Cell Components/Structure Flashcards
Plasma membrane
Separates the internal structures of the cell from the outside environment but allows for selective permeability
What is a plasma membrane made of
Phospholipid bilayer
Phosphate head = hydrophilic
Lipid tail = hydrophobic
Selective permeability
Selects what can get through from one side to another
What can permeable across a plasma membrane?
Non polar
Uncharged
e.g o2 co2 and steroids
What impermeable across a plasma membrane?
Ions and large uncharged molecules
e.g Glucose
What is slightly permeable across a plasma membrane?
Small polar molecules
e.g water
What other proteins and lipids are in the plasma membrane?
Cholesterol
Glycocalyx
Peripheral proteins
Integral membrane proteins
Role of cholesterol
helps shaping membrane
Role of glycocalyx (glycoproteins and glycolipids)
Functions in cell communication, immune system and cell adhesion
Role of peripheral proteins
Not securely attached to lipid bilayer, form relatively loose attachments with the polar heads or integral proteins
Role of integral membrane proteins
Securely embedded within or through the lipid bilayer (transmembrane proteins)
Transport proteins including ions and large uncharged particles that can not pass bilayer
Most proteins only bind with a specific molecule like the lock and key theory
Cytoplasm
Consists of structure inside the cell (organelles) and the surrounding fluid
Nucleus
A large structure inside the cell (organelle) that contains most of the cells genetic material (DNA)
Organelles in a cell
Ribosomes Endoplasmic reticulum (rough and smooth) Golgi Apparatus Lysomes Mitochondria Cytoskeleton Centrosome
Cytosol
Intracellular fluid that is 70-90% water and contains other components such as ions, ATP, proteins and waste products
Organelles
Specialised structures that perform specific functions within the cell
Ribosomes
Where proteins are manufactured
Composed of a large and small subunit
Found on rough ER, free floating in cytosol and in mitochondria
Endoplasmic recticulum
A network of membrane forming flattened sacs
Manufacturing and packing system
Rough ER
A network of membranes that is continuous with nuclear membrane and has ribosomes attached
Proteins made by attached ribosomes enter the sacs of the rough ER for further processing and sorting
Smooth ER
Extends from the rough ER but does not contain ribosomes.
It synthesises fatty acids and steroids and in the liver it helps to detoxify harmful substances
Golgi Apparatus
Composed of flattened membrane sacs (Cisternae)
It modifies, sorts, packages and transports proteins received by the rough ER
Processed proteins leave the cisternae in a vesicle
Lysomes
Vesicles of membrane pinched off from the golgi complex
They contain an array of enzymes capable of breaking down a wide variety of molecules not wanted or needed by the cell
Mitochondria
Performs the chemical reactions that use oxygen to produce ATP
Inner membrane is highly folded into structures called cristae which increases the surface area for chemical reactions to take place
Contaisn DNA molecule
Cytoskeleton
The cells internal supporting framework
Made up of tiny, flexible fibres and rigid, rod like pieces
Types of Cytoskeleton and their role
Intermediate filaments - Provide support and shape
Microtubules and microfilaments - Involved in the movement of cells or cell components
Centreosome
Composed of microtubules
Plays a role during cellular division, pulling chromosomes apart before cells split
Enzymes
Proteins which function to help metabolic reactions to occur
Chemical catalysts
Reduce the activation energy needed for a reaction
Effect of pH and temperature on Enzymes
At suboptimal temperature or pH it changes the shape of the active side on an enzyme so its substrate can no longer fit
Nuclear envelope
A double membrane that surrounds the nucleus separating the contents of the nucleus from the rest of the cytoplasm
DNA molecule
Stored as double stranded in the form of an double helix
DNA form when cell is ready to copy itself
Packed in chromosomes
DNA form when the cell is ready to make proteins
Unpacked so genes can be read
Stages of DNA formation
DNA double helix Nucleosome Chromatin Chromatin fibre Loop Chromatid Chromosome
Nucleosome
DNA wrapped around histones
Chromatin
Nucleosomes linked together
Chromatin fibre
Lots of chromatin
Chromatid
Chromatin fibre forming a loop shape which forms a chromatid
Chromosome
Two chromatids join with a centromere in the middle
Protein synthesis stages
Transcription
Translation
Transcription process and where it occurs
Make mRNA from DNA
Occurs in nucleus
DNA double helix is opened and the sequence of gene is converted (transcribed) into a sequence of mRNA
Transcribed mRNA exits nucleus through nuclear pores, entering cytosol and binding to a ribosome
Pairing sequence from DNA to mRNA
A/U, T/A, G/C, C/G
Translation
Protein formed for mRNA
Occurs in cytoplasm (at ribosome)
mRNA sequence is read and translated into an amino acid sequence by a ribosome
Three mRNA nucleotides = one amino acid
Translation of mRNA ends when a “Stop” mRNA sequence is reached
At that point the protein detaches from the ribosome
