A level Bio - Cell structure

SImilarities between Eukaryotic + Prokaryotic cells

• both contain organelles

• cell surface is called Phospholipid Bilayer → controls passage of substances across exchange surfaces

Differences between eukaryotic and prokaryotic cells

• prokaryotic → singled celled organisms whereas eukaryotic → complex organisms (larger and more complex)

• Prokaryotic cells don’t have membrane bound organelles

• prokaryotic → binary fission

• eukaryotic → meiosis/mitosis

whats in an animal cell

• mitochondria

• ribosomes

• nucleus

• cytoplasm

• enclosed in a cell membrane

• endoplasmic reticulum

• golgi

• lysomes

whats in a plant/algae cell

all of animal +

• vacuole (repository of cell sap)

• chloroplasts(photosynthesis)

• cell wall - made of cellulose, contains plasmodesmata → cells exchange surfaces

whats in a fungal cell

similar to plant but

• no chloroplasts

• cells walls made from chitin

• also multicellular

ultrastructure of EC - structure + function of nucleus envelope

structure - double membrane structure with pores, both membranes are phospholipid bilayers

function - pores control passage of ions, molecules, RNA between nucleuplasm and cytoplasm

ultrastructure of EC - structure + function of nucleus

structure - nucleoplasm is a semisolid fluid (chromatin + nucleolus are found), eukaryotes contains linear chromosomes made up of DNA

function - controls action of the cell, DNA has instructions for protein synthesis, Ribosomal RNA joined with associated proteins in the nucleolus to assemble ribosomal subunits,

ultrastructure of EC - structure + function of nucleolus

structure - largest substructure in the nucleus, made of proteins RNA + DNA

function - site at which ribosomes are made,

secondary roles → immobolising proteins, forming signal recognition particles

structure + function of mitochondria

structure - oval + double membraned organelle that has it’s own DNA + each membrane is a phospholipid bilayer embedded with proteins

the inner layer has folds which are called cristae + area surrounded by the folds is the mitochondrial matrix and contains enzymes for photosynthesis

function - makes ATP through aerobic respiration, (muscle cells have high conc as they are highly active and need energy to keep the body moving )

Structure + function of chloroplasts

structure - double membraned + have their own DNA + Ribosomes

enclosed in the inner membrane are a set of interconnected fluid-filled membrane sacks - thylakoid

a stack of thylakoids is a granum + granae are connected by lamellae(flat thin part of thylakoid membrane + fluid encolosed the membrane is stroma

function - chloroplasts allows plants + algae to make their own food, through a series of reactions that use carbon dioxide, water, light energy to make glucose + oxygen

what does ATP stand for

adenosine triphosphate

structure + function of Golgi apparatus

structure - series of flattened membranous sacs

function - transport vessicles (made from endoplasmic reticulum) fuse with golgi apparatus + empty proteins + lipids into it’s lumen

proteins + lumen are sorted, packaged + tagged so they can be sent to the right place

structure + function of Golgi vessicles

structure - membrane-bound, fluid filled vessicles in the cytpolasm

small + round and seen in high density near the edge of of golgi sacs

function - transport modified proteins and lipids to target cells from golgi apparatus, specific type is lysosomes and contains an enzyme lysozimes which helps breakdown proteins, polysaccharides, nucleic acids + old organelles

structure + function of ribosomes

structure - very small organelles made of protein subunits so they don’t have a membrane + found free floating in the cytoplasm or attached to the cytoplasmic end of the endoplasmic reticulum

function - essential for protein synthesis which is needed in every cell so practically every cell has ribosomes

function + structure of Endoplasmic reticulum(ER)

Structure - series interconnected membranous sacs + tubules, membrane is a phospholipid bilayer

smooth ER(SER) - no ribosomes

rough ER(RER) - many ribosomes on it’s surface

function -

RER - Folding + processing proteins

SER - Making + processing lipids

what is a plasma membrane

A partially permeable barrier between the cell’s interior and surroundings

what is a cell wall

Structure external to the plasma membrane found in plant, algal + fungal cells

structure of plasma membrane

Fluid mosaic model describes the structure - made up of many components(eg. cholesterol, phospholipids, proteins) that are continuously moving around.

