeleton

• Network of filaments and tubules that extends from the nucleus to the plasma membrane

• Made of proteins

• Helps cell maintain cell shape

• Also help move organelles around

• Types:

– Microfilaments – threadlike and made of Actin

– Microtubules – tubelike and made of Tubulin

– Intermediate filaments

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

Cilia & Flagella

• Made of protein tubes called microtubules

• Microtubules arranged (9 + 2 arrangement)

• 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

Cell Movement with Cilia & Flagella