Cell Structure & Diversity- Diversity, Building Blocks of Life & The Plasma Membrane Flashcards
What are the characteristics of life?
Metabolism, Reproduction, Sensitivity (Response to. Stimuli), Heredity, Cellular Organisation, Homeostasis, Adaptation through Evolution, Growth and Development
Are eukaryotic or prokaryotic cells larger?
Eukaryotic
Why are eukaryotic cells larger than prokaryotic?
Because they have a nucleus
What is evolution?
Change over time
What is natural selection?
The reproductive success of the members of a population best adapted to the environment.
What is required for natural selection?
Variation, Inheritance, Selection, Time
What does natural selection act on?
Organisms and biological molecules
What does a phylogenetic tree show?
The shared characteristics of different organisms
What does the endosymbiosis theory state?
Two key organelles in eukaryotes are derived from bacteria
What organelles are derived from bacteria?
Mitochondria and chloroplasts
How did mitochondria and chloroplasts become part of eukaryotes?
They were engulfed by the ancestors of eukaryotes.
What is the difference between prokaryotic and eukaryotic cells?
Membrane enclosed organelles are present in eukaryotes and not prokaryotes?
What evidence is there to show that mitochondria and chloroplasts weren’t originally parts of cells?
Double membranes, reproduction independent of mitosis and they have their own ribosomes and DNA.
What has a nuclear envelope?
Eukarya
What has membrane-enclosed organelles?
Eukarya
What has peptidoglycan in cell walls?
Bacteria
What has circular chromosomes?
Bacteria and Archaea
What grows at greater than 100 degrees celsius?
Archaea
What are the building blocks of life?
amino acids, nucleobases, simple carbohydrates, glycerol, fatty acids and hydrocarbon rings
What are the four macromolecules?
Protein, DNA+RNA, Complex carbohydrates and lipids
What are the supramolecular assemblies?
Membranes, ribosomes and chromatin
What are the main four organelles?
Nucleus, mitochondria, Golgi and endoplasmic reticulum
What are macromolecules?
Organic biological molecules necessary for life
How are macromolecules formed?
By the polymerisation of building blocks (except for lipids)
What are monosaccharides?
Single unit building blocks of carbohydrates
What is the name of a monosaccharide with 5 carbons?
Pentose
What is the name of a monosaccharide with 6 carbons?
Hexose
How are disaccharides formed?
When two monosaccharides join by glycosidic linkage with a covalent bond between them
What are oligosaccharides?
Formed when 3-10 monosaccharides link together
What are polysaccharides?
Formed when more than 10 monosaccharides link together
What are the functions of carbohydrates?
Recognition, Energy and Structure
What are the five nucleobases?
Adenine, Thymine, Cytosine, Guanine, Uracil
What makes up a nucleotide?
Phosphate, Nucleobase and Sugar
What is the structure of RNA?
Single stranded helix
What is the structure of DNA?
Double stranded helix
What do the phosphates join to in DNA and RNA?
The third carbon of the following sugar
What are proteins?
Polymers of amino acids
How many amino acids are there?
20
What is the difference between amino acids?
The R group
What are the functions of proteins?
Catalytic, structural, storage, contractile, regulatory, transport, toxic, protective
What is different about lipids compared to the other macromolecules?
The are not polymers and are hydrophobic
What is the function of lipids?
Structure, regulatory (hormones) and energy
What are the roles of cells?
Manufacture cell materials, obtain raw materials, remove waste, generated energy required and control all of these processes
What are cellular membranes composed of?
Phospholipid bilayer
Why are organelles needed?
Because many different processed require many different conditions which need separate compartments
What are organelles surrounded by and why?
Membranes to create separate environments
What are the 5 functions of organelles?
Providing special conditions for specific processes, keeping incompatible substances apart, allowing specific substances to be concentrated, forming concentration gradients and packaging substances for transport or export
What is the plasma membrane?
A semi-permeable barrier which controls movement of substances in and out of the cell
What is the effect of the plasma membrane?
Limiting the size of the cell
Large SA:V ratio in small cells means…
The cell has more ability to allow things to pass through the membrane
Small SA:V ration in large cells means…
the cell has less ability to get things it needs in and doesn’t need out
What are the phospholipids made of?
Hydrophilic phosphate heads which face towards the outside of the cell and hydrophobic lipid tails which align towards each other inside the cell
The plasma membrane is fluid when the lipid tails are…
unsaturated so packing is prevented
The plasma membrane is viscous when the lipid tails are…
saturated so packing can occur
What is found in the plasma membrane to affect fluidity?
Cholesterol which stabilises membrane fluidity
What is passive transport?
Movement across membranes which requires no energy
What are phospholipid bilayers permeable to?
Hydrophobic molecules such as steroid hormones and gases
What occurs during diffusion?
The molecules move down a concentration gradient
What do phospholipid bilayers restrict?
Movement of water soluble and charged molecules
What is facilitated diffusion?
The movement of hydrophilic molecules down a concentration gradient aided by membrane proteins called channels and carriers
What do channels and carriers do?
Help specific substances move through the cell membrane
How do carriers work?
They undergo a shape change to help guide the specific molecule which they carry
What is osmosis?
The facilitated diffusion of water
Describe the concentration gradient for water during diffusion
Water moves from an area of high water concentration (low solute) concentration to a low water (high solute) concentration
What is needed for osmosis?
Channels called aquaporins
What is osmoregulation?
The regulation of osmosis to create a balance and prevent shrinking or shrivelling under varying conditions
What is active transport?
Movement across membranes against the concentration gradient (from low concentration to high concentration) which requires energy (ATP)
What does active transport require?
Transport proteins and energy
What does active transport allow?
The cell to have an internal concentration of a substance which is different to its surroundings
Explain co-transport
One substance is pumped across a membrane to create a concentration gradient ad the co-transporter can then move a second substance against its concentration gradient
What are the roles of membrane proteins?
Signal transduction, cell recognition, intercellular joining, linking cytoskeleton and extracellular fluid
What is signal transduction?
When messages are transported from outside the cell to inside the cell. The protein receives a signal that is passed into the cell and the correct organelle
What type of messages are transported through signal transduction?
Telling the cell to grow, move and die
What is cell recognition?
Includes glycoproteins and is especially important for the immune system so regular cells can be differentiated from invader cells
What is intercellular joining?
When some proteins form connections between cells
What does linking cytoskeleton and extracellular matrix do?
Allows a cell to physically connect with protein structures outside the cell
