Biology xxx
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How do cells function?
1.2: Cells the basic unit of life
1. Study the Cell theory
2. Recognise Prokaryote
3. Identify eukaryote
Cell Theory:
Cells are the basic structural units of living organisms
The cell theory states that:
all organisms are composed of cells
all cells come from pre-existing cells
the cell is the smallest living organisational unit
The cell theory states that all cells arise from pre-existing cells. This is known as biogenesis.
very first cell: Zygote. -> came from the sperm and an egg.
All organisms follow attributes (MRS GREND):
M — movement: have some level of self-powered movement
R — respiration: the conversion of carbohydrates to a usable energy form (ATP)
S — sensitivity to stimuli: the response of an organism to its environment (e.g. plants responding to light, animals responding to external temperatures by sweating, shivering)
G — growth: an irreversible change in mass
R — reproduction: production of offspring, passing attributes from one generation to the next
E — excretion of wastes: produce wastes, such as dead cells or urine, that need to be removed
N — nutrition: intake of food or nutrients
D — DNA: the molecule that codes for the production of proteins
EVERY living organism uses reproduction.
Properties of Cells:
All cells contain:
Have a plasma membrane or cell membrane
Contain a jelly-like cytoplasm
Contain genetic material (DNA)
Ribosomes-organelles responsible for the synthesis of proteins
Many cells have extensions called flagella or cilia (for movement)
Prokaryote
On average, prokaryotic cells are about ten times smaller than plant and animal cells.
The general features of a prokaryotic cell are as follows:
1. Capsule — made of polysaccharides
2. Cell wall — made of peptidoglycan
3. Cell (plasma) membrane — controls which substances move into and out of the cell Large, circular DNA — free-floating in the cell
4. Ribosomes — synthesise proteins
5. Plasmids — smaller pieces of DNA
6. Cytosol — water environment that everything floats in
Differences:
Archaea have a different type of lipid structure in the plasma membrane
The cell wall in bacteria contains murein, but the cell wall in archaea does not
Both have diverse metabolic systems, but methanogenesis (in which methane is produced) is unique to archaea
Bacteria
Archaea
Microscopic single-celled organisms.
Live in environments of moderate temperature that are moist and low in salt, sunlight and in or plants /animals.
Need little oxygen to survive.
Play an important role in ecosystems because they break down many kinds of substances.
Either Gram-negative or Gram-positive.
used to classify what type of disease.
Classifies bacteria
can live in extreme conditions (hottest places 121 °C, the most acidic environments pH 0 and the saltiest water about 30% salt)
the dead sea 🤯
possess a membrane composed mainly of lipids
Eukaryotes:
Protists, Fungi, Animal and Plant Kingdoms
Linear, thread like form of DNA – chromosomes
Membrane bound organelles present
++++ organelles = small organ!!!
Some cells are able to move actively, and these self-propelled cells do not have fixed shapes because their outer boundary is their flexible plasma membrane.
1. cancer cells that migrate into capillaries and move around the body when a malignant tumour undergoes metastasis.
2. white blood cells that can squeeze from capillaries into the surrounding tissues where they travel to attack infectious microbes
3. amoebas as they move across surfaces.
1.3: Limitations to cell size
Plasma Membrane requirements:
enable enough exchange between the external and internal environments to support these life functions
ensure the exchange of materials occurs at rates sufficient to deliver substances fast enough into cells to meet their nutrient needs, and remove wastes fast enough from the cells to avoid their accumulation.
Surface area to volume ratio ➡➡➡➡➡➡
As cells increase in size through an increase in cytoplasm, both their surface areas and volumes increase, but not at the same rate.
The internal volumes of cells expand at a greater rate than the areas of their plasma membrane.
Therefore, the growth of an individual cell is accompanied by a relative decrease in the area of its plasma membrane.
Surface area = plasma membrane
Volume = cytoplasm
As cells increase in size, the continued decrease in SA : V ratio places an upper limit on cell size.
