Cell Structure and Function

Key Concepts:

All organisms are composed of cells

The cell is the basic unit of life

All cells have a double-layered plasma membrane

Membranes consist largely of phospholipid and protein molecules

Key Concepts:

Organelles are membrane-bound compartments inside eukaryotic cells

Prokaryotic cells do not have organelles

When cells grow, they increase faster in volume than in surface area

Different microscopes modify light rays or accelerated beams of electrons that

allow small images to be observed

Basic Aspects of Cell Structure and Function

Plasma membraneLipid bilayer

Proteins

•Channels, transport, pumps, receptors

DNA-containing region

Cytoplasm

Cell Size and Shape

Surface to Volume RatioVolume increases more rapidly than

surface areaRestrictions on

size and shape

MicroscopesA - Light microscopeB - Transmission Electron MicroscopeC - Scanning Electron Microscope

Defining Structures of Eukaryotic Cells

A Plant Cell An Animal Cell

Major Cellular Components

Nucleus

Ribosomes

Endoplasmic reticulum Smooth and Rough

Golgi body

Various vesicles

Mitochondria

Cytoskeleton

Components of the Nucleus

Nuclear envelope - Surrounds nucleus

Nucleoplasm - Fluid interior portion

Chromosome - One DNA molecule and associated proteins

Chromatin - Total collection of all DNA molecules and associated proteins

Nucleolus - RNA and proteins that will be assembled into ribosomal subunits

The Nuclear EnvelopeDouble - membrane system

Two lipid bilayers Surrounds nucleoplasm

Pores allow exchange

The Cytomembrane System

Organelles in which lipids are assembled and proteins are produced and modified

Endoplasmic reticulum

Golgi bodies

Vesicles

The Endoplasmic Reticulum

Rough and Smooth Presence or absence of ribosomes Rough: Proteins Smooth: Lipids

Rough ER Smooth ER

Golgi Bodies

Enzymatic finishes on proteins and lipids, and packaging in vesicles

Vesicles Lysosomes

Peroxisomes

Transport

Mitochondria

Production of ATP

Double-membrane system Two distinct

compartments

Have their own DNA

Divide on their own

Have ribosomes

Chloroplast

Found in photosynthetic eukaryotes

Two outer membranes

Semifluid stroma

Inner thylakoid membrane system

Photosynthetic pigments

Components of the Cytoskeleton

Microtubules

Tubulin subunits

Cell division and movement

Microfilaments

Actin subunits

Movement and shape

Components of the Cytoskeleton

Intermediate Filaments Only in animal

cells of specific tissues

Mechanically strengthen cells or cell parts and help maintain shape

Six known groups

Structural Basis of Cell Motility

Three Mechanisms Length of

microtubule can change

Parallel microtubules slide in opposite directions

Shunting of organelles

Sliding mechanism for beating of flagella

Cell Surface Specializations

Eukaryotic Cell Walls

A single-celledprotist

Plant Cell Wall

Cell secretions form lamella Plasmodesmata (channels) Primary and Secondary walls

Plant Cell Walls

Deposition of layers inside primary wall Stiffen wall

Maintain shape

Cell-to Cell Junctions

Plants Plasmodesmata

Animals Tight Junctions

Adhering Junctions

Gap Junctions

Prokaryotic Cells The Bacteria

No nucleus - DNA in free cytoplasm

Smallest of all cells

Most have a cell wall

Polysaccharides cover cell wall of many species

No membrane-bound organelles

Flagella lack 9+2 array of microtubules

Bacterial Cell

In Conclusion

The cell theory states All living cells are composed of cells

The cell is the smallest unit of life

New cells arise only from pre-existing cells

Cells have a plasma membrane, cytoplasm, and a region of DNA

The plasma membrane maintains the cell as a separate entity

In Conclusion

The cytoplasm is all the fluids, ribosomes and organelles in eukaryotic cells between the nucleus and plasma membrane

Membranes consist of a bilayer of lipids and proteins embedded in the bilayer or attached to the surface.

Proteins carry out most of cell membrane functions

In Conclusion

Membranes divide functional compartments into organelles

Prokaryotes do not have organelles

Organelle membranes separate metabolic reactions

developed by M. Roig