CELLS (2)
8 Factors living things must fufill (MRSGREEN)
Movement Respiration Sensitivity Growth Reproduction Equilibrium Excretion Nutrition
Cell theory
all living things are made up of cells
cells are the smallest and most basic unit of life
all cells come from pre-exisiting cells
What do both prokaryotic cells and eukaryotic cells have
membrane cytosol ribosomes DNA
What type of DNA do prokaryotes have
Single loop of DNA (circular)
What type of DNA do eukaryotes have
Multiple strand of linear DNA
What is/Role of plasma membrane
controls what can and cannot enter the cell
What is/Role of cytosol
contains salts, nutrients, and molecules (its fluid)
What is/Role of cytoplasm
cytosol and all organelles (not nucleus) make the cytoplasm
What is/Role of nucleus
double membrane, protect and confine DNA which codes for proteins
What is/Role of nucleolus
Site of ribosome production
What is/Role of ribosomes
rRNA and proteins, subunits makes proteins
What is/Role of rough endoplasmic reticulum
Synthesises and modifies proteins
What is/Role of smooth endoplasmic reticulum
Production of lipids
What is/Role of Golgi apparatus
Protein sorting, modifying and packaging
What is/Role of lysosome
breaks down cell waste and toxins
What is/Role of mitochondria
2 membrane, site of aerobic cellular respiration, producing ATP
contains its own DNA and ribosomes
What is/Role of chloroplast
double membrane, site of photosynthesis, own DNA and ribosomes
What is/Role of Vacuole
water and solute storage, turgor pressure of cell
What is/Role of cell wall
sturdy border outside plasma membrane and provides strength and structure
What is/Role of vesicle
membrane bound sac that transports substances in/out of cell or stores them
What is/Role of cytoskeleton
Protein filament, maintaining shape and transporting vesicles around cell
Aerobic cellular respiration formula (worded and equation)
Glucose + oxygen -> carbon dioxide + water + energy C6H12O6 + 6O2 -> 6CO2 + 6H2O + 36 ATP
Photosynthesis formula (worded and equation)
Carbon dioxide + water -> glucose + oxygen 6CO2 + 6H2O -> C6H12O6 + 6O2
What happens during photosynthesis and where does it occur
Occurs in chloroplasts Green pigment chlorophyll in chloroplast absorbs light to energise reactions Glucose produced is used to build cell walls and carry out metabolic reaction Excessive glucose stored in seeds as starch
Benefits of having small cells
Material exchange can occur efficiently due to high surface area to volume ratio Distance to travel within cell is smaller so transport of molecules is faster
Is a larger of smaller SA:V ratio more efficient and why
larger - more exposed area
MEMBRANE (3)
What is the plasma membrane made of and what does it do
Made of (phospho)lipids and is selectively permeable to seperate intra and extracellular environment
What does the phospholipid bilayer contain
Proteins, carbohydrates and cholesterol
What is the Phospholipid head made of
Glycerol and phosphate group
What charge is the phospholipid head
negatively charged
Does the phospholipid head love or hate water (hydrophilic or phobic)
Hydrophilic - loves water - polar
What is the phospholipid tail made of
fatty acids
Does the phospholipid tail love or hate water (hydrophilic or phobic)
Hydrophobic - hates water - non-polar
What charge is the phospholipid tail
uncharged
Why are phospholipids stable
Because they are amphipathic - contain both hydrophobic and hydrophilic components
Functions of proteins in the membrane
Transport - channels and pumps control what enters/exits cell Adhesion - Stick to other cells, extracellular matrix or cytoskeleton Catalysis - speeds up chemical reaction with proteins (enzymes) Communication - signals and regonise cells and molecules
Types of proteins and where are they in the membrane
Integral - permanent part of membrane Transmembrane - Integral proteins which span entire bilayer Peripheral - temporal attached to membrane
Structure of carbohydrates
In chains which extend outside of the cell Rooted in membrane to lipids (glyco) or proteins (glyco)
Function of carbohydrates
Signalling and Communication with cell Recognition of self or non-self molecules
Cholesterol structure
Lipid steroid embedded between fatty acid tails of phospholipid bilayer in animal cells
Role of cholesterol
Regulates membrane fluidity
If hot keeps molecules bound together (phospholipids)
If cold disrupts fatty acid tails, stopping phospholipids from being a solid boundary
What does the fluid mosaic model explain
Molecules in membrane are not static/ not held in one place Different molecules embedded in membrane Moves laterally (side to side)
What is diffusion
Movement of particles down a concentration gradient
from area of high concentration to area of low concentration
What molecules can freely diffuse across the membrane
non-polar
uncharged
hydrophobic
small molecules (uncharged)
What leads to even particle distribution
Kinetic energy causes molecules to randomly move and bounce off each other, eventually leading to even particle distribution
because of this higher temperatures = faster diffusion
What is a solute
thing being dissolved
What is a solvent
Thing being dissolved into
When is diffusion faster
When concentration gradient is steeper
What is facilitated diffusion and what does it allow
passive movement of molecules down the concentration gradient through a membrane bound protein (protein channel or carrier protein) Allows larger/polar molecules to pass through membrane STILL A PASSIVE PROCESS
What is a protein channel
Pores/holes in the membrane which let specific substances through
What is a carrier protein/what does it do
