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Chloroplast

Chloroplast

Chloroplasts are the food producers of the cell.

The organelles are only found in plant cells and

algae and some protists. Animal cells do not have

chloroplasts.

Chloroplasts work to convert light energy from the

Sun into sugars that can be used by cells during

respiration. Their main role is to conduct

photosynthesis, where the photosynthetic pigment

chlorophyll captures the energy from sunlight and

stores it in energy-storage molecules like ATP

while freeing oxygen from water.

The number of chloroplasts per cell varies from 1

in some algae up to 100 in plants like wheat.

Mitochondrion

Mitochondrion

One of the biochemical processes of the cell is

known as aerobic respiration. Many of the

reactions involved in aerobic respiration happen

inside a mitochondrion.

Mitochondria are the working organelles that keep

the cell full of energy. Mitochondria are often

referred to as the powerhouses of the cells.

Mitochondria range from 0.5 to 1.0 μm in diameter

and are found in nearly all eukaryotes.

Mitochondria are small organelles floating free

throughout the cell. Some cells have several

thousand mitochondria while others have none.

Muscle cells need a lot of energy so they have

loads of mitochondria. Neurons (cells that transmit

nerve impulses) don’t need as many.

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Nucleus

Nucleus

The nucleus is arguably the most important

organelle in the cell. It is the control centre, telling

all of the other organelles what to do and when to

do it. The nucleus also contains the cell's genetic

material.

The nucleus is surrounded by two membranes.

These membranes have many openings in them,

which allow for the transport of materials into and

out of the nucleus.

Prokaryotic cells lack a nucleus. In these

organisms (which include the bacteria), the genetic

material is free-floating within the cell membrane.

The genetic material of prokaryotes is a different

shape than that of eukaryotes, but it serves the

same function.

Nucleolus

Nucleolus

Found inside the cell's nucleus except in

prokaryotes. There may be more than one but

they disappear during cell division.

The nucleolus is the largest structure in the

nucleus of eukaryotic cells where it primarily

serves as the site of ribosome synthesis and

assembly. Nucleoli are made of proteins and RNA

and form around specific chromosomal regions.

Nucleoli also have other important functions like

assembly of signal recognition particles and

playing a role in the cell's response to stress.

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Plasmid

Plasmid

A plasmid is a small DNA molecule within a cell

that is physically separated from chromosomal

DNA and can replicate independently. Plasmids

can be found in bacteria as small, circular, double-

stranded DNA molecules; however, plasmids are

sometimes present in eukaryotic organisms.

Often, the genes carried in plasmids provide

bacteria with genetic advantages, such as

antibiotic resistance. Plasmids have a wide range

of lengths, from roughly one thousand DNA base

pairs to many thousands of base pairs.

When a bacterium divides, all of the plasmids

within the cell are copied. Each daughter cell

receives a copy of each plasmid. Bacteria can also

transfer plasmids to one another through a process

called conjugation.

Ribosome

Ribosome

Making proteins is a very important job for a cell.

Ribosomes are small pieces of RNA and protein

found throughout the cytoplasm and on some other

organelles. Their only job is to assemble proteins.

DNA coding tells them which proteins to make.

Prokaryotic cells can have tens of thousands of

ribosomes. Eukaryotic cells can have hundreds of

thousands, if not millions of them, all making

proteins.

Ribosomes link amino acids together in the order

specified by messenger RNA (mRNA) molecules.

Ribosomes consist of two major components — a

small one which reads the RNA and a large one

which joins amino acids to form a polypeptide

chain. Each subunit is composed of ribosomal

RNA (rRNA) molecules and a variety of proteins.

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Vacuole

Vacuole

Plant cells have a single, large vacuole. Animal

cells have small vacuoles but also usually greater

in number than plants and often used for storing

food.

Vacuoles are fluid-filled sacs. They are the largest

organelle in plant cells. In general, the functions of

the vacuole include:

isolating materials that might be harmful to the

cell

containing waste products

containing water in plant cells

containing small molecules

removing unwanted substances from the cell

allowing plants to support structures such as

leaves and flowers due to the pressure of the

central vacuole.

