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

Cell Specialization & Levels of

Organization

Organism Organization

• Organisms are highly organized.

• Organization begins with the basic unit of

matter – an atom

• Atoms join together to make molecules –

carbohydrates, proteins, lipids

• Molecules join with other molecules to

make cells

• Cells join with other cells to form tissues

• There are four types of tissues which make

up organs

• Organs make up organ systems

• Organ systems make up an organism

Levels of Organization

• Molecules

• Cells

• Tissues

• Organs

• Organ Systems

• Organism

Goes from smallest to largest

Cell Specialization

• The cells in our body are specialized to

perform certain functions.

– Ex. The cells lining our stomach are

specialized to secrete mucous and digestive

enzymes

Cells

• The body is made up of individual

cells.

Light receptor cells

muscle cells

nerve cells

mucous cells

Tissues

• Cells are grouped into specialized groups called tissues

– Some cells which line the stomach produce digestive enzymes. Together they make up a tissue.

– The cells in our eye which capture light are another type of tissue.

– The cells in our muscles can contract.

Organs• Organs are made up of groups of tissue

which work together to perform a specific

function.

– The Heart is made up of muscle tissue, nerve

tissue and connective tissue.

– The stomach is made up of muscle tissue and

epithelial tissue.

Organ System

• An organ system is a group of organs which work together to perform a specific function.

Nervous system Digestive system

Circulatory system

Chapter 5 - Cells

Cell Theory

1. All living things are composed of cells

2. Cells are the basic unit of structure and

function in living things

3. 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

micrometers (um)

• 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

https://learn.genetics.utah.edu/conte

nt/cells/scale/

• The larger the cell the larger their surface

area needed to maintain it

• As a cell grows its volume increases more

rapidly that its surface area

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

small

Size is limited by physical factors:

1. Flow of information

2. 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 boundary

2. 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

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

Cytoplasm

• Area between the cell membrane and the

nucleus which contains the various

organelles

• Jellylike

• Contains many important structures

• Many of the substances needed 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

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 organelle

– 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

1. 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

Homeostasis and

Feedback

Mechanisms

Living Things Maintain a Stable

Internal Environment

• Homeostasis: The ability to maintain stable

conditions that are necessary for life.

– Animals: Sweating, shivering, thirst, hunger.

– Plants: Plants grow towards the light and away

from gravity.

Feedback Mechanisms

• Homeostasis is maintained by internal

feedback mechanisms.

• Feedback mechanisms return the body to

its normal set point.

Feedback Mechanisms

• Negative feedback – puts the body

back into its original state by

inhibiting the stimulus that’s causing

the change.

– Temperature

– Blood pH

– Blood sugar

– Calcium levels

– Blood pressure

• Most feedback mechanisms in the

body are negative feedback

Feedback Mechanisms

• Positive feedback – Increases the stimulus

causing more of the effect.

– Childbirth – oxytocin

– Blood clotting

– Lactation

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

• https://www.youtube.com/watch?v=CNkP4

rycLbI – agar cubes revisited

•

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 concentration

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 deal

1. Ex. Cells in a fluid like blood not in water –

concentrations are equal

2. Plants and bacteria – cell wall keeps cell

from exploding even under high osmotic

pressure but they are very vulnerable

3. Pump it out

Ex. 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