High surface area:
A small unicellular organism has a large surface area relative to its volume
Materials can be moved directly in and out of the cell more adequately when the surface area to volume ratio increases
Low surface area:
The evolution of multicellularity overcame the problems of small cell size
Cells compartmentalise (organelles) - membranes of organelles carry out metabolic processes
Cells need to continually exchange material
1.4: Organelles for eukaryotes
Nucleus:
Most noticeable
Contains DNA
Double layered membrane – porous, fatty tissue
2 membranes
Nucleosis:
proteins, DNA and RNA, and is where ribosomes are assembled
Manufacture of proteins
Dark staining
Ribosomes -
1000s Small dense structures
composed of proteins and ribosomal RNA (rRNA),
Protein synthesis
Two Subunits
Attached to ER (proteins will be secreted outside the cell)
Not attached to ER (proteins will be used inside the cell )
Organelle: a subcellular structure that has one or more specific jobs to perform in the cell
Ribosome: the factories in the cell that produce proteins
Cytoplasm: where cellular activity occurs (place)
Cytosol: highly organsded fluid dissolving substances
Organelle
Plant/Animal/BOTH
Function
⬇⬇⬇⬇
Located
Structure
Plasma Membrane
Both
Forms the boundary between the cell and the extracellular environment
Regulates movement of substances in and out of the cell
Surrounds the cell forming a boundary between the cell contents and the extracellular environment.
Semi-fluid ohospholipid bilayer in which proteins are embedded. Some of the proteins fully span the membrane
Ribosomes
Both
Synthesis of polypeptides (proteins)
Free in the cytoplasm or bound to rough endoplasmic reticulum
Made up of ribosomal RNA and protein and composed of two subunits, a larger and a smaller
Mitochondria
Both
The site of cellular respiration (the production of ATP)
Cytoplasm
Rod shaped or cylindrical organelles occurring in large numbers
Bounded by a double membrane, the inner layer is folded to form partitions called cristae.
Contains some DNA
Rough Endoplasmic Reticulum
Both
Synthesis, folding, and modification of proteins
Transport of proteins through the cell
E.g. steak is protein based
(not in the red blood cell)
Nuclear membrane extending to the cytoplasm as part of the endomembrane system
Complex system of membranous tubules studded with ribosomes.
Connected to the smooth ER but structurally and functionally distinct from it.
Smooth Endoplasmic Reticulum
Both
Synthesis of lipids, including oils, phospholipids, steroids, and sugar
(absent from red blood cell)
In the cytoplasm as part of the endomembrane system
A system of membranous tubules similar in appearance to the rough ER but lacking ribosomes
Golgi apparatus
Both
Modification of proteins and lipids received from the ER
Sorting, packaging, and storing proteins and lipids
Transports materials through vesicle of the cell
Manufacture of some certain macromolecules, eg. hydrochloric acid
-> like a post office
Cytoplasm, associated with the ER
Stack of flattened, membranous sacs called cisternae
Nucleus
Both
Contains most of the cell's genetic material, which regulates all the activities of the cell.
Variable location; not necessarily near the centre of the cell
Surrounded by a nuclear envelope and encloses the genetic material (chromatin). Nuclear envelope compromises a double membrane perforated by pores.
Nucleolus
Both
Synthesis of ribosomal RNA
Assembly of ribosomal subunits
Within the nucleus.
Depending on the organism, there may be more than one.
A prominent structure which appears under the EM as a mass of darkly stained granules and fibres adjoining part of the chromatin
Centrioles
Both
Involved in organising microtubule assembly (spindle formation) but not essential as they are absent from the cells of higher plants
Cytoplasm - as part of the cytoskeleton
Usually next to or close to the nucleus
Found as a pair - each one composed of nine sets
Vacuoles and Vesicles
Both
Food vacuoles in animal cells are formed by phagocytosis of food particles
Contractile vacuoles of freshwater protists pump extra water from the cell
Central vacuole of plants provide cell volume and stores inorganic ions and metabolic waste
In the cytoplasm, often numerous
Vacuoles and vesicles are both membrane-bound sacs, but vacuoles are larger
The Cell Cytoskeleton
Both
Shape and mechanical support for the cell
Regulation of cellular activities eg. guiding secretory vesicles
Especially important in animals cells - involved in cell movement (motility)
A network throughout the cytoplasm
A dynamic system of microtubules, microfilaments, and intermediate filaments.
Chloroplast
Plant
Site of photosynthesis
*Chloroplasts contain some DNA.
Within the cytoplasm of plant leaves (and sometimes), cells.
