bio term 2 2024

prokaryotic cell

single cells and have no membrane-bound nucleus or organelles

bacteria and archaea

prokaryotic

eukaryotic cells

membrane-bound nucleus and membrane-bound organelles

microscope and cells

allowed scientists to see cells for the first time

magnification

how much an image has been increased in size

resolution

minimum distance objects need to be apart to be able to be seen separately

light microscope

pass light rays through thin specimens that are magnified by convex glass lenses, living and non-living specimens can be viewed

magnification and resolution in light microscope

up to 2000×, maximum resolution 200 nm

electron microscopes

transmission electron microscopes (TEM) and scanning

electron microscopes (SEM). No living specimens can be viewed with an electron microscope.

transmission electron microscopes

beams of electrons pass through a specimen and produce a two-dimensional image. Very high magnification and resolution are possible, up to ten million times

scanning electron microscopes

electron beams bounce off surfaces and create a three-dimensional image

organelle

membrane-bound internal structures, each with a specific function to ensure the efficient functioning of the cell

organelle surface area

most organelles have structures that maximise the surface area

organelles observable by light microscope

cell membrane, cell wall, nucleus,

chloroplasts and vacuoles

cell membrane

Selectively permeable boundaries, control the movement of substances into and out of the cell/organelle

nucleus

The control and information centre

smooth endoplasmic reticulum

transports lipids

rough endoplasmic reticulum

transports proteins

golgi apparatus

package and sort proteins

ribosomes

protein synthesis

lysosomes

Digestion and cell destruction

Mitochondria

Cellular respiration – production and storage of energy (ATP)

Vacuoles

Storage and support

Chloroplasts

Photosynthesis

Plant cell wall

Shape and support

cell membrane

selectively permeable barrier and performs the function of controlling the movement of substances into and out of the cell

fluid mosaic model

fluid’ phospholipid bilayer with different types of proteins embedded in it, creating a ‘mosaic’ effect. Proteins either penetrate from one side to the other or are only partially embedded

cell membrane proteins

form pores, some form active carrier systems or channels for transport, and others have carbohydrates attached for cell recognition.

scientific model

used in science for a number of reasons, including to simplify a concept, make a

visual representation of something that can’t be seen, or make predictions of expected results

scientific model validation

Before a model is accepted, it needs to be validated – that is, certain predictions should be made and, when tested using the model, should hold true

cell requirements

Gases, nutrients, water and ions are required by the cell, while wastes and cellular products need to be removed from the cell

permeability of membrane

depends on its size, electrical charge and its lipid solubility.

diffusion

movement of particles from a region of high concentration to a region of low concentration until equilibrium is reached.

equilibrium

no net movement of particles in either direction.

diffusion and energy

does not require the input of energy but occurs faster with a higher temperature or a steeper concentration gradient.

easily diffused molecules

Small, uncharged molecules such as oxygen and carbon dioxide

passive diffusion

allows larger molecules and small electrically charged ions to diffuse across the cell membrane aided by carrier or channel proteins

solution

a solute dissolves in solvent

concentrated solution

has a high concentration of solute and a low concentration of water

osmosis

the process by which water moves from a region of high concentration of water (dilute – low solute) to a region of low concentration of water (concentrated – high solute) which requires no energy input

osmotic pressure

the minimum pressure which needs to be applied to a solution to stop osmosis

Isotonic

fluids inside and outside a cell are of equal solute concentration – no net water movement

Hypertonic

a solution of higher solute concentration (lower water concentration) that surrounds a cell – net movement of water molecules will be out of the cell.

Hypotonic

a solution of lower solute concentration (higher water concentration) that surrounds a cell – net movement of water molecules will be into the cell.

Active transport

the movement of molecules from a region of low concentration to a region of high concentration. moves against the concentration gradient and requires the input of energy

passive transport

the movement of molecules from a region of high concentration to a region of low concentration. moves with the concentration gradient and doesn’t requires the input of energy

Endocytosis

moves large molecules that cannot cross the cell membrane into a cell by creating a vesicle around it. It requires the expenditure of energy

Exocytosis

reverse of endocytosis and used to remove waste

vesicles

small structures in a cell with a lipid layer

surface area to volume ratio

determine how efficiently substances move into and out of a cell.

high surface area to volume ratio

allows the most efficient movement of substances into and out of the cell and is mostly large cells

enzyme

proteins that control cellular reactions

enzyme-catalysed reactions

the substrate attaches to the shape on the surface of the enzyme (the active site) and forms an substrate–enzyme complex

substrate

substance where an enzyme acts on

enzyme models

lock and key model and induced fit model

enzymes and temperature

The activity of an enzyme increases as temperature increases until the optimal temperature is reached. With further temperature increases the enzyme activity decreases and then stops completely when the high temperatures denature the structure of the enzyme

enzymes and ph

Each enzyme has an optimum pH at which it functions most efficiently

enzymes and substrate concentration

As the substrate concentration increases, the activity of the enzyme increases until all the enzymes are saturated. After this, further increases in substrate concentration will not lead to increases in enzyme activity.

energy in cells

transported within cells by small and mobile ATP molecules

atp

stores energy in a high-energy bond that attaches the third phosphate group to the ADP molecule and when energy is required, the high-energy bond is broken, releasing energy, a phosphate group and ADP.