L2 eukaryotes and prokaryotes

Multicellular organism

Organisms made up of more than one cell.

Single-celled

Organism consisting of a single cell

Bacteria

Microscopic unicellular prokaryotes

Archaea

Bacteria-like unicellular prokaryotesExtreme aquatic environment

basic features of cells

1. All cells are surrounded by a plasma membrane.(also called cell membrane) 2. The semifluid substance within the membrane is the cytoplasm, containing the organelles. 3. All cells contain at least one chromosome containing genetic material (DNA) 4. All cells also have ribosomes, tiny organelles where proteins are made.

Organelles

1. Organelles are composed of macromolecules arranged into complex structures. 2. They perform specialized functions within the cell. 3. Specialization requires compartmentalization: formation of separate compartments within the cell

where are eukaryotic cells found in?

•Protists e.g. Amoeba •Fungi •Plants •Animals

difference in shape between plant and animal cells

plant cells have a fixed rigid shape animal cells can have a variety of irregular shapes. plant cells are generally larger than animal cells

what is the cell membrane

A thin, flexible layer round the outside of all cells made of phospholipids and proteins.

function of the cell membrane

Acts as a selective barrier that controls passage of substances into and out of the cell

cytoplasm

The solution within the cell membrane. It contains enzymes for respiration and other metabolic reactions together with sugars, salts, amino acids, nucleotides and everything else needed for the cell to function

cytoskeleton

A network of protein fibres extending throughout all eukaryotic cells, used for support, transport and motility. (3 types of protein fibres microfilaments, intermediate filaments and microtubules)

nucelus

•Surrounded by a nuclear membrane with nuclear pores - large holes containing proteins that control the exit of substances from the nucleus. •Interior is called the nucleoplasm, it contains chromatin- made up of DNA and attached proteins.

nucleolus

dark region of chromatin involved in making ribosomes

What's the difference between chromatin and chromosomes ????

When a cell is not dividing all the chromosomes together are referred to as chromatin and cannot be individually seen.During cell division the chromatin becomes condensed into observable chromosomes.

how mnay chromosomes does reproductive cells have

23

how many chromosomes does a typical human cell have

46 chromosomes

Lysosomes

small membrane-bound vesicles formed from the RER in animal cells

function of lysosomes

They contain digestive enzymes used to break down unwanted chemicals, toxins, organelles or even whole cells, so that the materials may be recycled

vacuoles

membrane-bound sacs containing water or dilute solutions of salt and other solutes

vacuoles in plant and animal cells

Animal cells can have small vacuoles that are formed as required, plant cells usually have one very large permanent vacuole that fills most of the cell, so that the cytoplasm (and everything else) forms a thin layer round the outside. Plant cell vacuoles are filled with cell sap, and are very important in keeping the cell rigid, or turgid.

do plant or animal cells contain plastids

plant cells

three types of plastids

chromoplastsamyloplastschloroplasts

Chromoplasts

synthesize and store different colour pigments, examples Carotene (yellow), Xanthophyll (red) and anthocyanin (purple). As Chromoplasts can determine the colouring of plants they play an important role in attracting pollinators.

amyloplasts

Function in the storage of starch within plant cells. (also known as starch grains). They are found in large numbers in fruit tissue and in underground storage structures such as potato tubers Plants store carbs in the form of starch

chloroplasts

Contain the pigment chlorophyll and are the site for photosynthesis. Photosynthesis is the process by which green plants(and some algae) can trap the energy of sunlight and synthesize sugar.

Chloroplast structure

•Surrounded by a double membrane, outer and inner •Inside the inner membrane is a third membrane celled the thylakoid which is arranged in stacks of thylakoid discs called grana •Between the inner membrane and the thylakoid is a watery matrix called the stroma •The light dependant phase of photosynthesis takes place in the grana •The light-independent phase of photosynthesis takes place in the strom

cell wall

A thick permeable layer outside the cell membrane used to give a cell strength and rigidity. Plant cell walls are made mainly of cellulose, but can also contain hemicellulose, pectin, lignin and other polysaccharides.

plasmodesmata,

channels through plant cells which link the cytoplasms of adjacent cells

Components common with Eukaryotic cells

1. Cell/Plasma membrane 2. Cytoplasm 3. Genetic component 4. Ribosomes

Cell Envelope

The cell envelope is all the layers from the cell membrane outward, including the cell wall, the periplasmic space, the outer membrane, and the capsule

what do all free-living bacteria have

cell wall- it dictates cell shape an prevents oosmotic rupture

what is found in gram-negatives

Periplasmic space and outer membrane

where is the capsule found

only found in some strains

three main layers in prokaryotic cells

1. Cell/Plasma Membrane 2. Cell Wall 3. Capsule

Plasma Membrane/Cell Membran

Phospholipid biolayer i.e structurally similar to eukaryotes, the membrane must be fluid for it to function correctly. Membrane integrity is required for survival as this barrier separates the cytoplasm from the environment allowing the cytoplasm to function properly Provides little protection from osmotic lysis but acts as a selective barrier. A very active area of the cell in prokaryotes- ATP synthesis- Enzyme activity involved in metabolism Proteins responsible for transport and sensing e.g. concentration of moelcules

Cell Wall prokaryotic

- Essential for maintaining cell integrity, preventing osmotic lysis and contributes to cell shape. (Osmotic pressure in bacterial cells due high concentration of solutes in the cytoplasm) - Main component is peptidoglycan. - Difference in this structure allows for differentiation of bacteria into gram negative and gram positive bacteria

capsule

The capsule is a condensed, well defined layer of polysaccharide that closely surrounding the cells Can compose a large portion of the cells Only found in some species. Common in pathogens.

functions of capsule

• Adherence • Niche Adaptation • Anti-Phagocytosis • Protection against desiccation • Drug Resistance

Genetic components

plasmid nucleoid

what do prokaryotes contain instead of a nucleus

•Prokaryotes lack a true nucleus instead they contain a region called the nucleoid.

nucleoid

region-made up of one circular chromosome. There is no nuclear membrane .

plasmids

Extra-chromosomal circular DNA present in some bacteria.Plasmids are NB in genetic engineering -used as vectors to carry genes from one organism to another

Flagellum

A rigid rotating helical-shaped tail used for propulsion or movement. Flagella may also be present in eukaryotic cells ( eg sperm cells) but have a more complex structure than those in prokaryotes.

pili

used for attachment between cells and have a role in exchange of genetic material between cells

external structures prokaryotes

flagellumpili

prokaryotes size

0.2-2um

prokaryotes complexity

less complex

prokaryotes membrane bound organelles

none

prokaryotes genetic component

nucleoid and plasmid

prokaryotes cell wall

yes and contains peptidoglycan

prokaryotes cell division

binary fission

eukaryotes size

10-100 um

eukaryotes complexity

more complex

eukaryotes membrane bound organelles

yes e.g mitochondria

eukaryotes genetic component

Dna stored in membrane bound nucleus

eukaryotes cell wall

Yes in some eukaryotes But does not contain peptidoglycan

Eukaryotes cell division

Mitosis & Meiosis