Specialised plastids containing green pigment called chlorophyll
Two outer membranes are separated by a narrow intermembrane space
Inside the chloroplasts are stacks of flattened sacs of thylakoids which are stacked together as grana
]
And stoma
Cell Wall
Plant
Protects the cell
Maintains cell shape
Prevents excessive water uptake
Surrounds the plant cell and lies outside the plasma membrane
Cellulose fibers, associated with hemicelluloses (branched polysaccharides) and pectins.
Between the walls of adjacent cells, is a sticky substance called the middle lamella.
Lysosome
Animal
Intracellular digestion of macromolecules (fats, proteins, polysaccharides, and nucleic acids)
Recycling of cellular components (autophagy)
Low internal pH maintained by the H+ pump in the lysosomal membrane
Free in the cytoplasm
Single-membrane-bound sac of hydrolytic enzymes
Lysosomes bud off the golgi apparatus
Cilia
Animal
To remove microbes and debris from the inferior of the lungs
Primary bronchus
Hair-like structures on the surface of cells
Flagella
Animal
To assist the cell in movement
Allows the cell to swim from one location to a more desirable one by royaying a rigid filament emerging from the cell
Hair-like structures on the surface of cells
Specialist Plant Cell Features: 🌱🪴🌵🌿☘
Cellulose cell wall
Plastids
Chloroplasts
Amyloplasts
Chromoplasts
Specialist Animal Cell Features:🐻🐻❄🐨🐰🐼
Lysosomes
Cilia
Flagella
Synthesis and processing proteins and lipids
1. DNA is transcribed inside the nucleus into RNA.
2. RNA moves out of the nucleus and binds to ribosomes.
3. Ribosomes synthesise proteins using the information on the RNA.
4. Proteins that will be secreted out of the cell are made in the ribosomes bound to the rough endoplasmic reticulum.
5. These proteins are modified and packaged in the Golgi apparatus.
6. Vesicles arising from the Golgi apparatus fuse with the plasma membrane, releasing their contents from the cell.
7. They also insert membrane-bound proteins into the plasma membrane.
8. Lipids are synthesised and processed in the smooth endoplasmic reticulum
Chloroplasts trap light energy, which is used to split water molecules into hydrogen and oxygen. The hydrogen then combines with carbon dioxide to make glucose, and the oxygen is released into the atmosphere as a waste product.
Plastids
The name given to plant organelles involved in the synthesis and storage of different chemical compounds.
They contain a double-stranded DNA molecule and possess a double membrane. 🧬
Plastids develop from simple organelles called proplasts.
Animal cells lack plastids
1. Chloroplasts: contain chlorophyll are involved in photosynthesis
2. Amyloplasts: Store starch
3. Chromoplasts: contain carotenoid (colour pigments) and occur in petals and fruit
Cytoskeleton
Centrioles
1. Consists of microtubules of the protein tubulin and filaments of the protein actin.
2. Supports the cell's structure, allows the cell to move and assists in the transport of organelles and vesicles within the cell
1. a pair of small cylindrical structures composed of microtubules
2. Eukaryotic cells not in plants
3. involved in cell division, formation of cilia and flagella.
The endosymbiotic theory
Endosymbiosis is a special case of symbiosis where one of the organisms lives inside the other.
Margulis’ proposal is now termed the endosymbiotic theory.:
1. Both contain their own genetic material, arranged as a single circular molecule of DNA, as occurs in bacteria.
2. Both contain ribosomes of the bacterial type that are slightly smaller than those of eukaryotes.
3. Both reproduce by a process of binary fission as occurs in bacteria.
4. Both have sizes that fall within the size range of bacterial cells.
Endosymbiosis
nitrogen-fixing bacteria that live in the cells of nodules on the roots of legumes, such as clovers
single-celled algae that live inside the cells of corals.
