the cell

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Key Points:

1. Structure (and importance) of cell membrane

2. Structure (and function) of organelles

3. Interconnections between cells to maintain structural stability in body tissues.

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Typical cell

1. Cell membrane

2. Cytoplasm

Organelles Cytosol

Membranous Non membranous

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Vault- large ribonucleoproteins; transport mRNA from nucleus to cytoplasm  

Cell membrane (plasma membrane)

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Fill in the blanks

•The ________ ________ model describes the structure of the plasma membrane.

•In this model the membrane is seen as a bilayer of ______________ in which protein molecules are embedded.

Name the functions of cell membrane proteins

1. _____________2. _____________3. _____________4. _____________5. _____________

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Cytosol (hyaloplasm)

• The liquid component of the cytoplasm surrounding the organelles and other insoluble cytoplasmic structures.

• It is the site of various chemical reactions. Eg : glycolysis• It consists of water (aqueous), organic

molecules and dissolved ions.

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Cytosol

Membranous Membranous OrganellesOrganelles

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The Nucleus

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•The nucleus is the control center of the cell.

• It is the largest organelle in the cell and contains the DNA.

•Nucleolus is inside the nucleus.

•It is responsible for synthesizing ribosomes.

•The fenestrations (openings) on the surface of the nucleus are the nuclear pores, through which molecules move in and out of the nucleus.

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The DNA of all cells is made up of ___________. DNA + _________ proteins = Nucleosome

____________ + Linker DNA = Chromatin

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Mitochondrion

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• Cellular power plants - generate Adenosine Tri-Phosphate(ATP) as a source of chemical energy.

• There are more mitochondria in more active cells. Eg: Skeletal muscle cells, cardiac muscle cells.

Q : From which gametocyte does the mitochondrion inherit its genome?

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A : Ovum

Smooth (SER) & Rough (RER) Endoplasmic Reticulum

Function : Synthesis Storage Transport

of proteins

•ER is a network of membranes throughout the cytoplasm of the cell.

•There are two types of ER

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Fill in the blanks

•When ______________are attached it is called RER and SER when there are no ______________ attached.

•The RER is where most ________________ occurs in the cell.

•The function of the SER is to synthesize __________in the cell.

•The SER also helps in the ___________of harmful substances in the cell.

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Golgi Apparatus

•Packaging and shipping of proteins •Cell membrane renewal

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Lysosomes • The recycling compartment of the cell.

• Engulf cellular and endocytosed proteins, lipids that need digestion.

• The resulting metabolites are transported either as vesicles or directly across the membrane.

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Name A , B, C & D

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Non-membranous Organelles

1. Cytoskeleton

2. Microvilli

3. Centrioles

4. Ribosomes

Cytoskeleton

Q. Name the 4 protein components:

1. ________________

2. ________________

3. ________________

4. ________________

Q. What is its function: ____________

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Direct formation of mitotic spindle.

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Centrosome

• An area in the cell where microtubles are produced (microtubule organizing center).

• It is composed of 2 centrioles, each made up of a ring of 9 groups of microtubules -3 fused microtubules in each group.

• One centriole is perpendicular to the other.• During cell division, the centrosome divides and the centrioles replicate

(make new copies). • It results in two centrosomes, each with its own pair of centrioles. • The two centrosomes move to opposite ends of the nucleus, and from

each centrosome microtubules grow into a spindle. • It is responsible for separating replicated chromosomes into the 2

daughter cells.

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RibosomesQ:

•Eukaryotic ribosomes are made up of 60% _______ & 40% _______.

•They are active in _______ synthesis.

•There are 2 types of ribosomes

1.__________

2.__________

A:

60% RNA + 40% Protein

Active in protein synthesis

There are fixed (on RER) and free ribosomes

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Intercellular Attachments

•channel proteins interlock and form pores

Q: Where are they abundantly seen?

A: in cardiac and smooth muscle

1) Gap Junctions

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2) Tight Junctions

• Interlocking membrane proteins

Q: Where are they abundantly seen?

A: surface of epithelial cells lining the digestive tract

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3) Desmosomes• Proteoglycan layer reinforced by transmembrane proteins (cell

adhesion molecules)

•3 types - Belt, button & hemi-desmosomes

Q: Where are they abundantly seen?

A: Found in superficial layers of skin

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ANSWERS

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•The fluid mosaic model describes the structure of the plasma membrane.

•In this model the membrane is seen as a bi-layer of phospholipids in which protein molecules are embedded.

Functions of cell membrane proteins

1.Cell adhesion2.Carriers 3.Pumps4.Ion channels5.Receptors6.Enzymes

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• The DNA of all cells is made up of nucleotides.

• DNA + Histone proteins = Nucleosome

• Nucleosome + Linker DNA = Chromatin

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Answer•When ribosomes are attached it is called RER and SER when there are no ribosomes attached.

•The RER is where most of the protein synthesis occurs in the cell.

• The function of the SER is to synthesize lipids in the cell.

•The SER also helps in the detoxification of harmful substances in the cell.

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The 4 protein components are,

1. Microfilaments (mostly actin)

2. Intermediate filaments

3. Thick filaments (composed of myosin subunits)

4. Microtubules (composed of tubulin subunits)

Function:

• Maintain cell shape & integrity

• Support & move cellular structures & materials35

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THE END

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