Biology B1.2 What Happen In Cells?

What Is The Correct Structure Of DNA:

The correct structure of DNA is a double helix, which consists of two strands of nucleotides twisted around each other. Each nucleotide is made up of a phosphate, a deoxyribose sugar, and one of four nitrogenous bases: adenine (A), thymine (T), cytosine (C), or guanine (G). The two strands are connected by specific base pairings - adenine always pairs with thymine (A - T), and guanine always pairs with cytosine (G - C) - which forms the inside of the twisted ladder.  This is known as complementary base pairing.

DNA Is Described As A Polymer. What Is The Definition Of Polymers:

A Polymer Refers To A Long Chain Of Molecules Made Up Of Smaller Molecules Called Monomers. The Monomers In DNA Are Called Nucleotides. Monomers Are Small Repeating Units Which Join To Form A Polymer.

Chromosomes: Chromosomes are thread-like structures found in the nucleus of most cells that are made of DNA and proteins. They package and organize the body's genetic material, with each chromosome containing a long strand of DNA that holds many genes. Humans typically have 23 pairs of chromosomes in their body cells, totaling 46.

Genes: Genes are short sections of DNA that are the basic units of heredity, passed down from parents to offspring. They contain the instructions for building the proteins and functional RNA molecules that determine an individual's physical traits and control cell and body functions, such as eye color and how the heart beats. Genes are organized on chromosomes within the nucleus of cells.

What Is Transcription And Translation:

Transcription: Transcription Takes Place In The Nucleus. The DNA Is Too Big To Leave The Nucleus. Only The Code From A Small Section Is Needed For Each Protein. This Section Unzips. This Section Is Copied Into Messenger RNA (mRNA). The Base 'u' (Uracil) Is Used Instead Of 't'.

Translation: The mRNA Attaches To A Ribosome. The Ribosome 'reads' The Triplets In The Base Sequence To Decide Which Amino Acid Should Come Next. Amino Acids Are Joined Together In A Long Chain. The Amino Acid Sequence Determines Which Shape The Protein Will Have.

What Is Protein Synthesis:

Protein Synthesis Begins With Transcription In The Nucleus, Where A Segment Of DNA Is Copied Making An mRNA Strand, Using Uracil Instead Of Thymine (DNA To RNA). This mRNA Then Moves To The Cytoplasm Where Translation Occurs On A Ribosome. Here, tRNA Molecules Read The Triplet Codons On The mRNA, Bringing The Correct Amino Acids To Form A Chain Of Amino Acids (RNA To Protein) Ultimately Creating A Protein.

What Is The Lock And Key Hypothesis:

The lock and key theory is a model for enzyme action that explains enzyme specificity. It states that an enzyme has a rigid, fixed active site (the "lock") with a specific shape that is complementary to the shape of its substrate (the "key"). For a reaction to occur, the substrate must fit precisely into the active site, like a key in a lock, to be catalyzed by the enzyme. 

Different Types Of Enzymes:

Enzymes are very specific, per one enzyme is one job.

Lipases - They break down lipids and fats into glycerol and fatty acids.

Protease - They break down protein into amino acids.

Carbohydrase / Amylase - Breaks down starch into simple sugar.

Catalase - Breaks down Hydrogen Peroxide into Water and Oxygen.

Describe How An Enzyme Works:

An enzyme is made out of protein and is a biological catalyst which speed up the reaction without changing itself. The enzyme has a specific shape called the active site. The active site is complementary to a specific substrate. The substrate binds to the enzyme's complementary active site to form an enzyme-substrate complex. Once bound, the substrate and enzyme react to form the product which is released from the surface of the enzyme and therefore once bound it catalyses the reaction. Once products are formed, the substrate is released and the enzyme is ready to catalyse another reaction.

Enzymes Reactions And Factors:

Enzyme reaction rates depend on several factors: temperature, enzyme concentration, pH, and substrate concentration.

Key Points

Low temperatures slow down reactions, while increasing temperature raises reaction rates, typically doubling for every 10°C increase until reaching an optimum around 37°C. High temperatures can denature enzymes, reducing their activity.

Low enzyme levels limit reaction rates, but increasing enzyme concentration speeds up reactions until the substrate is saturated.

Each enzyme has an optimal pH, and deviations can lead to denaturation, slowing or stopping activity.

Low substrate levels also slow reactions, but increasing substrate concentration speeds them up until saturation is reached, after which the rate remains constant.

Denaturing is when an enzyme is denatured, it loses its specific three-dimensional shape, primarily due to heat or extreme pH, causing its active site to change and no longer fit the substrate. This loss of function is often irreversible and prevents the enzyme from catalyzing its intended reaction.