Download CELL STRUCTURES

CELL STRUCTURES and
ORGANELLES
Nucleus

Identified by Robert Brown, a Scottish botanist in 1831.

The nucleus controls most of a cell’s processes.

Contains the cell’s genetic material, DNA

Nearly all eukaryotic cell types contain a nucleus.
Chromatin & Chromosomes

Chromatin is a granular material visible within the
nucleus
 It
consists of DNA bound to proteins.
 During
cell division chromatin condenses to form
chromosomes.
 Chromosomes
are distinct threadlike structures
containing genetic information that is passed form
one generation of cells to the next.
Nucleolus

Small, dense region within the nucleus.

Assembly of ribosomes begins in the nucleolus.
Nuclear Envelope

Covered with pores which allow material to move in &
out, especially a steady stream of RNA to the rest of the
cell.
Cytoskeleton

A network of protein filaments & tubules that helps a
cell maintain its shape.

Also involved in many forms of cell movement.
Organelles in the
Cytoplasm
Ribosomes

Small particles of RNA & protein,

Assembles proteins according to coded instructions
from the nucleus.

May be attached to the endoplasmic reticulum or freefloating in the cytoplasm.
Endoplasmic Reticulum

Internal membrane system where components of the
cell membrane are assembled.

Modifies some types of proteins.
Endoplasmic Reticulum

Two types of ER
 Rough
ER
 Studded
 Smooth
w/ ribosomes
ER
 Ribosome
 Involved
free
in the synthesis and movement of lipids
Golgi Apparatus

Modifies proteins by attaching carbohydrates and
lipids.
Lysosomes

Filled with enzymes.

Breaks down carbohydrates, lipids, and proteins.

Breaks down organelles that have outlived their
usefulness.
Vacuoles

Sac-like structures that store H2O, salts, carbohydrates,
proteins.

In plants, large vacuoles filled with H2O makes it
possible to support heavy leaves, flowers, stems.
Centrioles

Found only in animal-type cells.

Microtubule structure that helps separate
chromosomes during cell division.
Chloroplasts

Found in plants & algae.

Contain chlorophyll.

Use energy from sunlight to make energy-rich food
molecules by the process of photosynthesis.
Mitochondria

Double-membrane organelle.

Release energy from stored food molecules.

Energy used to power growth, development, &
movement.