Cells intro Flashcards
Recall the organisation of cells into an organism
Cells Tissue Organ Organ system Organism
What is the density of cells
1.06
What are cells usually measured in
volume (nano litres)
weight (density)
What is the size of a typical cell
25nm
What are the predominant types of molecules in a cell
Proteins Amino acids Lipids Sugars and carbohydrates RNA DNA Ions Cholesterol
Describe the movement of cells and molecules in the cells
Brownian motion - movement is spontaneous
Other forms of movement require energy
What are the main functions of blood
Transport Heat distribution Immunity Haemostasis Homeostasis
What are the major components of blood
Erythrocytes
Leukocytes
Plasma
Platelets
Explain the basic structure of haemoglobin
Quaternary structure protein with 4 polypeptide chains, each containing a haem group (Fe 2+)
When oxygen binds deoxyhaem becomes oxyhaem and Fe 2+ is oxidised to Fe 3+
Describe co-operative binding of haemoglobin
As first oxygen binds the structure becomes looser allowing other oxygen molecules to bind more easily (co-operative binding)
What is the role of haemoglobin
Transports O2 to tissues
CO binds much more easily (200x) and will prevent O2 from binding
Describe the structure of an erythrocyte
Concave disk for larger SA so quicker diffusion
Flexible so can flatten and squeeze through vessels
Formed from stem cells and when it still has ribosomes it is known as a reticulocyte
No nucleus - no DNA - no proteins - short life span
How is MCV found
Measure the MCV by finding haematocrit via centrifuging and dividing by the cell count
Explain the response to low oxygen concentration in the blood
- Kidney releases erythropoietin
- Marrow stem cells differentiate
- More red blood cells with harm produced
- Oxygen concentration increases
Why do men have a higher RBC count than females
Triggers erythropoietin release so males have a higher red blood cell count
Define anaemia
Anaemia is a lack of haemoglobin low haemoglobin concentration
Classify the types of anaemia according to red blood cell volume
Macrocytic : MCV too large, associated with deficiency in vitamin B12 which leads to deficiency in Folic acid (pregnancy) (needed for thymine synthesis) - failure of DNA synthesis and cell division
Normocytic : acute blood loss
Microcytic : MCV too small, associated with slow bleeding such as with menstruation failure of haemoglobin synthesis, GIT lesions, cancers and parasitic infections
Define leukocytosis and leukopenia
leukocytosis - leukocytes and platelets increase during infection
leukopenia - leukocytes and platelets decrease e.g. during chemotherapy
What are polymorphonuclear granules
Different shaped nuclei
multi lobed nuclei in neutrophils, eosinophils, basophils
Segmented nucleus full of granules
First to the seen, attaching to vessels
List the major functions of plasma
Exert osmotic pressure to maintain MCV
albumins - carrier
Globulin - carrier
Fibrinogen - clotting and platelet aggregation
What is the function of cholesterol in the phospholipid bilayer
decreases permeability and affects stiffness and interactions with the cytoskeleton
How are the membrane proteins contained in lateral movement
Intracellular fences consisting of the actin cytoskeleton
Explain how the proportion of protein to lipid is important for function
Myelin sheath has a higher proportion of lipid for insulation
Mitochondrial inner membranes have more proteins for the ETC proton pumps
What is the relationship between membrane proteins and fluidity
More membranes gives greater fluidity
Explain the movement of sodium and potassium ions across the cell membrane
Sodium potassium pump (antiporters)
2 potassium in, 3 sodium out
Explain how the entry of glucose and amino acids into the cell is coupled to ATP dependent transport
Example - glucose reabsorption in the proximal tubule in the kidney
Glucose is absorbed from the filtrate to the higher concentration in the cell
Glucose binds to a specific glucose transporter (symport)
Facilitated transport - co-transport with Na+
Explain how external chemical signals can be sensed at the interior of a cell
Some signals are lipid-soluble molecules e.g. steroid hormones, prostaglandins
Many impermeable signals rely on trans-membrane receptors
Give an example of each of the infectious agents: bacteria virus protozoa fungi Helminth parasite
Bacteria: Shigella Virus: HIV Protozoa: Malaria Fungi: Candida Albicans Helminth Parasite: Tapeworms, Flatworms, roundworms
Explain how bacteria replicate
Binary fission
Cell elongates and circular DNA replicates
What are the distinguishing features of bacteria
Cytoskeleton not well defined
Cell wall of peptide-glycan
Various routes of infection
Explain how viruses replicated
Retroviruses produce DNA from RNA using reverse transcriptase
Requires a host cell
Describe protozoa
Eukaryote, single cell
Complex life cycle which can involve two or more hosts
Intestinal, blood and tissue parasites
Infection via ingestion or vector
Explain how protozoa replicate
Infection via ingestion or vector
Describe fungi
Eukaryote, single cell
Yeast or filament
Causes cutaneous, mucosal, or systemic mycoses
Explain how fungi replicate
May be filaments (cross-walls) or will bud and divide
Describe helminth parasites
Eukaryote, multicellular Can have a life cycle outside of the host Visible to the naked eye Metazoa Life cycle complexity varies
