Cells Flashcards
What is the role of the plasma membrane?
- controls exchange between cell and environments
What are the functions of the plasma membrane?
- Has receptors for cell recognition
- selectively permeable
What is the role of the cytoplasm?
- suspended in the cytoplasm are number out specialised membrane-bound structures called organelles
- THE CYTOPLASM IS NOT AN ORGANELLE IT JUST CONTAINS ORGANELLES
What is the role of the nucleus ?
- the nucleus contains DNA and controls the activities of the cell
What are the functions of the nucleus ?
- the nucleus is the largest organelle surrounded by a double membrane called the nuclear envelope
What is the nuclear envelope (the double membrane) perforated with?
The nuclear envelope is perforated with nuclear pores.
What is the nucleolus? And what is its function?
- the nucleolus is a small densely staining disk within the nucleus
ALWAYS APPEARS DARKER THAN THE NUCLEUS - the nucleolus makes RNA and ribosomes
What is the nuclear envelope?
- the nuclear envelope is a double layered structure consisting of two adjacent membranes
The membranes are 40-70 nm apart
What is the diameter of the nuclear pores?
50-70nm
What is the function of the nuclear pores?
- the nuclear pore allows movement of substances in or out of the membrane such as RNA or ribosomes
What are often found attached to the Nuclear membrane?
Ribosomes cover the outer layer of the nuclear membrane
What are chromatin?
- when a cell is not dividing no chromosomes can be seen this is because DNA is unwound in the nucleus
- unwound DNA = chromatin
What are mitochondria ?
- mitochondria are rod-shaped organelles
- outer smooth membrane
- inner folded membrane
- the folds of mitochondria are called Cristae
What is the function of mitochondria ?
- they are concerned with energy production through making an energy storage molecule called ATP
- much of the process of aerobic respiration occurs within the mitochondria
Why do mitochondria look different?
- mitochondria vary in shape
- cut in different planes and angles
- or deformed during preparation of section
What is the ROUGH ENDOPLASMIC RETICULUM?
- the rough ENDOPLASMIC reticulum extends front the nucleus and is continuous with it
What is the function of the Rough ENDOPLASMIC reticulum?
The rough endoplasmic reticulum is responsible in transporting proteins which have been made in the ribosomes to where they are needed:
- some proteins may be secreted from the cell e.g. Hormones or enzymes
- some proteins may be placed on the cell surface membrane e.g. Antigen
What are on the surface of the RER?
- ribosomes
Which are the sites of protein synthesis
Nb: free ribosomes are also found within the cytoplasm
What is the function of the SMOOTH ENDOPLASMIC RETICULUM?
- the smooth endoplasmic reticulum is important in synthesising and transporting lipids/steroid based hormones/hormones
Are there any ribosomes on the surface of the smooth ENDOPLASMIC reticulum?
NO
What is the Golgi apparatus/ body ?
The Golgi apparatus is a stack if of 4 to 8 membrane bound sacks located close to the nucleus.
What is the function of the Golgi body?
- Receives proteins from rough endoplasmic reticulum/ribosomes
- The Golgi body MODIFIES and PROCESSES proteins e.g. Carbohydrate chain makes glycoproteins
- Protein is packaged –> vesicle to be released from the cell
SECRETION FROM THE CELL - Also the Golgi body can make lysosomes
- And is involved in lipid synthesising as well as the smooth endoplasmic reticulum
What are lysosomes ?
Lysosomes are membrane bound organelles that contain digestive enzymes known as acid hydrolases
What are the functions of lysosomes?
- involved in apoptosis - destruction of entire cell when damaged or diseased
- destruction of pathogens
- destruction of ageing, redundant cell organelles
- release of digestive enzymes from the cell to degrade other cells
What is the cytoskeleton ?
Cells contain a network of fibres made of Protein
These fibres keep the cell’s shape stable by providing an internal frame work known as the cytoskeleton
What are the two types of protein fibres:
- Microtubules = help move organelles and other cell contents e.g. Chromosomes
- Microfilaments = these are smaller than microtubules and act as a ‘Skeleton’ helping to support the cell
Microfilaments are also responsible for cell movement
What is the role of the cytoskeleton:
- provide STRENGTH and SUPPORT to cell
- determines cell SHAPE
- involved in MOVEMENT of ORGANELLES
- helps HOLD organelles in place
- make up CENTRIOLES And spindle fibres
What are centrioles?
Centrioles are small tubes of protein fibres microtubules
They come in a pair next to the nucleus
ONLY IN ANIMAL CELLS
Centrioles are at right angles to each other
What is the function of centrioles ?
- Centrioles are involved in cell division as they generate spindle fibres
- Spindle fibres are responsible for the separation of chromosomes
What is the difference between flagella and cilia?
- cilia and flagella are structurally the same
- they are HAIRLIKE extensions that stick out from the surface of cells are often involved in movement
- however, cilia are used for relatively short structures e.g. Ciliated epithelial cells
- whereas, flagella is used for relatively long structures which are often found in ones or twos e.g. Sperm cells