Organelle
Found in
Function/feature
Endoplasmic reticulum (ER)
Eukaryotes
Transport system within cells
Protein modification (rough ER)
Lipid synthesis and storage, and detoxification (smooth ER)
Golgi apparatus
Eukaryotes
Package and export of substances out of cell
Lysosome
Eukaryotes
Vesicle filled with digestive enzymes
Breakdown of non-functioning cell organelles and substances
Peroxisome
Eukaryotes
Breakdown of substances toxic to the cell
Cytoskeleton
Eukaryotes
Support and strength for the cell
Centriole
Eukaryotes — animals
Part of cytoskeleton
Role in cell division
Chloroplasts
Eukaryotes — photosynthetic species (such as plants)
Convert energy from the Sun using photosynthesis
Vacuole
Eukaryotes — plants
Storage of nutrients and mineral salts
Waste disposal
Large and central in plant cells
Cell Wall
Most prokaryotes Eukaryotes — plants, algae and fungi
Provides protection, shape and support to the cell
1.5: The Plasma Membrane
Environments of the cell -
1. All cells exist in a watery environment – extracellular fluid
all body water external to the cell
2. Multicellular organisms have an outer layer that acts as a barrier and creates an internal environment
Cell membrane:
Maintain cell stability
Enabling the cell to operate at optimum levels
Makes it an individual
Controls movement of substances (imports and exports of the cell)
EXTRACELLULAR FLUID IN UNICELLULAR ORGANISMS
Unicellular organisms can do little to control their environment - when it changes suddenly:
1) Some may die
2) yeasts can become dormant (not active but alive) until their environment returns to
normal again.
3) Unicellular algae can move towards light (place where conditions are more suitable)
Eg. algae swim towards the light, photosynthesis/warmer
Mechanical choice
EXTRACELLULAR FLUID IN MULTICELLULAR ORGANISMS
The more complex the organism - the more control it will have
Eg. frostbite, the body will stop circulating blood to small body parts to conserve
The outer layer creates an internal environment for the organism that is different from their external environment.
Can regulate the conditions of internal environment
Commonly regulated aspects of the internal environment are:
1) temperature
2) concentration of oxygen
3) concentration of carbon dioxide
4) pH (acidity or alkalinity)
5) osmotic pressure (concentrations of salts or ions) - heart beat 💗
6) concentration of nitrogen wastes
7) concentration of glucose.
Plasma Membrane Composition
Plasma membranes are phospholipid bilayers that enclose the cytoplasm and subdivide the cell into compartments (organelles).
According to the fluid mosaic model, plasma membranes consist of two layers of phospholipid molecules, with other molecules including proteins, carbohydrates and cholesterol scattered.
Most membranes are also asymmetrical, meaning one layer has different properties from the other
Plasma membranes are fluid structures,
-> which means that individual phospholipid molecules (and some proteins) are free to move about within the layers.
They rarely cross from one side of the membrane to the other.
The level of fluidity depends on the percentage of unsaturated fatty acids in the phospholipid molecules-the greater the percentage, the more fluid the membrane
Plasma Membrane Functions
1. Maintain a high concentration of materials in the cell.
2. Keep harmful materials out.
3. Control the movement of materials into and out of the cell.
4. Let the cell sense its environment.
5. Cell recognition and communication with other cells
Plasma membrane is impermeable to water-soluble particles, ions and polar molecules.
Protein channels, regulate the exchange of molecules with the environment
This control is central to important processes that keep the cell alive, such as cell respiration, digestion, and elimination of wastes.
Phospholipids
Phospholipid bilayer:
a double layer of phospholipids that forms the basis of cell membranes.
It acts as a barrier between the inside and outside of a cell, controlling what enters and leaves the cell.
Amphipathic - having both:
Polar hydrophilic heads:
the phosphate groups of phospholipid molecules that make up the cell membrane.
the heads are polar and hydrophilic, meaning they are attracted to water
Non Polar hydrophobic tails:
the fatty acid chains of a lipid molecule, (like in a phospholipid)
which are not charged and repel water
causing them to naturally orient inwards away from the aqueous environment
forming the core of a cell membrane
Cholesterol
Membranes contain many fatty molecules, including cholesterol molecules, between the phospholipid molecules.
From animal
Cholesterol gives:
Stability to the membrane without affecting its fluidity,
Reduces the permeability of the membrane to small water-soluble molecules
a waxy substance in your blood that's essential for your body to function properly, but too much can be harmful
Proteins:
Proteins in the plasma membrane are able to move about to some extent.
Proteins that are a permanent part of the plasma membrane are called integral proteins.🤯
Proteins that are a temporary part of the plasma membrane are called peripheral proteins. They bind to integral proteins or penetrate into one surface of the plasma membrane.
When integral proteins span both phospholipid layers they are also called transmembrane proteins, which involved in a number of important cellular and intercellular activities.
