Plasma Membrane

Fluid

Individual phospholipid molecules can move with the structure (increases with a higher percentage of fatty acids)

Phospholipid head

• Hydrophilic

• Polar (charged ends)

• Contains phosphorus

Phospholipid tail

• Hydrophobic

• Non-polar

• Contains lipids

Function of membrane

• Impermeable to water soluble particles, ions and polar molecules

• Controls the movement of materials into and out of the cell (selectively permeable)

• Recognition and communication between cells

• Allow ‘like’ cells to form tissues and organs

• Allows the body to distinguish foreign material from it’s own tissue

• Cellular respiration

• Removing waste

Glycoproteins

• Carbohydrate chaines

• Important in cellular recognition and immune responses.

• Help stabilise the membrane structure

Glycolipids

• Act as surface receptors

• Help stabilise the molecule

Plasma membrane

• Forms the boundary that separates the living cell from it’s non-living surroundings

• Is the boundary between extracellular fluid and the intracellular fluid (cytosol)

Cholesterol

• Disturbs the close packing of phospholipids

• Allows the membrane to remain fluid

Proteins on the bi-layer

• Can change position

• Provide selective transport through channels for water soluble particles/ions

• Catalyse reactions associated with the plasma membrane

• Communicate with the external environment and other cells

• Bind with other cells

• Others act as receptors that are able to detect hormones produced by other cells

Diffusion

The net movement of solute molecules from an area of HIGH concentration to an area of LOW concentration

• The passive movement of solute molecules

Equilibrium

Where there is no net exchange in diffusion (rate of diffusion slows down, molecules still move)’

• both sides stay the same concentration

Are able to diffuse

• small non-polar molecules

• fatty acids, vitamins

• water

• oxygen

• carbon dioxide

What can’t diffuse

• most water soluble and large particles (e.g. amino acids, carbohydrates etc.)

• small ions (e.g. Na+, K+, Ca+. H+ etc.)

Facilitated diffusion

The movement of particles from an area of high concentration to an area of low concentration using transport proteins in the plasma membrane

• still passive as no energy (ATP) is required

• more rapid than simple diffusion

Inhibitors

Can block the carrier proteins from functioning

• occupying entrances

• structurally blocking

Simple diffusion

The movement of particles from an area of high concentration to an area of low concentration without the assistance of proteins

Channel proteins

Allow water soluble and polar particles (ions) to travel across the membrane

Carrier proteins

Bind with molecules to pass through the cell membrane

Osmosis

The passive net diffusion of water molecules across a selectively permeable membrane from a solution of low solute concentration to a solutions of high solute concentration

• Free water molecules

Hypertonic

A solution that has a higher concentration of solute outside the cell than inside the cell

• H2O leaves the cell

• Cell becomes shrivelled (crenated)

• Cytoplasm shrinks (plasmolyse)

Hypotonic

A solution that has a lower concentration of solute outside the cell than inside the cell

• H2O enters the cell

• Cell becomes swelled (lysed)

• Cytosol expands within cell wall (turgid)

Isotonic

Where solute concentration is the same inside the cell as it is outside

• Even exchange of H2O entering and exiting the cell

Active transport

Performed by proteins embedded in the membrane, and moves molecules from a LOW area of concentration to an area of HIGH concentration (against the concentration gradient)

Includes:

• selectivity

• saturation

• inhibition

Exocytosis

When a cell secretes large molecules (exit out of the cell)

• Vesicle from Golgi travels to the cell membrane

• Two bi-layers rearrange so the vesicle can fuse with the membrane

• Contents of the vesicle spill to the outside of the membrane

Endocytosis

When a cell extends around external particles, surrounding them, with the membrane pinching them off and internalising the vesicle which now contains the particle.

Includes:

• Phagocytosis

• Pinocytosis

Phagocytosis

Entry of solids via endocytosis - “Cell eating”

Pinocytosis

Entry of liquids via endocytosis - “Cell drinking”

Selectivity

Where some substances are transported, others are not

Saturation

Where there is no increase in the rate of transfer when all transport proteins are open

Competitive inhibition

Where one substance can inhibit the transfer of another substance by using the same transport protein

Cell compartmentalisation

Allows organelles to have the right conditions and concentration of enzymes and reactants for a particular function, making the processes in organelles and turn the cell highly efficient

• reduces the amount of exchange that needs to occur across the plasma membrane

• creates more space for membrane-bound enzymes, allowing increased activity

Flattened shape

A way to counteract the distance from the centre of the cell to the plasma membrane increasing as cell increases in volume

• Flattening cell while keeping volume constant to result in larger surface area

Plasma membrane extensions

Extending the surface area of the plasma membrane rather than growing or flattening the cell

Autotroph

Organism that creates their own energy

Heterotroph

Organism that consumes food to get energy

Phototroph

Organism that consumes energy from the sun/light

Chemotroph

Organism that consumes energy from chemicals

Photosynthesis

The conversion of light energy from the sun into chemical energy (glucose)

Key factors of photosynthesis

• Endothermic: requires heat energy (absorbed)

• More energy required to break the bonds of reactants than energy required to form products

