Cells Flashcards
Describe the fluid mosaic model of cell membrane
Cell membrane is fluid in that phospholipids and proteins are not stationary but can move rapidly across the surface of the membrane
Cell membrane is mosaic in that many different protein molecules are randomly scattered and embedded throughout phospholipid bilayer
What is the function of cell membrane
It is partially permeable, functions to separate and protect cell from surrounding environment and control how substances move in and out of the cell
What does cytoplasm contain
Cytosol, cytoskeleton and organelles
Define cytosol
Aqueous solution of essential ions, soluble proteins and soluble organic compounds such as sugars and amino acids
Define cytoskeleton
Network of protein fibres that give support, mobility and regulation to the cell
Define cytoplasmic streaming
The movement of the fluid substance withiin a plant or animal cell and aids in transport of materials and organelles around the cell
Describe the structure of the nucleus
Largest organelle within the eukaryotic cell, usually spherical. Consists of nuclear envelope which separates nucleus from the cytoplasm. Contains nucleolus which synthesises ribosomes. Contains DNA. Found in all eukaryotic cells except matured red blood cells
What is the function of the nucleus
Contains hereditary material and controls activities of the cell. Cells normally contain one nucleus (uninucleated) but may be binucleated or multinucleated
Describe structure of RER
A system of flattened membrane-bound sacs. Appears “rough” under electron microscope because of presence of ribosomes on its surface
Describe function of RER
Protein synthesis, polypeptide chain synthesised by ribosomes will be folded in RER
Describe structure of SER
Consists of fine tubules
What are the functions of SER
Lipid synthesis, detoxification of drugs and poisons, storage and release of calcium ions
Describe structure of Golgi apparatus
Consists of stacks of flattened membrane-bound sacs
Describe function of Golgi apparatus
Chemically modifies products received from the ER and packages them, before sending them to destinations inside or out of the cell using vesicles
Describe structure of lysosomes
Small spherical vesicles surrounded by single membrane. Contains hydrolytic enzymes such as lipases, proteases and nucleases.
Describe function of lysosomes
To digest materials made in the cell or taken in from outside by phagocytosis
To digest worn-out organelles in the cell, process known as autophagy
Describe structure of animal vacuoles
Fluid-filled sac bounded by single membrane. Formed either by pinching-off part of cell membrane or enlargement of vesicle from Golgi apparatus. Usually relatively smaller and exists temporarily
Describe function of animal vacuoles
Can be food vacuoles formed by phagocytosis
Describe structure of plant vacuoles
Mature plant cells have permanent large central vacuole and occupies over 80% of cell volume. Enclosed by single, partially permeable membrane called tonoplast. Filled with cell sap, solution of dissolved substances such as sugars, ions, waste products and pigments
Describe function of plant vacuoles
Storage of nutrients such as protein storage in seeds and inorganic ions. Disposal sites for metabolic byproducts that would endanger cell if they accumulated in the cytosol. May contain pigments that colour cells(e.g. coloured petals to attract pollinators)
Describe structure of mitochondria
Rod-shaped or spherical, bounded by double membrane
Describe function of mitochondria
Involved in aerobic respiration. ATP is “energy molecule” living organisms. Mitochondria is abundant in metabolically active cells (e.g. muscle and liver cells)
Describe structure of chloroplasts
Bounded by double membrane, contains chlorophyll, contains thylakoids and stroma
Describe function of chloroplasts
Site of photosynthesis
Describe structure of ribosomes
Small, round structure found in all cells
May occur as free ribosomes suspended in the cytosol or bound to rough ER
Describe function of ribosomes
Sites of polypeptide synthesis.
Free ribosomes make proteins that function within the cytosol.
Bound ribosomes generally make proteins destined for insertion into membranes, for packaging within certain organelles such as lysosomes, or for export from the cell
Describe structure and function of centrioles
Small, hollow cylinders that occur in pairs, found in animal cells but absent in plant cells
They play a role in cell division in animal cells
Describe protein synthesis and secretion in a cell
Polypeptide chains are synthesised at the ribosomes and folded at RER. Transport vesicles containing substances made by ER pinched off from ER. Transport vesicles fuse and release substances into the Golgi apparatus. Secretory vesicles containing modified substances are pinched off from Golgi apparatus. Secretory vesicles move towards and fuse with cell membrane, releasing substances outside the cell by exocytosis
Describe formation of lysosome
Enzyme contents are synthesised on rough ER and transported via transport vesicle to the Golgi apparatus for further processing. Vesicle containing processed enzymes buds off from Golgi apparatus, forming a lysosome. Enzymes have to be kept apart from rest of cell or they will destroy the cell
What are similarities between animal and plant cells
Both cells contain cell membrane, mitochondria, nucleus and cytoplasm (and others)
Compare differences between animal and plant cell
Chloroplasts present in large numbers in photosynthetic cells(plant cell), absent(animal)
Centrioles present(animal), absent(plant)
Plant vacuole is present as single, large and central, animal vacuoles are small and numerous
Plant cell surrounded by cell wall in addition to cell membrane, cell wall absent and animal cell only surrounded by cell membrane
Define cell specialisation
Multicellular organisms are composed of different types of cells and structure of cells is differently adapted to perform specific function. Cells differ in size and shape and they perform specific functions.
Describe adaptation of root hair cell and how it helps function
Adaptation: Presence of long narrow extension
Function: Absorption of water and mineral salts
Use: Increased surface area to volume ratio due to presence of long narrow extension, increases rate of diffusion of mineral salts and osmosis
What are three adaptations of red blood cell and how do they help RBC in function
Presence of haemoglobin: Haemoglobin can combine with oxygen
Absence of nucleus: Allows more haemoglobin to be packed in the cell
Biconcave shape: Increases surface area to volume ratio to increase rate of diffusion of oxygen and carbon dioxide
What are adaptations of muscle cell and how does it help function
Elongated and cylindrical in shape, contains nuclei and mitochondria. Has mitochondria to provide energy for contraction of muscle cell
What is level of complexity of biological molecules in increasing order (e.g. macromolecule)
Macromolecule, organelle, cell, tissue, organ, organ system
Define organelle
Differentiated structure within cell which performs specific function
Define cell
The building blocks of life, simplest units that have all characteristics of life
Define organ
Structure made up of different tissues working together to perform specific function
Define tissue
A group of similar cells which work together to perform specific function
