Cells Flashcards
Describe plasma (cell) membrane
- encloses cell contents
- participates in cellular activities
- regulates what enters and leaves cell (semi-permeable or selectively permeable due to phospholipid bilayer)
Describe plasma (cell) membrane structure
- phospholipid bilayer: main structure with phospholipids as most prevalent molecule
- proteins within it act as specific transporters or channels
- cholesterol strengthens
Name types of protein in plasma membrane
- channels
- transporters
- receptors
- enzymes
- linkers
- cell identity markers
What is the function of this protein in the plasma membrane - channels?
pores in the membrane that allow passage of specific substances such as ions
What is the function of this protein in the plasma membrane - transporters?
change shape as they shuttle substances, such as glucose, across the membrane
What is the function of this protein in the plasma membrane - receptors?
allow for attachment of substances, such as hormones, to the membrane
What is the function of this protein in the plasma membrane - enzymes?
participate in reactions at the membrane surface
What is the function of this protein in the plasma membrane - linkers?
help stabilize the plasma membrane and attach cells together
What is the function of this protein in the plasma membrane - cell identity markers?
unique to a persons’ cells; important in the immune system & transplantation of tissue from one person to another
What is the cytoplasm (consists of)?
- activities of the cell mainly occur here
- consists of fluid (cytosol) or water with suspended or dissolved substances such as enzymes, glucose, electrolytes (sodium ions)
- consists of organelles (litle organs) of the cell that perform specific functions (eg nucleus and ribosomes)
Describe the plasma membrane and its function.
- outer layer of cell, composed mainly of lipids and proteins
- encloses cell contents; regulates what enters/leaves cell; participates in growth, reproduction, interactions between cells
Describe the microvilli and their function.
- short extensions of the plasma membrane
- absorb materials into cell
Describe the nucleus and its function.
- large, membrane-bound, dark-staining organelle near center of cell; enclose din nuclear membrane; contains nucleolus where ribosomes are made (required for protein synthesis)
- control center of cell
- contains chromosomes (hereditary structures that direct all cell activities, composed of DNA)
- involved in cell reproduction
Describe the nucleolus and its function.
- small body in the nucleus
- makes ribosomes
Describe the cytoplasm and its function.
- colloid that fills the cell from the nuclear membrane to the plasma membrane
- consists of cytosol & organelles
- site of many cellular activities
Describe cytosol and its function.
- fluid portion of cytoplasm
- contains water, enzymes, nutrients, etc
- surrounds organelles
- site of many chemical reactions & nutrient storage
Describe the endoplasmic reticulum and its function.
- network of membranes w/in cytoplasm
- rough ER (rER) has ribosomes attached, smooth does not
- rough ER modifies, folds & sorts proteins (site of protein synthesis)
- smooth participates in lipid synthesis (important for making more membranes, detoxifying substances, stores calcium ions in muscle and called sarcoplasmic reticulum)
Describe ribosomes and their function.
- small bodies free in the cytoplasm or attached to the endoplasmic reticulum
- composed of RNA & protein
- not membranous
- produced in nucleolus but leaves nucleus for cytoplasm (free in cytoplasm or bound to rough endoplasmic reticulum)
- manufactures proteins (involved in protein synthesis)
Describe the Gogi apparatus and its function.
- layers of membranous sacs
- further modifies proteins
- sorts & prepares proteins made at ribosomes for transport to other parts of cell or out of cell
- creates final functional protein for use by or release from cell (eg mucous in digestive tract/hemoglobin in RBCs)
Describe mitochondria and its function.
- tiny organelles w/ internal folded membranes that create separate compartments w/ different enzymes & functions
- convert energy from nutrients into ATP (aerobic cellular respiration - in presence of O2 convert glucose to energy - ATP)
Describe lysosomes and their function.
- small sacs of digestive enzymes
- digest substances w/in the cell
- important for recycling worn out organelles, destroying engulfed bacteria or viruses, self-destruction of a cell, detoxification of drugs
Describe peroxisomes and their function.
