The Cell and its parts

Why do we care about a cell?

•Basic unit of life.

•They make up EVERY living thing.

•You are made up of about 50 trillion different types of cells!

How did we get cells in the first place?•Robert Hooke (1665)

•Coined the term “cell” by looking at a piece of cork.

•This is what he saw…

We didn’t just know…

•Cells didn’t exist until the 1600s and even then scientists didn’t know what they were used for.

•It took multiple steps and scientists to come up with the ideas concerning cells.

•This has come to be known as the Cell Theory.

The scientists and their contributions to the cell theory•Matthias Schleiden: 1838 German

scientist▫Came to the conclusion that all plants were

made of cells

•Theodor Schwann: 1839 German scientist▫Based off of Schleiden’s work concluded all

animals were made out of cells

When we work together…

•Together Schleiden and Schwann founded the first and second points to the cell theory:

•All living things are made out of cells.

•Cells are the basic units of structure and function in living things.

The most famous Rudolf of all?

•Rudolf Virchow: 1855 German physician▫Studied the work of S & S and concluded

that all cells come from the division of existing cells

▫Cells cannot just “happen”

•This created the third point to the cell theory: New cells are produced from existing cells.

The Cell Theory

•All living things are composed of cells.

•Cells are the basic units of structure and function in living things.

•New cells are produced from existing cells.

So just because they say it happens we believe them?•No, over the course of hundreds of years

other scientists studied the same material as Schleiden, Schwann, and Virchow.

•They all observed similar findings, repeated experiments with the same outcome, which is why it is now referred to as the cell theory.

What are the types of cells

•Two main categories of cells:▫Prokaryotes▫Eukaryotes

•What separates them from each other is one part that is inside of them called the Nucleus.

But wait, a nucleus is apart of an atom?•Yes, it is

•Scientists also use this name to apply to cells as well because the name suits its purpose and function of the cell.

•Nucleus: A large membrane-bound structure that contains the cell’s genetic material. (DNA!)

Prokaryotes

•Pro= “Before”•Karyon= “kernel” refers to a nucleus

•Definition: A cell that does not contain a nucleus

Characteristics of Prokaryotes

•Don’t have a nucleus•Generally smaller•Single-celled only•Less complicated•They still do everything as normal•Most common example: Bacteria

Eukaryotes

•Eu= “true”•Karyon= “kernel”

•Definition: A cell that has a nucleus.

Characteristics of Eukaryotes

•Does have a nucleus with genetic material•Generally larger•Contain dozen of other types of structures•Single celled or multicellular•Examples: Plants, animals, fungi

Prokaryotes•Don’t have a nucleus•Generally smaller•Single celled•Less complicated•They still do everything as normal•Most common example: Bacteria

Eukaryotes•Do have a nucleus with genetic material•Generally larger•Contain dozen of other types of structures•Multicellular or single celled•Examples: Plants, animals, fungi

Detour: Molecules of Life

•Before we dive into the cell we will need to know the structures (molecules) that are needed in order for all this to happen

4 Organic Molecules

•Organic: It is made with Carbon

•Carbohydrates – sugars and starches•Lipids – fats•Proteins – made of amino acids, carry out

several functions•Nucleic acids – genetic information and

protein synthesis

Carbohydrates

•Carbon (C), Hydrogen (H), Oxygen (O)

•Use: Main source of energy for most life.▫Also used for structural (building) purposes

•When sugars are stored inside cells its called starch

Types of Sugars and Starches

•Monosaccharide: A single sugar molecule▫Ex: Glucose, galactose (milk), fructose

(fruits)

•Disaccharides: Two sugar molecules put together

•Polysaccharides: Many sugar molecules put together

Importance of Polysaccharides

•Store excess sugar away as glycogen or animal starch.

•Our bodies release it when our blood sugar runs low or when we do heavy activities and need to power our muscles

•Plants make cellulose which makes plants sturdy and rigid. It’s also in wood and paper.

Lipids

•Carbon (C), Hydrogen (H), Oxygen (O)

•Generally do not dissolve (soluble) in water• Items like oils and fats are lipids

•Uses: ▫Can be used to store energy (not best)▫Biological membranes and waterproof

surfaces

How lipids are made

•Simplest are made of 3 glycerol molecules and 3 fatty acid tails

•Two types of lipids Saturated = single bonds, max H

Unsaturated = double or triple bonds, fewer H

Proteins•Variety of sizes, shapes, and jobs

•Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Sulfur (S)

•Made of amino acids linked together▫20 different amino acids made with 20

different “R” groups

Special proteins…Enzymes

•Catalysts for living cells▫Speed up a reaction, but are not used up

▫Provides a surface for the reaction.

Nucleic Acids•Carbon (C), Hydrogen (H), Oxygen (O),

Nitrogen (N), Phosphorus (P)

•Uses: make DNA and RNA (Very important!)

•Made of Nucleotides▫5 Carbon Sugar▫Phosphate Group▫Nitrogen Base

Cellular Vision

•http://www.studiodaily.com/main/searchlist/6850.html

Taking a closer look at the eukaryotes

•Organelles▫Literally means “little organs”

▫They are specialized structures that carry out functions inside of the cell

▫Organs: Humans::Organelles: Cells

Two major subsections of a cell

•The nucleus and the cytoplasm

•Cytoplasm: The portion of the cell outside of the nucleus▫Its also the liquid portion of the cell

•Analogy: Lawns, Parks, Work floor, Classrooms

A closer look at the Nucleus

•Controls most of the cell processes

•Contains the cell’s DNA▫DNA: Coded instructions for making

proteins and other important molecules

•Analogies: Principal, Boss, Mayor

Nuclear Envelope

•Surrounds the nucleus

•Composed of two membranes, which protects

•Has thousands of nuclear pores that allow material into and out of the cell

•Analogy: Secretary, Body Guards

What’s inside the Nucleus

•Chromatin▫DNA bound to proteins. Found all over

nucleus.•Chromosomes

▫Condensed (Packaged) Chromatin. ▫Only occurs when the cell divides.