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a type

of organelle found in eukaryotic cells that forms an

interconnected network of flattened, membrane-

enclosed sacs or tube-like structures known

as cisternae. The membranes of the ER are

continuous with the outer nuclear membrane. The

endoplasmic reticulum occurs in most types of

eukaryotic cells, but is absent from red blood cells

and spermatozoa.

There are two types of endoplasmic reticulum: rough

(granular) and smooth (agranular). The outer

(cytosolic) face of the rough endoplasmic reticulum is

studded with ribosomes that are the sites of protein

synthesis. The rough endoplasmic reticulum is

especially prominent in cells such as hepatocytes.

The smooth endoplasmic reticulum lacks ribosomes

and functions in lipid manufacture and metabolism,

the production of steroid hormones,

and detoxification. The smooth ER is especially

abundant in mammalian liver and gonad cells.

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Golgi Apparatus

The Golgi apparatus, also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. It was identified in 1897 by the Italian scientist Camillo Golgi and named after him in 1898.

Part of the endomembrane system in the cytoplasm, the Golgi apparatus packages proteins into membrane-bound vesicles inside the cell before the vesicles are sent to their destination. The Golgi apparatus resides at the intersection of the secretory, lysosomal, and endocytic pathways. It is of particular importance in processing proteins for secretion, containing a set of glycosylation enzymes that attach various sugar monomers to proteins as the proteins move through the apparatus.

Cell Wall

A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism. Cell walls are present in most prokaryotes, algae, plants and fungi but rarely in other eukaryotes including animals. A major function is to act as pressure vessels, preventing over-expansion of the cell when water enters.

The composition of cell walls varies between species and may depend on cell type and developmental stage. The primary cell wall of land plants is composed of the polysaccharides cellulose, hemicelluloses and pectin. Often, other polymers such as lignin, suberin or cutin are anchored to or embedded in plant cell walls. Algae possess cell walls made of glycoproteins and polysaccharides such as carrageenan and agar that are absent from land plants. In bacteria, the cell wall is composed of peptidoglycan. The cell walls of archaea have various compositions, and may be formed of glycoprotein S-layers, pseudopeptidoglycan, or polysaccharides. Fungi possess cell walls made of the N-acetylglucosamine polymer chitin. Unusually, diatoms have a cell wall composed of biogenic silica

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Peroxisome

A peroxisome is a type of organelle known as a microbody, found in virtually all eukaryotic cells.They are involved in catabolism of very long chain fatty acids, branched chain fatty acids, D-amino acids, and polyamines, reduction of reactive oxygen species – specifically hydrogen peroxide – and biosynthesis of plasmalogens, i.e., ether phospholipids critical for the normal function of mammalian brains and lungs.[4] They also contain approximately 10% of the total activity of two enzymes in the pentose phosphate pathway, which is important for energy metabolism. It is vigorously debated whether peroxisomes are involved in isoprenoid and cholesterol synthesis in animals.

Other known peroxisomal functions include the glyoxylate cycle in germinating seeds ("glyoxysomes"), photorespiration in leaves,

glycolysis in trypanosomes("glycosomes"), and methanol and/or amine oxidation and assimilation in some yeasts.

Lysosome

A lysosome is a membrane-bound organelle found in nearly all animal and plant cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. Besides degradation of polymers, the lysosome is involved in various cell processes, including secretion, plasma membrane repair, cell signaling, and energy metabolism

The lysosomes also act as the waste disposal system of the cell by digesting unwanted materials in the cytoplasm, both from outside the cell and obsolete components inside the cell. Material from outside the cell is taken-up through endocytosis, while material from the inside of the cell is digested through autophagy.

Lysosomes are known to contain more than 60 different enzymes. Enzymes of the lysosomes are synthesized in the rough endoplasmic reticulum. The enzymes are imported from the Golgi apparatus in small vesicles, which fuse with larger acidic vesicles. Enzymes destined for a lysosome are specifically tagged with the molecule mannose 6-phosphate, so that they are properly sorted into acidified vesicles.

