cell structure & functioncpha.tu.edu.iq/images/lec_1_cell.pdf•however, as cell volume...

Cell Structure & Function

Source: http://koning.ecsu.ctstateu.edu/cell/cell.html

Definition of Cell

A cell is the smallest unit that is capable of performing life functions.

“Typical” Animal Cell

http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

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Cells

cells

-possess a membrane-bound nucleus

-are more complex than prokaryotic cells

-compartmentalize many cellular functions within organelles and the endomembrane system

-possess a cytoskeleton for support and to maintain cellular structure

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Eukaryotic Cells

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Cells

Nucleus

-stores the genetic material of the cell in the form of multiple, linear chromosomes

-surrounded by a nuclear envelope composed of 2 phospholipid bilayers

-in chromosomes – DNA is organized with proteins to form chromatin

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Cells

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Cells

Ribosomes

-the site of protein synthesis in the cell

-composed of ribosomal RNA and proteins

-found within the cytosol of the cytoplasm and attached to internal membranes

Cell Structure

• All Cells have:

–an outermost plasma membrane

–genetic material in the form of DNA

–cytoplasm with ribosomes

Cell Parts

Organelles

Surrounding the Cell

Cell Membrane

• Outer membrane of cell that controls movement in and out of the cell

• Double layer

http://library.thinkquest.org/12413/structures.html

Cell Wall

• Most commonly found in plant cells & bacteria

• Supports & protects cells


Inside the Cell

Nucleus

• Directs cell activities

• Separated from cytoplasm by nuclear membrane

• Contains genetic material - DNA

Nuclear Membrane

• Surrounds nucleus

• Made of two layers

• Openings allow material to enter and leave nucleus


Nucleolus

• Inside nucleus

• Contains RNA to build proteins


Cytoplasm

• Gel-like mixture

• Surrounded by cell membrane

• Contains hereditary material

Endoplasmic Reticulum • Moves materials around in

cell

• Smooth type: lacks ribosomes

• Rough type (pictured): ribosomes embedded in surface


Ribosomes

• Each cell contains thousands

• Make proteins

• Found on ribosomes & floating throughout the cell


Mitochondria

• Produces energy through chemical reactions – breaking down fats & carbohydrates

• Controls level of water and other materials in cell

• Recycles and decomposes proteins, fats, and carbohydrates


Golgi Bodies

• Protein 'packaging plant'

• Move materials within the cell

• Move materials out of the cell


Lysosome • Digestive 'plant' for proteins,

fats, and carbohydrates

• Transports undigested material to cell membrane for removal

• Cell breaks down if lysosome structure

is disrupted.


Vacuoles

• Membrane-bound sacs for storage, digestion, and waste removal

• Contains water solution

• Help plants maintain shape


1. Plasma Membrane

• All membranes are phospholipid bilayers with embedded proteins

• The outer plasma membrane

– isolates cell contents

–controls what gets in and out of the cell

–receives signals

3. Cytoplasm with ribosomes

–Cytoplasm – fluid area inside outer plasma membrane and outside DNA region

–Ribosomes – make proteins

Cell Structure

• All Cells have:

–an outermost plasma membrane

–genetic material in the form of DNA

–cytoplasm with ribosomes

Why Are Cells So Small? (4.2)

• Cells need sufficient surface area to allow adequate transport of nutrients in and wastes out.

• As cell volume increases, so does the need for the transporting of nutrients and wastes.

Why Are Cells So Small?

• However, as cell volume increases the surface area of the cell does not expand as quickly.

– If the cell’s volume gets too large it cannot transport enough wastes out or nutrients in.

• Thus, surface area limits cell volume/size.

Why Are Cells So Small?

• Strategies for increasing surface area, so cell can be larger:

– “Frilly” edged…….

– Long and narrow…..

• Round cells will always be small.

Cells

• Structures in all cells – Nucleus

– Ribosomes

– Endomembrane System • Endoplasmic reticulum – smooth and rough

• Golgi apparatus

• Vesicles

– Mitochondria

– Cytoskeleton

CYTOSKELETON

MITOCHONDRION

CENTRIOLES

LYSOSOME

GOLGI BODY

SMOOTH ER

ROUGH ER

RIBOSOMES

NUCLEUS

PLASMA MEMBRANE

Fig. 4-15b, p.59

VESICLE

CYTOPLASM

Nucleus (4.5)

• Function – isolates the cell’s genetic material, DNA

– DNA directs/controls the activities of the cell

• DNA determines which types of RNA are made

• The RNA leaves the nucleus and directs the synthesis of proteins in the cytoplasm at a ______________

