Cells

• The basic units of a living system or organism

Cell Theory –

• developed by 3 German scientists:

•  Matthias Schleiden, • Theodor Schwann, • and Rudolf Virchow

These scientists discoveries led to the cell theory…

What is the CELL THEORY??? Theory that states… 1.  All organisms are made of one or

more cells. 2. The cell is the basic unit of life

which can perform life processes. 3. All cells come from other living

cells.

How do we know cells exist?

•  Invention of the microscope made it possible for people to discover and learn about cells

•  Robert Hooke looked at cork cells

•  Anton van Leuenhock used a simple microscope and was the first person to see microorganisms.

2 Types of Cells:

•  Prokaryotic - Cells that don’t have a membrane-covered nucleus for example: bacteria

•  Eukaryotic – Cells with a nucleus covered by a membrane for example: plant and animal cells

Prokaryote Eukaryote

How are cells organized?

Ø  Complex living things are organized into 5 levels. Ø  Cells carry on the processes that keep us alive. Examples:

Red Blood Cells Muscle Cells Skin Cells CELLS

TISSUES

ORGANS

ORGAN SYSTEM

ORGANISM (BODY)

Representative Animal Cell

Animal Cell

Representative Plant Cell

Plant Cell

Organelles

• -Tiny cell structures that are specialized parts of a cell that have specific functions – a cell “organ.”

CELL MEMBRANE

• – “gate keeper” • outer boundary (or layer) of

the cell • controls the movement of

materials into and out of the cell

CELL WALL

•  found in plant cells •  tough rigid boundary – made

of cellulose • gives cells their shape (it also

provides protection, as well as support)

CYTOPLASM

• – “cell fluid” • a gel-like material inside the

cell • Many cellular activities occur

here and where the organelles are contained

NUCLEUS

– “brain of the cell” •  controls cell processes • Contains DNA or chromosomes

- the heredity material or genetic blueprint of the cell

DNA

•  Hereditary material

•  Chromosomes – DNA – Protiens – Form for cell division

•  Chromatin

NUCLEAR MEMBRANE

• – materials pass in and out through tiny holes called porins

Nucleolus

•  Most cells have 2 or more •  Directs synthesis of RNA •  Forms ribosomes

CHLOROPLASTS

•  – “energy processing organelles” •  found only in plant cells •  place where food is made for

plant cells

MITOCHONDRIA

• – “powerhouse” • converts food (glucose) to

energy (ATP)

RIBOSOMES

•  – “protein factories” •  place where protein is made in

the cells •  some are attached – some float in the cytoplasm

ENDOPLASMIC RETICULUM

•  – “conveyer belt” •  transports synthesized proteins

throughout the cell

GOLGI BODIES (Apparatus)

•  sort, modify, process, and ship the proteins through the cell

•  (Also known As GOLGI Apparatus)

VACUOLES •  – “storage” •  store water, sugar, salts,

nutrients, & wastes in cells •  maintains the proper pressure

to provide structure and support in plant cells

LYSOSOMES

•  contain chemicals that break down waste materials.

Unicellular organisms

•  Some organisms only consist of a single cell

•  But these do usually have the components of cells (nucleus, membrane etc)

Image Credit Paramecium

• Any life form that consists of a single cell.

•  They can move, digest food, and reproduce.

What is a unicellular organism?

•  Environment: Ponds or puddles with rich organic matter.

•  Movement: By flagella •  Important Structures:

–  Cell Membrane –  Nucleus: controls cell activities and contains DNA –  Flagellum: helps to move –  Chloroplast: helps with photosynthesis –  Contractile Vacuole: removes excess water –  Cytoplasm

•  Food: They make their own food or absorb food from their environment.

Euglena

Euglena

•  Unicellular, eukaryotic, both Heterotrophic and autotrophic

•  Moves- Flagella •  Reproduces- fission (cell splits) •  Eats- eyespot senses light to gather for

photosynthesis

Euglena

•  Environment: Mud at the bottom of freshwater ponds. •  Movement: They change shapes which allows them to

move with their psuedopods. •  Important Structures:

–  Cytoplasm: carries out chemical reactions –  Nucleus: controls the cell –  Cell Membrane: allows substances to enter and exit the

cell –  Food Vacuole: digests food –  Contractile Vacuole: gets rid of excess water –  Pseudopodium: what allows it to move over mud (false

foot) •  Capturing Prey: They surround their prey and engulf it.

Amoeba

Amoebas

•  Unicellular, Eukaryotic, heterotrophic •  Moves-using Psuedopods •  Reproduces- Binary fission •  Eats-engulfing

Amoeba

•  Environment: ponds, ditches, shallow puddles

•  Movement: They beat cillia which allows it to swim.

•  Important Structures: – Daughter colonies – Cillia: helps to move – Chloroplast: contains chlorophyll

•  Food: makes its own food by photosynthesis.