The roles of proteins in the plasma membrane
T — Transport
R — Reception
A — Anchorage
C — Cell identity
I — Intracellular joinings
E — Enzymatic activity
Carbohydrates
1. Carbohydrates associated on the outer surface of the membrane -> always on top
2. Linked to proteins (forming glycoproteins) or to lipids (forming glycolipids).
3. They play a role:
◦ in recognition and adhesion between cells,
◦ in the recognition of antibodies, hormones and viruses by cells.
Plasma Membrane Permeability
Lipid nature also makes plasma membranes permeable to:
Most water-soluble molecules
Ions (atoms or groups of atoms with an overall positive and negative charge)
Polar molecules (molecules with charged regions but no overall charge)
Diffusion:
Particles in a solution move from an area of high concentration to an area of low concentration. This process is called diffusion.
The solute particles are said to have moved along the concentration gradient.
Diffusion is called a passive process because it does not require energy.
DIFFUSION ACROSS MEMBRANES
1. Simple diffusion:
1. Solute molecules can diffuse across a membrane only if the membrane is permeable to them. 2. If the concentration of solute molecules is the same on both sides of the membrane, there will always be about the same number moving across in either direction.
Factors affecting rate of diffusion
1. Concentration: the greater the difference in concentration gradient, the faster the rate of diffusion.
2. Temperature: the higher the temperature, the higher the rate of diffusion.
3. Particle size: the smaller the particles, the faster the rate of diffusion through a membrane.
Types of membrane transport proteins
Channel proteins do not usually bind with the molecules being transported
They function like pores are mainly involved in the passage of water-soluble polar particles such as ions
Carrier proteins bind the molecules being transported, causing the protein to undergo changes in shape to be transported
After that, the original shape is restored
Facilitated diffusion
The membrane transport proteins are specific for particular particles, so transport is selective
Transport is more rapid than by simple diffusion
The transport proteins can become saturated (fully occupied) as the concentration of the transported substances increase
The transport of one particle may be inhibited by the presence of another particle that uses the same transport protein
No energy is required; the particles move down their own concentration gradient
OSMOSIS
Refers to the net diffusion of water molecules across a semipermeable membrane
The free water molecules will move across the membrane from the diluted to the concentrated solution
In osmosis, net diffusion of water occurs through a semipermeable membrane from a
If red blood cells are placed in fresh water, -> the cells absorb so much water by osmosis that they swell and may eventually burst, releasing red pigment into the water.
Conversely, if red blood cells are placed in a solution that is more concentrated than their cytosol, water leaves the red blood cells by osmosis and causes them to shrink. 🩸
Isotonic solutions: The solutions being compared have equal concentration of solutes
Active Transport
Involved the use of energy by the cell to transport particles across membranes
Active transport has the same properties as facilitated diffusion (selectively, saturation and competitive inhibition)
The differences are:
Active transport (carrier proteins) by facilitated diffusion, (channel or carrier proteins)
Active transport uses energy, it can move substances against a concentration gradient facilitated diffusion (no energy, down a concentration gradients)
Active transport: low to high concentration
Passive transport: high to low concentration
Endocytsosis
Endocytosis is the movement of substances into the cell.
Particles near the plasma membrane are enclosed by the membrane, which then pinches off to form a vesicle enclosing the particle.
this vesicle may then become fused with a lysosome so that its contents can be digested.
The two forms of endocytosis :
Pinocytosis is the entry of extracellular fluid and substances ( proteins and sugars).
Phagocytosis is the entry of large particles such as bacteria and cell debris.
Exocytosis
Exocytosis is the movement of substances out of the cell.
A transport vesicle fuses with the plasma membrane and the junction then breaks down.
Unicellular heterotrophs such as amoebas remove digestive wastes in this way.
