biology chapter 1 - life processes

accuracy (of experimental results)

Closeness of an experimental result to its true value.

active site

Area on the surface of an enzyme where the substrate attaches and products are formed.

active transport

Movement of molecules or ions against a concentration gradient, using energy from respiration.

adenosine triphosphate (ATP)

Chemical present in all cells which acts as an energy 'currency'. ATP is made by respiration and used up by any process that needs a supply of energy.

aerobic respiration

Reaction that releases energy from food. Uses oxygen and produces carbon dioxide and water.

agar

Jelly-like substance used as a culture medium for growing microorganisms.

algae

Photosynthetic protoctists. Mostly unicellular, some multicellular forms (seaweeds).

anaerobic respiration

Reaction that releases energy from food, without using oxygen. Produces lactate in mammals, carbon dioxide and ethanol in yeast.

bacteria (singular = bacterium)

Small single-celled organisms with no nucleus.

capsule (of bacteria)

Slime layer covering some bacterial cells. Protects the bacterium and stops it drying out.

catalyst

Chemical that increases the rate of a reaction but remains unchanged at the end of the reaction.

cell membrane

Thin surface layer around the cytoplasm of a cell. Forms a partially permeable barrier between the cell contents and the outside of the cell.

cell wall

Non-living layer outside the cell membrane of certain types of cell. Made of cellulose (plants and algae), chitin (fungi) or peptidoglycan (bacteria).

cell

Basic structural unit of living organisms.

chitin

Substance that makes up the cell wall of fungi and the outside skeleton of insects.

control

Part of an experiment which is set up to show that other variables are not having an effect on the outcome of the experiment.

controlled variables

Variables in an experiment other than the independent variable, which are kept constant by the person carrying out the experiment so that they do not affect the results.

cytoplasm

Jelly-like material that makes up most of a cell; the site of chemical reactions of a cell.

denaturing

Process where the structure of a protein is damaged by high temperatures (becomes denatured). If the protein is an enzyme, it will no longer catalyse its reaction.

differentiation

Process taking place during the development of an embryo, where cells become specialised to carry out particular functions.

diffusion

Movement of molecules or ions down a concentration gradient.

enzyme

Protein that acts as a biological catalyst.

eukaryotic

Cells that have a nucleus (the cells of all living organisms except bacteria).

lactate

Waste product of anaerobic respiration in muscle cells.

lock and key model

Model of enzyme action where the substrate is the 'key', fitting into the 'lock', which is the active site of the enzyme.

metabolism

Chemical reactions taking place inside cells.

mitochondrion (plural = mitochondria)

Organelle that carries out aerobic respiration, releasing energy for the cell. Place where most of the cell's ATP is made.

multicellular

Composed of many cells.

nucleus

Cell organelle that contains chromosomes. Controls the activities of the cell.

organ system

Collection of different organs working together, e.g. the heart and blood vessels of the circulatory system.

organ

Structure in the body of an animal or plant that is a collection of different tissues working together to perform a function.

organelle

Part of the cell with a particular function, e.g. the nucleus.

osmosis

Net diffusion of water molecules across a partially permeable membrane from a solution with a high water potential to a solution with a low water potential.

partially permeable membrane

Membrane (e.g. the cell surface membrane) that is permeable to some molecules but not permeable to others.

precision

(of experimental results) Smallest increment that can be usefully measured, i.e. the smallest division on the scale of any measuring instrument being used.

reliability

(of experimental results) Measure of how similar the results are, if the experiment is carried out several times.

respiration

Chemical reaction taking place in cells, where glucose is broken down to release energy.

selectively permeable

A membrane that allows certain molecules or ions to pass through it by means of active or passive transport.

substrate

Molecule upon which an enzyme acts.

tissue

Collection of similar cells working together to perform a function.

vacuole

Membrane-bound space in a plant cell, filled with a solution of sugars and salts called cell sap.

Define tissue.

A group of cells with similar function.

Define diffusion.

The net movement of particles from a region of high concentration to a region of lower concentration down a concentration gradient.

Define excretion.

The removal of waste products from the body.

Define growth.

An increase in the size or number of cells.

Define organ.

A collection of several tissues working together.

Define respiration.

The release of energy (from glucose).

Give the balanced chemical symbol equation for aerobic respiration.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Give the word equation for anaerobic respiration in muscles.

glucose → lactic acid

How do bacterial cells differ from Eukaryotic cells?

Peptidoglycan cell wall

No nucleus

DNA in the form of a loop

DNA not packaged around histone proteins

Plasmids

No mitochondria/chloroplasts.

How do enzymes increase the rate of a biochemical reaction?

By reducing the activation energy for the reaction.

In which organelle does respiration take place?

Mitochondrion (plural mitochondria).

List four components of a typical animal cell.

Cell surface membrane

Cytoplasm

Nucleus

Ribosomes

Mitochondria.

List four components of a typical fungal cell.

Cell surface membrane

Cytoplasm

Nucleus

Permanent vacuole

Ribosomes

Mitochondria

Chitin cell wall.

List four components of a typical plant cell.

Cell surface membrane

Cytoplasm

Nucleus

Ribosomes

Mitochondria

Chloroplast

Permanent vacuole

Cell wall.

State four factors that affect the rate of diffusion.

Concentration gradient

Temperature

Surface area or surface area:volume ratio

Distance.

State two differences between diffusion and active transport.

Active transport uses energy

Active transport is against a concentration gradient.

State two differences between diffusion and osmosis.

Osmosis is the movement of water molecules

Osmosis is movement across a partially permeable membrane.

What happens above the optimum temperature for an enzyme?

The enzyme molecules start to denature.

The shape of the active site changes.

The substrate no longer fits the active site.

Fewer enzyme-substrate complexes are formed.

The rate of reaction decreases.

What is a Prokaryote?

A bacterial cell.

What is meant by the term 'partially permeable membrane'?

Some molecules are able to pass across the membrane but others cannot.

What is the balanced symbol equation for photosynthesis?

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₆

What is the name of the site on an enzyme to which the substrate binds?

Active site.

What is the word equation for anaerobic respiration by yeast cells.

glucose → ethanol + carbon dioxide

What substances are found in the vacuole of plant cells?

Water

Dissolved ions

Dissolved sugars.

Which substance is used to absorb carbon dioxide in a respirometer?

Soda lime / potassium hydroxide.

Which two components of a cell are found in all types of cell?

Cell membrane