Unit 1 and Topic 1: Cells as the basis of life Flashcards
Describe the structure of the cell membrane based on the fluide mosaic phospholipid bilayer model.
The cell membrane is composed of 4 main components:
Phospholipid bilayer - hydrophobic tails, hydrophilic heads contributing to semi-permeability
Cholesterol - fluidity
Transport proteins - for facilitated transport
glycoproteins - help with signalling, adhesion and recognition.
Passive diffusion
With the concentration gradient, requires no energy.
osmosis, simple diffusion, facilitated diffusion
Active transport
Against the concentration gradient, requires ATP
pumps, bulk transport
Endocytosis
Transport into the cell
pinocytosis: for liquids
Phagocytosis: for solids, cell membrane invaginates to form a vesicle which gets transported into the cell carrying all the molecules.
Exocytosis
Transport out of the cell
Physical factors affecting the diffusion of substances
size
shape
Chemical factors affecting the diffusion of substances
polarity
charge
hydrophilic vs hydrophobic
and also the concentration G
SA:V
cell have a really high SA:V ratio for increased efficiency of nutrient absorption and wastee removal
Requirements for cell survival
- energy - glucose, light and chemical sources
- matter - CO2 and O2, for respiration and photosynthesis
- Simple nutrients - sugars
- macromolecules and simple molecules - amino acids, fatty acids and glycerol, nucleic acids, water, ions
- waste removal - nitrogenous waste, heat, CO2, O2, ions and water
Prokaryotes
no membrane-bound organelles
no nucleus
single circular chromosome
really small
have ribosomes and DNA
Eukaryotes
membrane-bound organelles
nucleus
linear chromosomes
larger
Organelles
mitochondria - cellular respiration
choloroplasts - photosynthesis
ribosomes - protein synthesis
lysosome - waste removal
RER - protein synthesis, studded with ribosomes
SER - carbohydrate and lipid synthesis
plastids - pigment synthesis
Significances
size of prokaryotes helps to increase efficiency as it does not have organelles to help it do so
organelles helps increase the efficiency of processes so happen more specifically and with greater efficiency due to compartmentalisation
Endosymbiotic theory
prokaryote ate another prokaryote and they formed an endosymbiotic relationship, this is why mitochondria and chloroplasts have DNA and internal membranes.
Explains why eukaryotes have membrane bound organelles
leads to genetic variation in prokaryotic cells
and also allows for varied structures and functions.
formula for the image
I = AM
3 advantages of membrane-bound organelles
- compartmentalisation so efficiency
- uses low number of enzymes that can be recycled
- allows for the concentration of reactants and storage of products
mitochondrion
site for cellular respiration
have inner membrane, folded (christae), studded with enzymes. This increases the efficiency of cellular respiration.
enzymes
reusable proteins that increase the rate of reaction as it reduces the activation energy required for processes. They are also highly specific which help in aiding multiple biochemical processes.
enzyme models
lock and key - exact fit
induced fit - becomes perfect
active site
part of the enzyme that binds to the substrate, they are very specific to the enzyme to make sure they dont start working when theyre not supposed to.
factors that affect ROR of enzymes
temp - range
pH - range
enzyme concentration - linear
substrate concentration - plateaus when enzymes are working at their maximum capacity
cofactors - some enzymes dont work without a cofactors
inhibitor - competitive and non - competitive
equation for photosynthesis
6CO2 + 12H20 > C6H12O6 + 6H2O + 6O2
stages of photosynthesis
light dependent - thylakoid membranes, splits water into H+ and O2 and ATP and NADPH
Light independent - cytoplasm, uses H+ and CO2 and ATP and NADPH into C6H12O6 and H20
equation for cellular respiration
C6H12O6 + 6O2 > 6H20 + 6CO2 + 36-38ATP
anaerobic respiration
produces lactic acid (glycolysis and fermentation)
photosynthesis and respiration are equal at the light compensation point, what does this mean?
during the day photosynthesis>respiration and opposite for the night.