Cells are the basic structural units of living organisms|Cell Theory
all organisms are composed of cells|Cell Theory
all cells come from pre-existing cells|Cell Theory
the cell is the smallest living organisational unit|Cell Theory
The cell theory states that all cells arise from pre-existing cells. This is known as biogenesis.|Biogenesis
Zygote|very first cell
M — movement|MRS GREND
R — respiration|MRS GREND
S — sensitivity to stimuli|MRS GREND
G — growth|MRS GREND
R — reproduction|MRS GREND
E — excretion of wastes|MRS GREND
N — nutrition|MRS GREND
D — DNA|MRS GREND
plasma membrane or cell membrane|All cells contain
jelly-like cytoplasm|All cells contain
genetic material (DNA)|All cells contain
Ribosomes|organelles responsible for the synthesis of proteins
flagella or cilia|Many cells have extensions called
Prokaryotic cells are about ten times smaller than plant and animal cells.|Prokaryote Cell Size
Capsule|Prokaryote Cell Feature
Cell wall|Prokaryote Cell Feature
Cell (plasma) membrane|Prokaryote Cell Feature
Large, circular DNA|Prokaryote Cell Feature
Ribosomes|Prokaryote Cell Feature
Plasmids|Prokaryote Cell Feature
Cytosol|Prokaryote Cell Feature
Archaea|different type of lipid structure in the plasma membrane
murein|cell wall in bacteria
methanogenesis|unique to archaea
Microscopic single-celled organisms|Bacteria
Live in environments of moderate temperature that are moist and low in salt, sunlight and in or plants /animals.|Bacteria
Need little oxygen to survive.|Bacteria
Play an important role in ecosystems because they break down many kinds of substances.|Bacteria
Gram-negative or Gram-positive|Bacteria
can live in extreme conditions (hottest places 121 °C, the most acidic environments pH 0 and the saltiest water about 30% salt)|Archaea
possess a membrane composed mainly of lipids|Archaea
Protists, Fungi, Animal and Plant Kingdoms|Eukaryotes
Linear, thread like form of DNA – chromosomes|Eukaryotes
Membrane bound organelles present|Eukaryotes
cancer cells that migrate into capillaries and move around the body when a malignant tumour undergoes metastasis.|Example of cell movement
white blood cells that can squeeze from capillaries into the surrounding tissues where they travel to attack infectious microbes|Example of cell movement
amoebas as they move across surfaces.|Example of cell movement
enable enough exchange between the external and internal environments to support these life functions|Plasma Membrane requirements
ensure the exchange of materials occurs at rates sufficient to deliver substances fast enough into cells to meet their nutrient needs, and remove wastes fast enough from the cells to avoid their accumulation.|Plasma Membrane requirements
Surface area to volume ratio|SA:V
The internal volumes of cells expand at a greater rate than the areas of their plasma membrane.|SA:V
The growth of an individual cell is accompanied by a relative decrease in the area of its plasma membrane.|SA:V
Surface area|plasma membrane
Volume|cytoplasm
Materials can be moved directly in and out of the cell more adequately when the surface area to volume ratio increases|High surface area
Cells compartmentalise (organelles) - membranes of organelles carry out metabolic processes|Low surface area
Contains DNA|Nucleus
Double layered membrane – porous, fatty tissue|Nucleus
proteins, DNA and RNA, and is where ribosomes are assembled|Nucleosis
Manufacture of proteins|Nucleosis
Small dense structures|Ribosomes
composed of proteins and ribosomal RNA (rRNA)|Ribosomes
Protein synthesis|Ribosomes
Two Subunits|Ribosomes
Attached to ER|Ribosomes
Not attached to ER|Ribosomes
organelle|a subcellular structure that has one or more specific jobs to perform in the cell
Ribosome|the factories in the cell that produce proteins
Cytoplasm|where cellular activity occurs (place)
Cytosol|highly organsded fluid dissolving substances
Plasma Membrane|Both|Forms the boundary between the cell and the extracellular environment. Regulates movement of substances in and out of the cell|Surrounds the cell forming a boundary between the cell contents and the extracellular environment. Semi-fluid ohospholipid bilayer in which proteins are embedded. Some of the proteins fully span the membrane.
Ribosomes|Both|Synthesis of polypeptides (proteins)|Free in the cytoplasm or bound to rough endoplasmic reticulum. Made up of ribosomal RNA and protein and composed of two subunits, a larger and a smaller
Mitochondria|Both|The site of cellular respiration (the production of ATP)|Cytoplasm. Rod shaped or cylindrical organelles occurring in large numbers. Bounded by a double membrane, the inner layer is folded to form partitions called cristae. Contains some DNA
Rough Endoplasmic Reticulum|Both|Synthesis, folding, and modification of proteins. Transport of proteins through the cell|Nuclear membrane extending to the cytoplasm as part of the endomembrane system. Complex system of membranous tubules studded with ribosomes. Connected to the smooth ER but structurally and functionally distinct from it.
