A-Level Biology Flashcards

Comprehensive set of 200 fill-in-the-blank practice flashcards covering A-Level Biology topics including cell structure, biological molecules, enzymes, membranes, genetics, and cell division.

Resolution is the minimum distance between two objects in which they can still be viewed as __________ objects.

separate

In an optical microscope, resolution is determined by the __________ of light.

wavelength

Magnification is calculated by dividing the size of the image by the size of the real __________.

object

An eyepiece graticule is a small piece of glass with a __________ scale etched on its surface.

measurement

To calibrate an eyepiece graticule, line it up with a stage __________ while looking through the eyepiece.

micrometer

On a stage micrometer, the scale is usually $1\text{ mm}$ long with 100 divisions, so each division equals __________.

$$10\,\mu m$$

Differential staining uses different chemical stains to stain different parts of a cell in different __________.

colours

Two examples of chemical stains used in differential staining are crystal violet and __________ orcein.

acetic

Scientific drawings must be drawn in __________ and use solid lines that do not overlap.

pencil

In a transmission electron microscope (TEM), a beam of electrons passes __________ the sample.

through

In a TEM, electron beams are focused using __________ in a vacuum.

electromagnets

In a scanning electron microscope (SEM), a beam of electrons passes __________ the sample surface.

across

A major limitation of TEMs and SEMs is that the specimen must be __________.

dead

TEM allows visualization of 2D images showing inner details, such as __________ in mitochondria.

cristae

SEM produces a __________ image of the surface of cells and organelles.

3D

The plasma membrane is composed of a phospholipid bilayer with embedded intrinsic and __________ proteins.

extrinsic

The nucleolus inside the nucleus functions to synthesize __________.

ribosomes

The nucleus is surrounded by a double-membrane called the nuclear __________.

envelope

Nuclear pores allow the movement of substances to and from the __________.

cytoplasm

Mobile cilia function to move substances in a __________ motion.

sweeping

Stationary cilia play an important role in sensory organs, such as the __________.

nose

Mitochondria contain an inner membrane folded into __________ to increase surface area.

cristae

The fluid-filled centre of a mitochondrion is called the __________.

matrix

Mitochondria contain small, circular DNA and __________ size ribosomes in their matrix.

70S

Flagella have a __________ structure used primarily for mobility.

whip-like

Centrioles are made of __________ and occur in pairs to form a centrosome.

microtubules

Centrioles are involved in producing __________ fibres during cell division.

spindle

The Golgi apparatus consists of stacks of flattened membrane sacs called __________.

cisternae

In the Golgi apparatus, carbohydrates can be added to proteins to form __________.

glycoproteins

Lysosomes are vesicles formed from the Golgi apparatus containing __________ enzymes.

hydrolytic

Lysosomes release hydrolytic enzymes called __________ to break down pathogens and cell debris.

hydrolases

The cytoskeleton consists of microfilaments, microtubules, and __________ fibres.

intermediate

In the cytoskeleton, microfilaments are responsible for cell __________.

movement

Microtubules in the cytoskeleton create a __________-like structure.

scaffold

Eukaryotic ribosomes have a size rating of __________.

80S

Ribosomes are composed of protein and __________.

rRNA

Rough Endoplasmic Reticulum (RER) has bound __________ attached to its membrane system.

ribosomes

Smooth Endoplasmic Reticulum (SER) is responsible for creating, storing, and transporting lipids and __________.

carbohydrates

Water is polar because oxygen has a slight negative charge and hydrogens have a slight __________ charge.

positive

Chloroplasts contain folded membrane structures containing pigments called __________.

thylakoids

The fluid matrix surrounding thylakoids inside a chloroplast is the __________.

stroma

Plant cell walls are made of the polysaccharide __________.

cellulose

Fungal cell walls are made of __________.

chitin

Bacterial cell walls are composed of __________.

peptidoglycan

Polypeptide chains synthesized in the RER are transported to the Golgi via the __________.

cytoskeleton

Modified proteins are transported from the Golgi to the cell membrane in __________ vesicles.

secretory

Proteins are released outside the cell from secretory vesicles via __________.

exocytosis

Prokaryotic cells differ from eukaryotic cells as they have no __________-bound organelles.

membrane

Prokaryotes contain smaller ribosomes rated as __________.

