3.1. tissues cells and organelles
TRANSCRIPT
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Edexcel AS Biology (8BIO 1) Mo Idriss, Quick Revision Notes
1 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
Cells and Organelles
Learning
O
bjective(s)
After studying this section, you will be able to:
Distinguish between eukaryotic and prokaryotic cells in terms of their structureand ultrastructure
Describe the ultrastructure of an animal (eukaryotic) cell (nucleus, nucleolus,ribosomes, rough and smooth endoplasmic reticulum, mitochondria, centrioles,
lysosomes, and Golgi apparatus) and recognise these organelles from EM images
Explain the role of the rough endoplasmic reticulum (rER) and the Golgiapparatus in protein transport within cells and including its role in formation of
extracellular enzymes
Prokaryotes and Eukaryotes
Living things are made of cells which contain organelles such as the cell membrane and
ribosomes sub-cellular structures that carry out specific functions. Some living things are
made of only one cell (unicellular e.g. cholera bacterium and amoeba) whilst many others are
made of many cells (multicellular e.g. humans and most plants).
All living organisms can be divided into two types: Prokaryotic and Eukaryotic organisms.
Prokaryotic organisms are simple, one celled organisms with a primitive (pro) nucleus (karyote)
which is not surrounded by a membrane. Their cells are also smaller; they lack membrane-
bound organelles like mitochondria and ER, have circular DNA, and have smaller ribosomes.
Prokaryotic cells are bacteria.
Eukaryotic organisms are made of one or more eukaryotic cells. Eukaryotic cells are larger and
more complex than prokaryotic ones, have a true nucleus (Eukaryote) surrounded by a nuclear
envelope and containing linear DNA, as well as other membrane bound organelles like
mitochondria, ER (endoplasmic reticulum) and Golgi apparatus.
The ultrastructure refers to the structure of the cell as seen under a powerful microscope like
an EM. The diagram on the next page shows the ultrastructure of an animal cell. We need to
know the structure in relation to the function of the following organelles:
1-nucleus, 2-nucleolus, 3-ribosomes, 4-rough and smooth endoplasmic reticulum,
5-mitochondria, 6 centrioles, 7-lysosomes, and 8-Golgi apparatus.
1. PowerPoint presentation on ultrastructure of animal cells; 2. Look at the diagram overleaf and/or
poster; 3. Annotate diagram provided.
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Edexcel AS Biology (8BIO 1) Mo Idriss, Quick Revision Notes
2 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
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7/30/2019 3.1. Tissues Cells and Organelles
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Edexcel AS Biology (8BIO 1) Mo Idriss, Quick Revision Notes
3 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
Mitochondrion
Surrounded by double
membrane. Inner membrane
folded into cristae around a
central matrix. Matrix contains
DNA & ribosomes. Site of aerobic
respiration,therefore
abundant in
active cells.
Golgi Apparatus
Cytoplasm
Smooth ER
------------ ER
Nucleus
Nucleolus
----------------------
Lysosome Plasma Membrane
------------------------
Two hollow cylinders
arranged at right angles
to each other.
Involved in spindle
formation during cell
division
Ultrastructure of animal cell. Complete the annotation make some notes about structure and function
of each organelle you may draw a diagram to help your explanation
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Edexcel AS Biology (8BIO 1) Mo Idriss, Quick Revision Notes
4 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
Make sure you can recognise the different organelles from the electron microscope images for (A)
Nucleus. Nucleoli are observed inside the nucleus. (B) Rough endoplasmic reticulum. Numerous
ribosomes (dark spots) bind to the surface. (C) Golgi body. The top is the cis side and the bottom is the
trans side. (D) Lysosome. Material being degraded is observed on the inside of this organelle. (E)
Peroxisome. A crystalline, dark region is observed at the centre. (F) Mitochondria. The dark granules
contain calcium. (G) Chloroplast. Grana are the membrane structures observed in the dark
Protein Modification and transport in Eukaryotes
The two organelles involved in this are the Endoplasmic Reticulum (ER) and the Golgi body.
ER is classified into rough ER and smooth ER depending on its structure. The rough ER with
attached ribosomes are where protein synthesis occurs. Newly synthesised proteins are also
stored here. Some initial processing of proteins may also occur here for example addition of
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Edexcel AS Biology (8BIO 1) Mo Idriss, Quick Revision Notes
5 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
carbohydrates. Eventually the proteins are pinched off in vesicles from the end of the Rough ER
and moved to the Golgi for modification into other products that the cell needs.
The Golgi body (also called Golgi complex or Golgi apparatus) is an organelle shaped like stacks
of several layers of flat smooth ER (Fig. 11-8C). The function of the Golgi apparatus is to further
process proteins received from the Rough ER into products depending on the needs of the cell,
and then send them on to their destinations.
The cis side of the Golgi is the face that receives proteins from Rough ER and the trans side is
where they are shipped off from.
Some of the modifications of proteins within the Golgi include formation of lysosomes, which
contain digestive enzymes that are used to recycle cell organelles inside cells or for
export/secretion out of the cells.
Modifications may also be by addition of polysaccharides, phosphate groups or sulphate groups
to the proteins.
The smooth ER is involved in various functions such as the synthesis of steroids, lipids &
phospholipids, glycogen metabolism, calcium ion regulation, and intracellular digestion.
