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)