3.4 Eukaryotic cell structure Flashcards
What are the features of a nucleus?
-10-20µm in diameter, spherical
-nuclear envelope (double membrane, surrounds the nucleus and is continuous with the endoplasmic reticulum) controls entry and exit of substances and contains internal reactions
-nuclear pores (approx. 3k per nucleus, 40-100nm diameter) allow passage of large molecules (e.g. mRNA) through nuclear membrane
-nucleoplasm (granular jelly-like substance, majority of volume)
-chromosomes (protein bound DNA)
-nucleolus (small and spherical) manufactures rRNA and assembles ribosomes. can be multiple in one nucleus
What is the function/s of a nucleus?
-be a control centre for the cell via mRNA and tRNA production
-retain genetic material of the cell (i.e. chromosomes, DNA)
-manufacture rRNA and ribosomes
What is the function of a nucleolus?
-site to assemble rRNA into ribosomes
What are the features of a mitochondrion?
-1-10µm in length, rod-shaped
-double membrane (inner one folds into cristae) controls entry and exit of substance
-cristae (extensions of inner membrane) provide large surface area for enzyme attachment/respiration involved proteins
-matrix (remaining space in mitochondrion) contains proteins, lipids, 70S ribosomes and DNA to allow mitochondria to produce some of their own proteins
What is the function/s of a mitochondrion?
-site of aerobic respiration (responsible for ATP production)
Why may a cell have many mitochondria?
in area where a lot of ATP is required (e.g. for active transport, for muscle cell function)
What are the features of a chloroplast?
-contains DNA and 70S ribosomes to manufacture photosynthesis proteins
-chloroplast envelope (double plasma membrane) controls entry and exit of substances
-thylakoids (disc-like, form stacks of up to 100 called grana) contain chlorophyll for first stage of photosynthesis (light absorption). adapted to have large surface area
-stroma (fluid-filled matrix, contains starch grains and all enzymes needed for sugar synthesis) site of second stage of photosynthesis (sugar synthesis)
What is the function/s of a chloroplast?
-site of photosynthesis
What are the features and functions of the rough endoplasmic reticulum (RER)?
-ribosomes on exterior
-provides large surface area for (glyco/)protein synthesis
-provide a pathway for material transport (especially proteins) throughout cell
What are the features and functions of the smooth endoplasmic reticulum (SER)?
-lacks ribosomes on exterior, is more tubular than RER
-synthesises, stores, and transports lipids and carbohydrates
Why may a cell have a very developed ER?
cell may manufacture and store large quantities of carbohydrates/proteins/lipids, e.g. liver and secretory cells
What are the features of a Golgi apparatus?
-similar to SER in structure, but more compact
-stack of membranes which make flattened stacks called cisternae, with small, bulbous, hollow structures called vesicles
What is the function/s of a Golgi apparatus?
-add carbohydrate to proteins to form glycoproteins
-produce secretory enzymes (e.g. pancreas)
-secrete carbohydrates (e.g. plant cell wall)
-transport, modify and store lipids
-form lysosomes
Why may a cell have a very developed Golgi apparatus?
cell is a secretory cell, e.g. the epithelial cells in the intestines
What is a lysosome?
a vesicle produced by the Golgi apparatus, which contains enzymes. up to 1μm in diameter, and can contain up to 50 enzymes per lysosome.
functions are:
-hydrolyse ingested material (e.g. in phagocytes)
-release enzymes (exocytosis) to destroy nearby material
-digest old organelles for material reuse
-break down dead cells (autolysis)
