Core Concepts: Cell Structure and Organisation Flashcards
What is the function of the nucleus
Contains the DNA which codes for protein synthesis
What is the function of the nuclear envelope
Separates the DNA from the cytoplasm
What is the function of the nuclear pore
Allows passage of molecules in and out on the nucleus
What is the function of the nucleolus
Synthesis of rRNA to make ribosomes
What is the structure of ribosomes
- 2 subunits made from ribosomal RNA (rRNA) and protein:
- Large subunit
- Small subunit - Can be free or attached to rough endoplasmic reticulum (RER)
What is the function of ribosomes
Protein synthesis
What is the structure of mitochondria
- Cylindrical and 1-10 um in diameter
- Double membrane separated by the fluid-filled, inter membrane space
- Inner membrane folded to form cristae
- The interior is called the matrix and contains enzymes
- contains DNA and ribosomes (70s)
What is the function of mitochondria
- Site of aerobic respiration, synthesises ATP
- Cristae increases surface area on which part of the respiratory process takes place
- Cells with high metabolic activity contain many mitochondria
What is the RER
Rough Endoplasmic Reticulum
What is the structure of RER
- A series of membrane, which enclose flattened sacs called cisternae
- Continuous with the nuclear membrane
- Has ribosomes attached
What is the function of RER?
Transports proteins which are synthesised by the ribosomes attached
What is the structure of smooth endoplasmic reticulum
- Forms a system of flattened sacs (cisternae) which are continuous with the nuclear membrane
- May link to the Golgi apparatus
- Has NO ribosomes attached
What is the function of smooth endoplasmic reticulum
The synthesis and transport of lipids
What is the structure of golgi body
- flattened sacs of membrane called cisternae
- Surrounded by vesicles
What is the function of golgi body
- Chemically modifies proteins
- Produces lysosomes
- Produces glycoproteins
- Packages proteins for secretion out of the cell
What is the structure of vesicles
Small membrane bound organelle
What is the function of vesicles
Act as a contractile vacuole to maintain osmotic pressure
What is the the structure of vacuoles
Large membrane bound organelle surrounded by a tonoplast
What is the function of vacuoles
- Storage of ions and organic molecules (e.g. proteins)
- Maintaining osmotic pressure
What is the structure of centrioles
Two hollow cylinders positioned at right angles to one another
What is the function of centrioles
Used in spindle formation (microtubles) in cell division
What is the structure of lysosomes
- Small vacuoles formed when small portions of the Golgi body are pinched off
- Contain and isolate digestive enzymes
What is the function of lysosomes
- Release digestive enzymes and destroy organelles
- Digestion of material which has been taken into the cell
- lysosomes isolate the potentially harmful enzymes from the rest of the cell
What is the structure of chloroplast
- Have a double membrane
- The interior is made up of a fluid called stroma containing:
- ribosomes
- lipids
- circular DNA
- starch granules. - There are thylakoids - flattened sacs. these form stacks which are called granum. Each granum consists of between 2-100 thylakoids. Between the grana the thylakoids form lamellae
What is the function of chloroplasts
- Site of photosynthesis
- The thylakoids contain photosynthetic pigments such as chlorophyll
What is the structure of a cellulose cell wall
Made of cellulose microfibrils in a polysaccharide matrix
What is the function of a cellulose cell wall
- To provide mechanical strength and support
- Freely permeable to water
What is the structure of plasmodesmata
A narrow thread of cytoplasm that passes through the cell walls of adjacent plant cells
What is the function of plasmodesmata
- Exchange of large organic materials via cytoplasmic streaming
- Allows communication between adjacent cells
What is the theory that describes the origin of chloroplasts and mitochondria
Endosymbiotic theory
What is the Endosymbiotic theory
Prokaryotes engulfed & internalised other prokaryotes
What is the evidence for the endosymbiotic theory
- Organelles self replicate
- Same DNA and Chloroplastss early Bacteria
- Inner membrane is similar in structure to original bacteria
State the 9 steps for protein production
- Nucleus contains DNA, codes for the amino acid sequences in proteins
- An mRNA copy of the DNA is made by transcription. This is small enough to fit through the nuclear pore and goes into the cytoplasm
- The nucleus synthesises rRNA for ribosome production
- Ribosomes synthesise the protein using the mRNA (translation)
- RER transports protein
- Glogi body modifies protein (e.g. adding a prosthetic group) which is then packaged into a secretory vesicle
- Vesicle carrying the protein migrates towards the plasma membrane
- Vesicle fuses with the plasma membrane then the contents of the vesicle are emptied by exocytosis
- Mitochondria produces ATP which is used in active processes
What is the definition of prokaryote