Binds to substance being transported and undergoes conformational change to push substance down concentration gradient through membrane
returns to its original shape once the molecule is transported
What is Osmosis
Diffusion of water from area of low solute (high solvent) concentration to area of high solute (low solvent) concentration
Why can water diffuse through membrane if hydrophilic
Can diffuse because of their small size
What are protein channels for water called
Aquaporins
What is Hypertonic and the related movement of water
High solute concentration (water moves in)
What is Isotonic and the related movement of water
Equal solute concentration (no net movement of water)
What is Hypotonic and the related movement of water
Low solute concentration (water moves out)
What happens when animal cells fill with too much water (hypertonic)
Lysed - Too much water moves in and cell swells and bursts
What is active transport
Transporting substances across the membrane using energy
Does active transport go with or against the concentration gradient
Against
What does active transport require
Energy (ATP) Membrane proteins - pumps and carriers
3 steps of active transport
Binding - binds to specific protein pump
Conformational change - energy released when bond is broken between 2nd and 3rd phosphate ions when ATP becomes ADP + P
Release - pushed through protein and into other side of membrane
What is bulk transport
Movement of groups of molecules across plasma membrane using vesicles
What are the stages of Exocytosis
Vesicular transport - vesicle containing secretory products transported to plasma membrane
Fusion - membranes of vesicle and cell fuse
Release - Secretory products released from vesicle and leave cell
Why is Exocytosis possible
Because membrane is fluid and fuses with vesicle When the vesicle fuses, it adds phospholipids and makes SA slightly bigger
What is Exocytosis
contents of vesicle released from the cell
Why does the cell expand when exocytosis happens
Phospholipids are added to membrane
What is Endocytosis
Transport into the cell
How is Endocytosis an effective defense mechanism
If invaded, a lysosome cans enter and digest invader
Endocytosis steps
Fold - membrane folds inwards and forms cavity that fills with extracellular fluid and target molecules
Trap - folds in on itself until 2 ends meet and fuse
Bud - Vesicle (endosome) pinches off from membrane
Why does the cell shrink when endocytosis happens
Phospholipids are removed from membrane
What is phagocytosis
Endocytosis of solid material or food particles
What is pinocytosis
Endocytosis of liquid or dissolved substances
CELL CYCLES (4)
Purpose of cell replication
growth and development
maintenance and repair
reproduction
What does binary fission result in
2 genetically identical copies of a cell
Binary fission steps
DNA unclouded and replicated
Cell elongates and DNA duplicate move to opposite sides
Cytokinesis - pinches inwards and creates a septum
New wall and membrane formed down middle
seperate and 2 genetically identical cells are formed
Why aren't plasmids evenly distributed during binary fission
plasmids replicate Independently therefore aren't distributed evenly
What happens during Interphase
Cell synthesises the DNA, proteins and organelles required for growth/replication
What form is DNA in during Interphase
chromatin threads not chromosomes
What happens in the G1 phase
Increase in cytosol volume
Synthesising proteins for DNA replication
Replicating its organelles At the end, cell either proceeds to S or exits cell cycle and enters G0 phase
What happens during G0 phase
cells which don't need to replicate rest here
What is a Quiescent cell
A cell which is dormant and can re-enter the cell cycle
Terminally Differentiated
A cell which is fully specialised and no longer replicates - remains in G0 indefinitely
What happens during the S phase
replicates DNA
1 chromosome becomes 2 genetically identical sister chromatids
centromere holds them together
What happens during G2 phase
increase of volume in cytosol
synthesis proteins to prepare for mitosis
What are the 4 stages of Mitosis and in order
Prophase
Metaphase
Anaphase
Telophase
What happens at Prophase?
Condensation of chromatin so chromosomes become visible Centrioles move to opposite poles Spindle fibres begin to form Nuclear membrane breaks down
What happens at Metaphase?
Spindle fibres are fully formed and attach to each chromosomes centromere
The fibres guide chromosomes to line up at equator of cell
What happens at Anaphase?
spindle fibres contract and splits centromere
sister chromatids pulled to opposite ends of cell
What happens at Telophase?
spindle fibres disintegrate
a cleavage furrow forms (animals)
a cell plate forms (plants)
What happens at Cytokinesis?
Cytoplasm divides and and organelles evenly distribute before separating into daughter cells
What happens at the G1 checkpoint?
Checks if
Cell has grown to correct size
DNA has been damaged
If there is sufficient nutrients for mitosis
What happens at the G2 checkpoint?
checks if
DNA replicated properly in S phase
Cell has enough resources for mitosis
What happens at the Metaphase checkpoint?
checks if
Spindle fibres have formed and formed correctly
Chromosomes are lined up in correct location
What are the 2 apoptotic pathways?
Mitochondrial (internal) Death Receptor (external)
What detects internal damage in the mitochondrial pathway, and how does apoptosis then begin
Mitochondria - then releases cytochrome C to bind with proteins
What starts apoptosis in the death receptor pathway and what happens afterwards
Death signalling molecules are recognised by death receptor proteins on a cells surface (generally released by immune cells)
Molecules then bind to death receptor surface protein