Cell Review

The Diversity of Cells in the Human Body

Over 200 different types of cells in the human body, all of them specialized to perform a specific function.

All human cells are EUKARYOTIC, meaning they are large, complex cells with a nucleus and specialized organelles.

Every organelle performs a specific function.

Nucleus Place where chromosomes are stored. In humans, 46 chromosomes contains approx. 25000 genes. 1 gene codes for one protein only!

Manufacture of mRNA & tRNA necessary to build coded proteins.

Smooth & Rough Endoplasmic Reticulum (SER & RER)RER: Building and modification of proteins in ribosomes.SER: Synthesis of lipids and carbohydrates, other cell-specific functions (detoxification of toxins and alcohols in liver cells. In testes,

testosterone secretion).

mRNA

Synthesis ofmRNA in thenucleus.

DNA

NUCLEUS

CYTOPLASM

1

DNA contains the instructions to make proteins. 1 gene = 1 protein.

Instructions coding for the amino acid sequence of a protein are copied to a molecule of mRNA.

MAKING PROTEINS

mRNA

Synthesis ofmRNA in thenucleus

DNA

NUCLEUS

mRNA

CYTOPLASM

Movement ofmRNA into cytoplasmvia nuclear pore.

1

2

mRNA

Synthesis ofmRNA in thenucleus.

DNA

NUCLEUS

mRNA

CYTOPLASM

Movement ofmRNA into cytoplasmvia nuclear pore.

Ribosome

AminoacidsProtein

Synthesisof protein.

1

2

3

Smooth ERLipids & carbohydrates synthesized here.

Nucleus

Rough ER

Plasma membrane

Rough & Smooth ER

RibosomesProtein factories.

Cytoplasm

cis face(“receiving” side of Golgi apparatus)

trans face(“shipping” side of Golgi apparatus)

TEM of Golgi apparatus

0.1 µm

Golgi ApparatusFine-tuning, folding and final modifications to proteins. Sorting and packing of finished materials.

Nucleus

Rough ER

Plasma membrane

GolgiModifies proteins. Ships proteins away.

LysosomeClean-up crew; contains enzymes.

VesiclesTransport materials

Smooth ERLipids & carbohydrates synthesized here.

RibosomesProtein factories

Golgi

Nucleus 1 µm

Lysosome

Lysosome

Digestive enzymes

Plasma membrane

Food vacuole

Digestion

Digestion

LysosomesClean-up crew.

Breakdown (digestion) of ingested food material (specialized lysosomes only in animal cells).

Disposal of old, worn out organelles.

Vesicle containingtwo damaged organelles

Mitochondrion fragment

Peroxisome fragment

Peroxisome

Lysosome

DigestionMitochondrionVesicle

Destruction of old organelles

1 µm

Mitochondrium Cellular power plants. Production of ATP from glucose molecules using oxygen.

Cytoskeleton Maintains cell shape, supports and anchors organelles, and allows transport of materials.

Plasma Membrane A flexible barrier that controls what enters and leaves the cell. Contains ID proteins used by the immune system.

Lipid structure1 glycerol molecule, up to 3 fatty acids.

Made of phospholipids.1 fatty acid replaced by a phosphate group.

Hydrophilichead

WATER

Hydrophobictail

WATER

PHOSPHOLIPIDS

CYTOPLASMICSIDE

EXTRACELLULARSIDE

Channel & carrier proteins allow materials to move in and out of the cell.

NATURE ABHORS

GRADIENTS!

Gradient: a difference in concentration.Diffusion: the movement of particles from areas of low concentration to areas of high concentration until an equilibrium is reached.

Molecules of dye Membrane (cross section)

WATER

Net diffusion Net diffusion Equilibrium

(a) Diffusion of one solute

Net diffusion

Net diffusion

Net diffusion

Net diffusion

Equilibrium

Equilibrium

(b) Diffusion of two solutes

Passive transport

Simple Diffusion

Facilitated diffusion

Active transport(Na+/K+ pump)

ATP

Na+

K+

Some proteins are ID proteins, used by the immune system to identify friend from foe.