Cell organisation and structure Flashcards
What is the cell surface membrane?
- partially permeable membrane to allow only some substances to pass through
- controls the substances entering and leaving the cell
What is a cytoplasm?
- where most of the cell activities occur
- contains specialised structures known as organelles
What are organelles?
- organelles carry out many functions
- many organelles are not visible under the light microscope and can only be studied under the electron microscope like the mitochondria, centrioles and ribosomes
What is the function of the nucleus?
- controls cell activities like cell growth and repair the worn-out parts
- essential for cell division and those without a nucleus are unable to divide like the human red blood cell
What is the function of the cell wall?
- encloses the entire plant cell surrounding the cell surface membrane
- made of cellulose
- protects the cell from injury and gives the plant cell a fixed shape
What is the rough endoplasmic reticulum?
- surface appears rough when viewed under the electron microscope as small particles called ribosomes are attached to its outer surface
- the outer surface of the RER is continuous with the nuclear envelope
What are ribosomes?
- either attached to the membrane of the RER or lie freely in the cytoplasm
- needed to synthesise proteins in the cell
- ribosomes attached to the RER make proteins that are usually transported out of the cell
- ribosomes lying freely in the cytoplasm make proteins that are used within the cytoplasm of that cell
- the RER transports proteins made by the ribosomes to the Golgi apparatus for secretion out of the cell
What are the functions of the smooth endoplasmic reticulum?
- synthesise substances like fats and steroids
- sex hormones in mammals are steroids
- converts harmful substances into harmless materials through a process known as detoxification
How is the RER different from the SER?
- SER does not have ribosomes attached to its membrane
- SER is more tuber compared to the RER
- it is connected to the RER
What are the functions of the golgi apparatus?
- chemically modifies substances made by the RER
- stored and packages these substances in vesicles for secretion out of the cell
What is the path of a protein?
- vesicles transport substances within the cell
- small vesicles containing substances made by the RER and pinched off from the RER - vesicles fuse with the Golgi apparatus and release their contents into the Golgi apparatus
- substances made by the RER may be modified inside the Golgi apparatus
3, secretory vesicles containing these modified substances are pinched off from the Golgi apparatus
- they move to the cell surface membrane - the secretory vesicles fuse with the cell surface membrane and their contents are released outside the cell
What is takes place at the mitochondria?
- aerobic respiration
- food substances are oxidized to release energy which may be used for
cell activities like growth and reproduction
Describe the chloroplast structure and function.
- oval structures are found in plant cells
- contains a green pigment called chlorophyll which is essential for photosynthesis to make food for the plants
What are vacuoles?
- fluid-filled space enclosed by a membrane
- store substances within a cell
- animal cells have many small vacuoles that contain water and food substances and exist temporarily
- plant cells have a large central vacuole containing a liquid called a cell sap
- it contains dissolved substances like sugars, mineral salts, and amino acids
- enclosed by a partially permeable membrane called the tonoplast
Differences between animal and plant cells
Plant cells
- Cell wall present
- Chloroplast present
- Large central vacuole
Animal cells
- Cell wall absent
- Chloroplast absent
- Many small vacuoles
