BIO Unit 1 New Flashcards

Cells in humans

70 kg human estimated to have 3.8 × 10¹³ cells (38 trillion)

Main statements of cell theory

• all cells are made from other cells

• all living organisms have cells

• cells are the basic unit of life

3 main structures that are common in all cells of all living organisms

• plasma membrane

• cytoplasm

• DNA

plasma membrane

• outer layer of cell

• controls the entry and exit of substances

• allows the cell to maintain substance concentrations that are different from the concentrations outside of the cell

• permeability relies on lipid structure

Lysis

• plasma membrane of cell bursts

• caused by excess pressure or viruses

• always leads to death of cell as plasma membrane is a vital structure

cytoplasm

• water is the main component but many substances dissolve or are suspended in the water

• holds enzymes that catalyse many different chemical reactions which is the metabolism of the cell

metabolism

• provides cell with energy and produces all proteins and other substances to make up the structure of the cell

• cytoplasm continuously breaks down and replaces proteins

proteins

• can be structural so needed for growth and repair

• can be enzymes that control chemical reactions and help with functioning metabolism

DNA

• genes that contain information needed for the cell to carry out functions

• can be copied onto daughter cells as information is heritable

• plant + animal cells have DNA in nucleus while bacterial has DNA in cytoplasm due to there being no nucleus

• universal genetic material

prokaryotes

• have a very simple cell structure

• small in size and can be found almost everywhere: soil, water, hot water near volcanos

• example is bacteria

structure of prokaryotes

• all cells have plasma membrane but prokaryotes have cell wall aswell

• prokaryotes have no nucleus so the interior is just the cytoplasm

• prokaryotes have small ribosomes s70

• DNA is naked, so not associated with proteins

• DNA is held in nucleoid instead of nucleus

cell wall in prokaryotes

• thicker and stronger than membrane

• protects the cell, maintains shape, and supports the membrane by stopping it from bursting

• contains peptidoglycan

cytoplasm in prokaryotes

• instead of many chambers, it’s just one uninterrupted chamber

• simpler structure because no nucleus and cytoplasm is only thing in cells other than enzymes and other biochemicals

Eukaryote cell structure

• basic cell structure with cytoplasm inside plasma membrane

• can also have cell wall

• cells can be compartmentalised so separated by single or double membranes

3 key organelle changes for eukaryotes

• nucleus

• s80 ribosomes

• mitochondria

Eukaryote differences for nucleus

• holds cell chromosomes with double membrane

• chromosomes have long DNA molecule attached to proteins except when cell must divide

• DNA is linear with histone proteins arranged into globular groups

Eukaryote differences for s80 ribosomes

• larger than in prokaryotes with s80 ribosomes instead of s70

Eukaryote differences for Mitochondria

• cytoplasm contains mitochondria surrounded by double membrane

• inner membrane folded inwards for more surface area

• carries out aerobic cell respiration

process of life in unicellular organism

7 key processes

• homeostasis

• metabolism

• nutrition

• excretion

• growth

• response to stimuli

• reproduction

Homeostasis

maintenance of constant internal environment in an organism

metabolism

sum of all biochemical reactions in living organisms

nutrition

supplying nutrients required for energy, growth, and repair of organism

Excetion

removal of waste products from metabolism

growth

increase in size or number of cells

response to stimuli

perception of stimuli and carry out correct response

reproduction

production of offspring (asexual or sexual)

Process of life - difference between unicellular and multicellular organisms

• multicellular organisms have different cells to perform different processes

• unicellular organisms have one cell to perform all functions

Unicellular organisms processes in one cell - paramecium

cilia - moves cell through water

food vacuoles - digests smaller organisms for nutrition to be absorbed into cytoplasm

cytoplasm - where metabolism occurs with enzymes to catalyse the reactions

nucleus - can divide to produce extra nuclei for reproduction which is usually asexual

cell membrane - controls what chemicals enter and leave like allowing oxygen to enter and waste products to exit

Contractile vacuoles - fill up with water to expel the water through plasma membrane for homeostasis

Plastids - animal/plant/fungi

family of organelles with two outer + inner membranes

animal - none

fungi - none

plant - plastids varied types like chloroplast and amyloplast

Cell wall - animal/plant/fungi

layer outside of plasma membrane to strengthen and protect cell

Animal - none

fungi + plant - cells have walls made from chitin for fungi and cellulose for plants

Vacuole - animal/plant/fungi

flexible fluid compartment with single membrane

animal - small and temporary

fungi + plant - large and permanent to store and pressurise cell

centrioles - animal/plant/fungi

cylinder organisms that organise structures made from microtubules

animal - construct spindle to move chromosomes in mitosis

Fungi + Plant - absent except with male gametes with centrioles at base of flagellum

Cilia + Flagella - animal/plant/fungi

gamete movement of cell

animal - present in many animal cells

fungi + plant - absent except with male gametes with centrioles at base of flagellum