Nucleus

• Structure

–Nuclear envelope

• Two Phospholipid bilayers with protein lined pores

–Each pore is a ring of 8 proteins with an opening in the center of the ring

–Nucleoplasm – fluid of the nucleus

Nuclear pore bilayer facing cytoplasm Nuclear envelope

bilayer facing nucleoplasm

Fig. 4-17, p.61

Nucleus

• DNA is arranged in chromosomes

–Chromosome – fiber of DNA with proteins attached

–Chromatin – all of the cell’s DNA and the associated proteins

Nucleus

• Structure, continued

–Nucleolus

• Area of condensed DNA

• Where ribosomal subunits are made

– Subunits exit the nucleus via nuclear pores

Structures of the Endomembrane System

• Endoplasmic Reticulum (ER)

–Continuous with the outer membrane of the nuclear envelope

–Two forms - smooth and rough

• Transport vesicles

• Golgi apparatus

Endoplasmic Reticulum (ER)

–The ER is continuous with the outer membrane of the nuclear envelope

–There are 2 types of ER:

• Rough ER – has ribosomes attached

• Smooth ER – no ribosomes attached

Endoplasmic Reticulum

• Rough Endoplasmic Reticulum (RER)

• Network of flattened membrane sacs create a “maze”

– RER contains enzymes that recognize and modify proteins

• Ribosomes are attached to the outside of the RER and make it appear rough

Endoplasmic Reticulum

• Function RER

• Proteins are modified as they move through the RER

• Once modified, the proteins are packaged in transport vesicles for transport to the Golgi body

Endomembrane System

• Smooth ER (SER) – Tubular membrane structure

– Continuous with RER

– No ribosomes attached

• Function SER – Lipids are made inside the SER

• fatty acids, phospholipids, sterols..

– Lipids are packaged in transport vesicles and sent to the Golgi

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Endomembrane System

Vacuoles

-membrane-bound structures with various functions depending on the cell type

There are different types of vacuoles:

-central vacuole in plant cells

-contractile vacuole of some protists

-vacuoles for storage

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Endomembrane System

Endomembrane system

-a series of membranes throughout the cytoplasm

-divides cell into compartments where different cellular functions occur

1. endoplasmic reticulum

2. Golgi apparatus

3. lysosomes

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Endomembrane System

Rough endoplasmic reticulum (RER)

-membranes that create a network of channels throughout the cytoplasm

-attachment of ribosomes to the membrane gives a rough appearance

-synthesis of proteins to be secreted, sent to lysosomes or plasma membrane

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Endomembrane System

Smooth endoplasmic reticulum (SER)

-relatively few ribosomes attached

-functions:

-synthesis of membrane lipids

-calcium storage

-detoxification of foreign substances

Endomembrane System

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Endomembrane System

Golgi apparatus

-flattened stacks of interconnected membranes

-packaging and distribution of materials to different parts of the cell

-synthesis of cell wall components

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Endomembrane System

Lysosomes

-membrane bound vesicles containing digestive enzymes to break down macromolecules

-destroy cells or foreign matter that the cell has engulfed by phagocytosis

Golgi Apparatus

• Golgi Apparatus

– Stack of flattened membrane sacs

• Function Golgi apparatus

– Completes the processing substances received from the ER

– Sorts, tags and packages fully processed proteins and lipids in vesicles

Golgi Apparatus

• Golgi apparatus receives transport vesicles from the ER on one side of the organelle

– Vesicle binds to the first layer of the Golgi and its contents enter the Golgi

Golgi Apparatus

– The proteins and lipids are modified as they pass through layers of the Golgi

– Molecular tags are added to the fully modified substances

• These tags allow the substances to be sorted and packaged appropriately.

• Tags also indicate where the substance is to be shipped.

Golgi Apparatus

Transport Vesicles

• Transport Vesicles

– Vesicle = small membrane bound sac

– Transport modified proteins and lipids from the ER to the Golgi apparatus (and from Golgi to final destination)

Mitochondria (4.15)

• Function – synthesis of ATP

– 3 major pathways involved in ATP production

1. Glycolysis

2. Krebs Cycle

3. Electron transport system (ETS)

Mitochondria

• Structure:

– ~1-5 microns

– Two membranes

• Outer membrane

• Inner membrane - Highly folded

– Folds called cristae

– Intermembrane space (or outer compartment)

– Matrix

• DNA and ribosomes in matrix

Mitochondria

Mitochondria (4.15)

• Function – synthesis of ATP

– 3 major pathways involved in ATP production

1. Glycolysis - cytoplasm

2. Krebs Cycle - matrix

3. Electron transport system (ETS) - intermembrane space

Mitochondria

TEM

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Mitochondria

Mitochondria

-organelles present in all types of eukaryotic cells

-contain oxidative metabolism enzymes for transferring the energy within macromolecules to ATP

-found in all types of eukaryotic cells

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Mitochondria

-surrounded by 2 membranes

-smooth outer membrane

-folded inner membrane with layers called cristae

-matrix is within the inner membrane

-intermembrane space is located between the two membranes

-contain their own DNA

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Mitochondria

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