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Cell Membrane

The cell membrane (also known as the plasma membrane or cytoplasmic membrane), is a biological membrane that separates the interior of all cells from the outside environment (the extracellular space). It consists of a lipid bilayer with embedded proteins. The basic function of the cell membrane is to protect the cell from its surroundings. The cell membrane controls the movement of substances in and out of cells and organelles. In this way, it is selectively permeable to ions and organic molecules.[3] In addition, cell membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity and cell signalling and serve as the attachment surface for several extracellular structures, including the cell wall, the carbohydrate layer called the glycocalyx, and the intracellular network of protein fibers called the cytoskeleton. In the field of synthetic biology, cell membranes can be artificially reassembled

Centrioles

In cell biology a centriole is a cylindrical cellular organelle[1] composed mainly of a protein called tubulin. Centrioles are found in most eukaryotic cells. A bound pair of centrioles, surrounded by a shapeless mass of dense material, called the pericentriolar material (PCM), makes up a structure called a centrosome.

Centrioles are present in the cells of most eukaryotes, for example those of animals. However, they are absent from conifers (pinophyta), flowering plants (angiosperms) and most fungi, and are only present in the male gametes of charophytes, bryophytes, seedless vascular plants, cycads, and ginkgo.[2][3]

Centrioles are typically made up of nine sets of short microtubule triplets, arranged in a cylinder. Deviations from this structure include crabs and Drosophila melanogaster embryos, with nine doublets, and Caenorhabditis elegans sperm cells and early embryos, with nine singlets.[4][5]

The main function of centrioles is to produce cilia during interphase and the aster and the spindle during cell division

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Cilia

A cilium (from Latin, meaning 'eyelash';[1] the plural is cilia) is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body.[2]

There are two types of cilia: motile cilia and nonmotile, or primary, cilia, which typically serve as sensory organelles. In eukaryotes, motile cilia and flagella together make up a group of organelles known as undulipodia.[3] Eukaryotic cilia are structurally identical to eukaryotic flagella, although distinctions are sometimes made according to function and/or length.[4] Biologists have various ideas about how the various flagella may have evolved.

Flagella

A flagellum is a lash-like appendage that protrudes from the cell body of certain bacterial and eukaryoticcells. The primary role of the flagellum is locomotion, but it also often has function as a sensory organelle, being sensitive to chemicals and temperatures outside the cell.[1][2][3][4] The similar structure in the archaea functions in the same way but is structurally different and has been termed the archaellum.[5]

Flagella are organelles defined by function rather than structure. Flagella vary greatly. Both prokaryotic and eukaryotic flagella can be used for swimming but they differ greatly in protein composition, structure, and mechanism of propulsion. The word flagellum in Latin means whip.

An example of a flagellated bacterium is the ulcer-causing Helicobacter pylori, which uses multiple flagella to propel itself through the mucus lining to reach the stomach epithelium.[6] An example of a eukaryotic flagellate cell is the mammalian sperm cell, which uses its flagellum to propel itself through the female reproductive tract.[7] Eukaryotic flagella are structurally identical to eukaryotic cilia, although distinctions are sometimes made according to function or length.[8] Fimbriae and pili are also thin appendages, but have different functions and are usually smaller.

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Blue border genetic material cards

Allele

Allele

An allele is one of a number of alternative forms of

the same gene. Different alleles can result in

different phenotypes, such as different eye colours

e.g. the gene for eye colour has an allele for blue

eye colour and an allele for brown. For any gene, a

person may have the same two alleles or two

different ones, i.e. they are diploid. These

chromosomes are referred to as homologous

chromosomes - one copy of each gene (and,

therefore, one allele) on each chromosome.

A recessive allele only shows if the individual has

two copies of it e.g. the allele for blue eyes is

recessive and two copies of this allele are needed

to have blue eyes. A dominant allele always

shows. Brown eyes are dominant. Only one copy

of it is needed to have brown eyes. Two copies will

still give you brown eyes.

Chromosome

Chromosome

Chromosomes are thread-like structures located

inside the nucleus of animal and plant cells. Each

chromosome is made of protein and a single

molecule of DNA. Passed from parents to

offspring, DNA contains the specific instructions

that make each type of living organism unique.

The unique structure of chromosomes keeps DNA

tightly wrapped around spool-like proteins. Without

such packaging, DNA molecules would be too long

to fit inside cells. For example, if all of the DNA

molecules in a single human cell were unwound

from their proteins and placed end-to-end, they

would be nearly 2 metres long.

