Cell Structure and Function

Chapter 7BiologyMiller • Levine

The Scientists…

Robert Hooke (1665) Viewed cork under a

microscope Called the chambers he

saw “cells” Anton van

Leeuwenhoek (1674) First to see living

organisms in a drop of water

The Scientists…

Matthias Schleiden (1838)All plants are made of cells

Theodor Schwann (1839)All animals are made of cells

Rudolf Virchow (1855)All cells come from preexisting

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

Unicellular vs. Multicellular

Unicellular – single-celled organism

Multicellular – many-celled organismCell specialization – cells are

specialized to perform certain functions

Cells → Tissues → Organs → Organ systems → Organism

Prokaryotes vs. Eukaryotes Prokaryotes

Have a cell membrane & cytoplasm, but do not have a nucleus

Ex. Bacteria such as E.coli Eukaryotes

Have a nucleus, cell membrane, cytoplasm & organelles

Ex. Plants, Animals, Fungi

Prokaryotes vs. Eukaryotes

Basic Cell Structures

Cell membrane – thin, flexible barrier around the cell; protects the cellPresent in all cells

Cytoplasm – material inside the cell membrane (not including the nucleus)Prokaryotes & Eukaryotes

Cell Wall

Found in many organisms, including plants, algae, fungi and nearly all prokaryotes

Not found in animal cells Lies outside the cell membrane Main function is to provide

support & protection for the cell

Nucleus

Almost all eukaryotic cells, including plants and animals have a nucleus

Prokaryotes do not have a nucleus

Controls most cell process and contains the DNA

Nucleolus and Nuclear Envelope

Nucleolus: Inside the nucleusWhere ribosomes are made

Nuclear Envelope:Double-membrane layer around

the nucleusAllows material to move into and

out of the nucleus

Nucleus

Cytoskeleton

Found in all eukaryotic cells Not found in prokaryotes A network of protein filaments

that helps the cell maintain its shape

It also is involved in cell movement

Ribosomes

Found in all cells Main function is to make

proteins Can be found floating in the

cytosol or attached to endoplasmic reticulum

Endoplasmic Reticulum (ER)

Found only in eukaryotic cells Where components of the cell

membrane are assembled Two kinds: Smooth ER & Rough

ERSmooth ER: no ribosomes; makes

lipidsRough ER: has ribosomes; involved

in making proteins

Endoplasmic Reticulum

Golgi Apparatus

Found only in eukaryotic cells

Enzymes attach carbohydrates & lipids to proteins

Send proteins to their final destination

Lysosomes

Found in animal cells only Break down lipids,

carbohydrates & proteins from food into particles that can be used by the cell

Also break down “dead” organelles

Vacuoles

Not found in prokaryotes Animal cells have small or no

vacuoles Plant cells have a large central

vacuole Store materials such as water,

salts, proteins & carbohydrates

Chloroplasts

Found in all plant cells Some prokaryotes have them,

but most do not Use the energy from sunlight to

make energy-rich food molecules during photosynthesis

Chloroplasts

Mitochondria

Found in eukaryotic cells only

Release energy from stored food molecules

Cell Membrane

Regulates what enters and leaves the cell (selectively permeable)

Provides protection and support Lipid bilayer – two layers of lipids

Proteins run through the layersCarbohydrates are attached to

some of the proteinsFluid Mosaic Model

Cell Membrane

Diffusion

Molecules move from an area of high concentration to an area of low concentration

Movement continues until equilibrium is reached

Many substances move across the membrane by diffusion

Does not require energy (passive transport)

Diffusion

Osmosis

The diffusion of water Isotonic – equal concentration

Nothing happensHypertonic – higher concentration

Water moves out of the cellHypotonic – lower concentration

Water moves into the cell

No energy is required

Effects of Osmosis on Cells

Osmotic Pressure

In pure water, an animal cell would burst

Plant cells are protected by their cell wall

Some freshwater organism have special structures like contractile vacuoles to get rid of extra water

Facilitated Diffusion

Some molecules cannot cross the membrane without help

Some of the proteins in the membrane form protein channels

Materials still move from higher to lower concentrations

No energy is required

Facilitated Diffusion

Active Transport

Materials move from lower concentration to higher concentration

Requires an input of energy

Works kind of like a pump

Transport of Large Amounts

Endocytosis – movement into the cellPhagocytosis – “cell eating” – solid

particlesPinocytosis – “cell drinking” –

particles dissolved in water Exocytosis – movement out of

the cell

Phagocytosis

Pinocytosis