DNA and Proteins PDF

Summary

This document provides an overview of DNA structure, protein synthesis, and the role of proteins and lipids in biological processes. The document also explains the basics of photosynthesis.

Full Transcript

## What happens in cells and (what do cells need)? ### DNA (1.2a-c) - DNA stands for deoxyribonucleic acid - It is a double helix made from 2 strands that have twisted around each other. - It is a polymer, meaning that it is made of many different molecules that join up to make a long strand: in th...

## What happens in cells and (what do cells need)? ### DNA (1.2a-c) - DNA stands for deoxyribonucleic acid - It is a double helix made from 2 strands that have twisted around each other. - It is a polymer, meaning that it is made of many different molecules that join up to make a long strand: in the case of DNA, these molecules are called nucleotides. - Each nucleotide is made from one sugar molecule, one phosphate group (which forms the backbone) and one of the four different organic bases - The 4 bases are A, C, G, T. - These nucleotides pair by complementary base pairing, meaning that only certain bases can join together: C joins to G and A joins to T - Each group of three bases codes for an amino acid and these then join together to make a protein - Chromosomes are structures made up of long molecules of DNA. ### Protein synthesis (1.2d and e) *Biology only* DNA is too large to leave the nucleus in order to make the proteins and therefore a series of steps must be taken to copy and transport the genetic information. ### Steps of protein synthesis: 1) DNA helix is untwisted and unzipped 2) mRNA nucleotides (messenger RNA: a different type of nucleotide) match to their complementary base on the strand. 3) The mRNA nucleotides themselves are then joined together, creating a new strand called a template strand of the original DNA. This process is called transcription. 4) The template strand of mRNA then moves out of the nucleus to the cytoplasm and onto structures called ribosomes. 5) At the ribosomes, the bases on the mRNA are read in threes to code for an amino acid (the first three bases code for one amino acid, the second three bases code for another etc). This is called translation. 6) The corresponding amino acids are brought to the ribosomes by carrier molecules. 7) These amino acids connect together to form a protein. It is therefore the triplet code of bases that determines which protein is produced and therefore expressed. 8) When the chain is complete, the protein folds to form a unique 3D structure. ### Glycogen is an energy store ### Proteins - Proteins are polymers made of amino acids (monomers) - Proteins are broken down by protease enzymes in the stomach and small intestine. - Amino acids can be built up into proteins by protein synthesis. ### Lipids - Lipids are broken down by lipase enzymes - Lipids → glycerol and 3 fatty acids - Bile made in the liver emulsifies fat (makes large fat molecules into small droplets) that makes it easier for lipase enzymes to work on lipids. ### Photosynthesis ### Photosynthetic Reaction (1.4a-c) Photosynthesis is the process of making glucose from sunlight in the leaves of the plant.

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