70S

Prokaryotic circular DNA is not associated with __________ proteins.

histone

The capsule surrounding a prokaryotic cell wall provides protection against the host's __________ system.

immune

Calcium ions ($Ca^{2+}$) function in nerve impulse transmission and __________ contraction.

muscle

Sodium ions ($Na^+$) are involved in co-transport, kidney water reabsorption, and __________ impulse transmission.

nerve

Potassium ions ($K^+$) are essential for stomatal opening and __________ impulse transmission.

nerve

Hydrogen ions ($H^+$) drive ATP synthesis during __________.

chemiosmosis

Nitrate ions ($NO_3^-$) are absorbed by plants to synthesize amino acids and __________.

nucleotides

Hydrogencarbonate ions ($HCO_3^-$) and chloride ions ($Cl^-$) are both involved in __________ transport.

carbon dioxide

Phosphate ions ($PO_4^{3-}$) are required to form nucleic acids, ATP, and __________.

phospholipids

Water molecules stick together due to hydrogen bonds, a property known as __________.

cohesion

Cohesion between water molecules forms a continuous column of water in the __________ of plants.

xylem

Water buffers temperature changes because it has a high __________ heat capacity.

specific

Sweating provides a cooling effect because water has a high latent heat of __________.

vaporisation

Ice floats on water because hydrogen bonds make ice __________ dense than liquid water.

less

Molecules that dissolve readily in water are polar or charged and described as __________.

hydrophilic

Non-polar molecules cannot dissolve in water and are described as __________.

hydrophobic

Monomers are small single units that act as __________ to form larger polymers.

building blocks

A condensation reaction joins two monomers together and involves the elimination of a __________ molecule.

water

Hydrolysis is the breaking of a chemical bond between monomers by adding a __________ molecule.

water

Glucose is a monosaccharide hexose sugar with two structural isomers: alpha glucose and __________ glucose.

beta

In beta glucose, the $-OH$ group on carbon 1 is located at the __________ of the hexose ring.

top

Alpha glucose monomers condense to form starch and __________.

glycogen

Beta glucose monomers condense to form the structural polysaccharide __________.

cellulose

Condensation of two alpha glucose molecules forms the disaccharide __________.

maltose

Condensation of alpha glucose and galactose forms the disaccharide __________.

lactose

Condensation of alpha glucose and fructose forms the disaccharide __________.

sucrose

Disaccharides contain monomers held together by a __________ bond.

glycosidic

Glycogen has 1-4 and 1-6 glycosidic bonds creating a highly __________ structure.

branched

Starch is composed of two polysaccharides: amylose and __________.

amylopectin

Amylose contains only 1-4 glycosidic bonds and forms a coiled __________.

helix

Amylopectin contains 1-4 and __________ glycosidic bonds giving it a branched structure.

1-6

Starch is insoluble in water, so it does not affect the __________ potential of plant cells.

water

Cellulose consists of unbranched chains of beta glucose linked by __________ glycosidic bonds.

1-4

Cross-linking hydrogen bonds between cellulose chains form strong structural __________.

microfibrils

A triglyceride is formed by the condensation of one glycerol molecule and __________ fatty acids.

three

The chemical bonds formed between glycerol and fatty acids in lipids are called __________ bonds.

ester

Fatty acids that contain no carbon-carbon double bonds are __________.

saturated

Fatty acids that contain one or more carbon-carbon double bonds are __________.

unsaturated

Triglycerides are non-polar and __________ in water.

insoluble

Phospholipids consist of one glycerol, two fatty acids, and one __________ group.

phosphate

The phosphate head of a phospholipid is hydrophilic, whereas the fatty acid tails are __________.

hydrophobic

Cholesterol is a lipid belonging to the class known as __________.

sterols

Cholesterol regulates membrane fluidity: it decreases fluidity at high temperatures and __________ fluidity at low temperatures.

increases

Proteins are polymers composed of monomer subunits called __________.

amino acids

Amino acids are joined together by condensation reactions forming __________ bonds.

peptide

Every amino acid contains an amine group, a carboxyl group, a hydrogen atom, and a variable __________ group.

R

There are __________ naturally occurring amino acids that differ only by their R group.

20

A carboxyl group consists of a carbon atom double-bonded to an oxygen and single-bonded to a __________ group.

hydroxyl

Primary protein structure refers to the specific sequence of __________ in a polypeptide chain.

amino acids

Secondary protein structure includes alpha helices and beta pleated sheets held by __________ bonds.

hydrogen

Tertiary protein structure is the overall 3D folding of a polypeptide held by ionic, hydrogen, and __________ bonds.

disulfide