Chapter 4 A tour of the cell

Cell Theory

All living matter is composed of one or more cells.

The cell is the structural and functional unit of life.

Cell Theory

“Omnis cellula e cellula” All cells are from other cells.

Types of Cells

Prokaryotic - lack a nucleus and other membrane bound structures.

Eukaryotic - have a nucleus and other membrane bound structures.

Both Have:

Membrane Cytosol Ribosomes (but the size is

different)

Prokaryotic Eukaryotic

Nucleus

Prokaryotes

Bacteria Came first in evolution Less complex Have cell wall but different

than plants

Eukaryotic

Protists, Plants, Fungi, Animals

More complex

Animal Cell

Plant Cell

Organelle

Term means "small organ” Formed body in a cell with a specialized function.

Important in organizational structure of cells.

Organelles - function

Way to form compartments in cells to separate chemical reactions.

Keeps various enzymes separated in space.

Plant vs Animal Cell

Plants Have a large central vacuole to

hold water Contain chloroplasts Have cell wall made of

cellulose

Animals

Have centrioles Have lysosomes Have flagella

Nucleus

Most conspicuous organelle. usually spherical, but can be

lobed or irregular in shape.

Structure

Nuclear membrane Nuclear pores Nucleolus Chromatin

Nuclear Membrane

Double membrane

Nuclear Pores Allow things in and out of

nucleus Ex. mRNA during

transcription

Nucleolus

0 - 4 per nucleus. Storage area for ribosomes. Synthesizes rRNA

Chromatin

Chrom: colored - tin: threads DNA and Protein in a “loose”

format. Will form the cell’s chromosomes.

Nucleus - Function

Contains the genetic instructions to make proteins and more DNA

Ribosomes

Structure: 2 subunits made of protein and rRNA. No membrane.

Function: protein synthesis. Site of translation

Endoplasmic Reticulum

Folded sheets or tubes of membranes.

Membrane is continuous with the nuclear membrane

Types of ER

Smooth ER: no ribosomes. Used for lipid synthesis,

carbohydrate storage, detoxification of poisons.

Rough ER: with ribosomes. Makes secretory proteins.

Function of Golgi Bodies

Processing - modification of ER products (lipids, carbs).

Distribution - packaging of ER products for transport.

Vesicles

Small sacs of membranes that bud off the Golgi Body.

Transportation vehicle for the modified ER products.

Lysosome

Structure: Single membrane. Made from the Golgi

apparatus.

Function

Breakdown and degradation of cellular materials.

Contains enzymes for fats, proteins, polysaccharides, and nucleic acids.

Over 40 types known.

Vacuoles

Structure - single membrane, usually larger than the Golgi vesicles.

Function – store water, and sometimes other molecules

Plants

Large single vacuole when mature making up to 90% of the cell's volume.

Mitochondria

Structure: 2 membranes. The inner membrane has more surface area than the outer membrane.

Matrix: inner space. Intermembrane space: area between

the membranes.

Function

Cell Respiration - the release of energy from food.

Major location of ATP generation.

“Powerhouse” of the cell.

Chloroplasts

Structure - two outer membranes.

Complex internal membrane. Fluid-like stroma is around

the internal membranes.

Function

Photosynthesis - the use of light energy to make food.

Cytoskeleton

Network of rods and filaments in the cytoplasm.

Functions

Cell structure and shape. Cell movement. Cell division - helps build cell

walls and move the chromosomes apart.

Flagella

Made of the same components as part of the cytoskeleton

Helps cell move through body

Centrioles

Usually one pair per cell, located close to the nucleus.

Found in animal cells. Help in cell division.

Cell Wall

Nonliving jacket that surrounds some cells.

Found in: Plants Prokaryotes Fungi Some Protists

Cell Walls

Function as the cell's exoskeleton for support and protection.