Atypical cell structures in eukaryotes

4 structures

• red blood cells

• Phloem Siene tube elements

• Skeletal muscles

• Asptate fungal hyphae

Atypical Red blood cells

no nucleus in mammals so only have lifespan of 100-120 years

Atypical Phleom siene tube elements

plants move sap through tubular vessels, made of cylindrical cells so tube must be hollow with no cells to allow the movement

Atypical Skeletal muscles

some large multinucleate structures are formed when groups of cells fuse to develop muscle fibres

Atypical Asptate fungal hyphae

nucleus can divide repeatedly without cell division leading to large multicellular structures

Organelles

• structures of cells adapted to perform one or more vital functions

• efficient as they can perform a limited range of functions (specialised)

• can be enclosed by single or double membrane or solid structure comprised of proteins and RNA instead of fluid

advantages of compartmentalisation

• enzymes and substrates can be more concentrated not spread out

• substances that can cause damage to cell can be kept inside membrane of organelle

• larger area of membrane available for processes to happen

• organelles can be moved in the cell

Origin of eukaryotic cells by endosymbiosis

• endosymbiosis is where one organism lives inside another

• organisms enter through endocytosis

Endocytosis

• process that cells use to make vesicle or small vacuole by pinching off from plasma membrane

• Ex: paramecium uses it to feed on ingested organisms with digestive enzymes

Endosymbiosis - Mitochondria

mitochondria were once their own prokaryote cell but is now part of all eukaryotic cells with could have happened through endocytosis

Endosymbiosis - chloroplast

chloroplast could have developed from prokaryote that did photosynthesis that was then ingested into plants and algae

Cell differentiation to develop specialised tissue in multicellular organisms

• specialised cells are more efficient as they are developed for one specific function

• Ex: red blood cells transport oxygen using the protein haemoglobin

• differentiation starts at early stage in human life when different genes are switched on or off

Gene expression

the control of which genes are turned on and off during cell differentiation

Evolution of multicellularity

• all plants and animals are multicellular

• multicellularity has evolved independently many times in plants and at least once in animals

• multicellular organisms live longer than uni because the death of one cell does not kill organisms

• multicellular organisms are more complex compared to uni because more cell types in the organisms

Benefits of a double membrane of the nucleus - nucleus function

• Stores the cells genetic material

• through gene expression, nucleus organise cell action like growth, metabolism, protein synthesis, and division

Benefits of a double membrane of the nucleus - Nucleus structure

• semifluid matrix is found inside nucleus called nucleoplasm

• DNA is called chromatin which is a less condensed form

• contains nucleoli that synthesize ribosomes

Benefits of a double membrane of the nucleus - Nucleus envelope

• two concentric membranes

• outer membrane is consistent with the rough endoplasmic reticulum

Benefits of a double membrane of the nucleus - Nuclear pores

• create passageway for molecules to travel between nucleus and cytoplasm

• larger than channel proteins due to double membrane

• proteins responsible for structure and function of the genome are transported into the nucleus

• EX: histones, DNA polymerase, RNA polymerase

Formation of mRNA + tRNA in nucleus

• mRNA and tRNA are formed in the nucleus during transcription and must be exported to cytoplasm for translation

Benefits of a double membrane of the nucleus - Nucleus during cell division

• disassembles and reassembles during cell division

• Prophase: membrane fragmented into vesicles that move to edge of cell

• Telophase: vesicles are moved around new sets of daughter chromosomes

Structure of Ribosomes

• composed of proteins and ribosomal RNA (rRNA)

• composed of a large and a small subunit that form a functional structure

• prokaryotes have s70 - Eukaryotes have s80

• have binding sites where tRNA + mRNA bind during translation

Function of ribosomes

• free floating ribosomes synthesize polypeptides used within the cell

• bound ribosomes in the rough endoplasmic reticulum synthesize polypeptides that are secreted from the cell or become integral proteins in cell membrane

Rough endoplasmic reticulum (rER)

• flattened membrane sacs with bound ribosomes

• synthesize proteins that are released into rER

• polypeptides transport elsewhere by vesicles with the usual destination being the golgi apparatus

structure of the golgi apparatus

• composed of flattened membrane enclosed sacs called cisternae

• polypeptides are synthesised in rER and transported through vesicles which orient to nucleus

• polypeptides are transported through golgi apparatus and removed from the concave trans face

Endomembrane system

• system of compartmentalised sacs within eukaryotic cells that work to modify, process, and move molecules within or outside the cell

Function of Golgi Apparatus

• polypeptides are modified into their functional state through adding carbohydrate to make a glycoprotein or combining polypeptides

• polypeptide is then a functional protein where trans face sorts, concentrates, and packs proteins into vesicles

Vesicles

• part of endomembrane system

• small membrane bound sacs where substances are transported or stored in cells

4 examples of vesicles

• peroxisomes contain enzymes used to break down fatty acids

• Lysosomes contain enzymes needed for cellular digestion

• Transport vesicles move molecules within the cell

• Secretory vesicles contain materials that will be excreted from the cell like neurotransmitters and hormones

Clathrin

• a protein that helps in the formation of vesicles

• create a coat that helps phospholipid create a round shape as vesicle is formed