phospholipids are the primary component and are useful since they are amphipathic( have hydrophilic and hydrophobic regions)

hydrophilic region faces outwards

hydrophillic region faces inwards

therefore polar substances can’t easily flow through the membrane

function of plasma membrane

protect the cell from their surrounding elements

partially permeable nature - allows some molecules to pass through while stopping others( mediate interactions between cell’s interior + surroundings)

used in several cellular processes(cell signalling)

attachment points for extracellular(cell wall) + intracellular (exoskeleton) structures

structure + function of cell walls

structure - rigid covering to protect the cell,

fungal → chitin

plant + algal → cellulose(polysaccharide from glucose)

function - provides structural support and gives shape to the cell

structure + function centrioles

structure - cylindrical shape made up of parallel microtubules that surround a central cavity

in most eukaryotic cells found in pairs that are at right angles to each other

only found in isolation at basal regions of flagella/cilia

function - important in the synthesis of cilia + flagella, + cell division

key component of centrosomes → crucial for organising microtubules in the cell

Centrioles help to organise mitotic spindle during cell division

structure + function of flagella

structure - hair like structure

in eukaryotes have a nine-plus-two structure( 9 pairs of microtubules surrounding a central pair), made of protein tubular

bacterial flagella mainly made of protein flagellin

function - used in organisms for locomotion

eukaryotes - create propulsion by use whipping motion

bacterial - creates propulsion in a propeller like way

structure + function cilia

structure - central core called axoneme

primary cilia - nine-plus-zero arrangement

motile cilia - nine-plus-two arrangement

function - generate locomotion of the phylum ciliophora

Cilia also help move substances internally in an organism by synchronising their beating

functions of the cytoskeleton

• maintaining shape of the cell

• securing some organelles into specific positions

• allowing cytoplasm + vesicles to move within the cell

• enabling cells within multicellular organisms to move

protein fibres of the cytoskeleton

• microfilaments - thicken the cortex around the inner edge of the cell + resist tension

• intermediate filaments - found throughout the cell + hold organelles in place

• microtubules - found in the interior of the cell where they maintain the cell shape by resisting compressing forces

structure + function of microfilaments(protein fibre of cytoskeleton)

structure - narrowest(7nm), made of intertwined strands of globular protein(actin)

actin works together with a motor protein(Myosin)

function - provide rigidity + shape to the cell

• disassemble + reform quickly so the cell can change its shape + move

• WBCs use this to move to site of infection for phagocytosis

structure + function of intermediate filaments(protein fibres of the cytoskeleton)

structure - made of several strands of fibrous proteins wounds together, 8-10nm diameter(in between)

function - structural role, bear tension to maintain shape of cell + anchor organelles, several fibrous proteins found in IF(keratin)

structure + functions of microtubules(protein fibres of the cytoskeleton)

structure - widest(25nm), hollow tubes, can disassemble + reform quickly

walls made from polymerise dimers of 2 globular proteins(a-tubulin-alpha + b-tubulin-beta),

functions

• helps resist compressions

• provide a track along which vesicles move through the cell

• pull replicated chromosomes to opposite ends of a dividing cell

Magnification + resolution

magnification - the process if enlarging an object in appearance

image - mm object - nm

image/object = magnification

resolution - the ability of a microscope to distinguish two adjacent structures as separate(higher resolution → better clarity image)

Light microscopes + uses

• specimens can be alive

• light is passed through + bent through the lens system to see specimen

• cells are usually transparent and not distinguishable unless coloured with a stain

• stains usually kills the cells

uses

• used by students

• max resolution - 0.2 micrometres max magnification - x1500

• can see the nucleus + mitochondria

electron microscopes + uses

• uses a beam of electrons

• higher magnification + resolving power

uses

• max resolution - 0.0002 micrometres

• max magnification - x1,500,000

Transmission electron microscopes(TEM)

beam of electrons penetrates the cell so provides detail of internal structures

• use electromagnets to focus electron beam

• high resolution magnets

• in thin specimens - see internal structures (chloroplasts)

scanning electron microscopes(SEM)

beam of electrons move back and forth across a cell’s surface creating detail of cell surface characteristics

• SEMs knock electrons off the specimens which come together to form an image

• SEM images can be 3D

• specimens don’t need to be thin

• Lower resolution then TEM