NCEA Level 2 Cell Biology

activation energy

The minimum amount of energy required to trigger a chemical reaction

active site

the site on an enzyme that attaches to a substrate

active transport

movement of molecules through protein channels in the membrane from low to high concentration requiring energy (ATP)

ADP

(Adenosine Diphosphate) The compound that remains when a phosphate group is removed from ATP, releasing energy

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

Catalyst

a substance that initiates or accelerates a chemical reaction without itself being affected or used during the reaction

Cell membrane

thin, flexible barrier around a cell; regulates what enters and leaves the cell

cell wall

a rigid structure that surrounds the cell membrane and provides support to the cell. Only found in plant cells and some bacteria.

concentration gradient

a measure of how the concentration of a solution changes from one place to another

cytoplasm

a jellylike fluid inside the cell in which the organelles are suspended

denatured

Enzymes that are destroyed by high temps (or changes in pH) that change their 3D structure so they can no longer function properly

endoplasmic reticulum

a cell structure that forms a maze of passageways in which proteins and other materials are carried from one part of the cell to another

enzyme

protein that acts as a biological catalyst

flaccid

lacking firmness or stiffness. Flaccid cells are plant cells that have lost water via osmosis.

golgi apparatus

A system of membranes that modifies and packages proteins for export by the cell

induced fit model

change in the shape of an enzyme's active site that enhances the fit between the active site and its substrate(s)

lock and key theory

This theory says that the enzymes active site is exactly complementary to the structure of the substrate.

lysosome

membrane-bound vacuole containing digestive enzymes that can break down proteins, nucleic acids, and polysaccharides

mitochondria

Powerhouse of the cell, organelle that is the site of ATP (energy) production

osmosis

diffusion of water molecules through a semipermeable membrane from a place of higher water potential to a place of low water potential until equilibrium is achieved

passive transport

transport of a substance across a cell membrane by diffusion - movement from high concentration to low concentration (WITH the concentration gradient).

Doesn't require energy.

phagocytosis

process in which cells engulf and digest microorganisms and cellular debris using their cell membrane.

pinocytosis

‘cell eating’, which involves the uptake of small liquid/dissolved particles through the cell membrane.

plasmolysis

when a cell is in a hypertonic environment, the cell will lose water to its surroundings, shrink, and its plasma membrane will pull away from the wall

ribosome

site of protein synthesis

semipermeable membrane

a membrane that allows some molecules to pass through but not others

substrate

The reactant on which an enzyme works.

turgor

a cell's swelling against its cell wall caused by the pressure of the cell's contents

vacuole

cell organelle that stores materials such as water, salts, proteins, and carbohydrates

vesicle

small membrane-bound sac that functions in moving products into, out of, and within a cell

enzyme inhibitor

any substance or molecule that slows down the rate of an enzyme-controlled reaction by affecting the enzyme molecule in some way. It could:

- sit in the active site

- change the shape of the active site

Limiting factors (enzyme controlled reactions)

Enzyme controlled reactions can be slowed down by:

- temperature (too cold)

- temperature (too hot - denatures enzyme)

- pH (denatures enzyme)

- not enough substrate

- too much substrate (not enough enzyme)

anabolic reactions

enzymes are used to build molecules

catabolic reactions

enzymes are used to break apart molecules

enzyme specificity

the concept that each enzyme is designed to work on a specific substrate, allowing only certain reactions to occur

Hypotonic

a solution with a lower concentration of solutes

Hypertonic

a solution with a higher concentration of solutes

isotonic

a solution with an equal concentration of solutes, resulting in no net movement of water across a semipermeable membrane.

lysed

when an animal cell is placed in a hypotonic solution, causing it to gain water, swell, and eventually burst

shrivels up

when an animal cell is placed in a hypertonic solution an it loses water

plasmolysed

when a plant cell is placed in a hypertonic solution and loses sufficient amount of water and turgor pressure that its cell membrane detaches from the cell wall

flaccid

when a plant cell is placed in a hypertonic solution and loses water and turgor pressure, but doesn’t become plasmolysed

turgid

when a plant cell is placed in a hypotonic solution and gains water and turgor pressure builds up