#3 the cell

what does the plasma / cell membrane do

encloses cell content

four components of the plasma membrane

1. phospholipid bilayer

2. membrane proteins

3. membrane carbohydrates

4. microvilli

phospholipid bilayer

forms the bulk of the membrane structure

what is the purpose of cholesterol in the plasma membrane

stabilizes the membrane, especially as temperature drops

2 kinds of membrane proteins

1. transmembrane proteins

2. peripheral proteins

transmembrane proteins

embedded in the membrane, passes all the way through

peripheral membrane

attached to the outside / inside surface of the membrane

functions of membrane proteins

• channels

• receptors

• enzymes

• etc

membrane carbohydrates

located on outer surface, functions in cell-to-cell recognition / identification

what are membrane carbohydrates attached to

• glycoprotein

• glycolipid

microvilli

• fold of the plasma membrane

• increases surface area (absorption, elimination, communication)

two primary components of cytoplasm

1. cytosol

2. organelles

cytosol

bathes organelles

contains:

• dissolved ions Na, Cl, K, Ca

• suspended carbohydrates and lipids

• melanin granules in certain cells

the 4 non-membranous organelles

• ribosomes

• centrosomes

• centrioles

• cytoskeleton

ribosomes

• non membranous

• composed of rRNA and protein

• responsible for protein synthesis

• located free in cell / attached to endoplasmic reticulum

centrosomes

• non membranous

• region located near the nucleus

• contains a granular looking matrix and 2 centrioles

centrioles

• Small, cylindrically shaped organelles composed of microtubules

• located perpendicular to one another

• Function to direct the movement of chromosomes during cell division

cytoskeleton

• determines / holds cell shape

• anchors organelles in place

• moves materials throughout the cell

the cytoskeleton is composed of 3 types of protein rods located in the cytosol…

1. microfilaments

2. intermediate filaments

3. microtubules

microfilaments

• composed of actin protein

• thinnest component of the cytoskeleton

• important for muscle contraction, cell movement, maintenance of cell shape

intermediate filaments

• composition differs based on tissue type

• works to support the cytoplasm

microtubules

• composed of tubuliin

• hollow tubes, largest component of the cytoskeleton

• structural function to anchor and move organelles

• comprises centrioles, flagella, cilia, and spindle apparatus used during cell division

3 types of membranous organelles

1. mitochondria

2. endoplasmic reticulum

3. golgi apparatus

mitochondria

• surrounded by a double membrane, convoluted for more SA

• powerhouse of the cell

• produces ATP (energy currency of the cell)

• contains DNA, RNA, protein, and water

endoplasmic reticulum

• network of membranous tubes (increases SA)

• functions in transport

rough endoplasmic reticulum

• ribosomes attached to its surface

• ribosomes work to synthesize certain proteins

smooth endoplasmic reticulum

• ribosomes are not bound

• functions to store calcium, detoxify substances (alcohol, drugs), synthesize lipids

golgi apparatus

• stacks of membranous disks

• modifies newly synthesized proteins

• packages protein into vesicles that carry protein to cell membrane, lysosomes, and extracellular environment

the nucleus

• control centre of the cell

• surrounded by double membrane with pores

• outermost membrane is continuous with rough ER

nucleolus

• consists of DNA, RNA, and proteins

• not separated from the nucleus by a membrane (located inside the nucleus)

• site of ribosome assembly

chromosomes

composed of DNA and histone proteins

• two forms

• 1. thread-like and dispersed (cells not dividing)

• 2. coiled / condensed (cell dividing)