- membrane-enclosed organelles containing digesting enzymes
- break down harmful substances
- important for recycling worn out organelles, destroying engulfed bacteria or viruses, self-destruction of a cell, detoxification of drugs
Describe proteasomes and their function.
- barrel-shaped organelles
- destroy improperly synthesized proteins
Describe vesicles and their function.
- small membrane-bound sacs in the cytoplasm
- store materials & move into or out of cell
Describe centrioles and their function.
- rod-shaped bodies (usually two) near nucleus
- composed of microtubule proteins
- help separate chromosomes during cell division so each daughter cell gets proper number
Describe surface projections and their function.
- structures that extend from the cell
- move the cell or the fluids around the cell
Describe cilia and their function.
- many short hairlike projections from the cell
- composed of microtubules
- move fluids around the cell
Describe flagellum and their function.
- single long whiplike extension from the cell
- composed of microtubules
- moves the cell
Name and describe the three types of cell transport.
- passive across plasma membrane: substances cross following their concentration gradients (high to low); eg diffusion, facilitated diffusion, osmosis, filtration
- active across plasma membrane: energy (ATP) required to move substances; against concentration gradient or for movement of large molecules
- vesicular: paghocytosis, pinocytosis, exocytosis
What is diffusion?
- the constant movement of molecules from an area of high concentration to one of low concentration to achieve equilibrium
- occurs with or without a plasma membrane
Do substances move up or down their concentration gradients during passive diffusion across semi-permeable membrane? Is energy required?
down; no
Which solutes (dissolved substances) are allowed to cross semi-permeable membrane during passive diffusion? Which are not?
- fat-soluble substances (lipids, alcohol) and water, CO2 and O2 can cross
- water-soluble substances (proteins, glucose) cannot
What is facilitated diffusion? Is energy required?
Movement of solutes (charged, water-soluble substances - glucose, amino acids, electrolytes) down their concentration gradient w/ help of transporter proteins that act as channels; energy not required
What is osmosis? Do water molecules move from solution of low solutes to one of high solutes or from high solutes to low?
- movement of water across a semi-permeable membrane when solutes cannot move
- from low solutes (high water) to high solutes (low water)
What is osmotic pressure?
the force needed to stop the flow of water by osmosis
Name the types of solutions and their effect on a cell.
- isotonic: same concentration as fluid w/in cell; no change
- hypotonic: cytosol more concentrated than surrounding solution; water moves into cell causing it to swell and perhaps burst
- hypertonic: cytosol less concentrated than surrounding solution; water moves out of cell and it shrinks (crenation)
Describe filtration
- mechanical force pushes substance through membrane
- membrane limits which particles can pass through
- pores in membrane restrict larger molecules from passing
- small particles go through & appear in filtrate
- eg movement of substances out of blood capillaries due to high blood pressure; filtration of blood at kidney nephrons - urine formation
What is active transport? Does it require energy?
- the movement of small solute particles in or out of the cell against the concentration gradient
- requires energy (ATP)
- requires protein pump (active transporter)
- important for muscle contraction and neuron function - creates resting membrane potential
Name and describe types of vesicular transport?
- phagocytosis: plasma membrane engulfs large particles from surroundings and brings them into cell (eg white blood cells phagocytize bacteria)
- pinocytosis: plasma membrane engulfs small droplets of liquid from its surrounds and brings it into cell
- exocytosis: materials moved out of the cell through creation of membrane-bound vesicles; often protein-based substances produced by ribosomes & packaged by Golgi complex (eg mucous secretion from cells lining upper airways; release of neurotransmitters at ends of neurons)
What are the two steps involved in protein synthesis?
- transcription (DNA to mRNA)
- translation (mRNA to protein)
Where is DNA found? What does it make up? What is its structure and composition?
