CELL STRUCTURE
Jan Homolak, 2nd year School of Medicine, Zagreb
4/28/2014Mentor: 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 smallest cell in the human body?
• The largest cell on earth?
• The smallest cell?
• which cell is the most abundant in the human body?There are more bacterial cells in the body than human cells.
the female ovum
male sperm (175,000 sperm cells weigh as much as a single egg cell)
an ostrich egg
a tiny bacteria
Eukaryotes vs. Prokaryotes
• Animals• Plants• Fungi
•Bacteria
true nucleus
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? CircularFree 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 reticulumsmooth 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)