Here’s what a “cell” is!

Cell - the smallest unit of an organism that carries on the functions of life

A cell can perform all the processes of life.

•Many Sizes:

•nerve cells - up to a meter long

•human egg cell - dot of an i

•bacteria - 80,000 could fit in the dot of an i

•Different shapes:

•Related to their function (job)

•Cell types:

•Prokaryotic cell - very simple; no

membrane-bound structures

(ex: bacteria)

•Eukaryotic cell - more advanced; has

membrane-bound structures

(ex: animal cells, plant cells)

Early Cell Scientists

Robert HookeRobert Hooke (1665)• An English scientist who looked at slices

of cork under a crude compound microscope and saw “a great many little boxes” that he called “cells.” First person to see cells.

• “Cell” comes from the Latin word for “little room.”

Early Cell Scientists

Anton van LeeuwenhoekAnton van Leeuwenhoek (1673)

• A Dutch shopkeeper who looked at pond water using a simple microscope and saw what he called “animalcules.”

• Today, we call them single-celled organisms.

An Early Simple Microscope

Early Cell Scientists

Matthias SchleidenMatthias Schleiden (1838)• A German botanist who discovered

that all plants are made up of similar units, or cells.

Early Cell Scientists

Theodor SchwannTheodor Schwann (around 1830)

• A German scientist who stated that all plants and animals are made up of building blocks, or cells.

• He also observed that there are similarities and differences between plant and animal cells.

Early Cell Scientists

Rudolph VirchowRudolph Virchow (1858)• This German physician also

reported that every living thing is made of up vital units, known as cells. He also predicted that cells come from other cells.

Cell Theory

1. All living things are made up of one or more cellsone or more cells.

2. Cells are the basic unit of basic unit of structurestructure and and functionfunction in living things.

3. All cells come only from other other livingliving cells cells.

Cell StructureAnimal Cell Plant Cell

Cell Structure

• A cell is like a small town:Different parts have different and specialized jobs.

• Plant cells and animal cells have many similar structures, but have several important differences.

Cell MembraneStructure:

•Outer boundary of the cell

•Double lipid membrane

•Selectively permeable

Cell MembraneFunction (job):

•Protects inside

•Supports/gives shape

•Controls what enters/leaves - “gatekeeper”

•Helps maintain homeostasis (ability to keep a stable environment)

Analogy:

Townline

Cell WallStructure:

•ONLY IN PLANTS

•Made of cellulose

•Strong & rigid

•Dead layer

Cell WallFunction (job):

•Protects/support

•Gives shape

Analogy:

Castle Wall

CytoplasmStructure:

•Jelly-like substance

•80% water

CytoplasmFunction (job):

•Organelles float in cytoplasm

•Materials for growth are found in cytoplasm

•Expels waste through cell membrane

Analogy:

•Town property

NucleusStructure:

•Surrounded by nuclear membrane

•Usually round/oval

•Near center

NucleusFunction (job):

•Control center of cell

•Controls cell activities

•Contains chromosomes

Analogy:

Mayor and city council

MitochondriaStructure:

•Has an outer membrane and an inner folded membrane

•Rod shaped

MitochondriaFunction (job):

•Cellular respiration

•Turns food into useable energy (ATP)

Analogy:

Power house (powerplant)

RibosomesStructure:

•Tiny, round, dark

•Can be free floating or attached to endoplasmic reticulum

RibosomesFunction (job):

•Protein factories

•Assembles proteins used in growth, repair and control

Analogy:

Factory

Endoplasmic ReticulumStructure:

•Network of tubes and canals

•Smooth ER - no ribosomes attached

•Rough ER - ribosomes are attached

Endoplasmic ReticulumFunction (job):

•Transports materials “intracellular highway”

Analogy:

Roads and highways

Golgi BodiesStructure:

•Series of flattened sacs

Golgi BodiesFunction (job):

•Processes, packages and secretes material

•Materials that are transported by the ER usually stop first at the Golgi bodies where they are stored or altered before moving to other parts of the cell

Analogy:

Center for Manufacturing and shipping (UPS)

LysosomesStructure:

•ONLY IN ANIMALS

•Contains powerful digestive chemicals

LysosomesFunction (job):

•Contains digestive enzymes (chemicals), breaks things down

•“suicide sac”

Analogy:

Garbage collectors

VacuolesStructure:

•Fluid-filled sacs that float in the cytoplasm

VacuolesFunction (job):

•Stores water and food materials

•Stores waste and helps the cell get rid of waste

•Plant cells contain a large central vacuole - filled with water - helps give shape

Analogy:

Storage warehouse

ChloroplastStructure:

•ONLY IN PLANT CELLS

•Green, oval-shaped

•Contains green pigment chlorophyll

ChloroplastFunction (job):

•Site of photosynthesis

•Traps the sun’s energy to make glucose

Analogy:

Greenhouse or solar cell

How are plant and animal cells different?

PLANT CELLS:

Have cell walls,

chloroplasts,

large vacuoles

How are plant and animal cells different?

ANIMAL CELLS:

Have lysosomes

How are different cells adapted to their functions?

Muscle Cells: Have large

quantities of mitochondria for

energy.

Plant Cells: Rigid cell walls allow plants to grow upright.

How are different cells adapted to their functions?

