2.1.1 CELL STRUCTURE Flashcards
what are the two main types of organism and what creates the distinction?
- Prokaryotic organisms made up of prokaryotic cells (single-cellled organisms, smaller and simpler e.g. bacteria)
- Eukaryotic organisms made up of eukaryotic cells (complex and include all animal and plant cells)
Define cell ultrastructure?
a cells organelles and internal structure
2 types of eukaryotic cells
- animal
- plant
What organelles are found in Animal cells? (structure and ultrastructure)
- plasma/cell surface membrane
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
- nucleolus
- nucleus
- nuclear envelope
- lysosome
- ribosome
- Golgi apparatus
- cytoplasm
- mitochondrion
What organelles are found in Plant cells? (structure and ultrastructure)
- plasma/cell surface membrane
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
- nucleolus
- nucleus
- nuclear envelope
- lysosome
- ribosome
- Golgi apparatus
- cytoplasm
- mitochondrion
- **cell wall with plasmodesmata **(‘channels’ for exchanging substances between adjacent cells)
- vacuole (compartment that contains cell sap)
- **choloroplasts **(involved with photosynthesis)
Difference between plant and animal cells?
Plant cells have the same organelles as animal cells with a few added extras:
* **cell wall with plasmodesmata **(‘channels’ / gaps in cell wall for exchanging substances between adjacent cells)
* vacuole (compartment that contains cell sap)
* **choloroplasts **(involved with photosynthesis)
Organelles of eukaryotic cells
inc description and function
Plasma membrane (aka cell surface membrane)
Desc:
* membrane found on the surface of animal cells and just inside the cell wall of plant cells and prokarytic cells
* made mainly of lipids and proteins
Fun:
* regulates movement of substances into and out of the cell
* has receptor molecules on it, allowing it to resond to chemicals like hormones
* compartmentalisation
cyoplasm
Desc:
* found in animal / plant cells
* jelly like substance
Fun:
* cell support / structure
* cite of chemical reactions
* cytoskeleton
Cell wall
Desc:
* a rigid structure that surrounds plant cells
* made mainly of carbohydrate cellulose
Fun:
* supports plant cells
Nucleus
Desc:
* large organelle surrounded by a nuclear envelope (double membrane)
* contains many pores
* contains chromatin (made from DNA and proteins)
* often contains a nucleolus (small, dense spherical structure present during interphase)
Fun:
* controls cells activities (by controlling transcription of DNA)
* DNA contains instructions too make proteins (translation)
* pores allow substances (e.g. RNA) to move between the nucleus and the cytoplasm
* nucleolus makes ribosomes
Lysosome
Desc:
* round organelles surrounded by a membrane with no clear internal structure
Fun:
* contains digestive enzymes kept speerate from cytoplasm by surrounding membrane, can be used to digest invading cells or to break down obselete / worn out components of the cell
Ribosome
Desc:
* very small organelle that either floats free in the cytoplasm or is atttatched to the RER
* made up of proteins and RNA
* not surrounded by a membrane
Fun:
* site where proteins are made
Rough endoplasmic reticulum
Desc:
* system of membrames enclosing a fluid-filled space
* surface is covered with ribosomes
* Cisternae flat membrane bound compartments
Fun:
* Folds and processses proteins that have been made at the ribosomes
Smooth endoplasmic reticulum
Desc:
* system of membrames enclosing a fluid-filled space
* no ribosomes
* Cisternae flat membrane bound compartments
* continuous three-dimensional network of tubules, vesicles, and lamellae.
Fun:
* synthesises and processes lipids
Vesicle
Desc:
* a smalll fluid-filled sac in the cytopalsm
* surrounded by a membrane
* formed by either the Golgi or SER/ RER or cell surface membrane
Fun:
* transports substances in and out of the celll (via the plasma membrane) and betweeen organelles
Golgi appparatus
Desc:
* group of fluid-filled, membrane bound, flattend sacs where vesicles are often seen at the edges of the sace
* Cisternae flat membrane bound compartments
Fun:
* processes and packages new lipids and proteins
* makes lysosomes
Mitochondrion
Desc:
* usually oval-shaped
* double membrane (inner folded to form structure called cristae)
* inner matrix containing enzymes involved in respiration
* Found in large numbers in cells that ar4e very activce and require a lot of energy
Fun:
* site of aerobic respiration where ATP is produced
Chloroplast
Desc:
* smalll, flattend structure found in plant cells
* surrounded by double membrane
* membranes inside called thylakoid membranes which are stacked in some parts of the chloroplast to form Grana which are linked by lamellae which are thin flat pieces of thylakoid membrane
* stoma - thick fluid found in chloroplasts
Fun:
* site of photosynthesis (GRANA/STOMA)
Centriole
Desc:
* small, hollow cylinders
* made of microtubules (tiny protein cylinders)
* found in alll animal cells but only some plant cells
Fun:
* involved with the seperation of chromsomes during celll division
Cillium
Desc:
* smalll, hair like strcutures
* found on csm of some animal cells
* in cross section they have an outer membrane and a ring of nine pairs of protein microtubules inside
* single pair of microtubules in the middle
* known as 9+2 formation becasue nine pairs surrounding two centeral mts
Fun:
* microtubules allow cillia to move
* used by cell to move substances along cs
Flagellum
Desc:
* like cillia but longer
* stick out from cs surrounded by plasma membrane
* in cross section they have an outer membrane and a ring of nine pairs of protein microtubules inside
* single pair of microtubules in the middle
* known as 9+2 formation becasue nine pairs surrounding two centeral mts
Fun:
* MTs contract to make flagellum move
* Flagella are used like outboard motors to propel cells forward (eg. when a sperm celll swims)
organelles working together 2 main examples?
- Protein production
- The cytoskleton
explain the process of protein production in eukaryotes
- proteins made at ribosomes
- ribosome at RER make proteins that are excretedor atttached to the cell membrane
- free ribosomes in cytoplasm make proteins that stay in the cytoplasm
- new proteins produced at RER are folded and processed (eg. sugar chains are added) in the RER
- transported from RER to Golgi in vesicles
- at Golgi proteins may undergo futher processing (eg. sugar chains are trtimmed or more are added)
- proteins enter more vesicles to be transported around the cell (eg. glycoproteins found in mucus move to the cell surface and are secreted
proteins may be stored at the RER until needed by the Golgi
What is the cytoskeleton
- dynamic (constantly changing) allowing it to respond to changes in the cell and carrry out its functions
- a network of protein threads running through a solution of chemicals in the cytoplasm
- In euk cells protein threads are callled mfs (very thin protein strands) / mts (tiny protein cylinders)
What are the four main functions of the cytoskeleton?
- The microtubules and microfilaments support the cells organelled, keeping them in position
- they also help to strengthen the cell and maintain its shape
- Responsible for the transport of organelles and materia; within the cell (eg. movement of chromosomes when the seperate during cell divisiom depends on contraction of microtubules in the spindle, movement of vesicles around the cell relies on cytoskeletal proteins)
- the proteins of the cytoskelton can also cause the cell to move (eg. movement of the cillia and flagella caused by cytoskeletal protein filaments that run through them so in the case of single cells that have a flagellum(eg. sperm cells), the cytoskeleton propels the whole cell)
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