Module 2 - Cells

Question 1

What is a cell and what are the 3 key structures?

Answer 1

The cell is the basic structural and functional unit of the body

3 structures:

• cytoplasm
• nucleus
• plasma (cell membrane)

Question 2

What is cytoplasm?

Answer 2

all cellular contents between the plasma membrane and nucleus

Includes:

1. Cytosol; fluid component, mostly water and proteins, carbohydrates, lipids, and inorganic ions
2. Organelles; specialized structures inside cells that perform specific functions

Question 3

4 functions of the cell membrane

Answer 3

1. physical barrier - separates the inside of the cell from what’s outside
2. permeability barrier - controls what gets in or out
3. allows communication between cells (e.g via chemicals such as hormones)
4. Binds with proteins outside the cell (e.g collagen) for anchorage and support

Question 4

Structure of cell membrane (3 components)

Answer 4

Lipid bilayer (45-50%)
-phospholipids
-cholesterol 
Proteins (45-50%)
Carbohydrates (4-8%)
glycoproteins 
glycolipids

Question 5

What is selective permeability?

Answer 5

the cell membrane regulates what gets in or out

Question 6

What are factors that determine selective permeability?

Answer 6

1. size of molecule
2. if hydrophobic or hydrophilic
3. electrical charge
4. special transport proteins called carriers (sugars, amino acids etc) and channels (for ions )

Question 7

Special transport proteins called carriers are for?

Answer 7

sugars, amino acids, etc

Question 8

Special transport proteins called channels are for?

Answer 8

ions

Question 9

Intracellular fluid ICF

Answer 9

Fluid inside cells 60%

Question 10

Extracellular fluid ECF, what are the 3 examples?

Answer 10

fluid outside cells 40%

1. interstitial fluid (between cells)
2. plasma (in blood vessels)
3. lymph (in lymphatic vessels)

Question 11

What is the nucleus?

Answer 11

the largest organelle
spherical or circular in shape
control centre of cell
controls of mitosis

Question 12

What is the nucleus composed of?

Answer 12

nuclear envelope with nuclear pores
nucleolus - manufactures ribosomes
nucleoplasm - contrains chromatin/DNA

Red blood cells do not contain a nucleus, what can’t these cells do?

Question 13

What is the endoplasmic reticulum?

Answer 13

A system of connected, folded membrane (lipid bilayer) sacs

1. Rough ER (closest to the nucleus)
2. smooth ER

Question 14

What is the rough ER?

Answer 14

its studdded with ribosomes

• receives instructions from the nucleus (mRNA)
• ribosomes manufacture proteins
• proteins are passed onto golgi complex

Question 15

What is the smooth ER?

Answer 15

function depends on cell type

• manufactures fatty acids
• manufactures steroid hormones in glands
• degrades drugs, alcohol (liver & kidney cells)
• stores calcium ions (skeletal & heart muscle) important in contraction

Question 16

What are ribosomes?

Answer 16

a protein with 2 subunits

function: protein synthesis

Question 17

What are free ribosomes?

Answer 17

They are ribosomes in the cytosol that make proteins that remain in the cytosol (e.g enzymes)

Question 18

What are ribosomes bound to the rough ER?

Answer 18

they synthesize proteins that are exported out of the cell

Question 19

What is the golgi apparatus?

Answer 19

3-20 flattened, membranous sacs (cisternae) stacked togehter

Question 20

What are the functions of the golgi apparatus?

Answer 20

protein shipping and finishing

• receives proteins from the rough ER
• modifies, stores and packages proteins into vesicles
• directs where the different proteins need to get to next

Question 21

What are vesicles?

Answer 21

Small transport/storage containers

• made from lipid bilayer
• deliver substances within the cell
• ship things in or out of the cell (like shuttle pods)

Question 22

What are specialized vesicle functions?

Answer 22

some become lysosomes - waste disposal units
some export proteins from the cell – secretory vesicle
some used in cell membrane renewal - membrane vesicle

Question 23

What are lysosomes?

Answer 23

vesicles that contain digestive enzymes

produced by golgi apparatus

Question 24

What are the functions are the lysosomes?

Answer 24

digest macromolecules or bacteria (phagocytosis)
digest worn out organelles
cause self-destruction of cells when injured (apoptosis_

Question 25

What are mitochondria?

Answer 25

The energy producers double membrane organelles with distinctive shapes matrix contains numerous enzymes (biological catalysts)

Question 26

What is the function of the mitochondria?

Answer 26

site of energy production (ATP)

Question 27

What is the cytoskeleton? What is its function?

Answer 27

a network of protein fibres within the cytoplasm maintains the shape and organization of the cell -controls organelle position -movement - during cell division, muscle contraction, phagocytosis, exocytosis -strength - keratin, collagen in skin cells

Question 28

What are the two different ways that substances may move across the cell membrane into or out of the cell?

Answer 28

Passive transport | Active transport

Question 29

What is active transport?

Answer 29

a special carrier and energy (usually ATP) is required to push solutes AGAINST their concentration gradient

Question 30

What is passive transport?

Answer 30

solutes move DOWN their concentration gradient until an equilibrium is established

Question 31

What are the 3 passive transport processes?

Answer 31

1. simple diffusion 2. facilitated diffusion (channel-mediated, carrier-mediated) 3. osmosis

Question 32

What is simple diffusion?

Answer 32

the movement of a substance from an area of higher concentration to an area of lower concentration (=concentration gradient) until equilibrium is reached

Question 33

What few things can move across the cell by simple diffusion?

Answer 33

small molecules like the gases O2, CO2, H2O lipid-soluble hormones

Question 34

What are the things that CAN NOT move across the cell membrane by simple diffusion?

Answer 34

large molecules such as sugars, amino acids, ions such as Na, K, Ca, Cl cannot due to their strong charge

Question 35

What is channel mediated diffusion?

Answer 35

For IONs - allows the passage of specific ions (K+ channel) - may have a special gate to regulate when ions can cross into/out of the cell - ions must have a concentration gradient in order to move

Question 36

What is carrier mediated diffusion?

Answer 36

Used for LARGE MOLECULES - such as monosaccharides and amino acids - a specific substance binds to specific receptor sites on one side of the membrane, binding causes a change in the shape of the transporter and opens on the opposite side - like ion channels, also requires a concentration gradient for the driving force

Question 37

What is osmosis?

Answer 37

the way water moves into/out of cells and across membranes

Question 38

Water molecules move by simple diffusion from HIGH to LOW concentration. For this to happen, you need 2 things:

Answer 38

1. special membrane: -that lets water molecules (which are small) through it -blocks larger molecules -called a selectively permeable membrae 2. a solute: molecule that is larger than the water molecule and therefore cannot get through the membrane

Question 39

What is hypotonic?

Answer 39

a solution LOWER in solute concentration than in the cell

Question 40

What is isotonic?

Answer 40

a solution with the SAME as solute concentration in the cell

Question 41

What is hypertonic?

Answer 41

a solution HIGHER in solute concentration than in the cell

Question 42

What is active transport?

Answer 42

the use of chemical energy (ATP) to move substances UP/AGAINST their concentration gradient

Question 43

Active processes include which 2 things?

Answer 43

1. Primary active transport - ion pumps 2. Vesicles - for EXOCYTOSIS and ENDOCYTOSIS

Question 44

What are ion pumps?

Answer 44

E.g Na+ and K+ pump - transports 3 Na out for 2 K in, both move AGAINST their concentration gradient - every cell in the body has Na/K pumps - VERY IMPORTANT - This is why K+ is high and Na+ low inside cells but Na+ is high and K+ is low outside cells