small projections of cell membrane function is to increase surface area best seen on cells of the small intestine and kidney Not all cells have these

Topic 3: Cellular level of Organization, part 2 Flashcards by gurleene bhathal

Cell

Basic structural and functional unit of the body

can perform all basic life functions

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Who is Robert Hooke?

1st discovered cells

-> cork cells (dead cells)

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What is the cell membrane composed of?

a) Phospholipid bilayer
b) Cholesterol
c) Membrane proteins
d) Membrane carbohydrates

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Phospholipid bilayer

i. phosphate head group (hydrophilic)
ii. FA tails (hydrophobic)
iii. divides ICF + ECF
* barrier, selective to what can enter or exit

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Intracellular Fluid (ICF)

inside cell

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Extracellular Fluid (ECF

outside the cell

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Cholesterol

i. scattered throughout membrane
ii. adds stability to the cell membrane

at high temp= membrane will be moving lots breaking bonds melting so you want it to be less fluid

at low temps it will be moving less, so you want it to be more fluid

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What are the 2 types of membrane proteins?

Integral

peripheral

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Integral proteins

integrated within the membrane, therefore have a
hydrophobic region

¦ some extend across entire membrane, and are called
transmembrane proteins

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peripheral proteins

¦ attached to either surface of integral proteins

i.e. on the periphery of the cell membrane

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Membrane Proteins - Functions:

enzymes
• transporters
• channels
• receptors- hormones 
• anchors
• identity	markers	(for	immune	system)

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Membrane carbohydrates

only on outer surface; not in contact with ICF only ECF

• bound to proteins (glycoproteins) or lipids (glycolipids)

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List the functions of membrane carbs:

i. cell recognition e.g. sperm recognize egg cell

ii. anchor cells together

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Microvilli

small projections of cell membrane
function is to increase surface area
best seen on cells of the small intestine and kidney
Not all cells have these

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Fluid Mosaic Model

fluid - membrane constituents can move around (phospholipids and some proteins)

mosaic – proteins dot surface like tiles in a mosaic

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Cytoplasm

AREA between the inside of the cell membrane and the outside of the nucleus.

LIKE CANADA IS AN AREA

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What are the 2 divisions of the cytoplasm?

a) Cytosol

b) organelles

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Cytosol =

gel-like intracellular fluid contains water, ions (e.g. K+, Na+ ) and a suspension of carbohydrates, proteins, and lipids

may contain inclusions e.g. melanin (pigment), glycogen (stored glucose)

Organelles

structures that perform a specific function and are essential for life

i. non-membranous
in direct contact with cytosol

ii. membranous
surrounded by membrane that isolates them from the cytosol

List the non -membranous organelles

a) Ribosomes
b) Centrosomes
c) Cytoskeleton

Ribosomes

sites for protein synthesis

contain ribosomal RNA (rRNA) + proteins
may be:

→ free in cytosol - make proteins destined for cytosol, mitochondria, nucleus

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

Centrosomes

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

Organizing centres for microtubules
• spindle apparatus (for cell division)
• organizes cytoskeleton

Cytoskeleton

ALL types support cell shape and are formed from PROTEINS

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

What are the 3 types of cytoskeleton?

a) microfilaments
b) microtubules
c) intermediate filaments

microfilaments

made of actin ``` Functions: • muscle contraction (with myosin) • cell locomotion • maintenance of cell shape and projections (e.g. microvilli) • cytokinesis ```

intermediate filaments

composition is tissue specific e.g. keratin Function: • support the cytoplasm (scaffolding for the cell)

microtubules

hollow tubes made of tubulin ``` Function: • form: 1. centrioles 2. spindle apparatus 3. cilia (short) 4. flagella (long) • structural • move or secure organelles in place ```

cilia

mulitple hair like projections (in resp, tract push mucous out) short

flagella

long 1 or 2 sperm only have this within human body

List the Membranous organelles

a) Mitochondria b) Endoplasmic reticulum (ER) c) Golgi Apparatus/Complex d) Lysosomes e) Nucleus

Mitochondria

site of ATP synthesis contains own DNA, RNA, + proteins have a double membrane (outer and inner, 4 phospholipids, 2 bilayers)

Who do you inherit your mitochondrial DNA from?

Mother

Endoplasmic reticulum (ER)

membranous network throughout cytoplasm | 2 types:

Rough ER (RER)

- ribosomes attached - synthesis of secretory, lysosomal and membrane proteins

• Smooth ER (SER)

- lacks attached ribosomes - continuous with RER - synthesizes lipids + steroid hormones

Golgi Apparatus/Complex

stacks of membrane discs 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) * like post office

Lysosomes

filled with digestive enzymes digest bacteria, viruses, worn-out organelles (clean up function) * part of immune function

Nucleus

largest membranous organelle cell control centre * dictating kinds and amount of proteins cells may have 1 or more nuclei (mulit nucleated, RBC; anucleated, no nucleus)

List the parts of the nucleus

a) nuclear envelope b) nucleolus (>1 in some plants) c) chromosomes/chromatids

nuclear envelope

double membrane with nuclear pores (2 bilayers), selective don't want to damage the DNA connected to ER

nucleolus

non-membranous; easily seen in microscope dense (less light gets through) region of DNA, RNA, + proteins where ribosomes are made and assembled

chromosomes/chromatids

contain DNA + histone proteins can be: • dispersed = Chromatin - DNA uncoiled + not individually visible - in this form MOST of the time (when cell is not dividing, so that we can read it and make DNA-> MRNA • condensed + individually visible - found in dividing cells (during mitosis/meiosis)

Can peripheral proteins be on either surface, in contact with ECF and ICF?

Yes

Keratin is found in which part of the cytoskeleton?