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DNA

DNA

A DNA molecule contains the biological

instructions that make each species unique. DNA,

along with the instructions it contains, is passed

from adult organisms to their offspring during

reproduction. In eukaryotes, DNA is found inside

the nucleus. In prokaryotes it is found it is in the

cytoplasm in a nucleoid region. DNA is made of

chemical building blocks called nucleotides. To

form a strand of DNA, nucleotides are linked into

chains, with the phosphate and sugar groups

alternating. The four types of bases found in

nucleotides are: adenine (A), thymine (T), guanine

(G) and cytosine (C). The sequence of these bases

determines the genetic code. For example, the

sequence ATCGTT might instruct for blue eyes,

while ATCGCT might instruct for brown.

Gene

Gene

Sections of DNA in each chromosome make up

genes. Each chromosome is made up of many

genes. The DNA also contains large sequences

that do not code for any protein and their function

is unknown. The gene of the coding region

contains instructions that allow a cell to produce a

specific protein or enzyme.

The genes that contain the information to make the

necessary proteins are therefore ‘switched on’ in

some of the specialised cells while the remaining

genes are ‘switched off’. For example, the genes

that are ‘switched on’ in kidney cells are different to

those that are ‘switched on’ in brain cells because

the cells of the brain have different roles and make

different proteins.

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RNA

RNA

RNA molecules are single stranded nucleic acids

composed of nucleotides. RNA plays a major role

in protein synthesis as it is involved in the

movement of the genetic code into the cytoplasm

where the proteins are constructed. It is also

involved in the ‘reading’ of the genetic code to

produce proteins. RNA nucleotides, like DNA

nucleotides, contain three components:

• a nitrogenous base

• a five-carbon sugar

• a phosphate group.

RNA bases are adenine (A), guanine (G), cytosine

(C) and uracil (U). Uracil is present instead of

thymine which is the 4th base in DNA.

messenger-RNA

messenger-RNA

Messenger RNA (mRNA) plays an important role in

the movement of the genetic code on DNA from

the nucleus to the cytoplasm.

A triplet of bases consists of three continuous

nucleotide bases that code for either an amino acid

or signal the end of the process of constructing a

chain of amino acids.

An enzyme is used to copy a single strand of DNA

making a messenger RNA molecule. When this

enzyme constructs the mRNA molecule from the

DNA strand, adenine pairs with uracil and cytosine

pairs with guanine (A-U and C-G).

At the end of the process, mRNA is transported to

the cytoplasm for the next stage of protein

synthesis.

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transfer-RNA

transfer-RNA

Transfer RNA (tRNA) plays an important role in the

construction of the amino acid chain – a

polypeptide. Its job is to convert the message

within mRNA into specific amino acid chains.

These are then folded to form a protein.

Transfer RNA is shaped like a clover leaf. It

contains an amino acid attachment site on one end

and a special section with a triplet of bases found

on it. This triplet is complementary to the triplet on

mRNA. Transfer RNA, along with ribosomes,

“reads” the mRNA triplets. When a complementary

base triplet is “read”, the tRNA with the correct

amino acid attached, adds the amino acid to the

polypeptide chain.

The polypeptide chain undergoes several

modifications before becoming a fully functioning

protein.

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Quiz

True False

1 Chloroplasts contain chlorophyll which captures light energy.

2 Mitochondria are organelles found inside the nucleus.

3 The nucleus is the control centre of the cell and is found in

eukaryotic and prokaryotic cells.

4 The nucleolus is the largest structure in the nucleus and is

where the ribosomes are made.

5

Some structures found in bacteria are small, circular and

made of a double-stranded DNA molecule and are separate

from the chromosomes. These structures are called plasmids.

6 Ribosomes are the site of protein synthesis.

7 Plant cells usually have cells with many small vacuoles that

are used for storing food.

8 A dominant allele only shows if the individual has two copies

of it.

9 A chromosome is made of protein and a single molecule of

deoxyribonucleic acid (DNA).

10 DNA is found inside the nucleus in prokaryotes.

11 The gene of the coding region encodes instructions that allow

a cell to produce a specific protein or enzyme.

12 RNA bases include adenine (A), guanine (G), cytosine (C)

and thymine (T).

13 Messenger RNA (mRNA) plays an important role in the

movement of the code on DNA into the cytoplasm.

14

Transfer RNA (tRNA) translates the message within the

nucleotide sequence on mRNA into specific amino acid

sequences.

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