Biology - Cells As The Basis Of Life

Vocabulary flashcards for Biology lecture notes.

Valid Experiment

Experiments are considered valid when scientists test the hypothesis that they intended to test and give consistent results when repeated.

Reliable Experiment

Experiments are considered reliable when they can be repeated to give the same results and random error is eliminated or minimised.

Accurate experiment

An experiment is considered accurate when its measurements are close to the true value – for this to be achieved, the risk of error in measurement must be kept to a minimum.

Purposes of Models in Biology

To explain how things work, and to predict what will happen.

Independent variable

We are testing and we therefore purposefully change

Dependent variable

The result that we measure

Controlled variables

Are kept constant so that they do not interfere with our results.

Cells

Cells are the basic units of life; they carry out essential functions for all living things.

Plasma membrane

An outer covering that separates the cell's interior from its surrounding environment

Cytoplasm

Consists of a jelly-like region within the cell

DNA

The genetic material of the cell

Ribosomes

Particles that synthesize proteins

Prokaryotic Cells

Basic simple, No membrane-bound organelles, Single-cell, Smaller than eukaryotic

Eukaryotic Cells

Complex, Membrane-bound organelles, Unicellular or multicellular, Larger than prokaryotic cells

Magnification

Increase in size of the image

Transmission electron microscope (TEM)

Electrons are transmitted (pass through) the specimen. produces a two-dimensional image. magnify up to 1 500 000 times resolution of about 2 nm.

Scanning electron microscope (SEM)

Bombards solid specimens with a beam of electrons, which causes secondary electrons to be emitted from the surface layers of the specimen poorer resolution (about 10 nm) excellent three-dimensional images of surfaces

Membranes

Selective boundaries surrounds the cell contents and separates the cell contents from their surroundings controls the passage of water and other chemical substances into and out of cells

Protoplasm

Making cellular products and respiration is carried out the protoplasm is composed of the nucleus and the cytoplasm

DNA (deoxyribonucleic acid)

Large chemical that holds, in a coded form, all the genetic information (the ‘blueprint’) necessary to control the cell’s function

Nucleus

The control and information centre oval structure in the cytoplasm stores the information needed to control all cell activities surrounded by a double nuclear membrane

Endoplasmic Reticulum

The ER provides a connection of pathways between the nucleus and the cell’s environment, allowing intracellular transport ER may have ribosomes attached (rough ER; Fig. 2.23) or may have no ribosomes (smooth ER) The main function of ER is transport, but it also plays a role in processing cell products:

Ribosomes

Ribosomes are small organelles that appear as dense, rounded granules in electron micrographs Each is made of the chemicals RNA and protein

Golgi Bodies

Is also made of flat membranes, but it differs from ER in that it does not have ribosomes attached and its membranes are arranged in stacks of four to 10. Golgi bodies process, package and sort cell products

Lysosomes

This is the job carried out by lysosomes (‘lysis’ 5 to break apart), special organelles found within the cytoplasm of animal cells. contain digestive enzymes that are responsible for splitting complex chemical compounds into simpler ones

Mitochondria

Powerhouses’ of a cell, producing energy in the form of energy-rich molecules by the process of cellular respiration cells need energy, in the form of a chemical called ATP

Vacuoles

Vacuoles are large, permanent, fluid-filled sacs in the cytoplasm watery solution called cell sap, surrounded by a single membrane Small, temporary vesicles may sometimes be found in animal cells

Chloroplasts

Chloroplasts are organelles that are green in colour, due to the presence of a pigment called chlorophyll Chloroplasts are responsible for photosynthesis

Plant cell wall

Its structure allows it to provide strength and support Cell walls are permeable to most molecules

Cell Membranes

The cell membrane controls the exchange of material between the internal and external environments of the cell. It is selectively permeable

Lipid Component

The ‘fluid’ part of the cell membrane is composed of two layers of phospholipids forming a phospholipid bilayer phospholipid in these layers can be represented by a head and two tails

Hydrophilic

Able to absorb water or dissolve in water

Hydrophobic

Water avoiding or unable to dissolve in water

Membrane Proteins

Protein molecules are scattered throughout, and suspended in, the lipid bilayer It seems that some proteins are fixed in place, while others travel about freely These proteins enable cell-to-cell interaction and communication, and the exchange of substances between the cell and the external environment.

Equilibrium

Molecules move the same amount in both directions, so nothing really changes. This doesn’t need any energy.

Osmosis

Water moves from an area where there’s more water (high concentration) to an area where there’s less water (low concentration), across a semipermeable membrane (a membrane that only lets some things through).

Hypotonic

Lower solute outside à water moves into the cell

Hypertonic

Higher solute outside à water moves out of the cell

Isotonic

Same solute concentration inside and outside the cell à water moves in and out equally.

Active Transport

molecules move from a low concentration to a high concentration. This goes against the concentration gradient and needs energy from the cell. It uses specific carrier proteins in the membrane to move the molecules.

Endocytosis

If a solid particle is taken in, the process is called phagocytosis, which means "cell eating". If fluid is taken in, it is called pinocytosis, which means "cell drinking".

Exocytosis

Substances are sent out of the cell.

Organic Nutrients

Organic substances are made by living things and contain both carbon and hydrogen.

Inorganic Nutrients

Inorganic substances come from the nonliving environment and do not contain carbon and hydrogen chains.

Biomacromolecules

Large organic molecules to build their structures and support the chemical processes that keep them working

Carbohydrates

Organic molecules made of carbon (C), hydrogen (H), and oxygen (O) in a 1:2:1 ratio, with the general formula (CH₂O)x.

Lipids

Made up of many carbon (C) and hydrogen (H) atoms, with a few oxygen (O) atoms. Fats and oils in cells are often triglycerides, consisting of a glycerol molecule with three fatty acid chains. Insoluble in water and have an oily, greasy, or waxy consistency.

Proteins

Made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

Nucleic acids

Large molecules made of carbon, hydrogen, oxygen, nitrogen, and phosphorus.

Enzymes

Proteins that control all metabolic reactions in cells. They act as biological catalysts by speeding up reactions.

Metabolism

The sum of all chemical reactions in an organism. Each reaction is catalysed by a specific enzyme, with over 1000 reactions happening in each cell.

Active site of an enzyme

Where the substrate binds during a reaction.

Substrate–enzyme complex

Formed when the enzyme and substrate bind.

pH

Each enzyme functions best within a narrow pH range. pH levels that are too high or too low change the shape of the enzyme and reduce or stop its activity. Extreme pH levels can denature enzymes, making them permanently inactive.

Energy

Essential for life processes, with glucose being the primary source used by cells to drive chemical reactions.

ATP

A small, mobile molecule that delivers energy to areas of the cell where it's needed. ATP consists of adenosine (adenine attached to a ribose sugar) and three phosphate groups.

Photosynthesis

The process by which plants use light energy, typically from the sun, to convert water and carbon dioxide into oxygen, glucose, and water.

Aerobic cellular respiration

Occurs in the presence of oxygen and produces more energy

Anaerobic cellular respiration

Occurs in the absence of oxygen and produces less energy.

Aerobic cellular respiration

Involves at least 20 separate reactions, each catalysed by a specific enzyme: