Continuity and Change

What are the four components bonded to the central (alpha) carbon in an amino acid?

An amine group, a carboxyl group, a hydrogen atom, and an R group.

What determines the uniqueness of each amino acid?

the R group

What is a condensation reaction in the context of amino acids?

A chemical reaction where two amino acids link together, releasing a water molecule.

What type of bond is formed between amino acids during a condensation reaction?

peptide bond

What are polypeptides?

Chains of 20 or more linked amino acids.

What are oligopeptides?

Chains of fewer than 20 amino acids.

What cellular structure facilitates the condensation reaction between amino acids?

ribosomes

How many amino acids are used to create polypeptides?

20

How do animals and plants differ in obtaining amino acids?

Animals get them from their diet, plants can synthesise all 20 amino acids through photosynthesis.

What is an essential amino acid?

must obtain from diet

How many essential amino acids are there?

9

What is a non-essential amino acid?

can be synthesised by the body

Why is there an infinite variety of polypeptides?

Because of the numerous combinations possible with 20 amino acids in various lengths

Name a protein composed of two short polypeptides.

Insulin

What maintains the 3D structure of proteins?

Weak bonds between amino acid R groups

What is denaturation?

A change in the protein’s shape, causing loss of function

How does heat cause protein denaturation?

It excites atoms, causing vibrations that break weak bonds.

How does extreme pH cause denaturation?

It alters the charges in R groups, disrupting or forming new ionic bonds.

What is the primary role of the plasma membrane?

To act as a barrier between the internal and external environment of a cell

What role do membranes play inside eukaryotic cells?

compartmentalise organelles

What is the structure of biological cell membranes?

A phospholipid bilayer

What property do phospholipids have that is essential for membrane formation?

Amphipathic

What is membrane permeability?

The ability of the membrane to control which materials can enter or exit the cell.

Why can’t glucose pass easily through the lipid bilayer?

it is hydrophilic and cannot pass the hydrophobic tails

Which types of molecules can pass easily through the lipid bilayer?

Small, hydrophobic molecules

What is simple diffusion?

passive process where molecules move from high to low concentration across a membrane without energy input

What causes the movement of molecules in simple diffusion?

Random thermal motion of the molecules

What types of molecules can pass through the membrane via simple diffusion?

Small, non-polar, and lipid-soluble molecules

What are the two main types of membrane proteins?

Integral and peripheral

What are aquaporins?

Protein channels that specifically facilitate water transport across cell membranes.

Why are aquaporins important in cells like kidney cells?

They increase water permeability to meet the cell’s specific water regulation needs.

What is facilitated diffusion?

The passive movement of molecules across membranes via specific protein channels, from high to low concentration

What types of molecules typically require channel proteins to cross membranes?

Ionic and polar molecules.

What is the function of protein pumps in the membrane?

To move particles against the concentration gradient using energy

How are protein pumps different from channel proteins?

Pumps require energy, channels allow passive movement

What does selective permeability mean?

The membrane allows only specific particles to pass through

What are glycoproteins?

Proteins with carbohydrate chains covalently attached to their polypeptide chain.

What are glycolipids?

Lipids with carbohydrate groups attached by glycosidic bonds.

Where are glycoproteins and glycolipids located in the membrane?

Embedded in the phospholipid bilayer

What is the glycocalyx?

A carbohydrate-rich layer on the cell surface formed by glycoproteins and glycolipids.

What is the main function of glycoproteins and glycolipids?

Cell-to-cell recognition and identifying foreign organisms.

What is compartmentalisation in a cell?

separation of cellular functions into different membrane-bound organelles

What is the advantage of concentrating enzymes and substrates in specific organelles?

It enhances the efficiency of cellular processes.

Which structures are not considered organelles?

Cell walls, cytoskeletons, and the cytoplasm.

Name two organelles without membranes.

Ribosomes and centrioles.

Name two organelles with a single membrane.

smooth ER, and lysosomes

Name two organelles with a double membrane.

Mitochondria and chloroplasts

What is a major advantage of having the nucleus separated from the cytoplasm?

It allows for more specialised cellular functions.

Why can transcription and translation occur more easily in prokaryotes?

Because their DNA is not separated by a nucleus and resides freely in the cytoplasm.

What is a stem cell niche?

specific location in tissue that supports and regulates stem cells

What is the function of a stem cell niche?

It keeps stem cells inactive or promotes proliferation and differentiation when needed.