• Energy difference is stored as chemical energy (carbohydrates) which is later used for cellular respiration

Chemical reaction of photosynthesis

Carbon Dioxide + Water = Glucose + Water + Oxygen (6CO2 + 12H2O = C6H12O6 + 6H2O + 6O2)

Grana

Solid stacks of thylakoid membranes found within chloroplast (more thylakoid membranes = greater rate of diffusion)

Stroma

Fluid filled space found within chloroplast

Light dependant stage

• Occurs in membranes of the granum

• Light energy is used to break bonds of H2O into H+ and O2

• Chlorophyll absorbs light energy to then be converted into chemical energy

• Oxygen is created as a byproduct and is then exported

(H2O = O2 + H(ATP + NADPH))

Light independent stage

• Occurs in the stroma

• Adds CO2 to the H+ ions to create glucose

• Does not require light energy

Stomata

Small pores found on leaves of plants (where molecules exit and enter cells in plants)

Cellular respiration formula

C6H12O6 + 6O2 = 6CO2 + 6H2O

Exothermic

releasing energy

• bonds in the reactants are broken to form products: LESS energy is required to break reactant bonds (net release of energy)

ATP in cellular respiration

• Used as an energy shuttle

• When energy needs to be released

ATP → ADP + P (Phosphate released)

• When energy needs to be stored

ADP → ATP (Phosphate added)

Pyruvate

A simpler type of sugar than glucose, made during glycolysis

Glycolysis

• Stage one of cellular respiration

• Occurs in cytosol

Glucose is broken down into:

• 2x Pyruvate molecules

• 1x NADH molecule

• 2x ATP molecules

Krebs Cycle

• Stage two of cellular respiration

• Occurs in the matrix of the mitochondria

The pyruvate from glycolysis is broken down into:

• CO2

• 2x ATP molecules

• NADH + FADH2 (electron carriers)

Electron Transport Chain

• Stage three of cellular respiration

• Occurs in the cristae of the mitochondria membranes

• NADH + FADH2 transports electrons to the electron transport chain

O2 + e- + H → H2O + 32 or 34 ATP

Electrons in ETC

Electrons move between energy levels, which create enzymes to synthesise ATP, hence the larger amount of ATP produced

Anaerobic

Cellular respiration without the presence of O2 (oxygen) - is less favourable

Aerobic

Type of cellular respiration with the presence of oxygen (O2)

Anaerobic respiration for eukaryotes

For plants, it creates ethanol and O2 which is key for fermentation. For animals, it creates lactic acid, which causes health problems and is painful. Harmful/toxic waste products are difficult to remove

Anaerobic respiration in need for cells

The cell adjusts its rate of respiration according to the levels of pyruvate it detects. If the cell does not continually break down pyruvate, a feedback mechanism detects the pyruvate levels as being too high and the cell will stop respiring altogether, so even the 2 ATP’s will stop being produced

• There are also times that the 2 ATPs produces are enough to keep the cell functioning in times of extreme stress

Control group

• Active ingredient in IV is absent or the IV is removed altogether

• Allows the experimenter to observe the size of the effect the IV is having on the DV (Provides a base level measurement for comparison)

Primary source

Information created by the researcher

Secondary source

Summaries or quotes information from other primary sources

Qualitative data

• Also known as categorical data - groups are described, numbers are used as labels

• Nominal: Order of data is not important (e.g. type of treatment)

• Ordinal: Order of data is important (e.g. colour indicators that indicate the acidic strength of a solution (acid, neutral, base))

Quantitative data

• Also known as numerical data- counted or measured data

• Discrete: counted (e.g. number of people left handed)

• Continuous: measured (e.g. volume of substance)

Sample size

• The number of participants/subject or number of repeats in a group used in the study

• The number should be large to prevent a chance event

• The assignment of participants to a group should also be non-biased and randomised

Random error

• Results from ‘natural’ variation when sampling results

• Variations are not directional and vary equally either side of the true value

• Addressed by: taking large unbiased samples and averaging the results

Systematic error

• Often called equipment error (occurs due to faulty equipment)

• Results are directional, to one side of the true value, by a consistent amount

• Results produces are inaccurate

• Corrected by: Recalibration (not averaging) then repeat experiment

Personal error

• Results from mistakes in the experiment due to carelessness/oversight

• Corrected by: repeating the experiment more diligently

Reliability

• Term for repeatability and reproducibility

A method’s ability to get the same results (precision) when repeated many times (large sample size)

Repeatable

The ability to obtain very similar results if repeated by the same group of scientists

Achieved by:

• Replication of samples within an experiment

• Repeat readings of each sample size

• Repeat trials (large sample size)

• Variation in results

Reproducible

The ability to obtain very similar results if the experiment is repeated by another scientific team under different conditions

Validity

• Only when the IV influences the DV

• Controlled experiment

It is: precise, accurate, repeatable (obtained multiple times in an experiment), reproducible

Design an experiment

• Sample size

• Similarity of the subject

• The organisation of the independent variable (what is being changed)

• Describe how and when the dependent variable (change being observed) will be measured

• Mention ‘all other variables will be controlled’, and give two examples of controlled variables