Do Now• What is a cell?• What are some parts of cells?• What is the function of a nucleus?• What do lipids make in cells?

Chapter 5 - Cells

5.1 • Fundamental discovery – all living things

are made of cells• Cells are the basic units of structure and

function in living things• First lenses – merchants of fabric• Quality of the weave• 1600’s Holland – telescope - microscope

Anton Van Leeuwenhoek• First microscope• Dutch• Tiny organisms in water• Made detailed drawings

Robert Hooke• English • Interest from van Leeuwenhoek• Thin slices of plant stems, wood and

pieces of cork• Cork – tiny chambers cells• Dead cells• Opened up the study of cells

Robert Brown• Scottish• Dark center near the center of the cell

nucleus

Matthias Schleiden• German• All plants made of cells

Theodor Schwann• All animals made of cells• Swans are animals

Rudolf Virchow• German• All cells arise from the division of

preexisting cells

Cell Theory1. All living things are composed of cells2. Cells are the basic unit of structure

and function in living things3. Cells come from preexisting cells

Cell Diversity• Cells differ in size, shape, and internal

organization• Your body has at least 200 types of cells

Size• Range in size from .2 um to 1000

microns• Most cells are between 5 to 50 um• A cell is limited in size by the ratio

between its volume and its outer surface area

• Food, oxygen and other materials must enter and exit through the cell’s surface

• The larger the cell the larger their surface area needed to maintain it

• As a cell grow its volume increases more rapidly that its surface area

• If a cell is to big the surface area is too small

Size is limited by physical factors:1. Flow of information2. Flow of materials

5.2 Parts of the Cell• Tasks of living cells – taking in food,

transforming food into energy, getting rid of wastes and reproducing

Three Main Components of Eukaryotic Cells

1. Cell membrane is the outer boundary2. Cytoplasm lies inside the cell

membrane, contains water and salts, and surrounds the organelles

3. Nucleus directs cell activities

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Eukaryotic Cell

Cell Membrane• plasma membrane• Separates the cell from the surrounding

environment• Controls the movement of materials in

and out of the cell – lets some in and some out

• Protection• Support

Structure of the Cell Membrane• The two layers are made of lipids and

proteins are embedded in them• Double layer = bilayer

Membrane Proteins• Peripheral proteins – proteins attached

to the surface of the cell membrane• Integral proteins – proteins that go

through the membrane – carbohydrates can be attached to them

• Transport molecules through the lipid bilayer (channels and pumps)

Fluid Mosaic Model• Lipid molecules that form the

membrane are fluid • The proteins are free to move about• The cell membrane has fluid properties

Carbohydrates• Attach to the proteins or lipids• Function as Id cards – allows cells to

interact with one another

Cell Wall• Surrounds cell membrane in plants• Function – protection and support• Made of 2 or more layers

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Cell Wall

• First layer – gluey substance called pectin – holds cells together

• Primary cell wall – made of cellulose – fibrous – elastic – stretches as it grows

• Third layer – only in woody plants – secondary cell wall – made of cellulose and lignin– makes cellulose more rigid

Nucleus• Large dark structure• Prokaryotes – cells that do not have a nucleus

– Ex. Bacteria

• Eukaryotes – cells that have a nucleus and membrane bound organelles– Karyon – nucleus– Pro – before– Eu - true

Nucleus• Information center• Contains DNA

– Info. To make 1000’s of molecules

• Directs all activities

Nuclear Envelope (membrane)• Consists of 2 membranes that surround

the nucleus• Nuclear pores

– in nuclear envelope– Small openings– Allows molecules in and out

Nucleolus• Small region in the nucleus• Made of RNA and proteins• Ribosomes (make proteins) made here

Chromosomes• Are DNA’s wrapped around proteins• Contain the genetic information• Fig 8-8

Cytoplasm• Area between the cell membrane and

the nucleus which contains the various organelles

• Jellylike• Contains many important structures• Many of the substances need for cell

metabolism are dissolved in the cytosol

5.3 Cytoplasmic Organelles

Organelles• Structures in the cytoplasm• Tiny structures that perform a

specialized function in the cell

Mitochondria• Powerstations• Change chemical energy stored in food into

compounds that are more convenient to use• Sites of chemical reactions that transfer

energy from organic compounds to ATP

• double membrane• Smooth outer membrane serves as the

boundary between the mitochondrion and the cytoplasm

• The inner membrane is tightly folded, forming cristae

• The cristae provide a large surface area on which many biogeochemical reactions occur

• “powerhouse of the cell”

Chloroplast• Trap energy of sunlight and convert it to

chemical energy• 3 membranes – two envelope like – 3rd

radiant energy changed to chemical (bonds)

• Only in plants

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Chloroplast

Ribosomes: Protein Factories• Small particles that are the sites of

protein synthesis • Spherical structure composed of

proteins and RNA• Ribosomes can be attached to the ER or

remain free• Smallest organelle

Endoplasmic Reticulum: Shippers• ER• Intercellular highway• Complex network of sacs• Transports materials through the inside

of the cell

Two types of ER• Rough ER (RER)

