CELL STRUCTURE
Jan Homolak, 2nd year
School of Medicine, Zagreb
4/28/2014
Mentor: A. Žmegač Horvat
The Cell
Discovery
The Cell
Theory
The Cell
Types
Parts of
the Cell
Cella = small room
Cell Discovery
Robert Hooke
- observed a thin slice of
cork (dead plant cells)
Microphagia
- described what he
observed as “little
boxes” (cells)
1665
Anton van
Leeuwenhoek
first person to
observe living cells
1675
Cell Theory
ALL LIVING THINGS
ARE COMPOSED OF
basic units of
structure and function
come only from
existing cells
Matthias Schleiden (1838)
-all plants are composed of cells
Theodor Schwann (1839)
- all animals are composed of cells
Rudolph Virchow (1855)
- cells come only from other cells
???
• The largest cell in the human body?
the female ovum
• The smallest cell in the human body?
male sperm (175,000 sperm cells
weigh as much as a single egg cell)
• The largest cell on earth?
an ostrich egg
• The smallest cell?
a tiny bacteria
• which cell is the most abundant in the human
body?
There are more bacterial cells in the body than human cells.
Eukaryotes vs. Prokaryotes
true nucleus
• Animals
• Plants
• Fungi
•Bacteria
Prokaryotes
Eukaryotes
nucleus?
NO (nucleoid)
YES
membrane-bound
organelles?
NO
YES (Many)
size
1 - 10 m
10 - 50 m
when evolved?
3.5 billion years ago
1.5 billion years ago
cytoplasm?
YES
YES
cell membrane?
YES
YES
cell wall?
Some Do
Plants
ribosomes?
YES
YES
DNA?
Circular
Free Floating
Chromosomes in Nucleus
examples
Bacteria
Plants, Animals, Fungi, and
Protists
Parts of the Cell
•
•
•
•
taking food
transforming food into energy
getting rid of wastes
reproducing
Cell Membrane
• Structure:
- phospholipid
bilayer
- proteins:
- channels
- markers
- receptors
• Function: “selectively permeable boundary
between the cell and the external environment”
Nucleus
• Structure: a sphere
• Function:
-storage center of cell DNA
-manages cell functions
Cytoplasm
• Structure:
- gelatin-like fluid
- inside the cell membrane
• Function:
-contains salts, minerals, and organic
molecules
-surrounds the organelles
Cytoskeleton
• Structure:
-network of thin, fibrous elements
microtubules
microfilaments (actin)
• Function:
-support system
-maintains cell
shape
Ribosomes
• Structure:
-two subunits made of protein and RNA
• Function:
-protein synthesis
Endoplasmic Reticulum
• Structure:
-a system of membranous tubules and sacs
• Function:
-”intercellular highway”
rough endoplasmic
reticulum
smooth endoplasmic
reticulum
Rough Endoplasmic Reticulum
• Covered with ribosomes
• Protein synthesis and export
Smooth Endoplasmic Reticulum
• Synthesis of lipids and breakdown of toxic
substances
Golgi Apparatus
• Structure:
-stacked flat sacs
• Function:
-distribution of
received proteins
(to other organelles or out of the cell)
(receiving, processing,
packaging, and shipping)
Mitochondria
• Structure:
-folded membrane within an outer membrane
• Function:
- energy conversion (food -> ATP)
Lysosomes
• Structure:
-spherical organelles
• Function:
-contain hydrolytic enzymes
Peroxisomes
• Structure:
-spherical organelles
• Function:
-degrade hydrogen peroxide
(toxic metabolic compound)
Centrioles
• Structure:
-nine sets of triplet microtubules
-arranged in a ring
• Function:
-cell division (mitosis)