Volvox

Volvox

•  Unicellular, eukaryotic, autotrophic •  Moves- flagella •  Reproduces- both sexually and asexually •  Eats- by using the eye spot to sense light

so photosynthesis can occur.

Volvox

•  Environment: Fresh water or stagnant water •  Movement: Cilia bend and straighten helping

propel the paramecium through water •  Important Structures:

– Contractile Vacuoles (2): removes excess water – Cytoplasm: water absorption – Cilia: hair-like projections that propel it through

water – Nucleus: controls cell activities

•  Food: uses cilia to sweep the food into the cell.

Paramecium

Paramecium

•  Unicellular, eukaryotic, heterotrophic •  Moves- cilia •  Reproduces-sexually and asexually •  Eats food from environment- through oral

grove, food vacuole, and anal pore.

Paramecium

• Many  organisms,  especially  unicellular  organisms,  reproduce  by  means  of  cell  division  –  called  asexual  reproduc/on  –  Ex:  bacteria

Cell  Division—Mitosis  Notes Cell  Division  —  process  by  which  a  cell  divides  into  2  new  cells   • Why  do  cells  need  to  divide?   1. Living  things  grow  by  producing  more  cells,  NOT  because  each  cell  increases  in  size

2.  Repair  of  damaged  Hssue 3. If  cell  gets  too  big,  it  cannot  get  enough  nutrients  into  the  cell  and  wastes  out  of  the  cell

• The  original  cell  is  called  the  parent  cell;  2  new  cells  are  called  daughter  cells

• Before  cell  division  occurs  ,  the  cell  replicates  (copies)  all  of  its  DNA,  so  each  daughter  cell  gets  complete  set  of  gene/c  informa/on  from  parent  cell

• Each  daughter  cell  is  exactly  like  the  parent  cell  –  same  kind  and  number  of  chromosomes  as  the  original  cell

Parent Cell

2 Daughter

Cells

DNA • DNA  is  located  in  the  nucleus  and  controls  all  cell  ac/vi/es  including  cell  division

• Long  and  thread-­‐like  DNA  in  a  non-­‐dividing  cell  is  called  chroma/n

• Doubled,  coiled,  short  DNA  in  a  dividing  cell  is  called  chromosome      Consists  of  2  parts:    chroma/d  and  centromere

o 2  idenHcal  “sister”            chromaHds  aVached  at  an  area  in  the  middle  called  a  centromere  

o When  cells  divide,  “sister”  chroma/ds  separate  and  1  goes  to  each  new  cell

ChromaHn

Duplicates  itself

Coils  up  into  chromosomes

• ChromaHn  to  chromosomes  illustraHon:

Why  does  DNA  need  to  change  from  chromaHn  to  chromosome? More  efficient  division

Mitosis  –  division  of  the  nucleus  into  2  nuclei,  each  with  the  same  number  of  chromosomes   • Mitosis  occurs  in  all  the  soma/c  (body)  cells  Why  does  mitosis  occur?     So  each  new  daughter  cell  has  nucleus  with  a  complete  

set  of  chromosomes  

Anaphase—(Apart)

Prophase Metaphase—(Middle)

Telophase—(Two) Anaphase—(Apart)

• 4  phases  of  nuclear  division  (mitosis),  directed  by  the  cell’s  DNA  (PMAT)

Phase Chromosome  Appearance  &  Loca/on Important  Events

Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

DNA replication, cell grows and replicates organelles Nuclear envelope disappears, spindle fibers form

DNA copies itself; chromatin

Chromosomes coil up

Chromosomes line up in the middle

Spindle fibers connect to chromosomes

Chromosome copies divide and move apart

Spindle fibers pull chromosome copies apart to opposite poles

Chromosomes uncoil back into chromatin

Nuclear envelopes reform, 2 new nuclei are formed, spindle fibers disappear Division of the rest of the cell: cytoplasm and organelles

Chromatin

SEXUAL REPRODUCTION

Sex cells formed by meiosis Requires 2 parents

Offspring not identical

The process that results in the formation of gametes

Sex cells, egg or sperm, which have haploid chromosomes

Haploid means HALF, as in the number of chromosomes, written as n

Meiosis

Gametes

Haploid

Fertilization

The union of an egg and a sperm

The cell that is formed when the egg becomes fertilized by the sperm. This results in a full set of chromosomes.

Diploid means they have chromosome found in pairs, written as 2n

n

n 2n Zygote

Diploid

Homologous Chromosomes

Similar chromosomes that are found in pairs. The paired chromosomes come from the mother and father.

* Human body cells have 46 chromosomes each * Human body cells have 23 homologous pairs

Meiosis and Fertilization

Important for survival of many species, because these processes result in genetic variation of offspring.

A kind of cell division that results in gametes (sex cells) with half the number of chromosomes.

Meiosis Overview

•  Human body cells have 46 chromosomes.

•  Each parent contributes 23 chromosomes.

•  Takes place in sex cells (gametes): egg and sperm

•  Delete the next line.