– Ribosomes attached to its surface– Protein synthesis in ribosomes– Move into RER for modification and

transport

• Smooth ER (SER)– No ribosomes– May store special enzymes and chemicals

Golgi Apparatus: Manufactures• Looks like – flattened sac of membranes

piled one on the other• Proteins sent here to be modified

(attaching carbs and lipids to them)• Modifies, collects, packages and

distributes molecules made at one location of the cell and used at another

Movement of materials – “eating”• Endocytosis – (In) process where a cell

takes in large particle too big to enter through the cell membrane

• Two types– Pinocytosis – cell engulfs liquids– Phagocytosis – cell engulfs large particles

• White Blood cells

Lysosomes: Clean-up Crews• Small membrane bound structures that

contain chemicals and enzymes for digesting certain materials

• Formed by Golgi apparatus• Only in animal cells• Break down organelles that are no

longer needed

Vacuoles and Plastids: Storage Tanks• Vacuole

– saclike structure– Stores water, salts, proteins and

carbohydrates

• Plastid – plant organelles– Store food and pigments – Ex. Chloroplast (chlorophyll)– Leukoplasts – store starch– Chromoplasts – store pigment

Cytoskeleton: Framework• Most cells are capable of some

movement – inside or out• Cytoskeleton is composed of a variety of

filaments and fibers that support cell structure and drive cell movement

• Two types

Microtubules• Hollow tubules made out of proteins• Functions

– Provide support for cell shape– Help move organelles and cytoplasm– Play a role in cell division by forming

centrioles (animals only) – spindle fibers move chromosomes

– Support and make up cilia and flagella

Cilia• Short thread like structures• Help unicellular cells move• Move substances along the cell’s

surface (humans)

Flagella• Long whip-like structures• Move single celled organisms about

Microfilaments• Long thin fibers that function in the

movement and support of the cell• Move the cytoplasm – cytoplasmic

streaming

5-4 Movement of Materials through the cell membrane

• Every cell is in a liquid environment• Liquid environment makes it easier for

food, oxygen and water to move in and out

Diffusion – Passive Transport (No energy, No ATP)• Molecules are in constant motion• Tend to spread out randomly in space• Molecules move from an area of greater

concentration to an area of lesser concentration

• Diffusion – process by which molecules move from greater to lesser

Equilibrium• Concentration of substances on both

sides of the membrane are the same• Molecules are still moving back and

forth but equally• Molecules always try to get to this

Permeability• Determines what moves across• Permeable – substance can move in and

out• Impermeable – substance can’t move• Selectively permeable – some things

can pass some can’t – characteristic of biological membranes

Osmosis – Passive Transport• Diffusion of water molecules across a

selectively permeable membrane• Water passes through cell membranes

rapidly• Moves greater to lesser

• Hypotonic solution – Solution in which the concentration of solutes is lower than inside the cell

• Isotonic solution – Solution in which the concentration of solutes in and outside the cell is equal

• Hypertonic solution – solution in which the concentration of solutes is higher than inside the cell

Osmotic pressure • Turgor pressure• force exerted by water molecules hitting

the membrane• Causes water to move• High pressure to low pressure

Osmotic pressure – Problems for a cell• Cytoplasm filled with salts, sugars and

proteins• Cell has a low concentration of water

inside as compared to outside• Water would continuously move in – cell

would burst

How cells deal1. Ex. Cells in a fluid like blood not in water –

concentrations are equal2. Plants and bacteria – cell wall keeps cell

from exploding even under high osmotic pressure but they are very vulnerable

3. Pump it outEx. Unicellular organisms – paramecium –

contractile vacuole – pumps it out

Facilitated Diffusion• Passive transport• Movement occurs from greater to lesser

conc.• Need a concentration gradient• Molecules brought in by a carrier protein• Fast, specific• Facilitates or helps

Active Transport – 2 types• Needs energy• Move materials against a concentration

gradient• Lesser to greater conc.

1. Protein Pumps• Pump molecules into the cell Ca, K,

Na• Need energy• Sodium potassium pump

2. Endocytosis (In)• Process of taking food into the cell by

surrounding it with the cell membrane• Brings in large molecules, clumps of

food and whole cells• Two Types

– Phagocytosis – large particles– Pinocytosis – liquid, small particles

• Exocytosis – large molecules out of cell - exit

5-5 Cell Specialization

• Specialization – cells are often uniquely suited to perform a particular function in an organism

Factory in Miniature• Pancreas – cells produce digestive

enzymes• Lots (100x) more ER and ribosomes• More golgi apparatus too

Light Sensitive Cell• Eye cells – one end lots of mitochondria,

the other end contains lots of sacs full of rhodopsin which detects light and signals the other cells vision

5-6 Levels of Organization

• Cells tissues organs organ system organism

Tissue• Group of similar cells that perform a

similar function• Animals have 4 types - muscle, nerve,

epithelial and connective

Organs• Group of tissues that work together to

perform a specific function

Organ system• Group of organs working together to

perform a specific function• Humans – 11 systems

• The overall specialization and interdependence of cells, is one of the remarkable attributes of living things

The End