L2 Life Processes at the Cellular Level

Cell

The smallest structural and functional unit of an organism. (The basic building blocks of a living thing).

Prokaryote

A unicellular organism that has no membrane bound nucleus. Eg. Bacteria.

Eukaryote

An organism that is made up of cells that have a nucleus and other membrane bound organelles. Eg. plants and animals.

Organelle

A structure within a cell that has a specialised function. (Like organs in the human body).

Chloroplast

The organelle which is the site of photosynthesis. Found in plants and other photosynthetic organisms.

Starch Granule

An energy storage unit found in plants. (Starch is made up of lots of glucose molecules joined together).

Mitochondria

The organelle where respiration occurs. (Respiration is the process where energy is released from glucose/food).

Endoplasmic Reticulum

A network of membranes found throughout the cytoplasm which are involved in the transport of materials.

Nucleus

The organelle that controls cell activity. Contains the DNA.

Ribosome

The site of protein synthesis. Found in the cytoplasm or attached to the RER.

Golgi Apparatus

Receives proteins and lipids from the endoplasmic reticulum. It modifies, sorts and packs them into sealed droplets called vesicles.

Cytoplasm

Jelly-like fluid that fills the cell. Gives the cell shape and is the site of many chemical reactions.

Plasma Membrane

A thin, flexible layer around the cell. It regulates what goes in and out of the cell.

Cell Wall

A semi-rigid layer surrounding a plant cell. Provides strength and support for the cell.

Large Central Vacuole

An organelle that provides storage, support and shape for a plant cell. (small vacuoles are found in animal cells and are used for storage).

Lysosome

An organelle that removes wastes. Contains digestive enzymes.

Cristae

The folded inner membrane of a mitochondrion. Increases the surface area so that more reactions can occur.

Respiration

The process where energy is released from glucose(food).

Glycolysis

Releases energy from glucose by splitting the molecule up.

Anaerobic Respiration

Respiration without oxygen.

Fermentation

A type of anaerobic respiration that occurs in plant cells and some microorganisms (bacteria and yeast).

Aerobic Respiration

Respiration with oxygen.

ATP

Adenosine Triphosphate. An energy storage molecule.

Photosynthesis

The process where plants use the energy from sunlight to make glucose (an energy source) from carbon dioxide and water.

Glucose

A simple sugar. An energy source found in food, particularly carbohydrates.

Starch

An energy source that contains many glucose molecules joined together.

The Light Dependant Phase

Photolysis. The first phase of photosynthesis. The energy from light is used to split water (H2O) into hydrogen (H) and oxygen (O2).

The Light Independent Phase

Carbon Fixation. The second phase of photosynthesis. Carbon dioxide and hydrogen are used to make glucose.

Chlorophyll

A green pigment found in chloroplasts that absorbs light. Essential for photosynthesis.

Phospholipid bilayer

A membrane made of 2 layers of phospholipid molecules. Hydrophilic (water "loving") heads on the outside, hydrophobic (water "hating") tails on the inside.

Semi-permeable membrane

A membrane that lets some molecules through and keeps others out.

Fluid mosaic model

The plasma membrane contains proteins that are randomly dispersed and can move around in the phospholipid bilayer.

Concentration Gradient

The difference in the concentration of a substance in one area compared with another. (eg. across a membrane).

Passive transport

Cellular transport that does not require energy (ATP). Moves molecules down the concentration gradient. Eg. Diffusion, Osmosis, Facilitated diffusion.

Active transport

Cellular transport that requires energy (ATP). Moves molecules against/up the concentration gradient. Eg. Carrier proteins, Cytosis (Phagocytosis, Pinocytosis)

Diffusion

The movement of small molecules from an area of high concentration to an area of low concentration.

Osmosis

The movement of water molecules from an area of high water concentration to an area of low water concentration.

Facilitated Diffusion

The movement of larger molecules from an area of high concentration to an area of low concentration using a transport protein.

Phagocytosis

The process of engulfing and ingesting particles into the cell (Cell "eating".). Involves a section of the plasma membrane forming a vesicle around the particles.

Pinocytosis

The process of taking fluid into the cell (Cell "drinking"). Involves a section of the plasma membrane forming a vesicle around the fluid.

Carrier Proteins

Proteins found in the lipid bilayer that allow the transport of small particles against their concentration gradient. ATP is required.

Hypotonic

A solution with a higher concentration of water molecules and lower concentration of solute molecules.

Hypertonic

A solution with a lower concentration of water molecules and higher concentration of solute molecules.

Isotonic

A Solution with the same concentration of solutes as another.

Turgid

A cell that is swollen due to a high water content. High pressure.

Flaccid

A cell that is limp due to loss of water. Low pressure.

Plasmolysis

When the plasma membrane separates from the cell wall of a plant cell as a result of low turgor pressure and water loss.

Lysis

When a cell bursts due to water gain and high pressure.

Protein

A molecule made up of amino acids. (Proteins have a large range of important functions in a cell eg. structure, transport, enzymes etc.)

Denature

When the bonds that give a protein its shape are broken (due to temperature or pH). As a result, the protein loses its shape and therefore cannot carry out its function.

Enzyme

A protein involved in biochemical reactions. A biological catalyst.

Active site

The area on an enzyme where the substrate binds during a reaction. The active site is specific to the substrate.

Substrate

The substance acted upon by an enzyme.

Anabolic

An enzyme controlled reaction that builds molecules

Catabolic

An enzyme controlled reaction that breaks down molecules.

Lock and Key Model

The shape of the substrate and the active site match each other exactly.

Induced Fit Model

The shape of the substrate and active site are not exactly matched. Enzymes are flexible and will adjust their shape to fit the substrate during a reaction.

Activation Energy

The minimum amount of energy needed to make a reaction occur.

Particle Theory

All matter is made up of particles (atoms, ions, molecules) that are in constant motion. (The particles move faster as temperature increases).

Collision Theory

In order for a reaction to occur, reactants must collide with sufficient force and in the correct orientation.

Optimum Temperature

The temperature at which an enzyme's reaction rate is fastest.

Cofactor

A substance which binds to the active site of an enzyme and helps the reaction to occur.

Inhibitor

A substance which binds to/distorts the active site of an enzyme and prevents the reaction from occuring.

Catalyst

A substance that increases the rate of a reaction without being permanently changed itself.

DNA

Deoxyribonucleic acid. A double helix shaped molecule that carries the genetic code. Found in the nucleus.

Nucleotide

The repeating unit that makes up DNA.

Base Pairing Rule

Adenine pairs with Thymine, Cytosine pairs with Guanine.

Semiconservative

One strand of a new DNA molecule comes from the parent molecule while the other is newly synthesised.

DNA Replication

The process where exact copies of the DNA are produced.(Occurs before cell division to ensure that daughter cells will have a complete copy of the genetic information).

Okazaki Fragment

The fragments that result from the synthesis of DNA on the lagging strand. Occur because DNA polymerase can only move in a 5' to 3' direction.

DNA Helicase

The enzyme that unwinds/unzips the DNA.

DNA Polymerase

The enzyme that binds the nucleotides together to form a new DNA strand.

DNA Ligase

The enzyme that binds the Okazaki fragments together.

Mitosis

Cell division for growth and repair. Produces somatic(body) cells.

The Cell Cycle

The series of events that occur in a cell leading up to cell division.

Chromosome

A section of DNA. (Humans have 46).

Daughter Cell

New cells produced by cell division (mitosis/meiosis).