INTRO TO CELLSEukaryotes vs Prokaryotes

Plasma Membrane

Two Basic Cell Types All cells contain organelles

Small, specialized structures Has a specific function in the cell

Prokaryotes Do not contain any membrane-bound organelles Most unicellular organisms Example: bacteria

Eukaryotes Contain membrane-bound organelles Most multicellular oranisms Example: humans Note: amoebas, algae and yeast are unicellular but

eukaryotes

Prokaryotes vs. Eukaryotes

Eukaryotic cells are generally 1- 100 time bigger than prokaryotes

CELL ORGANELLES

Animal Cell

Cell Organelles Organelle= “little

organ” Found only inside

eukaryotic cells Everything in a

cell except the nucleus is cytoplasm Clear, gelatinous

fluid inside the cell

Plasma Membrane Boundary of the cell Made of a phospholipid bilayer

Cytoskeleton Acts as skeleton

and muscle Provides shape

and structure Helps move

organelles around the cell

Made of three types of filaments

Nucleus Control center of the

cell Contains chromatin,

strands of genetic material (DNA) that condense to make chromosomes

Surrounded by a double membrane

Usually the easiest organelle to see under a microscope

Usually one per cell

Nucleolus Inside the nucleus Makes ribosomes

Ribosome Site of protein

synthesis Found attached to

rough ER or floating free in cytoplasm

Produced in a part of the nucleus called the nucleolus

That looks familiar…what is a polypeptide?

Endoplasmic Reticulum A.k.a. “ER” Connected to

nuclear membrane

Highway of the cell

Rough ER: studded with ribosomes; it makes proteins

Smooth ER: no ribosomes; it makes lipids

Golgi Apparatus Looks like a stack

of plates Stores, modifies

and packages proteins

Molecules transported to and from the Golgi by means of vesicles

Lysosomes Garbage disposal

of the cell Contain digestive

enzymes that break down wastes

Which organelles do lysosomes work

with?

Mitochondria “Powerhouse of

the cell” Cellular

respiration occurs here to release energy for the cell to use

Bound by a double membrane

Has its own strand of DNA

Which type of cell do you think has the most mitochondria present?

Cell Wall Found in plant

and bacterial cells Rigid, protective

barrier Located outside of

the cell membrane

Made of cellulose (fiber)

Chloroplast Found only in

plant cells Contains the

green pigment chlorophyll

Site of food (glucose) production

Bound by a double membrane

Vacuoles Large central

vacuole usually in plant cells

Many smaller vacuoles in animal cells

Storage container for water, food, enzymes, wastes, pigments, etc.

Centriole Aids in cell division Usually found only in

animal cells Made of microtubules

Where else have we talked about

microtubules?

Quick Review Which organelle is the control center of the cell?

Nucleus Which organelle holds the cell together?

Cell membrane Which organelles are not found in animal cells?

Cell wall, central vacuole, chloroplasts Which organelle helps plant cells make food?

Chloroplasts What does E.R. stand for?

Endoplasmic reticulum

A MORE IN DEPTH LOOK AT THE PLASMA MEMBRANE

Plasma Membrane Flexible boundary between the cell and

its environment Allows a steady supply of nutrients (ie:

glucose, amino acids, lipids) to come into the cell no matter what the external conditions are

Plasma Membrane maintains homeostasis

Too much of any nutrient can be harmful to the cell If levels become too high the excess is

removed through the plasma membrane Maintains cells balance (homeostasis)

The Plasma Membrane is Selectively Permeable

Selective permeability: a process in which a membrane allows some molecules to pass through while keeping others out Similar to a window screen (lets fresh air in

but keeps most insects out) Water is allowed to freely enter but other

particles such as sodium and calcium ions must be allowed into the cell only at certain times

Structure of Plasma Membrane Recall: Lipids are

large molecules composed of Glycerol + 3 fatty

acids If a phosphate group

replaces a fatty acid then a phospholipid is formed. Glycerol + 2 fatty

acids + phosphate group

Polar Head

(includes

phosphate groupNonpolar

tail (fatty acids)

Phospolipid Molecule

Plasma membrane is composed of a phospholipid bilayer

Has 2 layers of phospholipids back to back

Create a Drawing Drawing must be similar to drawing on

page 177 and must include: A title Labeled parts Colored On back of drawing:

Facts about the phospholipid bilayer All bold faced words (include definitions) Additional Facts should include information you

think is important? (at least 8 facts in addition to bold faced words)

Important Facts 2 fatty acid tails – nonpolar (hydrophobic)

Avoids water Head containing phosphate group – polar

(hydrophilic) Allows the cell membrane to interact with its

watery environment Water molecules will not easily move

through the barrieer because they are stopped by the water insoluble layer of fatty acid tails.

More important facts… Fluid Mosaic Model

Model of plasma membrane – describes the plasma membrane as a phospholipid bilayer with embedded proteins

Phospholipids move within the membrane just like water molecules move with currents in a lake

Proteins also move (like boats with their decks above water and hulls below)

Proteins create a “mosaic” or pattern

More facts… Other components of the membrane:

Cholesterol Helps to stabilize the phospholipids by

preventing fatty acid tails from sticking together Transport proteins

Span the entire membrane Help form the selectively permeable membrane

that regulates which molecules enter and which molecules leave

Move needed substances and waste through the plasma membrane