•Nucleolus▫Assembles ribosomes

Ribosomes•Small particles of RNA and protein found

throughout the cytoplasm

•They produce proteins, structures that we need to live

•They receive orders from the nucleus to make proteins

•Analogy: Teachers, Workers, lumber/brickyard

Endoplasmic Reticulum (The ER)•Internal membrane system

•Function: Lipid components of the cell membrane are assembled along with proteins and other materials

•Analogy: Roads, Highways, Hallways

•There are two types of Endoplasmic reticulum

Rough E.R.

•Portion of the E.R. involved with making proteins (otherwise known as protein synthesis)

•Given its name because it has ribosomes all over its surface

•Proteins that are released from the cell are made here

Smooth E.R.

•Ribosomes are not found on the Smooth ER

•Smooth ER contains enzymes that perform special tasks▫Detox of drugs

▫Making lipids for the membranes

Where we have been, where we are going• Nucleus

▫ Nuclear Envelope▫ Nucleolus▫ Chromatin/Chromosomes

• Cytoplasm• Rough and Smooth ER• Ribosomes

• Golgi Bodies• Lysosomes• Vacuoles• Mitochondria• Chloroplasts• Cytoskeleton

▫ Microtubules▫ Microfilaments

• Cell Membrane• Cell Wall

Golgi Bodies

•Stack of membranes one on top of another

•Function: Modify, sort, and package proteins and other materials that go outside the cell

•Analogy: Mailman, Shipping Dept.

Lysosomes

•Small organelles with enzymes in them.

•Functions: ▫Digestions of organic molecules▫Breaking down old organelles that have no

use

•Analogy: Janitors, Garbage dump

Vacuoles•Sac-like structures in the cell

•Store materials such as water, salts, proteins, and carbohydrates.

•Vacuoles in plants are different from animals▫Much bigger to support leaves and flowers

•Analogy: Storage closet, Water Towers and Warehouses

Mitochondria

•An organelle that contains two membranes

•Function:▫Convert chemical energy in food to a

usable energy for the cell

•We inherit this organelle from the egg (Mom)

•Analogy: Powerplant, “Powerhouse”, Electricity

Chloroplasts

•An organelle that also contains two membranes▫Found only in plants!

•Function: ▫Takes solar energy and converts into usable

cellular energy through photosynthesis

•Analogy: Greenhouse, Solar energy collectors

How did we get Mito’s and Chloro’s•They are the only two organelles that

contain their own DNA molecules.

•Believed that they were once prokaryotic cells that were “swallowed up” by eukaryotes

•Lynn Margulis: (1970): Endosymbiotic theory

Cytoskeleton

•Supporting structure in the cell

•Functions:▫Maintains shape and internal organization▫Involved with movement

•Analogy: Steel/Cement, Walls and roofs

Two parts of the CytoskeletonMicrofilaments Microtubules

• Thread-like structures

• Framework that supports the cell

• Also involved with the movement of the cell

• Analogy: Walls that keep the house up, our muscles

• Hollow structures

• Maintains cell shape

• Important in cell division

• Analogy: Bones

Cell Membrane vs. Cell WallCell Membrane Cell Wall

• Thin, flexible barrier

• All cells have them

• Made from lipids

• Function: Regulates what goes in and out of the cell

• Analogy: Border patrol, fence, city gates

• Strong supporting layer around the membrane

• Found in almost everything but animals

• Made from carbohydrates and proteins

• Function: Provided support and protection for the cell

• Analogy: Barbed wire, Electric Fence

Plants vs. Animals

•To the naked eye we look very different

•At a cellular level, they are very similar

•They contain a lot of the same characteristics with a couple of slight variations

The similarities

•Each has the following:▫Mitochondria▫Nucleus and its structures▫Cytoplasm▫Ribosomes▫Cytoskeleton (Including

microfilaments/tubules)▫Rough and Smooth Endoplasmic Reticulum▫Cell Membrane▫Golgi Bodies

Plant Differences•Chloroplasts

▫Why?▫They are responsible for making energy for the

plant to use from the sun▫Reason for why plants don’t need to take in food

like animals do

•Vacuole: One large structure▫Takes up ~90% size of the cell▫Aids in the support of leaves and flowers

•Cell wall: The protective layer outside membrane▫Rigid cell wall containing cellulose (carbohydrate)▫Also aids in the support and structure of the cell

Animal Differences

•Vacuoles: much smaller and more numerous▫Still has the function of storage

•Lysosomes: Are common in animals, very rare in plants▫Does that mean that plants are messy and

junk is everywhere?▫No, they have a similar structure that does

a very similar type job

The appearance of each one

•Because of the lack of a cell wall animal cells are always round/spherical shape

•Because they do have a cell wall and are “locked” in position, they have a square shape▫Also adds additional strength to the cells▫Lack motor function (being able to move)

▫Try stacking marbles compared to blocks