A single-celled organism with membrane-bound organelles and with its DNA free in the cytoplasm
What is the definition of eukaryote
An organism containing cells that have membrane-bound organelles, with DNA in chromosomes within the nucleus
What are the 2 types of viruses
- DNA viruses
- stable, do not mutate rapidly
- Single-stranded or double-stranded
- Smallpox, Hepatitis B - RNA viruses
- mutate rapidly, unstable
- Single-stranded or double-stranded
- Influenza, HIV
What types of cell do viruses infect
- animal, plant and fungal cells
- Viruses can also attack bacteria. These are called bacteriophage
Describe the DNA in Prokaryotes
- Circular
- Naked DNA
- Plasmids contain 1-3 genes
Describe the DNA in Eukaryotes
- Linear
- Found in the nucleus
- Associated with histone proteins
Describe the DNA in Viruses
Core contains DNA or RNA
Describe the organelles in Prokaryotes
- No membrane bound organelles
- Have Ribosomes (70s)
Describe the organelles in Eukaryotes
Have membrane bound organelles:
* Nucleus
* Mitochondria
* RER
* SER
* Golgi Body
* Chloroplasts
* Vesicles
* Lysozomes
* Permanent vacuole
* Ribosomes (80s)
Describe the organelles in Viruses
No organelles
For each one, state whether a cytoplasm is present:
- Prokaryotes
- Eukaryotes
- Viruses
- Prokaryotes - Yes
- Eukaryotes - Yes
- Viruses - No
Describe the boundaries of a Prokaryote
- Cell Membrane
- Cell Wall - peptidoglycan
- Slime Capsule
Describe the boundaries of a Eukaryote
- Cell Membrane
- Cell Wall:
- Plants - Cellulose
- Fungi - Chitin
Describe the boundaries of a Virus
- Capsid - Protein
- Lipoprotein Coat
Describe the replication of a Prokaryote
Self replication by Binary Fision
Describe the replication of Eukaryotes
Self replication by mitosis
What do all Prokaryotes contain
(5 answers)
- DNA molecules loose in cytoplasm
- Peptidoglycan Cell Wall
- 70s Ribosomes
- Cytoplasm
- Cell Membrane
What do some Prokaryotes contain that not all do
(5 answers)
- Slime coat
- Flagella
- Photosynthetic pigments
- Mesosome (possible site of respiration)
- Plasmids
Deffine Tissue
A group of layers of similar cells working together to perform a specific function
Define an Organ
A collection of different tissues working together to perform a specific function
Name 3 examples of tissues found in the human body
- Epithelial Tissue
- Muscle Tissue
- Connective Tissue
Describe the structure of epithelial tissues
- cells packed closely together
- rest on the basement membrane
What is the function of epithelial tissues
- Lining tissue that covers the surface of organs, cavities and tubes
- Protect cells underneath
- Secrete substances
- Absorb substances
- Excrete waste products
Describe the structure of squamous epithelial tissue
Flattened cells on a basement membrane
What is the function of squamous epithelial tissue
- Form the walls of the alveoli
- Line Arteries, veins & Capilliaries
What is the structure of cuboidal epithelial tissue
Box shaped cells that are 1 cell thick
What is the function of cuboidal epithelial tissue
Involved with secretion and absorption
Where is cuboidal epithelial tissue found
- Kidney tubules
- Glandular ducts
Where is cuboidal epithelial tissue found
- Kidney tubules
- Glandular ducts
What is the structure of columnar epithelial tissue
- column shaped cells
- some have cilia and some have microvilli
What is the function of columnar epithelial tissue
- Cilia waft dust & dirt trapped in mucus out of air passages
- Microvilli increase the surface area
Where is columnar epithelial tissue found
- Found in the trachea and bronchi with cilia.
- Found in the small intestine with microvilli
What is the structure of glandular epithelial tissue
Contain mucus secreting goblet cells
What is the function of glandular epithelial tissue
Secrete enzymes, hormones, salive etc.
Where is glandular epithelial tissue found
- Digestive system
- Pancreas
- Salivary gland
What is the structure of connective tissue
- Contains elastic and collagen fibres in an extracellular fluid / matrix
- Between fibres are fat-storing adipocytes and immune system cells
What is the function of connective tissue
- To support or separate tissues and organs
What is the structure of skeletal muscle
- Muscle cells are joined together to form fibres
- Striations are caused by overlapping of protein molecules in cell
- Attached to bones by tendons
What is the function of skeletal muscle
- Voluntary movement
- Skeletal movement
- Maintain posture and body position
- Support soft tissue
What is the structure of smooth muscle
Unstriated, individual cells that can shorten in length
What is the function of smooth muscle
- involuntary contractions e.g to move things around the body
Where is smooth muscle found
- Skin
- Walls of blood vessels
- Digestive tract
- Respiratory tract
What is the structure of cardiac muscle
- Striated and branched fibres
- Attatched at ends to adjoining fibres by thick plasma membranes called intercallated disks
What is the function of cardiac muscle
Rhythmic contraction to pump blood through the heart