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Edexcel AS Biology (8BIO 1) Mo Idriss, Quick Revision Notes
6 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
Differences between Plant and Animal cells
We have already outlined the differences between prokaryotes and eukaryotes. Plant and
animal cells as well as fungal cells are eukaryotic cells. The organelles we have described in the
section above are for animal cells. Plant cells are eukaryotic and share most of the
features/organelles described; however there are some differences between plant and animalcells which we will now discuss in the form of the table below.
1. Label the plant cell on the right.2. How does it differ from the animal
cell described on page 3 above?
3. In the form of a table (below),describe the structure and function
of the following plant organelles: cell
wall, chloroplasts, amyloplasts,
vacuole, tonoplast, plasmodesmata,
pits and middle lamella
A generalised plant cell
Organelle Structure Function
Cell Wall Rigid layer of cellulose and other
polysaccharides, proteins and
sometime lignin on the outside of
the plasma membrane of a plant
cell. Divided into 1ry - deposited
while a cell is growing; typically
extensible & 2ry - innermost layer,
deposited after cell enlargement
has ceased, often lignified.
Chloroplast Small flat/disc shaped &surrounded by double membrane
and filled with gel called the
stroma. Inside are thylakoid
membranes which are stacked in
places to form grana. Grana are
linked together by lamellae.
Site of photosynthesis. Separateenzymes are located on grana and in
stroma
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7 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
Organelle Structure Function
Plasmodesmata Small, cylindrical channels in the
cell walls of plants. They form
when parts of the endoplasmic
reticulum of a parent cell (during
cell division) get caught in the cellwall of the resulting daughter cells.
Act as bridges connecting the
cytoplasm of cells; important
for communication among cells. Allow
free movement of the contents and
can contract or dilate to allowdifferent sized molecules through.
Amyloplast Stores large amounts of starch, but no
chlorophyll, specialized for storage.
Abounds in storage tissues e.g. potato
Tonoplast
Vacuole
Single membrane which envelops
the central vacuole in plant cells.
It is relatively impermeable to
solutes but highly permeable to
water.
Large water filled and surrounded
by a single membrane (tonoplast).
For storage of metabolic wastes. May
also contain pigments that are water
soluble & phenolic compounds that
function in plant defense.
Pit
A region where the
secondary cell wall is
absent, but the primary
cell wall is present.
Middle Lamella
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Edexcel AS Biology (8BIO 1) Mo Idriss, Quick Revision Notes
8 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
This diagram represents a
prokaryotic (bacterial cell).
How does this cell differ fromeukaryotic (plant and animal) cells?
Feature
Prokaryotic Cell Eukaryotic Cell
Animal Cell Plant Cell
Nucleus with envelope
Membrane bound organelles
DNA found as
Flagella
Cell wall
Relative cell size
How Prokaryotic cells differ from Eukaryotic cells
Differences between prokaryotic and eukaryotic cells (Please complete)
Feature Prokaryotic (bacteria) Eukaryotic (plant/animal/fungi)
Size Small cells - 5m Large cells - 50mCapsule (protection) Present Absent
Cell wall Present (peptidoglycan) In fungi (chitin)In plants (cellulose)NOT in animals
Plasma membrane Present Present
Membrane bound organelles(indicate with examples
whether present or absent)
_________________________
_________________________
_________________________
_________________________
_________________________
_________________________
Nucleus- Nuclear envelope
- Nucleoli- Nature of DNA
Absent\ Absent
\ Absent_________________________
Present\ Present
\ Present____________________________
Centriole (for mitosis) Absent Only in animal cells
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Edexcel AS Biology (8BIO 1) Mo Idriss, Quick Revision Notes
9 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
Cellular Organisation
Multicellular organisms have many cells but
these cells are not randomly arranged. They are
specialised to carry out specific functions and
grouped into tissues. Structurally, cells ofmulticellular organisms are organized into four
levels:
Cells Tissues
Organs Organ systems
A tissue is a group of similar cells, that develop
from the same kind of cells and which work
together to perform a commonfunction; such as muscle tissue.
Some examples of animal tissues are
seen in the diagram on the right. They
include:
1. Connective tissue supportingtissue like bone and cartilage.
2. Epithelial tissue lines surfacesboth inside and outside thebody e.g. the skin is made
mainly of stratified epithelium.
3. Muscle tissue contracts to aid movement4. Nervous tissue in brain, spinal cord and nerves. Transmits electrical messages around
the body
Some examples of plant tissues are collenchyma and schlerenchyma tissues which are for
support as well as vascular/conductive tissue (xylem & phloem) which are for transporting
water and dissolved minerals/food.
Tissues are organised into organs the heart in humans; the root and leaf in plants are
examples of organs. Organs are groups of tissue collected into a structure to work together
effectively.
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Edexcel AS Biology (8BIO 1) Mo Idriss, Quick Revision Notes
10 Unit 2: Developments, Plants and the Environment Topic 3: The voice of the Genome
The diagram shows a section through the plant organ, the Leaf.
Label it to show the different tissues it has.
In animals, many organs are then grouped together into systems to carry out a large scale
function. A good example of an organ system is the digestive system which consists of many
organs (stomach, liver, oesophagus, small intestine, pancreas e.t.c) which in turn consist of
many combinations of tissues.