Cells as the basis of life

Question 1

Describe the structure of cell membrane

Answer 1

Cells are surrounded by membrane (phospholipid bilayer) The main components are phospholipids, proteins and cholesterol.

Known as “fluid mosaic model’ becauses P molecules more freely, making mem fluid and the prteins are distributed throughout mem more unevenly
Hydrophilic heads + hydrophobic tails

Question 2

What’s the role of cholesterol?

Answer 2

Regulates membrane fluidity. More Chol -> the less fluid and permeable membrane. Keeps the mem stable when temp fluctuations occur

Question 3

What is the role of glycoproteins?

Answer 3

Have many roles, including antigens, indentification or recog, cell signalling, being receptor sites for hormones and cell adhesion

Question 4

What the ways cell mem maintains stable internal conditions via passive movement?

Theres two

Answer 4

Diffusion and osmosis

Question 5

Define diffusion

Answer 5

Movement of molecules/ions from high conc to low conc

Passive Movement

Facilitated diffusion involves proteins but still passive

Question 6

Define osmosis

Answer 6

Movement of water molecules down a water potential gradient through a selectively permeable mem.
Water moves from low solute conc -> high solute conc

Passive Movement

Hypotonic - A solution with a lower solute conc when compared
Hypertonic - A solution with higher solute conc when compared
Isotonic - The same solute conc as another solution

Question 7

Define Active transport and different form

Answer 7

Requires ATP from aerobic respiration and takes place against concentration gradient

Endocytosis

Question 8

Recognise what endocytosis does

Answer 8

Endocytosis is a form of AT that moves large molecules that cannot pass through hydrophobic cell mem - small molecules are engulfed by cell and then enclosed by membrane to form vesicle to transport through cytoplasm.

Pinocytosis is fluids
Exocytosis is reverse.

Phagocytosis is where a large solid particle (bacterium) is engulfed, form vesicle …

Question 9

Predict general direction of movement of materials accross cell membrane

Based on factors: concentration, physical and chemical nature of materials

Answer 9

1. Small nonpolar molecules (oxygen+CO2) - Rapidly diffuse
2. Small polar molecules (water+urea) - Diffuse much more slowly
3. *Charged particles (Ions) *- unlikely to diffuse acrros membrane, even if small

Question 10

Explain SA:V ratio

Answer 10

The ratio decreases as cell gets bigger. If cell is to big, nutrients cannot enter cell quicky to accomodate the larger volume

Question 11

What do cells need for survival?

Five

Answer 11

• Energy Source (light/chemical)
• Matter (gases e.g. oxygen)
• Simple nnutrients
• Amino acid, fatty acids ions + more
• Removal of waste

Question 12

Differences between Eurkaryote and pro

Answer 12

Eucaryote
* Have a nucleus and membrane bound organelles e.g. er, mitocondria
Prokaryote
* None of above
* Dna is circular and free in cytoplasm
* Ribosomes are smaller
*

Question 13

What are some specialised roles of eukaryotic organelles

Answer 13

Photosynthesis - Chloroplast
Cellular respiration - Mitochondria
Lysosome - removal of waste
Synthesis of proteins - Rought Er and carbohydrates,lipids, steroids - Smooth Er

Question 14

Whats the use of internal membranes?

Answer 14

Prodive large SA for attatchment od enzymes.

Enxymes control/regulate biochemical processes

The folding of membrane in mito. increases SA for enzyme controlled reaction in respirations

Question 15

Describe the active site of enzymes

Answer 15

Substrates bind to active site of enxymes that is specific to it

Question 16

How is the reaction rate of enzymes affected?

Answer 16

1. Increased temp -> rise in kinetic enegry with no of successful collisions. At low temp -> enzyme inactive
2. High temps/ changes in pH cause change on protein structure (denature) - only pH is reversible
3. Increased substate conc, increases no of successful collisions until saturation - further increasing no affect
4. Increased enzyme conc increases the same

Also inhibitors (non and competeitive)

Question 17

Describe Comp/non comp inhibition

Answer 17

Competetive :
An inhibitor structurally similar to subrstate binds to active site, preventing the substrate binding
Non-competitive:
Inhibitor binds to enzyme (not at active site) but it alters enzymes shape so active site doesnt fit the substrate

Question 18

Role of digestive enzymes?

Answer 18

Amylase : breaks down starch into maltose
Protease : breaks down protein into amino acids
Lipase: Breaks down lipids to glycerol and 3 fatty acids