• helps anchor certain proteins to specific sites like the exterior plasma membrane

Basis of cell membrane - lipid bilayer

• phospholipids form continuous sheet-like bilayers in water due to hydrophobic + hydrophilic regions

• Bilayer forms due to the hydrophilic portion of phospholipid molecules being attracted to the water without water contact

• all cells have lipid bilayers

• lipid bilayers form spontaneously and are thought to have evolved in early evolution of life

• all cells have plasma membrane made from phospholipid bilayer but eukaryotes can have internal membrane bound organelles that compartmentalise the cytoplasm

Types of molecules involved with water

hydrophobic - repel and cannot dissolve in water due to their non-polar nature

Hydrophilic - attract water and can be dissolved in water due to polar nature

Amphipathic - contain both hydrophobic and hydrophilic parts

Lipid bilayers as barriers

• hydrophobic and hydrophilic regions cause phospholipids to naturally align as bilayers if water is present

• particles of plasma membrane are effective barriers due to hydrophobic hydrocarbon chain having low permeability to hydrophilic particles like ions and polar molecules

Membrane barriers lead to unique cellular chemistry

• due to barriers, cells can form internal conditions that are different from outside the cell

EX:

• accumulate nutrients in higher concentrations than outside

• accumulate charged ions to create an electrical potential across the cell membrane

Cell Compartmentalisation

• cells use membranes to create internal compartmentalisation which will separate the internal organelles in the cell

5 advantages of cell compartmentalisation

• enzymes and metabolites can be concentrated in a small space to increase collisions between active site and substrate

• substances that damage cells can be isolated within a membrane

• conditions like PTF can be maintained at optimum value for specific reaction

• large areas of membrane can be dense with proteins for specific processes

• organelles can be moved around the cell

Structure and function of glycoproteins and glycolipids

• both are components of plasma membrane

• form when carbs are linked to proteins or lipids

• carbs are usually chain of 3-10 sugar units called oligosaccharides

• found on extracellular surface of plasma membrane where they function in adhesion and recognition

Glycoproteins - recognition

• glycoproteins help with cell-to-cell recognition

• glycoprotein on surface of one cell is recognised by receptor on surface of another cell

• recognition is important so immune system does not attack own cells but only attacks the unknown cells

Glycolipids + Glycoproteins - Adhesion

• both can form a layer on the outside of the plasma membrane called glycocalyx

Glycocalyx

• a layer of carbohydrates that surrounds the cell membrane of many cells

Fluid mosaic model of membrane

• describes the structure of the cell membrane as a dynamic structure made of different parts

• 3 main components: phospholipids, proteins, cholesterol

Fluid mosaic model - 3 proteins

Membrane proteins - synthesised by bound ribosomes and are brought to the cell membrane via exocytosis

Integral proteins - embedded and may span the bilayer as they can establish hydrophobic interactions with the tails of phospholipids

Peripheral proteins - on membrane surfaces and don’t fully span the membrane as they attach to lipid bilayer by binding to one side of bilayer or integral protein

Enzymes as membrane bound proteins

• proteins that catalyze chemical reactions for various metabolic pathways

• ATP synthase is an enzyme that creates the energy storage ATP molecule during cell respiration and photosynthesis

Receptors as membrane bound proteins

Chemoreceptors - specific chemical signals attach to receptors on outside of cell, then protein triggers a response in cell - chemoreceptors in mouth detect taste

Hormone receptors - bind to receptors in plasma membrane of cell to activate cascade that is mediated by messenger in cell - insulin, melatonin, LH

Sensory receptors - respond to non-chemical stimuli that triggers protein to either open or close an ion channel that activates electron - baroreceptors, thermoreceptors

Transport proteins

• move specific molecules and ions across the membrane

• include chemical proteins for facilitated diffusion and pumps for active transport

Recognition proteins

• allows cells to identify each other and interact

• often glycoproteins, smaller proteins with carbs attached

Adhesion proteins

• form histones by adhering to neighbouring cells through specialised adhesion proteins in cell membrane

• often glycoproteins, smaller proteins with carbs attached

Anchorage

• most eukaryote cells release materials into extracellular space to create complex group of proteins and carbs called extracellular matrix (ECM)

• ECM provides support, segregates tissues, and regulates communication

Calculating magnification

• total magnification = ocular x objective

• 10X times 4X = 40X

Resolution

• the minimal distance between two points or objects where they still look like two different objects

Preparing a wet mount

• place small drop of suspension on glass slide

• gently lower coverslip and edges touching will spread suspension evenly

• slide then ready for viewing

Staining

• chemicals that bind to structures within sample and are used to make them show more clearly

• can be used on wet mounts for microscopes

Calculating FOV at low magnification

• place transparent ruler under low power objective of microscope

• count how many points on ruler are seen in FOV

• then convert answer into micrometers

• 1 milimeter = 1000 micrometers

calculating FOV at high magnification

• diameter at low power times magnification of low power divided by magnification of high power = diameter at high power

Calculating actual size / magnification / scale

• magnification = image size divided by actual size

• actual size = image size divided by magnification

• image size = actual size times magnification