Cells

I. Cells are the basic units of life and fall under 2 categories.

A. Prokaryotic cells have a nucleoid (area where DNA isconcentrated) instead of a nucleus and do not have

membrane-bound organelles. They are alsogenerally smaller and simpler. An example is bacteria.

B. Eukaryotic cells have a nucleus and other membrane-bound organelles and are generally larger and morecomplex. Examples include animals, plants, and fungi.

1. Although they are different in many ways, both types of cells have a cell membrane, cytoplasm, DNA, and

ribosomes.

Cells(basic unit of life)

Prokaryotic Eukaryotic

Characteristics(4)

Characteristics(4)

Smaller LargerSimpler Complex

Nucleoid Nucleus

No Membrane-Bound organelles

Membrane-Bound organelles

Bacteria Animal, Plant,Fungi

DNA, ribosomes,Cell membrane,

cytoplasm

II. Eukaryotic cells have membrane-bound organelles (“little organs”) that are mainly in the cytoplasm (area outside of the nucleus).

A. The nucleus is the “brain” of the cell because it contains most of the cell’s DNA which directs the making of proteins.

1. The nucleus is surrounded by the nuclear envelope that is double-membraned perforated by nuclear pores that allows certain things in and out of the nucleus.

2. Within the nucleus is the DNA found as chromatin (thin thread-like DNA wrapped around proteins) sectioned

into chromosomes that condense during cell division.

a. The nucleolus/nucleoli is the area within the nucleus where there is a dense collection of chromatin making

ribosomal parts.

Cell Organelles

Nucleus(Brain, contains DNA)

Nuclear Envelope(double-membraned)

Chromatin/Chromosomes (DNA + Proteins)

Nuclear Pores(Allows things in/out)

Nucleolus/Nucleoli(makes ribosomes)

B. Ribosomes are the “protein factories” of the cell andmake proteins from the directions of mRNA (messenger)produced in the nucleus.

1. Ribosome parts are made in the nucleolus, shipped out through the pores, and assembled in the cytoplasm and

are made out of rRNA (ribosomal) and proteins.

2. Ribosomes can be found “free” floating in the cytoplasm or “bound” on the surface of the endoplasmic reticulum and the nuclear envelope.

Cell Organelles

Ribosomes(Protein Factories, reads mRNA)

Made of rRNAand proteins

Types

Free(cytoplasm)

Bound(On ER and

nuclear envelope)

C. The endoplasmic reticulum is a membrane system consisting of sacs and tubules and is connected to the nuclear envelope. It is divided into two main types:

1. The rough ER has ribosomes giving it a rough look and makes secretory proteins that are released from the cell, membrane-bound proteins and also produces

membranes.

a. Its products are shipped in vesicles, which are membranous sacs made by the ER itself, and moved to destinations by motor proteins.

2. The smooth ER does not have ribosomes making it smooth. Its function is to make lipids (all three types) and detoxify drugs.

Cell Organelles

Endoplasmic Reticulum(membrane system connected

To nuclear envelope)

Rough ER(with ribosomes)

Smooth ER (without ribosomes)

Makes Membrane-Bound Proteins

Detoxify drugs

Makes Lipids(3 types)

MakesMembrane

Makes SecretoryProteins

Vesicle(membranous sacs)

Motor Proteins(moves vesicles)

D. The Golgi apparatus is like the “post office” of the cell and is located near the ER. It is a stack of membranous sacs.

1. The Golgi apparatus receives proteins in vesicles made by the ER, sorts and modifies these proteins before they ship the modified proteins to where they need to go

also using vesicles.

Cell Organelles

Golgi Apparatus(post office)

Receives, sorts, modifies,and ships proteins in vesicles

E. Lysosomes are the cell’s “chop shop” and “recycling” crew and are vesicles with enzymes that break things down inside.

They are made by the RER and then modified by the G.A.

1. Lysosomes break down macromolecules into small pieces for the cell to use in a process called phagocytosis (“cell

eating”) after they fuse with vesicles containing food.

2. Lysosomes also recycle damaged organelles to reuse their parts in a process called autophagy when they fuse with vesicles containing the damaged organelles.

Cell Organelles

Lysosomes(chop shop, recycling vesicles

with enzymes)

Phagocytosis(cell eating food)

Autophagy(recycle damaged

organelles)

F. Vacuoles are the cell’s “storage warehouse” and are large membranous sacs that can be filled with water and macromolecules.

1. The central vacuole in a plant cell holds a lot of the plant cell’s water, makes the cell grow, and helps give the plant

cell its shape.

2. A contractile vacuole, found in certain organisms, pumps water out to prevent the organism from bursting.

G. Mitochondria are the cell’s “power plants” and their job is to turn food into energy for the cell.

1. Mitochondria have two membranes, the outer membrane and the inner membrane which is very folded up.

2. Between the two membranes is an intermembrane space and within the inner membrane is the fluid called the mitochondrial matrix.

a. The matrix has its own DNA, ribosomes, and proteins unique from the rest of the cell.

H. Plant cells have chloroplasts which make food usingenergy from the sun in a process called photosynthesis.

1. Chloroplast also have an inner and outer membrane with an intermembrane space and the area within the inner membrane filled with fluid is called the stroma.

2. In the stroma are membranous sacs called thylakoids that are stacked into granum/grana.

a.The stroma also has its own DNA, ribosomes and proteins separate from the rest of the cell.

III. The cytoskeleton is used for maintaining the shape of the cell and various other functions and contain 3 main

components.

A. Microfilaments are thin rods made out of proteins called actin. They can be made and broken down quickly and

are used to change a cell’s shape.

1. Microfilaments create extensions called microvilli to increase surface area to help cells increase

absorption.

B. Microtubules are hollow tubes made of tubulin and they are used as highways for motor proteins to move things around in the cell and can also be made and

broken down quickly.

1. Microtubules come out of the centrosome which is also known as the “microtubule organizing center”.

a. The centrosome in animal cells have two centrioles that help in dividing chromosomes during mitosis.

2. Microtubules are used to make cilia and flagella that help cells move fluids or through liquid.

a. Cilia are usually shorter and occur in large numbers.

b. Flagella usually are longer and occur in small numbers.

C. Intermediate filaments are a more permanent componentof the cytoskeleton and are made out of keratins, a family

of proteins that make up hair, nails, and horns.

1. Intermediate filaments are used to keep organelles that are stationary, like the nucleus, in place.