Cells, cells, cells

Cells

• Smallest living unit• Most are microscopic

Review: Cell Theory

• The 3 Basic Components of the Cell Theory are:

• 1. All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39)

• 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39)

• 3. All cells are produced by the division of preexisting cells. (Virchow)(1858)

Modern Cell Theory• Modern Cell Theory contains 4 statements, in addition to

the original Cell Theory:• The cell contains hereditary information(DNA) which is passed

on from cell to cell during cell division.• All cells are basically the same in chemical composition and

metabolic activities.• All basic chemical & physiological functions are carried out

inside the cells.(movement, digestion,etc)• Cell activity depends on the activities of sub-cellular

structures within the cell(organelles, nucleus, plasma membrane)

Two Basic Cell Types:Prokaryotic vs. Eukaryotic Cells

Two Basic Types

• Remember….cells are the basic unit of life for ALL living things.

• There are two basic types of cells:1. Prokaryotic cells – found in bacteria2. Eukaryotic cells – found in protists, fungi, plants

and animals

Thr

ee C

ellu

lar

Dom

ains

Bac

teria

vs.

Euk

aryo

tes

Characteristics Shared

• Perform the same basic functions• Surrounded by plasma membrane to control

what enters and leaves the cell• “Filled” with cytoplasm• Contain ribosomes to make protein• Contain DNA to give the general instructions

for the cell’s life

What Makes Eukaryotic Cells Different?

• Much larger• Much more complex• Contain a true nucleus to house the genetic material

(DNA)• Linear DNA packaged into chromatin found inside the

nucleus• Contains specialized structures in the cytoplasm called

organelles to carry out various functions • Not all have a cell wall

Bacteria-Like Organelles(mitochondria and chloroplasts)

• Derived from symbiotic bacteria

• Ancient association

• Endosymbiotic theory– Evolution of modern cells from cells

& symbiotic bacteria (live together)

Eukaryotic Cells

What Makes Prokaryotic Cells Different?

• Much smaller

• Less complex

• No true nucleus• Circular DNA that is found in the cytoplasm• No organelles found in the cytoplasm• Surrounded by a cell wall

Prokaryotic Cell

Prokaryotic Cell

http://www.cellsalive.com/cells/bactcell.htm#top

What does size have to do with it?

• Prokaryotic cells are much smaller than eukaryotic cells. Why?– Smaller surface area- to- volume allows nutrients

to easily and quickly reach inner parts of the cell.– Eukaryotic cells are larger and can not pass

nutrients as quickly. They require specialized organelles to:

• carry out metabolism• provide energy• transport chemicals throughout the cell

But….back to Eukaryotes

• Eukaryotes are characterized by their membrane – bound organelles.

• You need to know them!!!!

Organelles are membrane-bound cell parts

• Mini “organs” that have unique structures and functions

• Located in cytoplasm

• Cell membrane– delicate lipid and

protein skin (phospholipids) around cytoplasm

– found in all cells

Cell Structures

Phospholipids

• Polar: has an uneven distribution of charges– Hydrophilic head– Hydrophobic tail

• Interacts with water

Plasma Membrane

Movement Across the Plasma Membrane

• A few molecules move freely– Water, Carbon dioxide, Ammonia, Oxygen

• Carrier proteins transport some molecules– Proteins embedded in lipid bilayer– Fluid mosaic model – describes fluid nature of a

lipid bilayer with proteins

Membrane Proteins

1. Channels or transporters– Move molecules in one direction

2. Receptors – Recognize certain chemicals

Membrane Proteins

3. Glycoproteins – Identify cell type

4. Enzymes – Catalyze production of substances

• Nucleus– a membrane-bound sac

evolved to store the cell’s chromosomes(DNA)

– has pores: holes

Organelles (continued)

• Nucleolus– inside nucleus– location of

ribosome factory– made of RNA

Organelles (continued)

• Mitochondrion– makes the cell’s

energy– the more energy

the cell needs, the more mitochondria it has

Organelles (continued)

• Ribosomes– build proteins from

amino acids in cytoplasm

– may be free-floating, or

– may be attached to ER– made of RNA

Organelles (continued)

• Endoplasmic reticulum– may be smooth:

builds lipids and carbohydrates

– may be rough: stores proteins made by attached ribosomes

Organelles (continued)

• Golgi Complex– takes in sacs of

raw material from ER

– sends out sacs containing finished cell products

Organelles (continued)

• Lysosomes– sacs filled with

digestive enzymes– digest worn out cell

parts– digest food absorbed

by cell

Organelles (continued)

• Centrioles– pair of bundled tubes– organize cell division

Organelles (continued)

Cytoskeleton

Cytoskeleton• made of

microtubules• found throughout

cytoplasm• gives shape to cell &

moves organelles around inside.

Structures found in plant cells• Cell wall

– very strong– made of cellulose– protects cell from

rupturing– glued to other cells

next door

• Vacuole– huge water-filled

sac– keeps cell

pressurized– stores starch

• Chloroplasts– filled with

chlorophyll– turn solar energy

into food energy

How are plant and animal cells different?

Structure Animal cells Plant cells

cell membrane

nucleus

nucleolus

ribosomes

ER

Golgi

centrioles

cell wall

mitochondria

choloroplasts

One big vacuole

cytoskeleton

Structure Animal cells Plant cells

cell membrane Yes yes

nucleus Yes yes

nucleolus yes yes

ribosomes yes yes

ER yes yes

Golgi yes yes

centrioles yes no

cell wall no yes

mitochondria yes yes

choloroplasts no yes

One big vacuole no yes

cytoskeleton yes Yes

Eukaryote cells can be multicellular

• The whole cell can be specialized for one job• cells can work together as tissues• Tissues can work together as organs

Advantages of each kind of cell architecture

Prokaryotes Eukaryotes

simple , grow more quickly

Complex; grow more slowly

Single-celled organismsSingle celled or

multicellular

all cells the sameSpecialized, different

cells

Examples of specialized euk. cells

• Liver cell: specialized to detoxify blood and store glucose as glycogen.

• Sperm cell: specialized to deliver DNA to egg cell

• Mesophyll cell – specialized to

capture as much light as possible

– inside a leaf