- found in nucleus
- makes up 23 pairs of chromosomes in humans
- double helix (twisting ladder)
- composed of four types of nucleotides/nitrogenous bases
Distinct regions of the DNA of a chromosome make up what?
- Genes, or sequence of nucleotides that code for a protein, determining hereditary traits or genetic diseases
What is the location, composition, structure and function of RNA?
- almost entirely in cytoplasm
- nucleotides contain adenine (A), guanine (G), cytosine (C) or uracil (U)
- sugar: ribose
- structure: single strand
- manufacture proteins according to the codes carried in the DNA (mRNA, rRNA, tRNA)
What is the location, composition, structure and function of DNA?
- almost entirely in the nucleus
- nucleotides contain adenine (A), guanine (G), cytosine (C), or thymine (T0
- sugar: deoxyribose
- structure: double-stranded helix formed by nucleotide pairing A-T; G-C
- makes up chromosomes, hereditary units that control all cellular activities; divided into genes that carry the nucleotide codes for the manufacture of proteins
What organelles are involved in transcription (protein synthesis)? What happens during this stage?
- ribosomes, rough endoplasmic reticulum, and Gogli apparatus
- genes, composed of DNA nucleotides coding for a specific protein, are copied in the nucleus
- DNA used as template to make messenger RNA or mRNA from free nucleotides suspended in nucleus
- mRNA leaves nucleus
What happens in translation stage of protein synthesis?
- after mRNA leaves the nucleus, it binds to ribosomes in cytoplasm or on rough endoplastic reticulum
- specific transfer RNA or tRNA molecule reads mRNA nucleotide sequence and brings the correct amino acid to the mRNA on the ribosome
- as sequence read by more tRNAs, amino acids are joined together forming long protein chain
What happens before any cell division?
DNA in nucleus precisely copied (mutations can occur)
What is mitosis and what is it important for?
- when nucleus of cell divides once; produces two cells genetically identical to each other and parent cell
- important for growth and repair
What is meiosis and what is it important for?
- process where single cell divides twice to produce four cells containing half amount of genetic information
- genetically unique from parent cell and each other
- sex cells (sperm and eggs)
- important for formation of gametes w/ half number of chromosomes (full number restored upon fertilization)
What are the four stages of mitosis and meiosis?
- prophase
- metaphase
- anaphase
- telophase (cytoplasm divides)
- cell divides twice in a row for meiosis
What happens during prophase (mitosis)?
- DNA strands coil into chromosomes
- nucleolus and nuclear membrane disappear
- centrioles move to opposite poles and form spindle
What happens during metaphase (mitosis)?
- chromosomes line up across centre of cell
- chromosomes attach to spindle
What happens during anaphase (mitosis)?
- centromeres split
- identical chromosomes move toward opposite centrioles
What happens during telophase (mitosis)?
- chromosomes continue to move toward centrioles
- nuclear membrane forms around each group of chromosomes
- plasma membrane pinches off in middle of cell to form two new identical daughter cells
What is cell aging? What are the types?
- as cells multiply, changes occur that may lead to their damage or death
- free radical injury: free radicals are highly reactive, destructive compounds produced during cellular activities; they can damage lysosomes which then release their destructive enzymes causing further cell injury; can result in gene mutations that could lead to cancer
- slowing cell activity
- apoptosis (preprogrammed cell death); also a normal process for replacing some types of cells that experience lots of wear and tear (eg stomach lining cells)
What is the link between cells and cancer?
- certain mutations may cause changes in cells leading to uncontrolled reproduction (cancer)
- cancer cells form tumours, crowding out normal cells and interfering w/ normal organ function
- can spread to other areas of body
What are risk factors for cancer?
- heredity (breast, colon)
- carcinogens (cigarette smoke)
- ionizing radiation (x-rays, UV rays)
- diets high in fat and calories and low in fibre, fruits and veggies
- viruses (some leukemias, cervical cancer from human papilloma virus)