Smooth Endoplasmic Reticulum|Both|Synthesis of lipids, including oils, phospholipids, steroids, and sugar|In the cytoplasm as part of the endomembrane system. A system of membranous tubules similar in appearance to the rough ER but lacking ribosomes
Golgi apparatus|Both|Modification of proteins and lipids received from the ER. Sorting, packaging, and storing proteins and lipids. Transports materials through vesicle of the cell. Manufacture of some certain macromolecules, eg. hydrochloric acid|Cytoplasm, associated with the ER. Stack of flattened, membranous sacs called cisternae
Nucleus|Both|Contains most of the cell's genetic material, which regulates all the activities of the cell.|Variable location; not necessarily near the centre of the cell. Surrounded by a nuclear envelope and encloses the genetic material (chromatin). Nuclear envelope compromises a double membrane perforated by pores.
Nucleolus|Both|Synthesis of ribosomal RNA. Assembly of ribosomal subunits|Within the nucleus. Depending on the organism, there may be more than one. A prominent structure which appears under the EM as a mass of darkly stained granules and fibres adjoining part of the chromatin
Centrioles|Both|Involved in organising microtubule assembly (spindle formation) but not essential as they are absent from the cells of higher plants|Cytoplasm - as part of the cytoskeleton. Usually next to or close to the nucleus. Found as a pair - each one composed of nine sets
Vacuoles and Vesicles|Both|Food vacuoles in animal cells are formed by phagocytosis of food particles. Contractile vacuoles of freshwater protists pump extra water from the cell. Central vacuole of plants provide cell volume and stores inorganic ions and metabolic waste|In the cytoplasm, often numerous. Vacuoles and vesicles are both membrane-bound sacs, but vacuoles are larger
The Cell Cytoskeleton|Both|Shape and mechanical support for the cell. Regulation of cellular activities eg. guiding secretory vesicles. Especially important in animals cells - involved in cell movement (motility)|A network throughout the cytoplasm. A dynamic system of microtubules, microfilaments, and intermediate filaments.
Chloroplast|Plant|Site of photosynthesis|Within the cytoplasm of plant leaves (and sometimes), cells. Specialised plastids containing green pigment called chlorophyll. Two outer membranes are separated by a narrow intermembrane space. Inside the chloroplasts are stacks of flattened sacs of thylakoids which are stacked together as grana
Cell Wall|Plant|Protects the cell. Maintains cell shape. Prevents excessive water uptake|Surrounds the plant cell and lies outside the plasma membrane. Cellulose fibers, associated with hemicelluloses (branched polysaccharides) and pectins. Between the walls of adjacent cells, is a sticky substance called the middle lamella.
Lysosome|Animal|Intracellular digestion of macromolecules (fats, proteins, polysaccharides, and nucleic acids). Recycling of cellular components (autophagy). Low internal pH maintained by the H+ pump in the lysosomal membrane|Free in the cytoplasm. Single-membrane-bound sac of hydrolytic enzymes. Lysosomes bud off the golgi apparatus
Cilia|Animal|To remove microbes and debris from the inferior of the lungs|Primary bronchus. Hair-like structures on the surface of cells
Flagella|Animal|To assist the cell in movement. Allows the cell to swim from one location to a more desirable one by royaying a rigid filament emerging from the cell|Hair-like structures on the surface of cells
Cellulose cell wall|Plant|Specialist Plant Cell Features
Plastids|Plant|Specialist Plant Cell Features
Chloroplasts|Plant|Specialist Plant Cell Features
Amyloplasts|Plant|Specialist Plant Cell Features
Chromoplasts|Plant|Specialist Plant Cell Features
Lysosomes|Animal|Specialist Animal Cell Features
Cilia|Animal|Specialist Animal Cell Features
Flagella|Animal|Specialist Animal Cell Features
DNA is transcribed inside the nucleus into RNA.|Synthesis and processing proteins and lipids
RNA moves out of the nucleus and binds to ribosomes.|Synthesis and processing proteins and lipids
Ribosomes synthesise proteins using the information on the RNA.|Synthesis and processing proteins and lipids
Proteins that will be secreted out of the cell are made in the ribosomes bound to the rough endoplasmic reticulum.|Synthesis and processing proteins and lipids
These proteins are modified and packaged in the Golgi apparatus.|Synthesis and processing proteins and lipids
Vesicles arising from the Golgi apparatus fuse with the plasma membrane, releasing their contents from the cell.|Synthesis and processing proteins and lipids
They also insert membrane-bound proteins into the plasma membrane.|Synthesis and processing proteins