Cell structure Flashcards
function, structure
Cell surface membrane
never write cell membrance, include surface
Strcuture:
* Partialy permeable and formed from a phospholipid bilayer
Function:
* controls and selects the exchange of materials between the internal cell environment and the external environment
* Acts as a barrier between cytoplasm and external environment
* For cell signaling
* For cell recognition
* Site for enzymes
* Cell-to-cell adhesion
structure
Nucleus
STRUCTURE:
- Has a double membrane
- Holds the DNA
- Has a nuclear membrane called nuclear envelope
- Nuclear envelope has the nuclear pores
- Nucleus has a region inside called nucleolus
FUNCTION:
* Contains chromatin: holds genetic information
* Responds to signals that control gene expression
* Codes information for protein synthesis
* Contains nucleolus which makes ribosomes
* DNA is protected from degradation
Function of nuclear pores
- allows mRNA and ribosomes to travel out of the nucleus
- allows enzymes and signalling molecules to move in
Function of the nucleolus
The site of ribosome production: Synthesises rRNA and combines it with proteins
Endoplasmic Reticulum
RER & SER
Structure:
Series of memebranes that form flattened sacs
Rough endoplasmic reticulum:
* Continuous folds of membrane
* Connected with the nuclear envelope: Continous with external nucear membrane
* The surface ofthe RER is covered in ribosomes
Function:
* To produce and transport proteins that are produced on the ribosomes
Smooth endoplasmic reticulum:
- The SER does not have ribosomes on the surface
- It is irregular
- It is tubular
Function: - Role is the production of lipids, and of steroid hormones
Golgi body
Structure:
a series of a flattened sacs of membrane
Function:
Modify proteins and package them into vesicles
Mitochondria
Structure:
* Has a double membrane
* An outer membrane present
* Inner membrane folded to cristae
* Has a matrix
Function:
* Site of aerobic respiration
* Matrix contains enzymes required for aerobic respiration
* Mitochondrial DNA and 70s ribosomes found in matrix: allows production of proteins required for respiration
* ATP production
* Lipid metabolism
Ribosomes
Found in:
cytoplasm or on the RER:
* 80s ribosomes found in eukaryotic cells
* 70s ribosomes found in prokaryotes, mitochondria and chloroplasts
Structure:
Each ribosome is a complex of Ribosomal RNA (rRNA) and proteins
Vesicles
Structure:
* Vesicles are small, membrane-bound sacs
* They can be pinched off the ends ofthe Golgi body;these are known as Golgi vesicles
Function:
* used by cells for transport and storage
* They can fuse with the cell surface membrane to allow exocytosis, or bud from the membrane during
endocytosis
Lysosomes
Structure:
Lysosomes are specialised vesicles which contain hydrolytic enzymes
Function:
Hydrolytic enzymes break down biological molecules, e.g.
* Waste materials, such as worn-out organelles
* Engulfed pathogens during phagocytosis
* Cell debris during apoptosis (programmed cell death)
* They speed up hydrolysis
Centrioles
Strutcure:
Centrioles are hollow fibres made of microtubules
Function:
Two centrioles at right angles to each other form a centrosome, which organises the spindle fibres during cell division
Microtubules
Structure:
Mictrotubules are hollow tubes made of tubulin protein
Function:
Make up the cytoskeleton of the cell
The cytoskeleton is used to provide support and movement of the cell
Cillia
Structure:
Cilia are hair-like projections made from microtubules
Function:
Allow the movement of substances over the cell surface
Microvilli
Structure:
* Cell membrane projection
Function:
Increases surface area for absorption
Found in:
* Lining of the small intestine
* The kidney tubules
microvilli found on villi
Cell wall
Structure:
* Made up of:
Polysaccharide celluslose: Plants
Chitin: Fungi
* Freely permeable
Function:
Structural support
Chloroplasts
Structure:
* Larger than mitochondria
* Has a double membrane
* Chlorophyll forund in Thylakoids
* Thylakoids stack to form grana
* Grana joined together by lamallae
* Contains DNA and 70s ribosomes to synthesise proteins for chloroplast replication and photosynthesis
Function:
* Chlorophyll absorb light energy for photosynthesis
- They are at the edge/periphery of the cells because they are pushed by the central and turgid vacoule.
Plasmodesmata
Structure:
Bridges of cytoplasm between neighbouring plant cells
Function:
They allow the transfer of substances between plant cells
Large permanent vacoule
Structure:
* Surrounded by the tonoplast, which is a partially permeable membrane.
* Found in animal cells, butthese will be small and temporary
Function:
* They store cell sap
* Stores minerals
* Structural support to cells
Organelles present only in plant cell
- Cellulose cell wall
- Large permanent vacuoles
- Chloroplasts
- Plasmodesmata
Organelles present only in animal cell
- Centrioles (Centrosomes, spindle fibres)
- Microvilli
- Central nucleus (In plants the nucleus is at periphery/edge of the cell)
Plant cells do have microtubules
State the importance of ATP in cells
This energy is required:
* In anabolic reactions to build larger molecules from smaller molecules
* To move substances across the cell membrane in active transport, or to move substances within the cell
In animals, energy is required
* For muscle contraction
* Conduction of nerve impulses
6 points
Differences between Prokaryotic and Eukaryotic cells
SIZE:
P: 0.5-15µm
E: Up to 100µm
CELL WALL:
P: Made of peptidoglycan
E: Made of Cellulose: plants and Chitin: fungi
ORGANELLES:
P: No membrane bound organelles (Mitochondria, nucleus, chloroplasts)
No RER/SER, No Golgi body
E: Membrane bound organelles
RIBOSOMES:
P: 70S
E: 80S
GENETIC MATERIAL
P: Circular chromosome in cytoplasm
E: Linear chromosomes in the nucleus
CELL DIVISION:
P: Binary fission
E: Mitosis/Meiosis
What are viruses?
Non-cellular particles that infect living cells
Desribe the structure of viruses
They have a:
* A nucleic acid core made of either single stranded DNA or RNA
* A protein coat called a capsid
* Some viruses have an outer layer called an envelope, made of phospholipds (from the cell membrane of the host)
Organelles with a double membrane
- Mitochondria
- Nucleus
- Chloroplasts
Organelles with a single membrane
- Vacuole
- Endoplasmic reticulum
- Golgi Body
- Lysosomes
vulture lie, eagles glide
Organelles with no membrane
- Ribosomes
- Centrioles
- Cell wall
ribs can cycle
Features mitochondrion have similar with prokaryotes
- Circular DNA
- 70s ribosomes
- Division by binary fission
- size: 0.5-15µm
