Cell Structure And Organisation🦠 Flashcards
(40 cards)
What is a eukaryote?🐯🌱
Any organism consisting of one or more cells that contain DNA in a membrane bound nucleus separate from the cytoplasm.
Large number of specialised membrane bound organelles.
What is a prokaryote?🔍
Has DNA suspended freely in cytoplasm.
Is simple and lacks membrane bound organelles.
Features of prokaryotes 🔍
- Peptidoglycan cell wall
- DNA suspended
- Ribosomes
- Cytoplasm
- Cell membrane with a phospholipid bilayer
- Mesosome for cellular respiration
- Capsule
- Sometimes have a flagellum
Features of eukaryotes🐯🌱
Membrane bound organelles Mitochondria ER Ribosomes Golgi body Lysosomes Centrioles Nucleus Nucleolus Nuclear envelope Chromatin Plasmodesmata🌱 Chloroplasts🌱
Features of plant cells (in comparison to animal cells)🌱
Cellulose cell wall Plasmodesmata Chloroplasts Large, permanent vacuole filled with cell sap Tonoplast Starch grains for storage No centrioles
Features of animal cells (in comparison to plant cells)🐯
No cell wall No plasmodesmata No chloroplasts Small, temporary vacuoles No tonoplast Glycogen granules for storage Centrioles
Plasma membrane
- Composed of a phospholipid bilayer with intrinsic and extrinsic proteins.
- Selectively permeable and controls movement of substances in an out of cell.
- Maintains different concentrations of molecules/ions inside and outside the cell.
- Gives the cell structure.
Cell wall
- Bacteria: murein/peptidoglycan🔍
- Plants: cellulose🌱
- Fungi: chitin🍄
- Provides support.
- Keeps plant cell rigid and stops it from bursting.
- Allows plants to become turgid during osmosis.
- Permeable.
- Pores called plasmodesmata which allows the cytoplasm of neighbouring cells to connect, enabling exchange of substances.
Nucleus
- Contains cell DNA which is passed on through generations and a provides coding for protein synthesis by making RNA.
- Nuclear membrane✉️ which enclose the nucleus. It has nuclear pores which allow RNA to leave the nucleus
- Nucleoplasm contains the cells DNA in the form of chromatin
- Nucleolus produces rRNA
Ribosomes
- Made up of protein and rRNA
- Protein synthesis
- Synthesise enzymes
Rough ER
- A series of double membranes with cisternae between
- Transports proteins
- Has ribosomes along its length which carry out protein synthesis
Smooth ER
- A series of double membranes with cisternae between
* Synthesis of lipids
Golgi body/Golgi apparatus
- A stack of flattened membranous sacs
- Assembles glycoproteins
- Produces lysosomes
- Modifies and packages proteins
- Transports and stores lipids
- Produces digestive enzymes
Describe the process of the exportation of proteins by the Golgi body
- Vesicles containing proteins formed by the RER fuse at the end of the Golgi sacs
- The protein is modified inside the Golgi sacs
- The modifies protein is budded off in a vesicle at the other end of the Golgi sacs
- The vesicle travels to the outer plasma membrane where the protein is released by exocytosis
What are lysosomes?
- Vesicles which contain digestive enzymes
- Has a membrane which prevents the enzymes digesting the cell itself
- Destroy worn out organelles
- Digest material taken into the cell, such as bacteria
- The material is taken into the cell and trapped in vacuoles which the lysosomes then fuse with to release their enzymes into them
Mitochondria
- Release chemical energy in the form of ATP during aerobic respiration
- Double membrane
- Inner membrane is folded to form the cristae which increase the S.A on which ATP synthesis can occur
- Filled with matrix which contains ribosomes and mitochondrial DNA
What is the significance of mitochondrial DNA?
- Allows the mitochondria to divide to meet the needs of the cell
- Is evidence that mitochondria may have once been free living organisms that were ingested by the ancestors of eukaryote cells
Centrioles
Cylinders that separate from each other during the early stages of mitosis to form the spindle fibres
Chloroplasts
- Large organelles with a double membrane
- The site of photosynthesis
- Stroma (cytoplasm-like material) contains starch grains and ribosomes
- Thylakoids which are membrane bound compartments; the membrane contains chlorophyll which absorbs light energy
- Grana are stacks of thylakoids and are linked by lamellae
- Have chloroplast DNA - evidence of free living organism like mitochondria
Which three organelles have a double membrane?
Nucleus
Mitochondrion
Chloroplast
Vacuole
Plants: large, permanent and contain cell sap; surrounded by tonoplast🌱
Animals: small and have no tonoplast🐯
What is a mesosme?
An infolding of the prokaryote’s plasma membrane.
The infolding increases the S.A for respiration and other chemical reactions.
DNA in a prokaryote🔍
Free in the cytoplasm in an area known as the nucleoid.
Usually found in a single circular chromosome.
May also have circular pieces of DNA called plasmids.
Viruses👾
- No cytoplasm
- Nucleic acid and a protein coat
- Infect prokaryotes and eukaryotes
