UNIT 3: Cell Anatomy

What is the cell membrane composed of

1. phospholipid bilayer

2. cholestrol: adds stablility

3. integral proteins: inegrated within the membrane, has a hydrophobic regoin,

4. Transmembrane protein: type of integral protein that extend across entire membrane

5. peripheral proteins: attached to either surface of integral proteins i.e. on

the periphery of the cell membrane

6. Carbohydrates: only on outer surface, bound to proteins or lipids, used for cell recognition & anchor cells together

7. Microvili

What are microvili and their function

small projections of cell membrane

function is to increase surface area

best seen on cells of the small intestine and kidney

Functions of membrane proteins

• enzymes

• transporters

• channels

• receptors

• anchors

• identity markers (for immune system

What types of proteins are on the membranes

1. integral proteins: inegrated within the membrane, has a hydrophobic regoin,

2. Transmembrane protein: type of integral protein that extend across entire membrane

3. peripheral proteins: attached to either surface of integral proteins i.e. on the periphery of the cell membrane

What organells are non-membranous

1. Ribosomes

2. Centrosome

3. Cytoskeleton

What are the three types of cytoskeleton

Microfilaments, Intermediate filaments, Microtubules

What are the membranous organelles

1. Mitochondria

2. Endoplasmic reticulum

3. Golgi apparatus

4. Lysosomes

5. Nucleus

Nucleus structure

• double membrane nuclear envelope

• contains nucleolus

• contains chromosomes/chromatids - DNA + histone proteins

  • dispersed = chromatin

  • condensed – tightly coiled – during cellular division – mitosis + meiosis

Ribosomes function

sites for protein synthesis

Ribosome structure/characteristics

contain ribosomal RNA (rRNA) and proteins

May be:

a) free ribosomes – float in cytosol and make proteins that go to cytosol, mitochondria, and/or nucleus

b) attached to endoplasmic reticulum (ER) - make proteins destined for all other sites

Centrosomes structure

Consist of 2 components: a pair of centrioles and the pericentriolar matrix

Centrosome function

Organizing centres for microtubules

a) spindle apparatus (for cell division)

b) organizes cytoskeleton

Cytoskeleton function

ALL types are for structural support (for cell shape) and are formed from proteins

important in cell movement, cell division, movement/anchoring of organelles and proteins e.g. receptors, enzymes

Microfilaments composistion and function

Type of cytoskeleton

Made of actin

Function: muscle contraction (w/ myosin), cell locomotion, and cytokinesis

intermediate filaments composistion

type of cytoskeleton

composition is tissue specific e.g. keratin

Microtubules function and composistion

type of cytoskeleton

hollow tubes made of tubulin

Function:

1. forms: centrioles spindle apparatus cilia (short) flagella (long)

2. move or securorganelles in place

Mitochondria function and composition

site of ATP synthesis

contains own DNA, RNA, + proteins

have a double membrane

What is Endoplasmic Reticulum (ER) and the 2 types

membranous network throughout cytoplasm

2 types: rough ER and smooth ER

Rough ER function and structure

ribosomes attached

continuous with nucleus and smooth ER

function: synthesis of secretory, lysosomal and membrane proteins

Smooth ER function and structure

lacks attached ribosomes

continuous with RER

function: synthesizes lipids and steroid hormones

• Also involved in detoxification

Golgi apparatus/complex function

modifies proteins (e.g. trims or adds carbs and lipids), sorts, packages, and delivers them to cell membrane, lysosomes, or for secretion (cellular post office)

Lysosomes function and structure

filled with digestive enzymes

Function: digest bacteria, viruses, worn-out organelles (clean up function)

Can cells have more than 1 nuclei?

yes!!

What is the nucleus

largest membranous organelle

cell control centre

Structure/parts of nucleus

1. nuclear envelope

• double membrane with nuclear pores connected to ER

2. nucleolus (>1 in some plants)

• non-membranous

• dense (less light gets through)

• region of DNA, RNA, and proteins where ribosomes are made and assembled

3. chromosomes/chromatids made of DNA + histone proteins

• can be:

  • a) dispersed = Chromatin

    • DNA uncoiled + not individually visible

    • in this form MOST of the time (when cell is not dividing)

  • b) condensed + individually visible)

    • found in dividing cells (during mitosis/meiosis)

protein destinations of proteins translated by ER-attached ribosomes?

Proteins destined for plasma membrane, lysosomes, or secretion outside the cell

• Ribosomes bound to the ER synthesize protteins tatgeted for membranes, organelle lumens, or extracellular release

Where are proteins translated by free ribosomes in the cytosol typically destined to go?

Cytosol, mitochondria, and/or nucleus

• free ribosomes attached to memebranes synthesize proteins USED LOCALLY within the cytosol or targeted to mitochondira and the nucleus

What specifically distinguishes a transmembrane protein from other integral proteins?

It extends entirely across the phopholiplid bilayer