Red Blood Cells: Thin, flexible discs allow them to squeeze through tiny blood vessels.

Nerve Cells: Have long projections through which

messages are sent throughout the body.

VocabularyPermeableDiffusionOsmosisMitosis

ChromosomeCentriole

Centromere

Organization of Living Things

Five main levels of organization1. Cell2. Tissue3. Organ4. Organ System5. Organism

Tissue

• Example: Muscle• Tissues are made of

specialized cells.

Organ

• Examples: Heart, Lung, Brain• Found in both plants and

animals.• Composed of tissue that is

organized into groups that work together to perform special functions.

Organ System

• Example: Circulatory System• A group of organs that work

together.

10 Organ Systems in complex organisms

(humans, dogs, birds, etc.)

1.Circulatory2.Digestive3.Nervous4.Respiratory5.Skin

6.Skeletal7.Muscular8.Reproductive9.Excretory10.Endocrine

ORGANISMS

• Different organ systems work together to keep the organism alive.

QUESTION:• Classify the following as a tissue,

organ, or organ system.a. Brain, spinal cord, and nerves b. Heartc. Group of muscle cells

QUESTION:

• Can a single-celled organism contain tissue? Explain.

QUESTION:

• Give one example of each:a. Cell c. Tissueb. Organ d. Organism

Cell Processes• Think of the cell membrane as

being like a gatekeeper at an ancient castle.

• It was the gatekeeper’s job to decide when to open the gate and allow people to pass into and out of the castle.

• The gatekeeper controlled the permeability of the castle walls.

Permeable• If the gatekeeper allowed friendly

folk to enter, he or she was allowing the castle walls to be permeable.

• Permeable means that in cells certain substances can move freely through the membrane.

Impermeable

• If the gatekeeper prevented enemies from entering, he or she was allowing the castle walls to be impermeable.

• Impermeable means that in cells substances cannot pass freely through the membrane.

Selectively Permeable• Because the gatekeeper can select

those that can enter the castle, he or she was allowing the castle walls to be selectively permeable.

• Because the cell membrane allows some materials to pass through and is impervious to others it is selectively permeable.

Substances that move into or out of a cell do so by one of

three methods:

Diffusion• This is the main way by which

substances move into and out of cells.• The process by which molecules tend

to move from an area of higher concentration to an area of lower concentration.

• Eventually there is an equal concentration of molecules inside and outside of the cell.

Osmosis……is the diffusion of water

molecules through a permeable membrane.

Osmosis is important to cells because cells cannot function properly without

adequate water.

Osmosis• In osmosis, water molecules move

by diffusion from an area where they are highly concentrated…through the cell membrane…to an area where they are less concentrated.

*The cell doesn’t need to use energy to move materials across the membrane.

Active Transport•Requires the cell to use energy to let things pass through the membrane.

•Large proteins in the cell membrane are involved in active transport.

Cell Division

• The cells in your body are constantly changing. Most new cells replace damaged or dead cells. These new cells are made during a process called cell division.

• When cell division takes place two identical cells are produced.

Cell Division

• In single celled organisms, cell division results in the formation of two new organisms.

Dividing Paramecium

Cell Division• In many celled organisms, cell

division increases the number of cells making up the organism.

• As the cells increase in number, the organism grows.

Feeling Fine

Cell Cycle

The cell divides.

The cell prepares for division.

The cell grows and develops.

This cycle may take a few hours or a few days!

Growth9 hours

Mitosis:Cell Division

1 hour

Preparation for Division2 hours

DNA Replication10 hours

This process by which a cell’s nucleus divides into two identical nuclei is called

Mitosis

• Mitosis occurs in several phases.

• Most of a cell’s life is spent in the growth and development phase, called ‘interphase.’

Interphase

•The cell is making enough protein, mitochondria, and other substances for two cells.

•In the nucleus, each chromosome is forming an exact copy of itself.

•In animal cells, two pairs of centrioles are forming in the cytoplasm.

Prophase

•The nuclear membrane dissolves.

•The centrioles migrate to opposite sides of the cell.

•Spindle fibers form between the centrioles.

•Chromatid pairs are pulled to the center of the cell by the spindles.

Metaphase

•The chromosomes align across the center of the cell.

•Each chromosome attaches to a spindle fiber at its centromere.

Anaphase

•The centromeres split and the chromatids become two identical chromosomes.

•The spindle fibers shrink, pulling the chromosomes to opposite sides of the cell.

•The cell stretches out to prepare for division.

Telophase

•The chromosomes reach opposite ends of the cell.

•The spindles disintegrate.

•A nuclear membrane forms around each set of chromosomes, forming two new nuclei.

•A furrow forms in the cell membrane, deepens, and divides the cell completely.

Mitosis in Plants

• Plants do not have centrioles. But they do have spindle fibers.

• The rigid cell wall can’t form a furrow in the middle, so a cell plate forms across the middle.

....is different!

Mitosis in Plants

• After the cell divides into two new cells, each forms its own cell wall.

....is different!

QUESTION:

During what phase of mitosis does a cell divide into two new

cells?

Answer:

During telophase!

QUESTION:

How does mitosis differ in plants and animals?

Answer:

Plants do not have centrioles. Plants form

a cell plate before dividing.