3.2.1 - Structure of eukaryotic cells Flashcards
Topic 2
What are the distinguishing features of eukaryotic cells?
- Cytoplasm containing membrane-bound organelles
- So DNA enclosed in a nucleus
Eukaryotic cells make up eukaryotic organisms
- examples of eukaryotic organisms…
- animals, plants, algae, fungi
Algal cells have all the same organelles as ….
Algal cells have all the same organelles as plant cells
2 main differences between fungal cells and plant cells
- Fungal cell walls are made of chitin whereas plant cell walls are made of cellulose
- Fungal cells do not have chloroplasts (so do not photosynthesise) whereas plant cells do
Describe the function of the cell-surface membrane
- It is selectively permeable and so enables the control of the passage/movement of substances in and out of the cells
- has molecules/receptors/antigens on its surface allowing cell recognition/signalling
Describe the structure of the nucleus
- Nuclear envelope
> double membrane
> has nuclear pores - Nucleoplasm
- Nucleolus (dense region)
- Protein/histone-bound, linear DNA
> Chromatin = condensed
> Chromosome = Highly condensed
Describe the function of the nucleus
- Holds/stores genetic information which codes for polypeptides (proteins)
- Site of DNA replication
- Site of transcription (part of protein synthesis), producing mRNA
- Nucleolus makes ribosomes/RNA
What do nuclear pores allow?
Substances (eg: RNA) to move between the nucleus and the cytoplasm
Describe the structure of a ribosome
- Made of ribosomal RNA and protein (two subunits)
- Not a membrane-bound organelle (not surrounded by a membrane
Describe the function of a ribosome
- Site of protein synthesis (translation)
Describe the structure of the rough endoplasmic reticulum
- System of membranes enclosing a fluid-filled space
- Surface covered with ribosomes
Describe the function of the rough endoplasmic reticulum
- Ribosomes on surface synthesise proteins
- proteins processed/folded/transported inside the rough endoplasmic reticulum
- proteins are packaged into vesicles for transport eg: to golgi apparatus
Describe the structure of the smooth endoplasmic reticulum
System of membranes enclosing a fluid-filled space
Describe the function of the smooth endoplasmic reticulum
- Synthesises and processes lipids
> Eg: cholesterol and steroid hormones
Describe the structure of golgi apparatus and golgi vesicles
- Golgi apparatus
> Group of membrane-bound flattened sacs filled with fluids - Golgi vesicles
> often seen at edges of golgi apparatus
> small membrane-bound sac filled with fluid
Describe the function of the golgi apparatus
- Golgi apparatus
> Modifies proteins (eg: adds carbohydrates to produce glycoproteins)
> Modifies lipids (eg: adds carbohydrates to make glycolipids)
> Packages proteins/lipids into golgi vesicles
> produces lysosomes (a type of golgi vesicle)
Describe the function of golgi vesicles
- Transports proteins/lipids to their required destination
- Eg: moves to and fuses with cell-surface membrane
Describe the structure of lysosomes - a type of golgi vesicle
- Round organelle surrounded by a membrane
- Contains hydrolytic enzymes
Describe the function of lysosomes
- Release hydrolytic enzymes (lysozymes)
- to break down/hydrolyse pathogen or worn-out cell components
Describe the structure of mitochondria
> Double membrane
- Outer membrane
- Inner membrane is folded to form cristae
Matrix which contains
- small 70s ribosomes
- circular DNA
- enzymes involved in respiration
Describe the function of the mitochondria
- Site of aerobic respiration
- inwhich ATP is produced for energy release
(eg: for protein synthesis/vesicle movvement/active transprt)
Describe the structure of chloroplasts in plant and algal cell
- Surrounded by a double membrane
- Stroma, containing:
> thylakoid membranes, which stack up to form grana > grana are linked together by lamellae
> small/70S ribosomes
> circular DNA
> starch granules/lipid droplets
Describe the function of chloroplasts in plants and algae
- Absorbs light energy for photosynthesis
- which produces organic substances (eg: carbohydrates/lipids)
Describe the structure of the cell wall in plants,algae and fungi
- Cell wall in plant and algal cells:
> composed of cellulose (a polysaccharide) - Cell walls in fungal cells
> composed of chitin (a nitrogen-containing polysaccharide)
Describe the function of the cell wall in plants, algae and fungi
- Supports the cell by providing mechanical strength
- this prevents the cell from changing shape or bursting under pressure due to osmosis
Describe the structure of the cell vacuole in plants
- Surrounded by Tonoplast membrane (membrane-bound organelle)
- contains cell sap
What is cell sap?
A weak solution of sugar and salts
Describe the function of the cell vacuole in plants
- Maintains turgor pressure in cells (keeps cells rigid, stopping the plant wilting)
- Contains cell sap - which stores sugars, amino acids, pigments and any waste chemicals (isolates unwanted chemicals inside the cell)
Describe how eukaryotic cells are organised in complex multicellular organisms
- In complex multicellular organisms, eukaryotic cells become specialised for specific functions
- specialised cells are organised into tissues, tissues into organs and organs into systems.
Tissue
a group of specialised cells with a similar structure working together to perform a specific function, often with the same origins
Organ
Aggregations/ a group of tissues working together to perform specific functions
Organ systems
Group of organs working together to perform specific functions
