WEEK TWO - CELL STRUCTURE/ SURFACE, MEMBRANE TRANSPORT, CELL Flashcards
List and describe the 9 different cell shapes and give examples of where they’re found in the body
squamous
thin/flat - bulges at nucleus
found - alveoli of lungs
discoid
disc shaped
found - regular blood cells
stellate
star shaped
found - cell bodies of nerve cells
columnar
taller than they are wide
found - small intestine cells
fibrous
long/slender/threadlike
found - skeletal muscle cells
polygonal
irregular, angular shapes [4/5 or more sides]
found - epidermis
cuboidal
squarish looking
found - kidney tubule cells
fusiform
spindle shaped, elongated with thick middle and tapered ends
found - smooth muscle ends
spheroidal
round-oval shape
found - egg cells, white blood cells
state the size range of human cells + limitations on their size
10-15 µm in diameter [micrometre]
limitations
cell growth increases volume more than surface area
- if cell grows too big = ability to absorb nutrients + ability to remove waste = REDUCED
state and identify the three major components of cells
plasma membrane
- semi-permeable barrier between ICF and ECF
nucleus
cytoplasm
describe the general structure of the plasma membrane
45-50% lipids, 45-50% proteins, 4-8% carbohydrates
State the functions of the lipid portion of the plasma membrane
allows substances that are lipid soluble like oxygen, carbon dioxide and steroids to dissolve through the membrane easily
State 6 functions of the protein portion of the plasma membrane [REIIG]
- Receptor that binds to chemical messengers eg hormones sent by other cells
- Membrane enzymes = break down chemical and messengers and terminate their effect
- To act as ion channels that are constantly open and allow ions to pass into and out of the cell
- To act as gated ion channels = open and lose to allow ions through only at certain times
- To act as a cell identity marker [glycoprotein] = distinguishes the body’s own cells from foreign cells
State the functions of the carbohydrate portion of the plasma membrane
sugary coat of glycolipids and glycoproteins = glycocalyx
glycocalyx functions
- Unique fuzzy cell surface coating that acts as a cell’s identity tag
- Cell recognition, adhesion and protection
- The body to identify ‘self’ form from foreign organisms, diseased cells and transplanted tissues
Define microvilli & cilia & compare & contrast their functions
microvilli
- extensions [1-2µm in length] of plasma membrane
- serve primarily to increase a cell’s surface area
cilia
- small hair-like extensions [7-10µm in length] of the plasma membrane
capable of movement - substances across cell surfaces
comparisons
- both are extensions of plasma membrane
- both cylindrical shaped extensions
contrasts
- cilia moves whilst microvilli DOES NOT
- different functions
- microvilli supported by actin filaments
- cilia supported by microtubules
Explain what is meant by a selectively permeable membrane and exemplify its significance
only allows certain substances through
sig.
- allows cell volume to remain unchanged and helps prevent rupture
- concentration gradient helps move substances through membrane - osmosis/diffusion
- difference in distribution of + - charged ions [electrical gradient] - important in nerve conduction + muscle contraction
Explain simple diffusion and distinguish it from filtration
Diffusion = Movement of particles from HIGH → LOW concentration
Filtration = particles driven through selectively permeable membrane by hydrostatic pressure [force exerted onto membrane by water]
List & describe 5 factors that affect the rate of diffusion [TWCSP]
- Higher Temp = molecules move faster = greater diffusion rate
- Molecular Weight
Larger molecules move slower - Steepness of Concentration gradient
INCREASE in concentration gradient = INCREASE in rate of diffusion - Membrane Surface area
INCREASE in area = INCREASE in diffusion rate - Membrane Permeability
INCREASE in permeability = INCREASE in diffusion rate
Explain osmosis and osmotic pressure
Movement of water from LOW - HIGH through selectively permeable membrane
Osmotic pressure = amount of hydrostatic pressure required to stop osmosis
Define osmolarity and tonicity and explain their importance
Osmolarity - Number of osmoles of solute per litre of solution
One osmole - one mole of dissolved particles
tonicity - ability of solution to affect fluid vol and pressure within cell
Isotonic solution - normal saline
Hypotonic
LOW concentration of non-permeating solutes
Cell absorbs water → becomes filled and round
Hypertonic
HIGH concentration of non-permeating solutes [lower water concentration]
Cells lose water, shrivel/crenate
State and describe 3 methods of carrier-mediated transport
Facilitated diffusion
Solute binds to carrier, changes shape then releases solute on other side of membrane
Transport of protein through a membrane DOWN concentration gradient
Primary active transport
Transport of solute across membrane through a carrier protein up [against] its concentration gradient
ATP required to change shape
Eg sodium potassium pump
Secondary active transport [piggyback transport
move BOTH an ion and second solute across a plasma membrane
Movement of ion usually Na+ DOWN concentration gradient - coupled with another molecule eg glucose
Define vesicular transport and distinguish between the processes of endocytosis and exocytosis
Transport of large particles/numerous molecules at once through membrane bound sac called vesicle
Exocytosis - transport OUT of cell
Endocytosis - transport of material INTO cell