Where are some stem cell niches found in the human body?

bone marrow, hair follicles

What are totipotent stem cells?

Stem cells that can become any type of cell

What are pluripotent stem cells?

Cells that can become many, but not all, types of cells

What are multipotent stem cells?

Stem cells that can differentiate into a limited range of cells within a specific tissue

Where do metabolic reactions occur in the cell?

cytoplasm

What are the three main properties of effective gas exchange surfaces?

Large surface area, thin and permeable membranes, and a moist environment

Why must gas exchange surfaces be moist?

Moisture helps dissolve gases

What role do collagen fibers play in the lungs?

They provide strength and elasticity to support inhalation and exhalation.

What are alveoli and why are they important?

Tiny air sacs where gas exchange occurs, with a large total surface area due to their abundance.

What is the function of surfactant in the alveoli?

It reduces surface tension, preventing alveolar collapse during exhalation

What is Tidal Volume (TV)?

volume of air inhaled or exhaled during normal breathing

What is Inspiratory Reserve Volume (IRV)?

The extra volume of air that can be inhaled after a normal inhalation

What is Expiratory Reserve Volume (ERV)?

The extra volume of air that can be exhaled after a normal exhalation

What is Residual Volume (RV)?

The volume of air that remains in the lungs after a maximal exhalation

What is transpiration?

The loss of water vapour from the leaves and stems of plants

How does humidity affect transpiration?

High humidity reduces transpiration

How do temperature and humidity influence transpiration?

Higher temperatures increase transpiration

What is stomatal density?

The number of stomata per unit area of leaf surface

What is the structure of capillary walls?

a single layer of cells with tiny pores between them

What are fenestrated capillaries, and where are they found?

found in tissues to help speed up the exchange of substances

What is the difference between arteries and veins in terms of wall thickness?

Arteries have thick, muscular walls, while veins have thinner walls with less muscle

What role do elastic fibres in arteries play?

Elastic fibres stretch and recoil to help maintain blood pressure

What are the risk factors for coronary heart disease?

High blood pressure, smoking, high-fat diet

What is xylem sap?

Xylem sap is the water and minerals

What is the process by which water evaporates from the leaves?

transpiration

What is capillary action, and how does it relate to water movement in plants?

the process where water is drawn through tiny pores in the cell walls, helping water move up from the xylem vessels to the leaves

What is transpiration pull?

the force generated when water is lost from the leaves

How are xylem vessels adapted for efficient water transport?

long tubes formed by cells joined end-to-end, with smooth pathways and thick walls strengthened by lignin

Where is the xylem located in a vascular bundle?

the inner side

Where is the phloem located in a vascular bundle?

the outer side

What is the function of the epidermis in plant stems?

help reduce water loss.

What is the function of the cortex in a plant stem?

The cortex provides support and protection for the stem.

What are prop roots and how do they help mangrove trees?

grow above ground to anchor the tree and provide stability in muddy, unstable soil

What are pneumatophores and their function in mangroves?

vertical roots that rise above water to absorb oxygen in oxygen-poor soil

How do mangrove trees manage high salt concentrations?

They excrete excess salt through their leaves

How are mangroves adapted to fluctuating water levels?

They tolerate both submerged and dry conditions during tidal cycles

What is the function of thick waxy leaves in mangroves?

reduce water loss

What are abiotic variables?

Non-living environmental factors

What is the range of tolerance?

The range of environmental conditions within which an organism can survive, grow, and reproduceWhat happens if an abiotic factor is outside an organism’s tolerance range?

What happens if an abiotic factor is outside an organism’s tolerance range?

The factor becomes limiting and can harm or kill the organism

What is the preferred salinity range for coral reef environments?

Between 32 to 42 parts per thousand

At what depth are coral reefs usually found?

Between the surface and around 50 meters deep.What are the two main abiotic factors influencing terrestrial biomes?

What are the two main abiotic factors influencing terrestrial biomes?

Temperature and precipitation.

What climate characterizes a tropical rainforest?

Warm and wet year-round.

What are the key features of a desert biome?

Low precipitation and wide temperature fluctuations.

What are the typical conditions in a tundra biome?

Cold, dry climate with permafrost.

What defines a biome?

A large region with similar ecosystems

What is convergent evolution in biomes?

When unrelated species develop similar adaptations due to similar environmental pressures

What is stored in the camel's hump?

Fat