Biology

Movement Of Substances Down A Concentration Gradient

Through Either A Channel Or Carrier Protein

Movement of water molecules from higher to lower water potentialdown a water potential gradient

Across partially permeable membrane

• Thin So There Is A short diffusion pathways
• Many stomata providing a Large surface area for gas and so gases do not have to pass through cells to reach mesophyll
• Air spaces in mesophyll to allow faster diffusion 

Mitochondrion   -  Aerobic Respiration To Produce ATP

Rough Endoplasmic Reticulum   -   Protein Synthesis

Smooth Endoplasmic Reticulum   -    Transport Of Proteins/Lipids + Production Of Lipids

Golgi Body    -     Modifying And Packaging Proteins

• Many chloroplasts  to trap or absorb light energy
• Elongated cells for maximum light absorption and light penetration
• Chloroplasts move  to trap or absorb more light energy
• Rangeof pigments can absorb a range of wavelengths and colours for max light absorption
• Large Surface Area. for rapid CO2  absorption

• protection
• maintain shape 
• preven tlysis
• strength
• support

Nucleus With Nuclear Envelope

Mitochondria / chloroplasts / SER / RER/  Golgi apparatus / linear DNA / chromosomes / lysosomes / vacuole / vesicles / cellulose cell wall

involves carrier proteins

Requires energy/requires use of ATP

Moves substances  against a concentration gradient

Phospholipid bilayer forms a barrier to water soluble / charged substances and allows non-polar substances to pass whichalso maintains a different environment on each side  -compartmentalisation

Bilayer is fluid; can bend to take up different shapes for phagocytosis

Channel proteins to let water soluble/charged substances through in facilitated diffusion;

Carrier proteins allow facilitated diffusion / active transport;

Glycoproteins / glycolipids for cell recognition / act as antigens / receptors; 

Increased Surface Area For Respiration Enzymes

• Plasmid
• Capsule
• smaller ribosomes
• complex cell wall
• mesosome

• Pathway from cells along cell walls / through spaces and out through stomata by diffusion
• Down a Water Potential / diffusion / concentration gradient

Sunken stomata, reduce air movement/diffusion gradient;

Rolled leaves reduce surface area for evaporation / encloses still air around stomata;

Waxy cuticle, reduce cuticular evaporation /impermeable to water

Few stomata, to reduce SA for diffusion

Small leaves reduce SA for diffusion

• HydrostaticPressure forces water out;
• Hydrostatic Pressure  is higher than Water Potential
• Proteins remain in blood Which increases Water Potential So Water Potential is now higher than Hydrostatic Pressure
• Water returns by osmosis along Water Potential gradient            
• Water moves out at arteriole end and back in at venule end

• long cells - tubes with no end walls 
• Continuous water columns
• No cytoplasm / no organelles to impede or obstruct flow which allows easier water flow;
• Thickening - lignin support  to withstand tension and
• is waterproof
• Pits in walls allow lateral movement and water to get round blocked vessels

Adhesion/attraction of water molecules to walls of xylem results in tension as water is pulled up the stem

Which Pulls In The Walls 

Its waxy so impermeable to water / is waterproof which stops water from passing through

Water evaporates/transpires which reduces water potential and creates water potential gradient increasing the osmotic gradient so water moves via the apoplast pathway

Water drawn out of xylem creates tension/pulling effect

Cohesive forces or H bonding between water molecules causes water moves as a column 

Elastic tissue/fibres expand and recoils to smooth the pressure surges 

Endothelium is one cell thick and is made of flattened cells giving a short diffusion pathway

Narrow lumen reduces rate of flow allowing more time for diffusion

Gaps / pores between cells increase rate of diffusion and fluid movement out of vessel

Larger wider lumen so greater volume carried

Supply Oxygen And Glucose To The Heart Muscle

So more blood can be forced towards the aorta/pulmonary 

• Artery so ventricles can empty completely; 
•  
• So semi lunar valves are forced open and Atrioventriculer valves forced closed 

Hydrostatic Pressure 

Osmosis Due To The Lower Water Potential In The Capillary 

• Root hair cells have lower water potential than soil due to active uptake of ions so water enters root hair cells by osmosis
• Then passes along apoplast pathway through cell wallsb passes along symplast pathway through plasmodesmata /cytoplasm
• Casparian strip forces water from apoplast into symplast
• Water moves from cell to cell and enters xylem by osmosis
• Salts are pumped into xylem to lower water potential

Contain semilunar valves and valves work in one direction only

Swelling caused by fluid build up

Because fluid cannot be drained into lymph vessels

Sucrose made in leaves by photosynthesis from breakdown of storage compounds; 

Sucrose actively transported into phloem by companion/transfer cells

Water potential decreases so water enters by osmosis; 

Hydrostatic pressure increases in growing areas/sinks /storage areas so sucrose is removed

Partial pressure of oxygen is high in lungs

O2 binds to Haemoglobin  and forms oxyhaemoglobin  in red blood cells

Haemoglobin has a high affinity for oxygen so dissociation occurs when partial pressure of O2 is low

Dissociation is increased by high CO2

Partial pressure of O2 is low in respiring tissues

Interphase

Prophase    –    Chromosomes Supercoil

Metaphase   –   Chromosomes Line Up At The Equator And Spindles Attach To Centromeres

Anaphase – Centromere Splits And Chromosomes Move Apart To Opposite Poles Of The Cell

Alveoli

To Provide A Large Surface Area

To Recoil And Prevent Bursting

To Return The Air Sac To Its Original Shape

To Help Expel Air

• Increases Partial Pressure And Concentration Of Oxygen In The Alveoli
• So Concentration Of Oxygen Is Higher In The Alveoli Then In The Blood

• Decreases Partial Pressure And Concentration Of Carbon Dioxide In The Alveoli
• So Concentration Of CO2 Remains Lower In The Alveoli Than In The Blood 

• Xylem – Consists Of Vessels In Which The Walls Are Lignified And Made Waterproof.
• They Are Also Hollow With No Organelles. This Allows A Continuous Transpiration Stream To Transport Water And Minerals

• Phloem – Contains Sieve Tube Elements And Companion Cells.
• Sieve Tubes Have No Nucleus And Few Organelles And Very Little Cytoplasm.Allowing Translocation To Take Place In Order To Transport Sucrose Around ThePlant 

To Maintain Higher Blood Pressure

Increase Rate Of Flow And Delivery

Blood Flow Can Be Diverted And Directed

• Thick Wall Contains Thick Layer Of Fibrous Protein Collagen Which Provides Strength    
•   
• EndotheliumWall Is Folded So It Is Not Damaged When Wall Stretches
•   
• Thick Layer Of Elastic Fibres To Cause Recoil And Return Artery To Original Shape

Thick Layer Of Smooth Muscle Constricts The Lumen Of The Artery Which Makes It Narrow 

Magnification is the number of times the image is compared to the actual object

• Resolution is the ability to distinguish between two
• separate points 

• Stomata are open to allow, gaseous exchange for the entry of carbon dioxide and exit of oxygen which is essential for photosynthesis
•     
• Water vapour leaves the leafdown a water vapour potential gradient

Higher temperatures during the daycauses greater evaporation

So some water vapour loss through leaf surface happens all the time

Microtubules and Microfilaments in Cytoskeleton provide, pathways for movement

Vesicles moves along these

Microtubules can extend and break down to guide the vesicle

The process uses metabolic energy known as ATP

Exocytosis

When The Vesicle Fuses With The Plasma Membrane Of The Cell

Then Discharging And Releasing Its Contents; The Enzymes